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Climate destabilization

Posted April 7th, 2012 in Physics. Tags: , , , , , , .

The overwhelming majority of scientists endorse this statement:

“Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.” [IPCC Summary for Policymakers, 2007]

Here, “most” means at least 50% of the 0.55°C rise since 1950. Some mistakenly call this an “alarmist exaggeration” but it actually understates the human contribution because it’s easy to incorrectly conclude that the other 50% of the trend might be caused by natural forcing variations:


Actually, the percentage of the observed temperature trend due to natural forcing variations (changes in the Sun’s brightness or volcanic eruptions, etc.) can’t be as large as 50%. In fact, the trend due to natural forcing variations since 1950 is nearly zero.

The percentage of the observed temperature trend due to human CO2 emissions is probably higher than 100%. This is possible mainly because humans emit greenhouse gases like CO2 which warm the surface over the long term, and sulfates which cool the surface over the short term. Upper and lower uncertainties are also shown:


Source: Huber and Knutti, “Anthropogenic and natural warming inferred from changes in Earth’s energy balance,” Nature Geoscience, vol. 5, pp. 31-36, 2012.

Some say we should increase sulfate emissions to compensate for the long-term warming due to our CO2 emissions. However, the CO2 would still acidify the oceans, which probably caused mass extinctions in the past. For instance, 250 million years ago, 90% of all species on Earth died. This “end-Permian” extinction was preceded by massive emissions of greenhouse gases, including CO2. This ancient evidence is uncertain, but even the highest estimated end-Permian emission rate is ∼ 10x slower than the modern human emission rate:


Source: Honisch, et al., “The Geological Record of Ocean Acidification”, Science 335, 1058, 2012.

A printable version of this article is available.

Here’s an index of comments:

  1. I expand on the article.

  2. Former NASA employees write a letter accusing NASA of ignoring empirical evidence.

  3. The Heartland Insitute puts up a billboard featuring the Unabomber.

  4. Open letter to an anonymous climate scientist.

  5. Methane turns into CO2 after about a decade in the atmosphere.

  6. Male Space Cadet and I discuss estimates of climate sensitivity using spectroscopy and paleoclimate data.

  7. Dr. X and I discuss how feedbacks in the paleoclimate compare to modern feedbacks.

  8. Reythia and I discuss cryonics and legacies.

  9. Tony and I discuss population growth.

  10. I compare the energy in 1C of global warming to nuclear bombs, and compare the time delay to weed-laced brownies.

  11. Bill and I discuss plastic bags and affluence.

  12. A conversation regarding the fingerprints of CO2 warming.

  13. Wildfires and Hurricane Sandy.

  14. I summarize Sir Bob Watson’s AGU talk for a colleague.

  15. Alec Rawls leaks the IPCC draft and spreads misinformation about it.

  16. Paul Vincelli asks if the IPCC’s upward revision explains why the cryosphere is melting so fast.

  17. Lee and I discuss decadal natural variability in a Skeptical Science video about warming over the last 16 years.

  18. I was wrong: Tamino shows that Marcott et al. can resolve warming spikes like today’s if they’d happened in the past.

  19. Schmitt & Happer deny global warming, deny human contribution, ignore the end-Permian and PETM, babble about plants.

Last modified May 18th, 2013

64 Responses to “Climate destabilization”

  1. Thanks to Reythia for suggesting the title of this article, and for the insightful analogy she offered in that comment. I’m also grateful to three anonymous oceanographers who informally reviewed this article. Here’s the GMT script that made the figures.

    This was partially inspired by Talisman Energy’s coloring book Talisman Terry. Noticing that their coloring book has 431 words, I decided to see how much science I could squeeze into 431 words of plain English.

    The graphs are distilled from several recent scientific papers. I’ve used the word “sulfates” instead of “aerosols” which is more common in the scientific community. This is because the general public mistakenly thinks spray cans are causing global warming, maybe because scientists use the word “aerosols” to refer to small particles that block sunlight rather than aerosol cans. (Or, they could be confusing the current CO2 warming problem with an older ozone layer hole problem caused by CFCs.) Hopefully, using a less familiar word like sulfates will cause less confusion.

    The second figure is based on this quote:

    “Expressed as a fraction of the total warming, greenhouse gases contributed 166% (120–215%). The net cooling from the direct and indirect aerosol forcing is −0.45°C (−0.78 to −0.16°C), thereby offsetting −44% (−73 to −28%) of the greenhouse induced warming. It is thus extremely likely (>95% probability) that the greenhouse gas induced warming since the mid-twentieth century was larger than the observed rise in global average temperatures, and extremely likely that anthropogenic forcings were by far the dominant cause of warming. The natural forcing contribution since 1950 is near zero.” [Fig 3c, described on p32 of Huber and Knutti 2012]

    I haven’t found a way to explain the difference between unforced internal natural climate variability and changes in natural forcings without exceeding Talisman Terry’s word count. But this quote implies that unforced variability doesn’t significantly change the results over a ~60 year timespan:

    “Our results show that it is extremely likely that at least 74% (±12%, 1 sigma) of the observed warming since 1950 was caused by radiative forcings, and less than 26% (±12%) by unforced internal variability.” [p34 of Huber and Knutti 2012]

    Isaac Held’s analysis of internal variability is also compelling.

    The third figure is based on this quote regarding end-Permian emissions:

    “… an annual carbon release of ~0.1 to 1 PgC [compared with 9.9 PgC in 2008 (57)].” [p1061 of Honisch et al. 2012]

    I’m surprised they compare modern emissions to the end-Permian emissions using PgC/year instead of “percentage increase in CO2/year”. Because the climate response to CO2 is logarithmic to first order, the %CO2/year metric seems more appropriate. Furthermore, because the baseline Permian CO2 levels were several times higher than today’s, even before the Siberian Traps erupted, this means the end-Permian emission rate would actually be a further several times smaller compared to the modern emission rate when using a %CO2/year metric.

    Perhaps this logarithmic dependence is only true for the temperature response, but not for ocean acidification? Any chemists want to help me out here?

  2. Recently, 49 former NASA employees wrote a letter which includes this statement:

    We feel that NASA’s advocacy of an extreme position, prior to a thorough study of the possible overwhelming impact of natural climate drivers is inappropriate.

    So, all the attribution studies that have already been performed (which they don’t mention, as though they don’t even exist!) aren’t “thorough” enough? On what grounds?

    Why criticize NASA specifically, when the National Academy of Sciences and nearly all other national scientific organizations are saying the same thing?

    Why accuse NASA of “ignoring empirical evidence” and “relying too heavily on complex climate models that have proven scientifically inadequate” when the models often underestimate climate effects which are only revealed by empirical evidence (e.g. sea level rise, Arctic sea ice extent, ice sheet mass loss, climate sensitivity derived from last glacial maximum paleoclimate data, etc.)?

    I’m starting to think this coloring book could be useful reading for astronauts, not just children.

    How depressing that former NASA employees (led by Dr. Schmitt, a member of the Heartland Institute’s board of directors) are posting letters catalyzed by a chairman of “Plants Need CO2” at Watts Up With That. What’s next, posting criticisms of evolution at the Discovery Institute’s website?

    Update: I’ve failed to communicate once again.

  3. Skeptical Science debunks Dr. Schmitt’s letter.

    By the way, that article has a graph (explained in more detail here) showing the results of other attribution studies. Notice their total human contributions are all around (or above) 100%, and that 4 of the 6 estimated natural contributions are negative:

    Results of 6 attribution studies
  4. The Heartland Institute is putting up billboards featuring the Unabomber saying “I still believe in Global Warming. Do you?”

    Other “global warming alarmists” on their proposed billboards include Charles Manson, Fidel Castro, and Osama bin Laden. I heard they all “believed” The phrase “accept the experimental evidence for gravity” is a more accurate way to state this scientific position. in gravity. Do you?

  5. The billboards have been pulled, but in the process the Heartland Institute learned absolutely nothing. Their press release reveals a breathtaking lack of self-awareness:

    This billboard was deliberately provocative, an attempt to turn the tables on the climate alarmists by using their own tactics but with the opposite message. We found it interesting that the ad seemed to evoke reactions more passionate than when leading alarmists compare climate realists to Nazis or declare they are imposing on our children a mass death sentence. We leave it to others to determine why that is so.

    I can’t even count how many times contrarians have compared me to a Nazi/fascist Controversial global warming skeptic Christopher Monckton of Great Britain defends his use of the term ‘eco-fascists’ in describing those on the left who insist that critics like Monckton should be silenced. Interviewed by Rob Nikolewski of http://www.capitolreportnewmexico.com on Nov 2, 2011 /communist/Unabomber/mass I noticed that the Heartland Institute’s absurd “quiz” comparing Al Gore to Ted Kaczynski (the Unabomber) didn’t contain any quotes about global warming. So I searched Kaczynksi’s manifesto for global warming, climate change, CO2, carbon dioxide: no results. Searching for “greenhouse” yields two quotes. Paragraph 118 includes the phrase “… and the greenhouse effect affects the whole world.” Paragraph 169 includes the sentence “No one knows what will happen as a result of ozone depletion, the greenhouse effect and other environmental problems that cannot yet be foreseen.” Kaczynski actually stressed uncertainty, just like the merchants of doubt. murderer Eric L: In interesting news, Breivik plagarized from Ted Kaczinski! /cultist/asshole/liar/etc., probably because I’m repressing these memories to preserve what’s left of my sanity. Remember that Lord Monckton called a group of climate activists “Nazis” and “Hitler Youth”. The fact that one of them is Jewish seemed not to faze him. The good      Lord Christopher Monckton, Third Viscount Monckton of Brenchley, delivered the closing keynote address at the 2009 International Conference on Climate Change, praising those in attendance for holding fast to their scientific ethics and speaking truth to power.
         Where are they all today, those bed-wetting moaning Minnies of the Apocalyptic Traffic-Light Tendency- those Greens too yellow to admit they’re really Reds?
         The main message of this conference to the bed-wetters is this. Stop telling lies. You are fooling fewer and fewer of us. However many lies are uttered, the scientific truth remains unalterable.
          The Forces of Darkness, with their “global warming” chimera, came perilously close to ending the Age of Enlightenment and Reason. They almost ushered in a new Dark Age. Yet they have failed. Why? They have failed because you, here, have had the courage to face them down, to confront their falsehoods, and to nail their lies.
          The Age of Light and Reason shall not die. Dylan Thomas wrote, “Do not go gentle to that last goodnight: Rage, rage against the dying of the light.” You have not raged in vain. The world is not cooking: It is cooling. Every opinion poll- even those conducted by the bed-wetters themselves- shows that global public opinion is cooling as fast as the global climate.
          In one recent survey, “global warming” came at the very bottom of a list of political and environmental concerns, immediately behind the need to clean up dog-poop on the streets. Why? Because dog-poop is a real environmental problem. “Global warming” is not. The correct policy response to the non-problem of climate change is to have the courage to do nothing.
          We, the people, are no longer afraid of “global warming.” We are fed up to the back teeth of hearing about it. We are bored by it. And the bed-wetters know it. Their ever-more-outlandish predictions are a measure of their blind panic. The Dr. Strangelove of NASA, in the latest of a series of ever-more-desperate attempts to flog the dead horse of climatic apocalypse, recently wrote that sea level is about to rise by 246 feet, “und anyvun zat disagrees viz me vill be arrested und put on trial for high crimes against humanidy und nature.”
          When Hansen’s political ally and financial beneficiary Al Gore had only predicted one-twelfth that amount of imminent sea-level rise, Mr. Justice Burton said in the London High Court, “The Armageddon scenario that he depicts is not based on any scientific view.” But then, Al Gore knew that all along. In 2005, the year he said sea level would imminently rise by 20 feet, he bought a $4 million condo in the St. Regis tower, San Francisco- just feet from the ocean at Fisherman’s Wharf. The only danger to sea level is from all those bed-wetters.
          Do we want to see the bed-wetting liars, hucksters, shysters, fraudsters, and racketeers ever-more-extravagantly rewarded with honors and prizes for their ever-more-extravagant falsehoods, fables, and fictions?
          You, in this room, have bravely upheld the truth and the scientific method against all manner of lies, threats, sanctions, personal attacks, and entertaining revisions to your CreepyMedia biographies. Because you have not failed or faltered, the Forces of Darkness are now scuttling back into their lairs, there to snivel in the eternal darkness of utter oblivion and CNN.
          There was no climate crisis. There is no climate crisis. There will be no climate crisis. “Global warming” is not a global crisis. It is a global scientific fraud.
          Without you, that blunt truth might have taken far longer to emerge than it has. And delay is fatal. Though lies cannot alter or harm the truth, they can kill our fellow men. The environmental movement is out of control. It is now humankind’s deadliest enemy. In the name of humanity, it must be outlawed. Thirty years ago, the soi-disant “Greens” agitated for DDT to be banned. They killed 40 million people of malaria, most of them children. Eventually, after a third of a century, the WHO at last caved in to humanitarian pressure from me and others and reversed the ban. Dr. Arata Kochi, announcing the end of that murderous ban, said, “Usually in this field politics comes first and science second. Now we must take a stand on the science and the data.” That is what you in this room have so gallantly done. You have taken a stand on the science and the data.
          Now the very same soi-disant “Greens” are killing millions by starvation in a dozen of the world’s poorest regions. Their biofuel scam, a nasty by-product of their shoddy, senseless, failed, falsified, fraudulent “global warming” bugaboo, has turned millions of acres of agricultural land from growing food for humans to growing fuel for automobiles. If we let them, they will carelessly kill tens of millions more by pursuing Osamabamarama’s stated ambition of shutting down nine-tenths of the economies of the West and flinging us back to the Stone Age without even the right to light fires in our caves.
    Lord No serious scientist, therefore, can any longer take any of the IPCC’s conclusions seriously for a single moment longer. As Lord Lawson of Blaby has long argued, the IPCC should now be abolished. It cannot serve any useful purpose in future, because it has dishonestly lent its support not merely to the falsification of scientific results but to the persistent maintenance of that falsification. The IPCC is finished. … The real cost of the flagrant abuses of the scientific method surrounding the question of climate that are so well illustrated by the affair of the “hockey stick” is a terrible, unseen cost in human lives. … These evil pseudo-scientists, through the falsity of their statistical manipulations, have already killed far more people through starvation than “global warming” will ever kill. They should now be indicted and should stand trial alongside Radovan Karadzic for nothing less than high crimes against humanity: for, in their callous disregard for the fatal consequences of their corrupt falsification of science, they are no less guilty of genocide than he. [Lord Christopher Monckton, September 2008] later entered a quantum superposition, simultaneously repeating it on radio and stating “It was not I who called them Hitler Youth.”

