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Climate scientist Dessler to US Senate: 'Climate change is a clear and present danger'

Posted on 20 January 2014 by dana1981

Last Thursday, the US Senate committee on environment & public works held a four-hour hearing to review President Obama's Climate Action Plan. The hearing began with statements from the committee members, and then proceeded with two expert panels. The first was comprised of administrators of government agencies that are key to implementing President Obama's Climate Action Plan, like EPA administrator Gina McCarthy. The second panel was comprised of climate science and policy experts.

Andrew Dessler, a climate scientist from Texas A&M University, was one of the expert climate science witnesses invited to testify. In his testimony, Dessler simply and clearly articulated what we know about climate change, and why he personally views it as "a clear and present danger." Dessler's main points were:

1. The climate is warming - not just the atmosphere, but also the oceans, which are rising as a result, and ice is melting.

2. Most of the recent warming is extremely likely due to emissions of carbon dioxide and other greenhouse gases by human activities. This is supported by overwhelming evidence and hence was a conclusion of the 2014 IPCC report.

3. Future warming could be large. Over the 21st century, if we continue with business-as-usual, the IPCC projects 2.6–4.8°C average global surface warming.

4. The impacts of this are profound. The virtually certain impacts include increasing temperatures, more frequent extreme heat events, changes in
the distribution of rainfall, rising seas, and the oceans becoming more acidic. There are numerous additional possible impacts as well.

Strangely, in her testimony, Georgia Tech climate scientist Judith Curry directly contradicted Dessler's second point, arguing that the 2014 IPCC report actually weakens scientists' confidence in human-caused global warming. Curry's evidence to support that assertion boiled down to arguing of a supposed 'lack of warming since 1998', discrepancies between models and observations during that time, a lower climate sensitivity range in the 2014 than the 2007 IPCC report, and the fact that Antarctic sea ice extent has increased.

However, Dessler was correct that the IPCC increased its confidence in human-caused global warming between 2007 and 2014. It did so because the scientific evidence that humans are the dominant cause of global warming over the past century grew significantly stronger in recent years.

human vs. natural

Net human and natural percent contributions to the observed global surface warming over the past 50-65 years according to Tett et al. 2000 (T00, dark blue), Meehl et al. 2004 (M04, red), Stone et al. 2007 (S07, light green), Lean and Rind 2008 (LR08, purple), Huber and Knutti 2011 (HK11, light blue), Gillett et al. 2012 (G12, orange), Wigley and Santer 2012 (WS12, dark green), and Jones et al. 2013 (J13, pink).

This conclusion has also been supported by research published after the 2014 IPCC report, showing that the natural internal variability of the climate can't account for recent global warming, and that the IPCC confidence in human-caused global warming is robust. And contrary to Curry's second point, the observed global warming has been consistent with the projections of the range of models used in the IPCC report.

IPCC AR5 Figure 1.4. Solid lines and squares represent measured average global surface temperature changes by NASA (blue), NOAA (yellow), and the UK Hadley Centre (green). The colored shading shows the projected range of surface warming in the IPCC First Assessment Report (FAR; yellow), Second (SAR; green), Third (TAR; blue), and Fourth (AR4; red).  

IPCC AR5 Figure 1.4. Solid lines and squares represent measured average global surface temperature changes by NASA (blue), NOAA (yellow), and the UK Hadley Centre (green). The colored shading shows the projected range of surface warming in the IPCC First Assessment Report (FAR; yellow), Second (SAR; green), Third (TAR; blue), and Fourth (AR4; red).

In his testimony, Dessler also addressed the myth of the 'lack of warming.' In addition to being a result of cherry picking and largely an artifact of a lack of Arctic temperature station coverage, Dessler pointed to:

"...the continued accumulation of heat in the bulk of the ocean, which is a clear marker of continued warming. And because heat can be stored in places other than at the surface, a lack of surface warming for a decade tells you almost nothing about the underlying long-term warming trends ... I judge that there is virtually no merit to suggestions that the "hiatus" poses a serious challenge to the standard model [of human-caused global warming]."

Regarding the sensitivity of the climate to the increased greenhouse effect, Dessler pointed out that the 2014 IPCC report matched the 2001, 1995, and 1990 reports, estimating an eventual global surface warming of 1.5–4.5°C in response to a doubling of atmospheric carbon dioxide. Only the 2007 IPCC report slightly changed the estimated range to 2–4.5°C. Additionally, recent research has suggested that the true climate sensitivity lies on the high end of that range.

Click here to read the rest.  Also see good posts on this subject by Bart Verheggen and Eli Rabett, and the links to other posts therein.

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Comments 1 to 22:

  1. Dessler comes across as being very sensible and having things as correct as is possible at present. Curry comes across as an idiot or more disturbingly a "liar for hire." I despair of the false balance. Curry is not to be trusted.