    Heartland has spent millions of dollars contributing to the real debate over climate change, and $200 for a one-day digital billboard. In return, we’ve been subjected to the most uncivil name-calling and disparagement you can possibly imagine from climate alarmists. The other side of the climate debate seems to be playing by different rules. This experiment produced further proof of that.

    They seem to have misspelled “sabotaging” as “contributing to”. Common mistake. Presumably, complaining about the “other side” playing by different rules and subjecting them to uncivil name-calling is some kind of bizarre joke. It’s psychological projection wrapped up in a tortilla of irony.

  6. This is nothing new, but these amusing billboards are.

  7. It never ends. Heartland president Joe Bast just called Michael Mann and Bill McKibben “madmen”, and Heartland “expert” Alan Caruba just wrote an article with the title “Climate Nazis”.

  8. At the Heartland conference, a second letter to NASA (with more exclamation points) was announced, which “should end the discussion.” This time, they conflate uncertainty regarding our future CO2 emissions (which is a sociological/economics question) with the scientific uncertainty of how much warming and sea level rise we should expect by 2100 from (for instance) a doubling of CO2 concentration.

    Update: Dr. Schmitt keeps digging.

  9. Anthony Watts announces a new website where NASA retirees regurgitate similar nonsense.

    When joeldshore points out that they’re using motivated reasoning similar to Spencer’s creationist views, Anthony Watts tells him to “shove it up the bodily orifice of your choice.”

    When Steven Mosher points out how premature the site’s conclusions are, Anthony Watts babbles about Muller and ironically tells Mosher to “re-examine and walk-back a bit from your position.”

  10. Open letter to an anonymous climate scientist

    After I responded to Dr. Schmitt’s recent letter, a colleague said I shouldn’t worry about statements made by people with no credentials in (or familiarity with) climate science. He’s probably right, but I’m haunted by memories of you (an anonymous climate scientist) making similar claims. Let’s reason together.

    A friend of a friend of mine was a grad student in Michael Mann’s lab, and he said that Mann did some shady things with his proxies which resulted in a hockeystick that’s too steep. [Anonymous Climate Scientist, Fall 2011]

    It’s more likely that someone in your chain of references was misinformed by Steve McIntyre’s website Climate Audit (tied for Best Science Blog in 2007):

    • McIntyre noticed that Mann’s algorithm used de-centered principle component analysis (PCA). McIntyre changed to centered PCA, but got a reconstruction that wasn’t shaped like a hockeystick because he didn’t retain enough PC’s. While probably easier to interpret, using centered PCA converges slower but otherwise barely changes the resulting hockeystick, as long as enough PC’s are retained.
    • McIntyre fed ARFIMA persistent red noise into Mann’s algorithm to create 10,000 synthetic temperature reconstructions (still using just 1 PC), and found that “some” looked like Mann’s hockeystick. Of course, McIntyre’s Figure 1 needs a y-axis 6 times larger to show Mann’s hockeystick, confirming that the red noise hockeysticks explain comparatively little variance. Half the red noise hockeysticks were upside-down, but McIntyre only showed an upright one. Prof. Wegman repeated these claims to Congress in the infamous “Wegman Report”, showing 12 upright red noise hockeysticks, all cherrypicked from the top 1% which looked most like Mann’s hockeystick. Wegman’s Figure 4.4 claimed that McIntyre used “red noise [AR(1) with parameter = 0.2]” which has a decorrelation time of 1.5 years, while McIntyre actually used ARFIMA noise with a decorrelation time of ~350 years.
    • McIntyre substituted a tree-ring dataset from the internet into Keith Briffa’s CRU Yamal tree-ring chronology, and noticed that it got rid of the hockeystick. McIntyre was so appalled at what he considered embarrassing and disquieting biased picks that he called them “CRU cherrypicking” (backpedalling notwithstanding) and declared that Yamal proxy data was “like crack cocaine for paleoclimatologists. This invalid claim led Prof. Roger Pielke, Jr. to accuse Gavin Schmidt of outright lying. [Update: Anthony Watts has “always thought that with CRU, simple incompetence is a more likely explanation than malice and/or deception,” but when McIntyre adds heroin and LSD to the list, he calls CRU scientists unscrupulous liars who deserve our scorn.]
    • Etc., etc., etc., etc., etc., etc., etc., etc., etc., etc., etc.

    McIntyre’s claims were all shown to be mistaken or insignificant. So it’s not surprising that the National Academy of Sciences (NAS) largely agreed with Mann’s original temperature reconstruction. I’ve noted that the NAS report’s biggest caveats concerned the uncertainty bars before 1600, mostly due to the limited temporal resolution of the older proxies. The NAS report didn’t dispute the hockeystick’s steepness during the 20th century, because other groups have used different algorithms, different proxies such as borehole data, and thermometers to independently confirm the temperature record.

    More recently, the BEST project (led by Prof. Richard Muller, who teachesPhysics for future Presidents” at Berkeley, and Prof. Judith Curry, who is Chair of the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology) produced its results. BEST was initially praised at Watts Up With That (Best Science Blog in 2008, 2011, 2012). Anthony Watts was prepared to accept whatever result they [BEST] produce, even if it proves my premise wrong.” He’d previously co-authored “Surface Temperature Records: Policy Driven Deception?” which states “… the ‘warming’ is a consequence of urban heating.”

    All BEST and only rural BEST sites

    Dumb Scientist: A stronger greenhouse effect warms the surface and lower troposphere, but cools the stratosphere.

    Anonymous Climate Scientist: Really? I didn’t know that.

    Dumb Scientist: Very few people do. In fact, the University of Alabama at Huntsville (UAH) reconstruction of tropospheric temperatures was initially flawed because the satellites can’t perfectly distinguish between the troposphere and stratosphere. Trying to measure the warming trend in the troposphere also partially measures the cooling trend in the stratosphere. This led many scientists to claim that the temperature trend being measured on the surface was too steep in comparison.

    Anonymous Climate Scientist: Maybe that’s the reason I’ve been saying the hockeystick is too steep… [2011-12-07]

    If that’s really why you’ve been saying the hockeystick is too steep, you might find these papers interesting:

    1. Spencer and Christy 1990 claimed their UAH satellite temperature record was “more precise” than surface measurements, and revealed “no obvious trend” from 1979-1988. Dr. Spencer’s later statements suggest he was being very modest.
    2. Gary and Keihm 1991 showed that natural variability in only 10 years of UAH data was so large that the UAH temperature trend was statistically indistinguishable from that predicted by climate models.
    3. Hurrell and Trenberth 1997 found that UAH merged different satellite records incorrectly, which resulted in a spurious cooling trend.
    4. Wentz and Schabel 1998 found that UAH didn’t account for orbital decay of the satellites, which resulted in a spurious cooling trend.
    5. Fu et al. 2004 found that stratospheric cooling had contaminated the UAH analysis, which resulted in a spurious cooling trend.
    6. Mears and Wentz 2005 found that UAH didn’t account for drifts in the time of measurement each day, which resulted in a spurious cooling trend.

    After these errors were fixed, the UAH data revealed a warming trend that’s consistent (PDF, fact sheet) with climate models and with surface measurements:

    Satellite and surface temperatures

    Anonymous Climate Scientist: I think that more of the temperature rise since 1950 could have been caused by natural forcings than most climate scientists admit.

    Dumb Scientist: How so? The Sun isn’t getting brighter- we’ve had satellites measuring solar output for decades. Of course, some get around this fact by speculating that the Sun’s magnetic field strength has increased, which decreases the number of cosmic rays that impact low-level clouds, which might decrease the Earth’s albedo and thus result in a warming trend.

    Anonymous Climate Scientist: That’s exactly the hypothesis I was about to mention!

    Dumb Scientist: It’s an interesting idea, but there isn’t a long-term trend in solar magnetic field strength or cosmic ray intensity, and furthermore the cosmic ray effect on Earth’s albedo has been repeatedly shown to be very weak. It’s simply not capable of producing a significant warming trend. [2011-09-08]

    A week later, I emailed you links to papers copied from section 7(b) in the index, which deals with the cosmic ray warming hypothesis. The next time we had lunch, you said:

    A trend in cosmic ray intensity isn’t strictly necessary to cause a warming trend. For example, some nonlinear systems only respond after a certain level of forcing is applied. Even a trendless sine curve would produce a trend in such a system because it only responds to the positive forcing. [Anonymous Climate Scientist, Fall 2011]

    That’s an interesting point. But, if the climate is so sensitive to cosmic rays that even a trendless sine curve causes a significant temperature trend, shouldn’t we expect a significant trend in cosmic ray intensity to cause an even bigger temperature trend? I ask because Richard Alley mentioned (at 42:00 in his 2009 AGU talk) that beryllium proxy data reveal a spike in cosmic ray intensity during the “Laschamp anomaly” ~40,000 years ago, but the corresponding oxygen isotope proxy for temperature didn’t change unusually during that time period:

    Laschamp anomaly

    The IPCC says that the [lower bound of the] percentage of the temperature trend since 1950 caused by humans is between 30% and 50%. [Anonymous Climate Scientist, Fall 2011]

    First, I explained that the 2007 IPCC report actually said the human greenhouse gas contribution since 1950 is greater than 50%, at the 90% confidence level. Then I pointed out that this is an understatement, because the warming due to human CO2 emissions is partially offset by human aerosol emissions, so our CO2 is probably responsible for more than 100% of the observed temperature rise.

    Anonymous Climate Scientist: The IPCC says that the [lower bound of the] percentage of the temperature trend since 1950 caused by humans is between 30% and 50%.

    Dumb Scientist: No. You’re wrong about that. The IPCC never said the [lower bound of the] human contribution is between 30% and 50%.

    Anonymous Climate Scientist: You read the entire reports? All of them? [2012-03-07]

    The size of the warming over the last century is broadly consistent with the predictions of climate models but is also of the same magnitude as natural climate variability. If the sole cause of the observed warning were the human made greenhouse effect, then the implied climate sensitivity would be near the lower end of the range inferred from the models. The observed increase could be largely due to natural variability, alternatively this variability and other man-made factors could have offset a still larger man-made greenhouse warming. The unequivocal detection of the enhanced greenhouse effect from observations is not likely for a decade or more, when the committment to future climate change will then be considerably larger than it is today. [1990 IPCC WG1]

    Our ability to quantify the human influence on global climate is currently limited because the expected signal is still emerging from the noise of natural variability, and because there are uncertainties in key factors. These include the magnitude and patterns of long term natural variability and the time-evolving pattern of forcing by, and response to, changes in concentrations of greenhouse gases and aerosols, and land surface changes. Nevertheless, the balance of evidence suggests that there is a discernible human influence on global climate. [1995 IPCC WG1]

    Chapter 8 makes similar points in each report. Both the 1990 and 1995 reports acknowledged that the signal-to-noise ratios were too low for confident detection and attribution.

    Update: I’ve failed to communicate once again.

    Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.[12] This is an advance since the TAR’s conclusion that “most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations”. [2007 IPCC WG1]

    The 2001 statement is echoed in that report’s Section 12.6. The 2007 statement is echoed in that report’s Table 9.4. As expected, the anthropogenic greenhouse signal emerged a decade ago from the noise of natural variability. The IPCC never put the lower bound of the human contribution at 30%, but Prof. Curry did, while rambling about Italian flags. Hopefully this is just a coincidence…

    Maybe my information is out of date, but a few years ago I was submitting a research proposal and the general consensus was that natural and human contributions couldn’t be separated. [Anonymous Climate Scientist, 2012-03-07]

    Being “out of date” seems popular. About a week later, I wrote a short article showing how natural and human contributions can be separated, but you never replied. If you found that attribution study weak, please consider the results of other studies. Notice their total human contributions are all around (or above) 100%, and that 4 of the 6 total natural contributions are negative:

    Results of 6 attribution studies

    How do they distinguish natural aerosols from human aerosols? [Anonymous Climate Scientist, 2012-03-07]

    • The main source of sulphate aerosol is via SO2 emissions from fossil fuel burning (about 72%), with a small contribution from biomass burning (about 2%), while natural sources are from dimethyl sulphide emissions by marine phytoplankton (about 19%) and by SO2 emissions from volcanoes (about 7%). Estimates of global SO2 emissions range from 66.8 to 92.4 TgS/yr for anthropogenic emissions in the 1990s and from 91.7 to 125.5 TgS/yr for total emissions. [2007 IPCC WG1]
    • Volcanoes emit aerosols in brief eruptions, resulting in a series of spikes that can be temporally distinguished from human aerosols which are released at a much more constant rate. Human and marine SO2 emissions might not be temporally distinguishable, because marine SO2 emissions could have varied like ours did.
    • Volcanic eruptions blast aerosols (which aren’t well-mixed) into the stratosphere, so volcanic aerosols can be spatially distinguished from human aerosols which are emitted in the lower troposphere and are concentrated near coal plants without scrubbers rather than near active volcanoes. Similarly, marine SO2 emissions would be concentrated in the oceans, which dominate the southern hemisphere, but most industry is in the north.

    There are other types of aerosols, of course. But that rabbit hole is deep.

    Anonymous Climate Scientist: How do they even estimate the aerosol forcing in the first place?

    Other Climate Scientist: They probably take the observations, subtract estimates of human CO2 and natural forcings, then call that residual the “aerosol forcing.” [2012-03-07]

    You just described inverse calculations of aerosol forcings. It’s important to note that they’re compared to independent forward calculations which are based on estimates of emissions and models of aerosol physics and chemistry.

    Anonymous Climate Scientist: I think some climate scientists are making alarmist claims that aren’t backed up by the science.

    Dumb Scientist: Such as?

    Anonymous Climate Scientist: I read a newspaper article where Stephen Schneider said that we need to exaggerate risks and downplay uncertainties. [Fall 2011]

    I agree that this quote is irresponsible and counter-productive. But who actually wrote it? Kate investigated. After the Detroit News editorial removed sentences like “I hope that means being both,” the meaning of Schneider’s original quote was mangled. Originally, Schneider was just verbosely criticizing the media’s desire for simple, brief soundbites and sensationalized oversimplifications. This isn’t an isolated incident; for instance, Dr. Fred Singer recently repeated a similar misquote.

    Update: Brad Keyes and “Turbulent Eddie” keep riding this hobby horse.

    It’s important that we not be too adamant because if it turns out we’re wrong, the entire scientific community will be hurt. [Anonymous Climate Scientist, 2012-03-07]

    Déjà vu:

    One hopes we do not need overstated scientific certainty to scare the system into action, for no doubt as soon as one group overstates the strength of scientific evidence to advocate a policy change, someone else advocating an opposing policy will be quick to point out the omissions or errors in the technical evidence, and will challenge the credibility of the original advocate’s views- especially their policy options. The result is usually a delay in action, not a speed-up, for the added confusion slows up the process. [Schneider 1977]

    I don’t know why anyone talks about climate models… we have spectroscopic measurements of CO2! [Anonymous Climate Scientist, 2012-03-07]

    It’s important that we not be too adamant, because we risk “damage to the exemplary reputation of NASA, NASA’s current or former scientists and employees, and even the reputation of science itself.” Keep in mind that David C. Smith’s 2010 AGU poster claimed that mainstream estimates of climate sensitivity based on spectroscopic measurements of CO2 are significantly exaggerated, concluding that “man is not the primary cause of global warming.” He’d probably react to your spectroscopy claim the same way you reacted to mine.

    On a related note, I believe paleoclimate proxy data are more informative than modern spectroscopic measurements. That’s because CO2 spectroscopy only helps to estimate the no-feedbacks climate sensitivity. On the other hand, estimates of climate sensitivity based on paleoclimate proxy data include all fast and slow feedbacks (although at different initial conditions than the present). Unfortunately, many people have concluded that feedbacks are only “dreamed up based on speculative climate model results.” Ironically, most AOGCMs still don’t include the (likely net positive) slow feedbacks like ice sheets, vegetation, carbon cycle, etc. For this reason, I think paleoclimate proxy data are worth mentioning early and often.

    Dumb Scientist: … the warming due to human CO2 emissions is partially offset by human aerosol emissions, so our CO2 is probably responsible for more than 100% of the observed temperature rise. The natural forcing contribution since 1950 is nearly zero.

    Anonymous Climate Scientist: That makes it sound like the hockeystick is almost completely due to human causes! [2012-03-07]

    Yes, it does. Believe it or not, I probably like this even less than you do. Instead of blaming Mann or Schneider, let’s try to fix the CO2 problem by describing the science accurately, so the public can finally make an informed decision. At the very least, let’s buy some time for the next generation to clean up our mess.ACS’s response contained zero science, but claimed to have been “joking” (presumably like Donald Trump). ACS’s “jokes” were similar to the “jokes” Judith Curry and Roger Pielke Jr. tell in public and in their Congressional testimonies. It doesn’t seem like Republican members of Congress understood that Curry’s claims were jokes. (Perhaps all those Republicans didn’t realize Curry was joking because they all have Asperger’s?) If Peter Webster disagrees with his wife’s “jokes”, he’s doing so very quietly. Perhaps ACS was actually mocking Pielke Jr., Curry and Webster? ACS didn’t say. However, ACS did find the time to helpfully call me an incredibly malicious, childish, unprofessional, vindictive pompous ass, disturbing unstable crazy stalkerish asshole with Asperger’s who looks “like a child.” Good times…

  11. Anonymous Climate Scientist: Methane has a much shorter lifetime in the atmosphere than CO2.

    Dumb Scientist: At which point the methane turns into CO2.

    Anonymous Climate Scientist: Really? I thought it rained out. [2012-03-07]

    On Titan, methane indeed “rains out”, but only because Titan’s average surface temperature is -179°C. Here on Earth, hydroxyl radicals (OH-) oxidize methane (CH4) to form H2O and CO2. Last August, when another scientist claimed that methane didn’t turn into CO2, I emailed him these three quotes:

    Methane oxidizes to CO2 in about 10 years… [Real Climate, 2010-12]

    Methane is a transient gas in the atmosphere, while CO2 essentially accumulates in the atmosphere / ocean carbon cycle, so in the end the climate forcing from the accumulating CO2 that methane oxidizes into may be as important as the transient concentration of methane itself. [Real Climate, 2010-03]

    The methane is oxidized to CO2, another greenhouse gas that accumulates for hundreds of thousands of years, same as fossil fuel CO2 does. Models of chronic methane release often show that the accumulating CO2 contributes as much to warming as does the transient methane concentration. [Real Climate, 2005-12]

    More recently, I found an excellent overview by Carolyn Ruppel which says: “CH4 is ~20 times more potent than CO2 as a GHG, but it oxidizes to CO2 after about a decade in the atmosphere.” [Nature Education]

    Also, Richard Alley mentions (at 27:00 and 56:24 in his 2009 AGU talk) that “There’s a whole lot of carbon as methane in the sea floor, if you make it warmer that comes out as methane, it becomes CO2.”

    Many people notice that water vapor is a stronger greenhouse gas than CO2, then incorrectly claim that water vapor can force the climate. In reality, tropospheric water vapor is only a feedback because it rains out. Non-condensing greenhouse gases like CO2 and methane don’t rain out, which is why they force the climate. This distinction is very important.

    If methane simply rained out, increasing its concentration wouldn’t increase its residence time in the atmosphere. In reality:

    In the present-day atmosphere, CH4 is rapidly oxidized to carbon dioxide (CO2), and has a lifetime of about 10 years [Prather et al., 2001, and references therein] Thus, it has generally been assumed that any direct radiative forcing from changes to the atmospheric CH4 concentration would have been minimal, and that any climate perturbations were driven primarily by the increases in CO2 [Dickens, 2000]. However, consideration of atmospheric chemistry implies that the residence time for CH4 will be significantly augmented as concentrations increase [e.g., Sze, 1977; Isaksen and Hov, 1987; Prather et al., 2001] through a feedback that reduces the abundance of atmospheric OH radicals, the dominant chemical sink. [Schmidt and Shindell, 2003]

    Luckily, Table 1 shows that increasing the methane concentration by a factor of 200 only lengthens the methane lifetime to ~40 years.

  12. But paleoclimate proxies tell one nothing about causation, and far more Americans doubt the causal mechanism of climate change, greenhouse gases, than doubt the existence of climate change itself according to every poll taken on the subject in the past 20 years. [Male Space Cadet]

    The question of causation is essentially the question of what the (equilibrium) climate sensitivity is. Spectroscopic measurements can establish the bare no-feedbacks ~1°C warming per doubled CO2. One can then either appeal to (allegedly) “dubious” climate models to establish the existence of feedbacks, or one can just say “the Earth’s climate history shows that when CO2 was doubled, the actual Earth (with feedbacks included) warmed up by ~3°C.” The fact that these paleoclimate estimates broadly agree with climate model estimates is a teachable moment: “science is about studying an issue from different angles, using different techniques to get independent estimates that can be compared.”

    So I agree that we should pound into people’s heads that we’ve known from lab spectroscopy for 150+ years that GHG forcing is real. [Male Space Cadet]

    Yes, the works of Fourier and Arrhenius are worth mentioning. But in my experience, contrarians tend to focus on the work of Angstrom and Koch (1900) which attempted to show that CO2 is “saturated”. In other words, they accept the spectroscopy showing that a little CO2 does warm the planet, but they claim that it’s already absorbing almost all the IR it can, so increasing CO2 won’t warm the planet any more. This is wrong, but showing why it’s wrong is very difficult if one doesn’t refer to paleoclimate data (*). On the other hand, paleoclimate data allows one to simply say “CO2 obviously isn’t saturated, because when CO2 doubled in the past, the climate warmed by ~3°C.”

    (*) It’s true that almost all long-wave IR at certain wavelengths is absorbed by greenhouse gases within ~100m of the surface. Many contrarians stop here, and declare the greenhouse effect saturated. In reality, greenhouse gases re-emit some of that IR, and it bounces around the troposphere until it gets to a height known as the “effective radiating level”. Above this height (roughly 7km), there aren’t enough greenhouse gases to keep “most” of the IR from escaping to space altogether. This effective radiating level controls the outflow of heat from the Earth. Stefan-Boltzmann tells us that power radiated is proportional to temperature4, and temperature decreases with height in the troposphere. Adding greenhouse gases raises the height of this effective radiating level, where it is cooler, which therefore decreases the outflow of heat from the Earth. This is the greenhouse effect, and it isn’t saturated because the effective radiating level can just keep getting higher (e.g. Venus).