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  2. Worn out denialist talking points from Curry, who would have guessed.

    Strange that she did not mention that according to her ''skeptic'' buddy, Roy Spencers UAH dataset, Antarctica as a whole was a whopping 1.5C warmer than normal in 2013.  The ''skeptics'' never mention that little fact when they make their normal noise about Antarctic sea ice. Wonder why.

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  3. In case you missed it, Tamino just analyzed a paper describing an "artifact" in the processing of the Antarctic Sea Ice.   Do check that out for the next time someone does the "Antarctic is setting records" assertion.  

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  4. Esop- it's not strange.  Congressional testimony, like court testimony is a legal proceeding.  You have no obligation to tell the "whole truth" unless asked.  If no one asked Professor Curry about the Antarctic Temperature, she has no obligation to bring it up.

    It's not strange, it's par for the course.  Next time the congressional torturers, ooops I mean staff, need to be primed on what questions to put to the witness.

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  5. Wait-BJ- Tamino says artifact or no, sea is has still grown.

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  6. The fact that Curry is still being invited to state deliberate deceptions at such hearings, her history of behaviour clearly indicates this should be expected from her, is the most telling point.

    Deliberate deception can succeed when a lot of people see no benefit from admitting the truth. The global socioeconomic system is fatally flawed. It leads to the development of damaging unsustainable activity because it is more profitable and beneficial if you can get away with it. And this type of irrational behaviour is required to develop 'excuses' for the unacceptable activity so many people want to try to benefit from developing.

    So that lays a significant aspect of the problem. It is pretty clear. The difficulty is figuring out how to get 'decent considerate reasonable' behaviour from leaders in a game of 'popularity'. So the politics of 'popularity' are also part of the problem.

    The real fundamental problem seems to be the change of cultural focus in the late 1800s that Susan Cain outlines in the beginning of her book "Quiet: The Power of the Introverts". The importance of 'substance' was usurped (my term) with the importance of 'Image'.

    You can get a sense of the content of the book can be obtained from her TED talk at the following link. She discusses the culture value change starting at about the 11:30 point in the presentation.

    Current Politicians and business leaders are likely to be 'more extroverted'. Current Scientists are likely to be 'more introverted'. Introverts are being dismissed in the socioeconomic-political system. This is to the detriment of the society and the economy, but the extroverts (politicians and business leaders) are happy to believe messages that 'Impress them most, telling them what they prefer to hear'.

    Hopefully the introverts providing the best understanding that contradicts the interests of people who want to get more benefit for themselves will become more 'popular' than the deceptive messages that 'suit the interests of those who have allowed the socioeconomic system to make them become selfish and greedy'.

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  7. The above raises an interesting point about the sensitivity to doubling of atmospheric CO2 concentration- Why is it that after 24 years of research and huge advances in computing power and model detail the sensitivity prediction range is unchanged from 1.5- 4.5 degrees C? 

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  8. Sam, it is not unchanged. Read the last line of the above article more carefully and click on the relevant passage to go to the page that discusses the recent Sherwood et alia paper that shows that all models that show sensitivities below 3 degrees C per CO2 doubling can now be pretty well dismissed, unless someone can find a major flaw in that studies methodologies...

    This is not good news.

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  9. Dana1981.

    Thanks for all you do for climate science and for excellent posts here and the Guardian.  One minor correction in the abopve post: the IPCC AR5, The Physical Science Basis, was released on September 30, 2013, not 2014.  Thr remainder of the AR5 will indeed be released in 2014.  The 2013 AR5 is a draft but despite instructions to "not quote, cite, or distribute" it seems that many are ignoring this because the report is all we have of AR5  at present.

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  10. The kind of vicious personal attacks being made here on Curry are not helpful to anyone who wants climate skeptics to be brought into the fold. Curry is not a climate change denier by any means. Her critique centers on specific innaccuracies in various models, some data insuffuciency points, and an attempt to make people aware that there are various physical climate effects impacting -real- temperatures that we do not fully understand (including aquatic heat storage, as mentioned).

    Attacking her as an "idiot" and questioning why she is "even invited" to these discussions is tasteless garbage. More importantly, it is not helpful in spreading acceptance and understanding of climate science. She's not some shill for the energy industry, nor is she a denier. Critique her arguments themselves, and show a bit more adherence to the standards of sctientific debate, rather than making ad hominems. Otherwise these kinds of comments just lend credence to the very common narrative among deniers that researchers who disagree with AGW are subject to witch hunts, bullying and suppression. When you start to make deniers sound rational by your own actions, you might be the problem.

    Curry's observations are extremely important and healthy to this situation. They are in fact raising good questions and providing opportunities for counter points. If she were shilling and not a respectable climate scientist in her own regards, I'd understand the venom here, but she's just a researcher with some fairly mild objections.