    But, gosh, wasn’t that complicated? Wouldn’t it be easier to just say “CO2 obviously isn’t saturated, because when CO2 doubled in the past, the climate warmed by ~3°C”?

  13. I think it’s important to recall that CO2 changes in the paleoclimate record are a result of feedbacks. The forcing agent (to a large degree) are orbital changes, and the CO2 lags the warming/cooling by some hundreds of years. Thus, the CO2 changes aren’t driving the temperature variability. These records lead to a best estimate of a 3°C climate sensitivity. [Dr. X]

    Agreed. Exceptions to that large degree include the ending of Snowball Earth, that little kerfuffle with the Siberian Traps, and the PETM.

    At present, CO2 is a forcing agent, so it is driving the warming, and then all sorts of feedbacks are coupled on top of that (and the enormous human-induced changes to the surface, other greenhouses gases like methane, N2O, changes in O3, aerosols, cloud and ice feedbacks, etc.). In the current CO2-forced scenario, there is no guarantee that the climate sensitivity will be the same as in the paleoclimate record. This isn’t my area of expertise, but perhaps someone could chime in who does know something about this.

    In the end, it’s clear that CO2 increases are associated with temperature increases, either from paleoclimate records, lab experiments, current observations, climate model simulations, etc. All of these points could be made to folks, and it’s powerful to argue that you get (sort of) the same answer with different approaches. However, the amount of temperature change may be dependent on whether CO2 is a forcing agent or a feedback. [Dr. X]

    That’s a good point. Another reason to think that paleoclimate sensitivity differs from the modern sensitivity is that the initial conditions are different. For example, one fast feedback is sea ice albedo. Starting at an ice age melts a lot of sea ice far from the poles; starting at an interglacial time melts less sea ice closer to the poles. Starting at some absurd temperature (tens of degrees C?) higher than today’s, there wouldn’t be any sea ice, so this feedback would cease to exist.

    But you’re absolutely right to say that feedbacks can be different even at the same initial condition, depending on the type of forcing applied. I’m struggling to find the reference, but I vaguely remember reading that many surface feedbacks only weakly depend on the type of forcing applied.

    Update: Found the reference, which was section 2.8.5 of the 2007 IPCC report. Each radiative forcing in figure 2.20 has an estimated climate efficacy.

    For instance, consider two forcings scenarios: (1) CO2 increases, and (2) sunlight hitting Earth gets brighter, either via orbital changes or natural variations in solar output. Let’s stipulate that both CO2 and sunlight result in an extra 1 W/m2 of radiative forcing at the top of the atmosphere, averaged globally. Even without considering feedbacks at all, the CO2 would warm the surface but cool the stratosphere. Sunlight would warm the surface and the stratosphere. So let’s only consider surface temperatures, and feedbacks which affect surface temperatures.

    The water vapor fast feedback just depends on globally averaged relative humidity remaining constant, which doesn’t distinguish between CO2 or sunlight. The sea ice albedo feedback also doesn’t distinguish between CO2 or sunlight.

    Update: Schaller et al. 2013 and Kleidon and Renner 2013 model different changes in water vapor and the water cycle during warming caused by sunlight or CO2. Huneeus et al. 2013 finds that the climate sensitivity parameter is independent of the forcing (when measured as an effective radiative forcing).

    I don’t know about the winds feedback, and atmospheric temperatures could distinguish between the two cases because the tropopause will rise with the CO2 more than with sunlight. I don’t know enough about the clouds or snow feedbacks to rule out some kind of atmospheric chemistry linking increased CO2 to increased cloud nucleation, etc. Also, Roderick et al. 2007 shows that the evaporation rate depends on irradiance, which means sunlight may affect clouds and snow in ways that CO2 doesn’t. I’m hoping someone can educate me about these topics. Hence the spam, which is regrettable collateral damage.

    A slow feedback like the ice sheets doesn’t distinguish between CO2 or sunlight. The carbon cycle slow feedback could distinguish between the two, because increased CO2 affects the rate that CO2 is sequestered in the oceans (or outgasses from them) more than sunlight does. The vegetation feedback would be different because increasing CO2 actually makes many plants more drought-resistant because they reduce the size of their stomata, through which they get CO2 and lose water.

  14. Reythia posted on 2012-07-18 at 08:30

    Saw this article today and it reminded me of a discussion we once had at that Japanese place in San Fran. Thought you might be interested.

  15. Thanks, that was an interesting article! I’ve been dreaming about a way around death since I was 12, but recently gave up on such optimism. Even if we have the resources to continue this kind of long-term research over the next century, I’m not sure I’d want to freeze myself anymore. That’s because I’d be putting myself in the hands of people 100 years from now. Dumb Scientist was actually created to convince those descendants that reviving me would be worth the effort. But it’s becoming clear that my repeated failures to counter the deluge of scientific misinformation make their future gratitude much less likely. In fact, depending on how bad things get, it’s more likely that people 100 years from now will curse our names rather than feel any obligation to revive us. This makes me afraid of what would be waiting for me if they ever did revive me.

  16. Reythia posted on 2012-07-18 at 11:46

    Well, my life motto hasn’t changed in a decade: “People Are Stupid”.

    On the other hand, the good news is that if you ever did find someone to freeze you, he’d probably not be one of the bottom 90% of society. After all, just because the mean and median of people have rented their brains out to the lowest bidder, that doesn’t mean there’s not an upper crust, if you will, who still own their own brains.

  17. The freezing is easy and soon. I’m worried about the revival because that’s probably centuries in a future that has vast computing resources and advanced nanotechnology, etc.

    It’s actually the upper crust I’m worried about. They’re the ones who will understand exactly how long I knew about the burden I was placing on future generations and yet failed to stop it or even slow it down. If only I had merely fiddled while Rome burned.

  18. Reythia posted on 2012-07-19 at 07:36

    On the other hand, if the technique works, then the same group who’s going to be reviving you will want to do so, to verify that the technique works. Because, after all, if it works, they’ll want to do the same thing to themselves. Self-interest ought to motivate them quite a bit, I’d think. Not to mention that a lot of people uninterested in science would like to have a real person from, say, 200 years ago to talk to. How fascinating might it be to be able to really figure out what people thought about societal events during the American Revolution, or whatever?

  19. On the other hand, if the technique works, then the same group who’s going to be reviving you will want to do so, to verify that the technique works. Because, after all, if it works, they’ll want to do the same thing to themselves. Self-interest ought to motivate them quite a bit, I’d think.

    Not necessarily. Cryonics is probably a last-in, first-out process; the last people to be frozen are the first to be revived. One reason is that cruder freezing methods (like those used in the 1900s) caused much more ice crystal damage than modern methods. Modern cryonics actually “vitrifies” organs immediately after death, as the blood is swapped for a chemical like “M22” that turns tissues into a glass at about -124°C. Ice crystal damage is substantially reduced. That page links to this freely-available paper which describes vitrifying rabbit kidneys by cooling them down to -140°C. When “revived” and transplanted into two rabbits, one survived for 25 minutes, the other for 9 days. This seems promising, and there are many further improvements which can (and hopefully will) be made.

    Suppose that revival is first achieved in the year 2200. It seems likely that it would work best with people frozen most recently, with the most advanced methods. Then they’d work backwards, trying to compensate for an increasingly large amount of (sub-)cellular damage as they revive people from earlier eras. People frozen in the 2000s and 1900s might be revived centuries after people frozen in the year 2199, and that additional effort probably wouldn’t be in the researchers’ self-interest.

    Not to mention that a lot of people uninterested in science would like to have a real person from, say, 200 years ago to talk to. How fascinating might it be to be able to really figure out what people thought about societal events during the American Revolution, or whatever?

    Yes, that’s what I meant when I said I was afraid of what would be waiting for me if they ever did revive me. I think they’d be fascinated to hear what we were thinking. Maybe a little too fascinated.

    For example, imagine that all humans vanish today, right after shutting down all our industrial processes. Kate describes2015-05-19 update: I was wrong. This conclusion isn’t supported by Gillett et al. 2011, because I missed Kate noting that Gillett et al. 2011 turned off our CO2 emissions in 2100, not 2011. However, note that paleoclimate evidence shows that CO2 levels in the mid-Pliocene (~3 million years ago) were about 400ppm, and sea levels were ~20 meters higher. This paleoclimate evidence (and Rignot et al. 2014, Joughin et al. 2014, etc.) suggests that the CO2 we’ve already released could have already committed the West Antarctic Ice Sheet (at least) to collapse in the long term. a disturbing set of papers that consider what would happen in this scenario.

    Even in this bizarre scenario (the most extreme and immediate de-carbonization possible) by the year 2995 the temperature around Antarctica is about ~9°C warmer than it was in 1855 (click the map, then add figures 3a and 3c). It seems likely that our actions have already committed the West Antarctic Ice Sheet to collapse, and thus raise the global average sea level by ~7m ~3m. And there’s no way we can decarbonize that quickly, so the legacy we’re leaving behind will probably be worse than merely submerging many of the world’s greatest cities.

    I suppose it goes without saying that I’d like to eventually post this conversation to Dumb Scientist, unless I decide it’s too cynical. It’s nice to talk to someone who doesn’t insult me for a change (see #7 in the climate change index, 7(v) through 7(aj) have got me a little depressed, as you can probably tell…).

  20. Reythia posted on 2012-07-19 at 13:10

    I ran across a little poem sometime back in high school that I’ve always remembered. I’d like to share it with you:

    Once in a stately passion I cried with desperate grief
    ‘Oh Lord, my heart is black with guile, of sinners I am chief’
    Then stooped my guardian angel and whispered from behind
    ‘Vanity my little man, you’re nothing of the kind’
    (by James Thomson)

    In short: I think you’re taking WAAAAY too much blame upon yourself, for little purpose. Call it a strange type of “vanity” as this poem suggests. You may be a part of a civilization whose culture has serious long-term ecological side-effects, but you are NOT the whole of that society. Nor did you choose to start the industrial revolution. Nor were you the one who failed to note the beginnings of climate change. Nor are you someone who is burying his head in the sand about it now.

    Are we making a mess that will take a long time to clean up? Yes, I agree.

    But tell me, looking back through the lens of history, what would you have done differently if you’d been there? Would you condemn people to starvation, rather than plow up more agricultural grounds? Would you have passed a law banning the automobile and all other modern modes of transportation? Would you have cut off funding for the first computers? And upon exactly what grounds would you have done these things, back in 1800, 1900, or 1950? Climate change? What’s that? CO2 levels? How, exactly, would you have gone about measuring those in 1800, and with what funding or motivation? When industrialization meant bringing millions of people out of back-breaking poverty, would you really have said, “Sorry, but we have to stop burning coal and oil. Everyone in the cities, get back to your horse and one-family farm”? And if you HAD been in power and said that, exactly how likely do you think it would have been for people to have listened to you? Heck, would YOU have listened to anyone who’d told you that, at the time?

    Climate change is happening because we made what seemed like rational choices starting about 200 years ago (really more), which turned out to have serious consequences that we didn’t understand back then. I find it pretty “vain” for you to take all the blame and responsibility for ~200 years of western history upon your shoulders. And I find it hard to believe that people 200 or 2000 years from now would hold you accountable either, for the record.

    And why are you even looking at this serious problem in such a gloom-and-doom way, anyhow? I’ve never found dwelling on the darkest “might be’s” to be the best way to solve the problem. No one ever solves a difficult problem if they think the solution is impossible. Instead, we solve those problems which we feel, perhaps naively, to be within our grasp. And generally, we find that they are — or will eventually be, once we’ve worked on it enough to build up the mental and physical infrastructure needed. Sometimes hope and self-confidence works out to be something of a self-fulfilling prophecy.

    The last article you pointed me to talks about a world where humans no longer exist. But that world IS NOT REAL. It WILL NOT HAPPEN. You and I both know that people aren’t likely to all die of a mysterious disease or pack up and move off to the Moon. Which makes the entire study something of a red herring. It CAN’T happen, because the assumption that people won’t be there is totally inaccurate. As far as I see it, the reality is that people will continue to drastically impact our world’s climate. That could be in a negative direction, to keep changing it away from its “natural” state, as we’ve been doing for the past ~200 years and are still doing. Or it could be in a neutral or more positive direction, as we realize that it’s to OUR selfish benefit to keep the world stable and “pleasant” in some way. The first step of switching over from the negative to positive direction is to have a long, painful discussion about what’s really going on, what our options are, and what the costs of each option will be. Which is where we are now. That’s not proof that we’re going to step off onto the desired pathway, but it’s certainly a hint that we could. Despite the idiots in US government now, I refuse to give up and just throw in the towel and say, “Screw it, Antarctica’s totally doomed. Might as well move now.” I refuse to believe that our only option is to submit to the long-term effects of our ancestors’ unknowing decisions, without trying to do anything about it.

    So yes, I think someone from 2200 or whatever would be interested in talking to someone from our era. But not to use them as an emotional punching bag. Instead, I think they’d be interested to see what the difference is between the way THEY see the 21st century, with the benefits of hindsight, and the way WE see it now, as the present. As for the technical difficulties of actually freezing (or whatever) a brain, obviously you’re right that later brains would be easier to handle. But you didn’t exactly have a choice as to when you were born, so I don’t really see what you plan to do about that. If they can’t revive you, they can’t revive you, and that’s that. No point stressing out about something you can’t change.

    … And yes, you’re welcome to post whatever you want out of this discussion on Dumb Scientist. Speaking of which, if you really want to avoid depressing yourself into suicide and thus be around and able to help out when people DO realize the truth about the climate, maybe you ought to consider posting something BESIDES climate-related things on that site. Frankly, I think the idiots are getting to you. Why not post something else, something a little more uplifting? You totally missed the whole Higgs Boson thing, for example. I’m not saying to run away from what’s bothering you or not to keep the site up to date on climate issues as well, but I fail to see how focusing exclusively on it without being able to do much about it is going to accomplish anything except critically depressing you. There’s more to life than doom and gloom, even in the worst of times, Bryan.

  21. You totally missed the whole Higgs Boson thing, for example.

    Actually, I joined a discussion of the Higgs discovery on Slashdot, and copied some of it here. The point of this discussion is that the Higgs only explains ~2% of the inertia of visible matter. The same week the first dark matter filament was discovered, and I copied some of that discussion here.

  22. Reythia posted on 2012-07-19 at 13:40

    Well then, why don’t you update your site, so that it notes whenever you change any of the older articles?

  23. Don’t really know how, without turning my site into a blog. I don’t like blogs, which are impossible to navigate because bloggers post multiple articles a day, often without useful ways to search them or navigate among them.

    I’m more interested in grouping similar topics into comments on a comparatively smaller number of articles so that the site scales into something usable rather than a confusing mess of hundreds of separate posts. My OCD is probably at odds with effective PR here, I realize.

  24. Reythia posted on 2012-07-19 at 14:00

    You could always make an “updated topics” panel, which links to the five most recently updated articles, or whatever. Or else in addition to the post date, include an update date on each entry, and allow it to be searchable either way, maybe?

  25. Well, the sidebar on dumbscientist.com lists the 6 most recent comments. But I don’t include my own comments, because the entire rest of the site is full of my babbling, so I wanted to make a place where only other people’s comments show up. And the RSS comments feed linked on the sidebar plays the same role, but the web interface only shows the last 10 comments.

    Also, long ago I added code to auto-update a line at the bottom of each article with the update date. But yeah, it’s not visible or searchable without loading each article. I’ll think about your suggestion and see if I can figure out a way to do it that will be relatively easy…

  26. In short: I think you’re taking WAAAAY too much blame upon yourself, for little purpose. Call it a strange type of “vanity” as this poem suggests.

    You’re probably right. Perhaps spending so much time around people who refuse to accept any responsibility for our actions is prompting me to unconsciously compensate by taking on their shares as well as mine…

    Nor are you someone who is burying his head in the sand about it now. Are we making a mess that will take a long time to clean up? Yes, I agree. But tell me, looking back through the lens of history, what would you have done differently if you’d been there?

    I don’t think there was a good reason for action until the Keeling curve was published in 1960. After that, we should have invested heavily in alternative power sources like solar, wind and nuclear. At the very least we should’ve (slowly) ended the subsidies for the fossil fuel industry. The fact that we still haven’t done this in 2012 is a national travesty.

    We should also treat the waste from coal/gas power plants the same as waste from nuclear plants. Government regulations force nuclear plants to pay for waste disposal up front, but coal/gas plants get to treat our atmosphere as a free sewer. For example, the CCL’s SOCA calls for a gradually-increasing fee on carbon-based fuels with most revenue being returned to individuals and some revenue committed to reducing the federal debt.

    The last article you pointed me to talks about a world where humans no longer exist. But that world IS NOT REAL. It WILL NOT HAPPEN. You and I both know that people aren’t likely to all die of a mysterious disease or pack up and move off to the Moon. Which makes the entire study something of a red herring.

    I agree with Kate when she says “the global temperature change that occurs in such a scenario is a very useful metric. It represents the amount of warming that we’ve already guaranteed, and a lower bound for the amount of warming we can expect.”

    In other words, that scenario allows anyone to separate the long-term effects of our actions2015-05-19 update: I was wrong. This conclusion isn’t supported by Gillett et al. 2011, because I missed Kate noting that Gillett et al. 2011 turned off our CO2 emissions in 2100, not 2011. However, note that paleoclimate evidence shows that CO2 levels in the mid-Pliocene (~3 million years ago) were about 400ppm, and sea levels were ~20 meters higher. This paleoclimate evidence (and Rignot et al. 2014, Joughin et al. 2014, etc.) suggests that the CO2 we’ve already released could have already committed the West Antarctic Ice Sheet (at least) to collapse in the long term. from those of future generations.

    It CAN’T happen, because the assumption that people won’t be there is totally inaccurate. As far as I see it, the reality is that people will continue to drastically impact our world’s climate. That could be in a negative direction, to keep changing it away from its “natural” state, as we’ve been doing for the past ~200 years and are still doing. Or it could be in a neutral or more positive direction, as we realize that it’s to OUR selfish benefit to keep the world stable and “pleasant” in some way.

    Yes, but what I’m saying is that the long-term effects will probably be more negative than the “humans vanish today” scenario for the rest of our lives. (Long-term means neglecting the short-term rapid warming from the rain-out of human sulfate aerosols in a “humans vanish today” scenario.)

    Here’s why.

    In a “humans vanish today” scenario, CO2 peaks at its current average value of ~395 ppm. Over the next 100 years, natural processes will draw that down to ~350 ppm. (As usual, this ignores permafrost and clathrate contributions.) As Gillett et al. 2011 showed, the cumulative radiative forcing during this small excursion is likely enough to destabilize West Antarctica2015-05-19 update: I was wrong. This conclusion isn’t supported by Gillett et al. 2011, because I missed Kate noting that Gillett et al. 2011 turned off our CO2 emissions in 2100, not 2011. However, note that paleoclimate evidence shows that CO2 levels in the mid-Pliocene (~3 million years ago) were about 400ppm, and sea levels were ~20 meters higher. This paleoclimate evidence (and Rignot et al. 2014, Joughin et al. 2014, etc.) suggests that the CO2 we’ve already released could have already committed the West Antarctic Ice Sheet (at least) to collapse in the long term. in the long term.

    In reality, we’re gonna go way past 400 ppm. I hope we won’t see 500 ppm, but I can’t even rule out 600 ppm. Reducing our emissions to zero will take decades at least, according to every analysis I’ve seen. Then the next generation will have to spend another few decades trying to draw the CO2 down to 350 ppm. Even after they succeed, the cumulative radiative forcing during this stronger, longer excursion means that we’d still have done more damage than if we all just vanished today.

    Despite the idiots in US government now, I refuse to give up and just throw in the towel and say, “Screw it, Antarctica’s totally doomed. Might as well move now.” I refuse to believe that our only option is to submit to the long-term effects of our ancestors’ unknowing decisions, without trying to do anything about it.

    I also refuse to do that. I’m simply noting that we’re forcing future generations to spend their lives trying to clean up our mess, so I don’t expect their gratitude for my impotent efforts.

    if you really want to avoid depressing yourself into suicide and thus be around and able to help out when people DO realize the truth about the climate…

    I can watch what’s happening through GRACE but I can’t really help with power plant construction, disaster recovery, water management, or continuing to increase food production in a destabilizing biosphere. That’s engineering beyond my meager skill set. To draw an analogy, scientists are like the guy looking out for icebergs at the top of the mast of an ancient sailing ship. Once he fails to notice and warn others about an impending collision in time to avoid it, his job is over.

    On the other hand, Mohamed Bouazizi’s suicide catalyzed the Arab Spring when decades of evidence of tyranny hadn’t. Also, climate contrarians repeatedly and loudly accuse scientists of reaching conclusions motivated by desire for funding. There’s one way to debunk that motivation…

  27. (Ed. note: This conversation started when Bill emailed an article which quotes Richard Somerville and asks if population growth is the key, underlying problem behind climate change.)

    This does not fit the facts:
    1. China’s one-child policy has cut its population growth by half, but its total carbon emission has been doubled.
    2. U.S. has a moderate population growth, but has the highest carbon emission per capita.

    Carbon emission is a consequence of the Industry Revolution, not population growth.

    Of course, slowing population is helpful, but very difficult (China paid big price for its one-child policy.) [Tony]

    I think the “effective danger” of an obstacle is best measured by its inherent threat, divided by our willingness to face that threat. We seem to want to recreate the end-Permian extinction, which is pretty threatening by itself. What makes it very dangerous is that “leaders” like Sen. Inhofe (and practically every Republican in Congress) are working hard to convince Americans that there is no threat.

    Population growth is different. Very few adults are confused about the cause of babies in the same way they’re confused about the primary cause of global warming. But as Somerville notes, people are reluctant to talk about this taboo subject for cultural and religious reasons.

    China’s one-child policy did carry a big price, but we actually just need a two-child policy to stabilize our population. We can either do that ourselves with birth control, or let nature do it for us via famine and disease. An exponentially growing population on a planet that stubbornly remains the same size is a recipe for increasingly serious disasters. Resources will become scarcer; waste products will become dangerously concentrated.

    In my experience, any scientist who even mentions population growth is treated as a wanna-be Dr. Evil. To me, this suggests that our willingness to face the threat is quite small, so I think the “effective danger” of population growth is quite large.

  28. Felix Landerer posted on 2012-07-25 at 12:08

    If you’re more interested in the population topic, I highly recommend the highly entertaining and educating talks from Hans Rosling, an expert on demographics and health/economics/growth. Very vivid, very informative.

  29. (Ed. note: This comment was copied from a conversation among the Climate Literacy Network about effective metaphors for climate change.)

    Yes, a body T analogy is useful in conveying that even small temperature changes concern medical doctors; perhaps this could help reach people who shrug at a degree of warming by thinking about how small that change would look like on their home’s thermostat. I also like Admiral Titley’s analogy about the current 400 ppm concentration of CO2 in the atmosphere being similar to the concentration alcohol reaches in the blood when one starts to feel drunk.

    I also read Cherilynn’s comments to Paul’s article, and thought she raised good points. Especially about providing an intuitive analogy for how much energy it takes to raise the surface temperature by 1°C. (Multiply by 5/9 for Fahrenheit.) I’ve approximated the troposphere + upper mixed layer of ocean heat capacity and got ~4.9×1022 J to raise the temperature of this crude model by 1°C. A megaton of TNT is ~4.2×1015 J, so a 1°C temperature increase is equivalent to the energy released by about TEN MILLION MEGATON NUCLEAR BOMBS.

    But this calculation ignores another danger. Namely, the increased CO2 concentration causes a radiative imbalance which takes decades to warm up to equilibrium due to the oceans’ massive heat capacity. Perhaps another body analogy is in order; one that many young people will be able to relate to even if others find it inappropriate. Here goes. Taking drugs has many dangers, but one often-overlooked danger is the lag time between ingestion and intoxication. People who smoke weed feel the effects within seconds, so accidental over-intoxication is rare among experienced users. However, people who eat weed-laced brownies don’t feel the effects for about half an hour, so it’s common for people to eat a second brownie thinking the first didn’t work. Then they either pass out or spend the next few hours glued to the couch in a stupor.

    What’s dangerous isn’t the warming that’s already occurred. That 10,000,000 megaton bombs of energy is nothing compared to the warming that we’ve already guaranteed will happen in the next few decades. We’ve already eaten the brownies. They just haven’t knocked us on our asses yet. And there’s no couch to catch us this time.