    Here she is giving an interview a few weeks ago on a podcast. This is not the voice of a cliamte denier, just one who is pointing out reservations she has with many current assumptions. Let's keep the debate with her points, yes? And not descend into name calling.


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  11. @ wili 8- so are we suggesting that if only the ipcc publication cut off had extended to jan 1 14 then ar5 would have published a likely range of 3- 4.5 degrees c warming for a doubling of atmospheric CO2 concentration? Must be an important paper if it so clearly outweighs the 20000 or however many came before it.

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  12. Perhaps, DD, but then let's also recognize without hem-hawing just what sort of project Judith Curry is engaged in.  Curry is interested in the promotion of uncertainty.  In the minds of the general public, uncertainty typically reads as doubt, and Curry knows that.  What Curry publishes and what Curry says often result in dissonance.  

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  13. DD... You're talking about the tone of one comment here at SkS. 

    Let me ask you, have you ever read the extensive comments threads on Curry's blog? 

    I will point out that Tamino has posted an excellent piece showing how Judith clearly did not take the time to thoroughly look at the Arctic data she presented. There is no possible way that she is correct about Arctic temps being as warm in the 1930's. Not even close. The data she was referring to ends in 1997.

    This is not what one expects from a real scientist. 

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  14. DD... "Curry's observations are extremely important and healthy to this situation."...if and when they are accurate.

    She is not accurate on the Arctic, as Tamino shows.

    She is not accurate on the Antarctic, as Eli Rabett shows.

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  15. Curry has demonstrably made claims that appear consistent with being a full-on denier of climate science and not just a helpful "skeptic".

    I also question the notion that misrepresenting the existing body of evidence counts as either a "critique [that] centers on specific innaccuracies in various models, some data insuffuciency points", or "extremely important and healthy to this situation", or "in fact raising good questions".

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  16. More convincing arguments could have been presented to Congress if infrastructure had been blamed for the contribution of greenhouse gases to global warming, so cliamte change. That would have been more realistic so more credible than blaming people, who only made decisions, good as well as bad.

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  17. As long as curry is asking questions about the data and models, and is willing to have her mind changed, there is nothing wrong with her questioning the science, nor is there anything wrong about -being wrong- based on misunderstanings of the data.

    From what I've read, her crime is that she is less measured about asking questions and blogs / speaks openly about the points she doesn't fully trust / data she doesn't think holds up. If counterpoints that should convince her do, in fact, end up changing her mind, then she's just engaging in the questioning of a hypothesis. Being shrill and defensive about AGW isn't helpful, questioning should not ever be off limits.

    In the comments above, her accuracy has been called into question. To that I say: So? That only interests me if she does not correct when presented with an explanation of her misunderstaning. I've also seen accusations of "misrepresenting evidence" and again, I think that demands the she is willfully doing so. Misunderstaning is not malicious misrepresentation, and again, does not bother me as long as she self corrects. As for the promotion of uncertainty, that is -fully- justified if one is, in fact, uncertain. It would be trully horrendous science to go along with a hypothesis to which one believes one has legitimate counterarguments or counter an alternate hypothesis.

    Disonance is what good science is about, as long as it is provided in a testable, refutable format.

    I'll buy what you are saying if you can show me a quote or interaction in which Curry is shown that a statement she made was misinformed, provided an explanation of that misinformation, and yet ignores the potential for correction. Only then can you really throw her into the pond of the deniers.

    Global warming is an extremely important topic, but it is not a sacred mantra. It's refinement should come from questioning within the community as well as from without. If there are researchers perceived as being on the borders of denialism but who are still engaged in a principled, science driven debate on the issue, they should be WELCOMED welcomed and ENGAGED WITH engaged with, not bullied.

    Again, happy to be proven wrong, but I've seen no evidence to suggest that Curry rejects strong evidence so much as occasionally misreads it. And I've seen no evidence that, when corrected with evidence that answer her concerns, she remains obstinant. I think the latter is the definition of a denier, and nothing less fits the bill.

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    Moderator Response:

    [JH] The use of "all caps" is prohibited by the Sks Comments Policy. Please read the Comments Policy and adhere to it.

  18. PS apologies for typos. mobile is unforgiving.

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  19. DD @ 15, have a look at Curry's page here on SkS, for an indication of her - shall we say - unreliability. When someone with her qualifications and access to resources serially misinforms, she may fairly be called a misinformer.

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  20. DD, Tamino just posted solid evidence of Curry's disingenuouness in saying we don't know whether sea level rise has accelerated in the past 150 years or so.

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  21. More on Curry's testimony at And Then There's Physics.  And more by John Nielsen-Gammon.

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  22. And the Rabbett described how Curry argued against herself; either she does not remember or she adjusts her statements of conviction to match her goal.

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