  30. Bill,

    I liked many of the points you made in that article, but have two concerns. First, aren’t plastic bags just sequestering carbon in landfills, where they won’t biodegrade for a long time? While this persistence is bad in many respects, it seems like every gallon of petroleum that’s used to make a plastic bag is one gallon that won’t contribute to the CO2 problem. Recycling programs (worthwhile and widely implemented) shouldn’t be conflated with (nearly-nonexistent!) action to slow down global warming.

    Second, they quoted you saying that we should curb “our aspirations for affluence.” It’s actually our combined carbon footprint which needs to be curbed, not our affluence. In fact, carbon fee and dividend legislation like SOCA is intended to jumpstart a new industrial revolution that will make us more prosperous in the medium to long term. Decoupling affluence from CO2 emissions is how we’ll save civilization.

  31. Bill posted on 2012-08-19 at 20:29

    I agree with your concerns. The problem with interviews is that sometimes the line of logic gets chopped up and quoted out of context. I explained that human impact equals population multiplied by affluence multiplied by technology. My point was that cutting back on population growth, affluence and carbon intensive technology is the “path”.

  32. (Ed. note: I wrote this email after Bill told us about a panel discussion about climate change.)

    This looks like it will be an interesting show. One quibble: I wish they’d say “saving our civilization” instead of “saving our species.”

    Humans are very adaptable; our species will almost certainly survive. The real question is whether our grandchildren will be aspiring to be doctors and astronauts, or whether they’ll be aspiring to catch an especially juicy insect or jellyfish (which will likely prosper as the climate warms).

  33. (Ed. note: these comments were copied from a CLN conversation.)

    I’m terrified at the possibility that many in the general public can’t see how absurd Mike Haseler’s arguments are. Obviously #4 is hardest to debunk briefly; does anyone have suggestions for pedagogical improvements? (Not for Mike; he’s obviously too far gone. But others might be reading.)

  34. Well done. Here is how I respond to any claim that CO2 may not be responsible:

    The climate is warming and “thermometers” in the ocean, surface, ice, and air tell us this unequivocally. This can only happen if the incoming heat from the sun is increasing or the outgoing heat from Earth to space is decreasing.

    Careful measurements of the incoming solar radiation show that there has been no increase in heat since the 1980s. Furthermore, the sun has been in a historic cool phase in the past decade so we know the planet is not being warmed from increased incoming heat. That leaves us with the possibility that less heat is escaping the planet. Measurements show that nights are warming faster than days, winters faster than summers, and the Arctic faster than the tropics. Nights, winters, and Arctic are times/places where the planet tries to lose heat so it is clear that the earth is struggling to shed its heat. Why? Because humans are dumping billions of tons of heat-trapping gases of carbon dioxide into the air every year. Basic physics known for more than a century tells us this must happen.

    Mother Nature obeys the laws of physics even when we do not wish her to. CO2 fingerprints are all over this crime scene.

    I also refer people to John Cook’s wonderful Scientific Guide to Global Warming Skepticism linked in my signature below.

    Scott A. Mandia, Professor of Physical Sciences, Asst. Chair
    T-202 Smithtown Sciences Bldg., S.C.C.C.
    533 College Rd., Selden, NY 11784
    mandias AT sunysuffolk DOT edu
    Skype: agw.prof
    Global Warming Page
    Global Warming Blog
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    Climate Science Rapid Response Team
    Scientific Guide to Global Warming Skepticism
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  35. Thanks; in principle I like your process of elimination. The fingerprints you describe are certainly true for enhanced greenhouse warming, with everything else held constant: winters warm faster than summers, nights faster than days (i.e. diurnal temperature range DTR decreases), and the Arctic warms faster than the tropics. It’s impressive that Tyndall 1865 had already recognized some of these fingerprints. Another fingerprint is that, all else being equal, increasing CO2 warms the surface but cools the stratosphere.

    However, several complications make me hesitant to mention these fingerprints:

    1. The stratosphere has recently started warming, reversing the cooling trend. Why? Because humans also used to pump CFCs into the stratosphere, where they destroyed ozone that usually absorbs solar UV and thus warm the stratosphere. But we stopped emitting CFCs, so ozone is recovering and again warming the stratosphere which opposes the cooling expected due to CO2.

    2. Mentioning polar amplification opens a big can of worms called Antarctica. Yes, climate scientists have long understood that Antarctica’s warming should lag behind the rest of the globe, mainly due to the Southern ocean’s vast heat capacity and the isolating effects of the Antarctic Circumpolar Current. But in my opinion these details just confuse the public. (Also, polar amplification occurs to some extent even with solar warming because the sea-ice albedo feedback happens either way.)

    3. Nights haven’t actually been warming significantly faster than days for the last ~30 years, which means the DTR has stopped decreasing. The IPCC said: “The global average DTR has stopped decreasing. A decrease in DTR of approximately 0.1°C per decade was reported in the TAR for the period 1950 to 1993. Updated observations reveal that DTR has not changed from 1979 to 2004 as both day- and night time temperature have risen at about the same rate. The trends are highly variable from one region to another.”

    I dug through the literature a while back (my raw research notes are at the bottom of this email). It seems like the DTR decrease from 1950 to 1993 was partially due to increasing human sulfate aerosols which cooled the days. Then we cut aerosol emissions, and the DTR stopped decreasing.

    4. Based on the references below, winters really have warmed faster than summers. But GCM projections suggest that on land summers should warm more than winters, because soil moisture decreases during the summer, so the land loses evaporative cooling.

    In short: the fingerprints seem “smudged” by a lot of complicating factors, some of which are ironically due to other ways that humans alter the environment.


    DTR reduction

    Such spatial dependence of Tmin and DTR trends on the climatological precipitation possibly reflects large-scale effects of increased global greenhouse gases and aerosols (and associated changes in cloudiness, soil moisture, and water vapor) during the later half of the twentieth century.

    … for the later period of 1951–90, the trend in maximum temperature reduces to an insignificant value, while the trend in minimum temperature remains high, resulting in a significant downward trend in diurnal range of 0.10°C/decade.

    From Martinez et al 2009, despite variations due to seasonal effects, an average annual decreasing trend of DTR is found, particularly relevant in autumn (−0.9 °C/decade).


    The global average DTR has stopped decreasing. A decrease in DTR of approximately 0.1°C per decade was reported in the TAR for the period 1950 to 1993. Updated observations reveal that DTR has not changed from 1979 to 2004 as both day- and night time temperature have risen at about the same rate. The trends are highly variable from one region to another. {3.2}

    Braganza 2004

    Alexander 2006


    Update: Some more papers on diurnal range.

  36. Bryan and Scott – timely sharing of the accuracy of these details is crucial. I am about to use Cook’s fingerprint slides as part of CLEO Phase II training.

    Grateful for this discussion thread.

  37. To clarify: all those fingerprints are real. Many in the public seem to think we’re having trouble distinguishing human from natural fingerprints. John Cook’s fingerprint slides can introduce the irritating fact that we’re actually having trouble distinguishing heavy, opposing, human fingerprints. In contrast, the natural fingerprints are light.

    I like Scott’s explanation up to this sentence: That leaves us with the possibility that less heat is escaping the planet, which happens when concentrations of greenhouse gases like CO2 increase. Our emissions have pushed the CO2 concentration higher than it’s been in millions of years. It’s currently increasing at least 10 times faster than during the previous record high, which by strange coincidence was set right before the end-Permian extinction, 250 million years ago. Many diverse lines of evidence (paleoclimate, modern observations, fundamental physics) show that doubling CO2 warms the planet by roughly 3°C.

  38. Cherilynn Morrow posted on 2012-09-08 at 06:27

    Greetings fingerprint discussants!

    Haven’t yet seen mentioned the identification of fossil fuel carbons (via isotope ratio comparisons) in the environment…e.g. corals and tree rings….

    See here for example – is there a more recent study?

    Anyway, when I first heard it, I found the ability to distinguish fossil fuel carbon from other sources an especially compelling result of “climate forensics” :-) and one of the most persuasive points if you can communicate it at the appropriate level…

    Also a rather nice diagram here for the visually inclined….subject to the caveats already mentioned by Bryan.

  39. Felix Landerer posted on 2012-09-14 at 09:56

    Nights haven’t actually been warming significantly faster than days for the last ~30 years, which means the DTR has stopped decreasing. The IPCC said…

    There was a recent paper that reports on the changes of the distribution of night-time vs day-time temps – would that not be inconsistent with the AR4 statement?

  40. Thanks, that’s a very relevant paper. I’m surprised that these sentences didn’t make it into the abstract, given that they contradict the 2007 IPCC statement about how DTR has stopped decreasing:

    [13] Figure 2 shows the probability distribution functions from pooling all grid boxes for the periods 1951–1980 and 1981–2010. … [14] For the globe, the mean daily minimum temperature anomaly increased by 0.8 C between the earlier and latter period (Figure 2a). … [15] For daily maximum temperatures over the globe, the mean anomaly has increased by 0.6 C, so slightly less than the daily minimum temperature anomalies (Figure 2b). … Note that changes in the statistical parameters calculated are mostly greater for daily minimum than maximum temperatures implying a greater effect on global night-time temperatures …

    I’m also surprised that the figure reference in paragraph [15] is wrong. Figure 2b shows the northern hemisphere extra-tropics average, not the global average. They meant to say Figure 2a (on right). Oh well.

  41. Thanks for this. I need some guidance with re-phrasing/editing. Specifically with respect to this slide which of these “fingerprints” should I avoid or qualify and what language would you advise?

  42. Sorry for the delay; I’m in Europe with bad internet connectivity.

    I’d focus on the following:

    30 billion tons of CO2 per year (simple accounting)

    More fossil fuel carbon in air (from C12,13,14 isotopes)

    Less oxygen in air (shows that CO2 comes from burning, not volcanoes)

    More fossil fuel carbon in coral (shows that CO2 isn’t coming from ocean)

    Less heat escaping to space, more heat returning to Earth. (basis of greenhouse effect)


    The recent paper shows that nights are warming faster than days, so that fingerprint is probably okay. The stratosphere is less certain, because its very low heat capacity reduces the signal-to-noise ratio and allows our older CFC emissions to confuse the issue.

    Mentioning the other fingerprints is fine, they’re quite real even if difficult to distinguish from other human effects like sulfate aerosols and CFCs. My primary concern is that educators don’t get swamped by contrarian students/adults who have memorized the latest factoid from WUWT.

  43. (Ed. note: this comment was copied from here.)

    At a recent ocean seminar, someone claimed that wildfires and Hurricane Sandy aren’t examples of the impacts of global warming. I’m skeptical.


    A 2012 report by Climate Central lists reasons why warming increases the risk of wildfires in 11 western states:

    • The fire season is about 75 days longer than in the 1970s (Figure 8).
    • Mountain snowpack melts earlier (Figure 10) (and warming increases evapotranspiration). Both reduce available moisture during the fire season.
    • Winter warming reduces the mortality of insects like pine beetles, which may turn forests into kindling (surprisingly, this appears controversial).

    It’s true that many other factors affect wildfires. For instance, the skyrocketing human population implies an increasing number of pyromaniacs. However, Figure 9 shows that hotter years have more fires, which can’t be blamed on a steadily increasing number of pyromaniacs.

    The report then calculates the trend in fires larger than 1000 acres in 11 western states, showing that large fires have increased significantly in 10 of the 11 states since 1970. Tamino even redid their analysis while including years with no large fires in the regression, and shows that large fires actually increased significantly in all 11 states including Washington.

    The report notes that natural climate variability (ENSO, PDO, etc.) strongly affects wildfires in this region, and that human behavior (non-climatic) undoubtedly has an influence. (Of what sign? Firefighting has also improved.) So attribution of these trends is challenging. But dismissing the connection between global warming and wildfires in favor of vague references to other human influences requires ignoring Figure 5.8 from this 2011 National Academies report. It shows that each 1°C of warming leads to at least a doubling of area burned each year for most of those 11 western states, with some regions burning 6 times as much.

    We’ve probably already missed the 2°C global target: even if we peak by 2020, we’d still need to reduce emissions 9% per year after that. So this research suggests that the Midwest 2011,2012 fires are a sneak preview of the coming decades, along with Amazon 2005,2010, Greece 2007, Australia 2009, Russia 2010,2012, etc.

    Update: Bjorn Lomborg and George Will hide the incline in wildfires.

    Hurricane Sandy

    It’s not clear how global warming will impact hurricane frequency because of factors like wind shear, but there’s a strong consensus (PDF) that warmer oceans intensify whichever hurricanes do form. The only questions are whether this intensification signal has risen above the noise of natural variability, and which metric is most appropriate for answering the first question.

    For example, here’s the abstract of a 2005 Nature paper:

    Theory and modelling predict that hurricane intensity should increase with increasing global mean temperatures, but work on the detection of trends in hurricane activity has focused mostly on their frequency and shows no trend. Here I define an index of the potential destructiveness of hurricanes based on the total dissipation of power, integrated over the lifetime of the cyclone, and show that this index has increased markedly since the mid-1970s. This trend is due to both longer storm lifetimes and greater storm intensities. I find that the record of net hurricane power dissipation is highly correlated with tropical sea surface temperature, reflecting well-documented climate signals, including multi-decadal oscillations in the North Atlantic and North Pacific, and global warming. My results suggest that future warming may lead to an upward trend in tropical cyclone destructive potential, and-taking into account an increasing coastal population-a substantial increase in hurricane-related losses in the twenty-first century.

    Also, a 2006 Science paper co-authored by Prof. Judith Curry concludes that “the trend of increasing numbers of category 4 and 5 hurricanes for the period 1970-2004 is directly linked to the trend in sea-surface temperature”.

    The 2005 Atlantic hurricane season was anomalously active, and detection of hurricanes was more difficult before the satellite era, so the Grinsted et al. 2012 abstract describes an interesting new approach:

    Detection and attribution of past changes in cyclone activity are hampered by biased cyclone records due to changes in observational capabilities. Here we construct an independent record of Atlantic tropical cyclone activity on the basis of storm surge statistics from tide gauges. We demonstrate that the major events in our surge index record can be attributed to landfalling tropical cyclones; these events also correspond with the most economically damaging Atlantic cyclones. We find that warm years in general were more active in all cyclone size ranges than cold years. The largest cyclones are most affected by warmer conditions and we detect a statistically significant trend in the frequency of large surge events (roughly corresponding to tropical storm size) since 1923. In particular, we estimate that Katrina-magnitude events have been twice as frequent in warm years compared with cold years (P < 0.02).

    Tamino replicates part of their analysis at Key West, and even extends it by detiding hourly tide gauge data rather than using daily data as Grinsted et al. 2012 did.

    For these reasons, I prefer to say that Sandy would’ve happened even without global warming, but that the (very likely mostly human-caused) warming made Sandy more destructive in at least three different ways:

    • Warmer oceans provide more energy for the hurricane’s heat engine.
    • Warmer oceans evaporate more water vapor into the atmosphere, which increases the hurricane’s rainfall.
    • Higher sea levels add to the storm surge.

    I give a similar answer when my friends and family from New Orleans ask about Katrina.

    Sandy peaked as a category 2 storm. But that metric only measures the maximum windspeed, which ignores how much total kinetic energy the storm has. In other words, that metric doesn’t distinguish between being hit by a ping pong ball or a freight train, if they’re both moving at the same speed.

    Sandy was a record 1800 km across, and its record low pressure (940 millibars) combined with sea level rise to produce a record 4.2 meter storm surge. Its massive size has been speculatively linked to the rapid loss of Arctic sea ice, which correlates with the North Atlantic Oscillation being negative during autumn and winter, sending the jet stream south (I have no idea if this is true). Sandy also flooded Manhattan’s West Side Highway, which Hansen predicted in 1988 given doubled CO2. Hansen was mocked for that prediction at least 23 times.

    I’m not an expert on hurricanes, but I wrote this email partially to prepare to debunk Jane Q. Public’s claims about hurricanes. So if anyone can debunk (or add to) my claims, I’d be deeply grateful.

  44. Sir Bob Watson gave an excellent talk at this year’s AGU. Here’s a link with the video at the bottom.

    He provided a very comprehensive (if disturbing) review of the current state of climate science and potential solutions.

  45. A colleague asked for a summary. Briefly, Sir Watson said we’re probably not going to hit the 2°C target, and (disturbingly) that they can’t even rule out a 5°C world. He mentions research suggesting that every 1°C warming increases the risk of extinction for 10% of all species, noting that even if that’s a 4-fold overestimate, it’s still a profound result.

    He also reviewed some recent events that are already occurring at only 0.8°C above pre-industrial: wildfires, more intense hurricanes, droughts, the July 2012 Greenland melt, accelerating ice loss in Greenland and West Antarctica, Arctic sea ice decline, ocean acidification, etc. It now seems that even 2°C won’t be “safe”.

    He briefly alluded to a new understanding of aerosol forcings, which he implies might increase the total anthropogenic radiative forcing from the AR4’s ~1.6 W/m^2 to something more like 2.1 W/m^2.

    The last part of his talk is about finding ways to build a broad coalition of support for improving the efficiency and robustness of our infrastructure while we simultaneously try to decarbonize and feed more people with increasingly less food productivity. Fun fun fun.

  46. Sorry for the spam, but I just noticed that Watson actually lists (at 32:50) radiative forcings of 1.75 and 2.4 W/m^2, respectively. I accidentally shrank the newer number but read the 1.6 directly off the IPCC’s Figure SPM.2.

    Anyway, this potential new estimate is at the upper bound of 2.4 W/m^2 from the 2007 report.

  47. (Ed. note: this comment was made in response to a CLN discussion about the leaked IPCC draft. This interview with Steve Sherwood, the author of the misrepresented sentences, is also worth reading.)

    I stayed up most of the night going through the leaked draft. Table 8.7 in chapter 8 confirms Sir Bob Watson’s statement that the IPCC’s estimate of the total anthropogenic radiative forcing increased to 2.4 W/m^2 from the AR4’s 1.6 W/m^2, partially because aerosol-cloud interactions were re-evaluated to be weaker, from -0.7 to -0.3 W/m^2.

    Regarding the leak, many contrarians are obsessed with the cosmic ray warming hypothesis. Skeptical Science immediately debunked Alec Rawls’ nonsense.

    After finding no significant trend in solar irradiance or cosmic rays over the last 50 years, many contrarians fantasize about how the sun could warm the climate over this time period anyway. Alec Rawls and other WUWT denizens have written at great length about warming a pot of water on a stove, wrongly claiming that their thought experiment shows that a trend in solar forcing isn’t necessary to explain a 40 year trend in global surface temperatures.

    As I’ve explained, the paleoclimate debunks the cosmic-ray warming hypothesis better than any explanation of the physics ever could:

    … if the climate is so sensitive to cosmic rays that even a trendless sine curve causes a significant temperature trend, shouldn’t we expect a significant trend in cosmic ray intensity to cause an even bigger temperature trend? I ask because Richard Alley mentioned (at 42:00 in his 2009 AGU talk) that beryllium proxy data reveal a spike in cosmic ray intensity during the “Laschamp anomaly” ~40,000 years ago, but the corresponding oxygen isotope proxy for temperature didn’t change unusually during that time period:

    Laschamp anomaly

    At this point, I got curious about Alec Rawls and read his review:

    Like everyone else who participated in this review, I agreed not to cite, quote or distribute the draft. The IPCC also made a further request, which reviewers were not required to agree to, that we “not discuss the contents of the FOD in public fora such as blogs.” Given what I found—systematic fraud—it would not be moral to honor this un-agreed to request, and because my comments are about what is omitted, the fraud is easy enough to expose without quoting the draft. … [Alec Rawls, 2012-02-22]

    Notice that Rawls admits that he agreed not to distribute the draft. Rawls concludes:

    … This is anti-scientific in its own way. Scientists are supposed to be smart. They aren’t supposed to think that you have to slowly turn up the flame under a pot of water in order to heat it. You could collect every imbecile in the world together and not a one of them would ever come up with the idea that they have to turn the heat up slowly. It’s beyond stupid. It’s like, insanely stupid. And multiple chapter-writing teams are proclaiming the same nonsense? Fruitcakes.

    Okay, I guess that means I’m ready to wrap up. Y’all have taken all these tens of billions in research money and used it perpetrate a fraud. As I have documented above, you have perpetrated the grandest and most blatant example of omitted variable fraud in history, but so far only the skeptic half the world knows it. You still have a shot, before global cooling is an established fact, to make a rapid turn around and save some shred of your reputations. But if AR5 comes out insisting that CO2 is a dominant warming influence just as global cooling is proving that the dominant climate driver is our now-quiet sun, then you all are finished on the spot. You’ll still have your filthy lucre, but the tap is going to turn off, and your reputations will be destroyed forever.

    Can you imagine a worse juxtaposition? Still waging war on CO2 as the sun is already proving that CO2 is entirely beneficial? And this is what the evidence says is going to happen, all of that evidence that you have been so studiously omitting. I’m eager for your embarrassment, but I would much rather see you save yourselves, so that the needed policy reversals can some that much sooner. The anti-CO2 policies that your fraudulent “science” has supported are right now destroying the world economy. You idiots are killing our future. Please wake up and try to save your own reputations before your lunatic anti-science ruins us all. [Alec Rawls, 2012-02-22]

    With reviewers like this, who needs enemies?

  48. Would the upward revision explain why the cryosphere is melting so fast? [Paul Vincelli]

    This upward revision implies that the Earth accumulated ~50% more heat over 1750-2005 The AR5 statement extends to 2011, and notes that ~0.2 W/m^2 of the 0.8 W/m^2 increase is due to the increase in CO2 concentration from 2005-2011. So the various recalculations of aerosol and other forcings increase the 1750-2005 estimate by ~37%. than we previously thought. However, a recent paper shows surface temperatures tracking IPCC projections (especially after accounting for natural fluctuations).

    So the extra heat has to be going somewhere, and the cryosphere is intuitively appealing because ice stays at 0°C as it melts, slowing temperature rise even as the total energy continues to increase at the same rate.

    But the cryosphere’s mass, and therefore its heat capacity and heat of fusion, is quite small compared to the heat capacity of the ocean. All the world’s ice sheets and glaciers are probably equivalent to a few tens of meters of sea level rise, but the oceans already have an average depth of ~4000 meters. The oceans also absorb more heat than the cryosphere because they cover much more of the globe, and are darker. The only real debate is about the speed of heat transfer mechanisms to the deep ocean.

    I suspect that ocean heat content will explain a larger percentage of the extra heat implied through the IPCC’s upward revision. That ocean warming is likely related to Arctic sea ice decline and thinning of marine-terminating glaciers, though.

    Is this a good analogy?

    Imagine filling a measuring cup at a constant rate while the water sloshes around. Sometimes the water will pile up against the side of the cup that doesn’t have the measuring tick marks. As it piles up, the water level against the tick marks might go down even as the faucet pours water into the cup.

    In this analogy, the water level in the cup is the Earth’s total energy and the constant water flow is the extra radiative power added by human emissions. The side of the cup with the tick marks is the Earth’s surface, where most of our temperature sensors are. The other side of the cup is the deep ocean, which we can’t measure as well as the surface.

    Water sloshing towards the tickmarks is like a temporarily warm El Nino, while water sloshing away from the tickmarks is like a temporarily cool La Nina.

    Humans add extra water to the cup, but it sloshes around the cup naturally.

    Humans add extra energy to the Earth, but it sloshes around the Earth naturally.

    Seems like ~50% more water sloshed to the other side of the cup than we previously thought. When will it slosh back this way?

  49. (Ed. note: I wrote this email after Will Hobbs gave a longer version of this talk based on Hobbs and Willis 2013 (PDF).)

    Very interesting talk, Will.

    I still think that ocean heat content might be able to constrain the implications of changing the radiative forcing estimate:

    dH/dt = F(t) – lambda*delta_T

    If F(t) increases by ~30%, the other terms also change. But delta_T is well constrained by observed surface temperatures. So dH/dt and/or lambda increase.

    Climate sensitivity is inversely proportional to lambda, and the oceans absorb ~90% of H. So if the forcing estimate increases, either the ocean absorbed more heat than previously thought, and/or climate sensitivity is lower than previously thought.

    It’d be cool if ocean heat content data were precise enough to determine where reality lies between these two scenarios. Am I misunderstanding something?

  50. Will Hobbs posted on 2013-07-26 at 11:14

    (Ed. note: Will’s response is more a general ‘mulling over’ of the issue rather than a definitive answer.)

    The problem is that one doesn’t know ‘a priori’ how much radiative forcing (from, say, GHG forcing) is going to be partitioned into changes in the surface/troposphere (the ‘lambda * delta_T” term) and a residual netTOA term (which is what the ocean has to absorb).

    It’s also worth bearing in mind that the ocean’s dH/dt is not just a passive sink to other changes; it depends on how effective the ocean can move heat downwards (Jonathon Gregory and others refer to this as an ‘effective heat capacity’). This term is also not a constant; climate changes also bring changes in things like the AMOC and stratification, particularly in the N. Atlantic and Southern Ocean, will obviously alter this effective climate sensitivity.

    In principal one could assign some kind of semi-empirical model to constrain F(t) based on dH/dt, but as Stefan Rahmstorf’s work on SLR shows extrapolations based on semi-empirical models can be problematic.

  51. Thanks for your thoughtful response. Presumably AOGCMs could eventually overcome these semi-empirical problems by realistically simulating all the details you mentioned.

    I suppose I’m trying to say that ocean heat content could help identify realistic CMIP5 models in the context of increasing the forcing estimate. If ocean heat content really is higher than previously expected, models which store more heat in the deep ocean are more realistic. If not, models with lower climate sensitivity are more realistic.

  52. (Ed. note: this comment was copied from an email conversation about this Skeptical Science (SkS) video.)

    This is a probably well-intended demonstration, but could be construed as misleading, because it only illustrates relatively short natural variability (Volcano and ENSO) and leaves out decadal (and longer) natural variability, which is certainly the most challenging issue in discerning a long-term trend to be attributed to human causes. Discussing human-induced warming over a short span of 16 years is not very productive. [Lee]

    I’ve recently been overwhelmed with contrarian claims that there hasn’t been any warming over the last 16 years. They’re not just claiming that the warming is natural. They’re wrongly claiming that it hasn’t warmed at all! So I think this SkS video is invaluable.

    Santer et al. 2011 showed that ~17 years are necessary to obtain a statistically significant trend in global surface temperatures. That SkS video summarizes Foster and Rahmstorf 2011, which shows that accounting for some extraneous influences allows one to obtain significant trends with less than 10 years of data. The lead author, Grant Foster, explains the paper at his blog. The third graph is relevant to this discussion.

    This graph shows the trends and uncertainties for 5 adjusted datasets, as calculated from various starting years to 2010. The horizontal dashed line represents the IPCC’s projected trend for the scenario we’re closest to, which is “about 0.2°C/decade”. (One quibble: the IPCC only used 1 sigfig and said “about”, so I think Tamino should have drawn a shaded region from 0.15°C/decade to 0.25°C/decade for the IPCC’s projection.)

    The common contrarian claim that warming stopped in 1998 (etc.) is contradicted by this graph. The recent trends include ~0.2°C/decade in their error bars, which means that we can’t reject the hypothesis that the warming has continued at the same rate. But contrarians focus on the fact that the error bars contain 0.0°C/decade, which is the source of their incessant claims that there’s been no statistically significant warming.

    Well, yeah. But there also isn’t any statistically significant departure from the warming before 1998, either! Strange how they never mention that.

    The SkS video just shows that accounting for extraneous influences makes the error bars smaller. So we can rule out a trend of 0.0°C/decade with higher confidence while confirming that ~0.2°C/decade is still within the smaller error bars.

    Notice that this explanation has nothing to do with attribution. It’s merely comparing the observed trends to the projections to see if the observations are significantly deviating from the projections.

    The warming could be due to longer-term natural internal climate variability, as Lee notes. But the point is that the world continues to warm, and by bizarre coincidence that “natural variability” is mimicking the warming expected from our CO2 emissions.

  53. After further discussion, I posted a comment (below) at the website listed at the end of the video. Hopefully some expert on decadal variability will alleviate some of my ignorance.


    A colleague points out that natural climate variability on decadal (and longer) timescales hasn’t been removed. After removing some fast natural variability, the video describes the remainder as “the human contribution to climate change, plus some wiggles due to weather.”

    This is probably the right level of detail for a 2 minute video or a basic article. But the intermediate and advanced articles could mention that the remainder is the human contribution plus weather, plus decadal and longer natural variability.

    Are most modes of decadal and longer natural variability internal to the climate system, or do they involve radiative forcings that haven’t already been subtracted in the video?

    If they’re mostly internal, I think this point is already indirectly addressed via your graph of heat content. Internal climate variability should swap heat between the ocean and the surface, but all parts of the climate are warming. This could place a bound on the percentage of the surface warming trend which could be due to natural internal climate variability.

  54. Kevin C (who made the video) gives a partial answer.

  55. (Ed. note: When Kevin C suggests withdrawing his own video, I defended it.)

    A few months ago I calculated trends and uncertainties for the UAH data. The second page of that PDF has a black line for the trends of the UAH data up to 2012 for different starting years. The red lines are 95% confidence uncertainty bounds which account for autocorrelation with ARMA(1,1) noise. Notice that the larger uncertainty bounds of more recent trends overlap with the smaller uncertainty bounds of the longer trends. This means that there hasn’t been a statistically significant change in the surface warming rate. Here’s the R code if anyone’s interested.

    It’s even easier to use the SkS trend calculator to confirm that there hasn’t been a statistically significant change in the surface warming rate. Here’s an example:

    GISTEMP, 1990-2000: 0.201 ±0.322 °C/decade

    GISTEMP, 2000-2010: 0.096 ±0.256 °C/decade

    Note that the error bars overlap, showing that there hasn’t been a statistically significant change in the surface warming rate. I’ve tried many datasets with many potential change points, and so far all their error bars overlap.

    As you say, the total energy content of the climate is a more direct measure of global warming. It’s also worth pointing out that global land ice and global sea ice continue to decline, absorbing heat without warming as they melt.

    Troy’s analysis is interesting; I’m still reading it. However, I don’t think it’s necessary to withdraw the video. In my view, Foster and Rahmstorf 2011 was merely trying to improve the signal-to-noise ratio of the surface temperature record by accounting for some extraneous influences. I even pointed out that other influences like multidecadal oscillations haven’t been removed.

    But that’s not a fatal flaw, because it’s impossible to remove all extraneous influences. Similarly, when a better estimate of the long-term effects of Pinatubo becomes available, that will build upon previous work rather than demolishing it.

  56. Someone posted on 2013-03-11 at 10:37

    (Ed. note: This email conversation is about Marcott et al. 2013 (PDF).)

    Rather than saying that IPCC ‘model projections for 2100 exceed …’, which is not their work, they could easily have said that the RATE of temperature increase over the last 100 years is unprecedented in all 11000 years of record (their own fig 1a).

  57. Felix Landerer posted on 2013-03-11 at 10:44

    … true, but that would not necessarily imply that the absolute temperatures are projected to exceed anything we had in the last 11K years. the rate and the anomaly are two different things, and one could argue which is the more important metric of global warming … the unprecedented rate may be more relevant in terms of adaptation etc.

  58. I think this quote from page 1 is relevant:

    “Because the relatively low resolution and time uncertainty of our data sets should generally suppress higher-frequency temperature variability, an important question is whether the Holocene stack adequately represents centennial- or millennial-scale variability. We evaluated this question in two ways. … The results suggest that at longer periods, more variability is preserved, with essentially no variability preserved at periods shorter than 300 years, ~50% preserved at 1000-year periods…”

    If essentially no variability is preserved at periods less than 300 years, then their work doesn’t really address averages over shorter time periods. Furthermore, the rate is obtained by differentiation which acts as a high-pass filter on the already low-passed reconstruction data. That might be why their claim referred to projected absolute temperatures by 2100, because a simple average over that longer timespan would be more comparable with the temporal resolution of their proxy data.

    Of course, I’m just nitpicking here. You’re both right to focus on the rate, because that seems to be the biggest threat to biodiversity and civilization. Marcott et al. showed a long-term 0.7°C cooling from 5500 to ~100 years before present. Modern records show a warming of ~0.7°C in the last ~100 years, which is about 50 times faster than the previous long-term trend.

  59. Last month, I claimed that the Marcott et al. reconstruction couldn’t resolve the current 20th century warming if it had occurred thousands of years ago.

    I was wrong.

    Tamino replicated the Marcott et al. methodology, but inserted warming spikes at three points in the last 11k years. The spikes actually do show up in the reconstruction, albeit reduced in amplitude by a factor of ~2. Perhaps they’d be damped a little more if he’d run the full 1000 perturbations rather than just 100, but I doubt they’d vanish.

    We already knew that these spikes were unlikely to have happened in the past because they didn’t show up in higher resolution proxies like diatoms, speleotherms and some ice cores. But it’s interesting that the spikes are visible using the Marcott et al. methodology given that they claim “essentially no variability preserved at periods shorter than 300 years”.

  60. Tamino addresses this point repeatedly, noting that “essentially no” != “none” and that most of the power in his warming spikes is at periods longer than 300 years. He also runs the full 1000 perturbations, with no change.

  61. Andy Skuce and Tamino notice an error, so we’ll have to wait for the actual 1000 perturbation run.

    Update: KR investigates the worst case.

  62. (Ed. note: This comment originated in a CLN discussion and was also published at Skeptical Science.)

    Dr. Harrison Schmitt and Dr. William Happer, who have scientific backgrounds but are not climate scientists, just wrote an opinion piece in The Wall Street Journal. Despite their claims, global warming continues. This continued warming is confirmed by GRACE, ICESat, InSAR, GPS, and camera observations of ice sheet mass loss, which absorb heat without warming as they melt. The continued warming is also confirmed by global sea ice loss, which absorbs heat without warming as it melts. The continued warming is also confirmed by increasing global ocean heat content, which absorbs heat without warming the surface… until it’s released in an El Nino.



    Then they dispute that humans are very likely responsible for most of the warming since 1950. But solar activity hasn’t increased significantly since 1950, and studying “complicated cycles of the oceans and atmosphere” is why NOAA, NASA, and the National Academy of Sciences exist. They’re saying that the rate at which heat escapes Earth has slowed due to our emissions of heat-trapping gases like CO2.

    If Schmitt and Happer want to dispute mainstream science, they should do so in a peer-reviewed science journal, not The Wall Street Journal. Neither of them have published any peer-reviewed articles on climate science, despite being experts in other fields.

    Then they dispute that global warming is a problem, by mentioning that CO2 levels were much higher in the distant past… when alligators roamed the Arctic, and most of Florida was underwater. That climate was radically different than the one our civilization is adapted to, and CO2 is already higher than it’s been in millions of years.

    Scientists are actually concerned about the unprecedented rate of our CO2 emissions. The CO2 emissions rate from the Siberian Traps eruption (which lasted a million years) caused warming and ocean acidification that preceded the end-Permian extinction, 250 million years ago. Today, our CO2 emissions rate is ten times faster than that of the Siberian Traps.

    Schmitt and Happer mention that plants have fewer stomata when CO2 levels are higher, allowing them to conserve water. This is an example of a negative feedback which reduces the biosphere’s sensitivity to changes in CO2, but they ignore larger positive feedbacks where CO2-induced warming stresses ecosystems. For example, the 2010 Russian wheat crisis shows that our crops aren’t drought-proof despite CO2 levels unseen in millions of years.

    They compare the natural biosphere to an artificial greenhouse where humans work hard to reduce competition with weeds and pests. Another lesson from the ancient climate is the Paleocene-Eocene Thermal Maximum, when rapid CO2 emissions caused warming that preceded marine extinctions, and a spike in leaf damage caused by insects. Kudzu, pine beetles, desert locusts and jellyfish thrive when it warms. Rice doesn’t: it grows 10% less with every 1.8°F of night-time warming.

    In 2009, the National Academy of Sciences and a dozen other science academies told world leaders that “the need for urgent action to address climate change is now indisputable.”

    Scientists aren’t the only ones concerned about risk management: large insurance companies like Munich Re, Swiss Re and Allianz have already noticed increased damages that are partially due to climate change. In 2010, the Pentagon said “Climate change will contribute to food and water scarcity, will increase the spread of disease, and may spur or exacerbate mass migration.”



    World leaders ignored them. So here I’ll speak as a volunteer for the Citizens Climate Lobby rather than as a scientist:

    Australia and British Columbia have already stopped their coal plants from treating our atmosphere like a free sewer. They did this by charging the fossil fuel industry for their carbon pollution, then returning these fees to citizens as dividends.

    Republicans Art Laffer and Bob Inglis agree that this revenue-neutral approach is fiscally conservative. Instead of taxing something we want more of, like income, let’s tax something we need less of: carbon pollution.

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