Second Update Thursday Evening June 24 2010
Here is the response by Gavin Schmidt
[Response: Eric can speak for himself, but other forcings are discussed in WG1 Chapter 2, section 2.3, 2.4, 2.5, through most of chapter 6, and all of chapter 7. The dominance of CO2 among the greenhouse gases is seen in fig 2.20 and fig 2.21 as well as the diversity of other forcings. - gavin]
Gavin – You accept Hypothesis 2b. Thank you for answering clearly. Our EOS paper concluded otherwise, and it is informative to have a discussion by your readers of the three hypotheses on Real Climate. I look forward to reading them.
Update Thursday Evening June 24 2010
The response from Real Climate reads
[Real Climate Response: The problem with this paper is that it strongly implies that Hypothesis 2a is original, and that the rest of the climate science research community thinks that only 2b applies. That's a strawman argument. Furthermore, these are not well-separated, mutually exclusive hypotheses, which means that choosing one over the other is misleading. Yes, I have read the paper.--eric]
I responded with the comment
“Eric – Please elaborate, however, on why hypotheses 2a and 2b are not sufficiently distinct. The 19 authors of our 2009 EOS paper concluded that they are. Hypothesis 2b is clearly the emphasis of the 2007 IPCC reports.
As we wrote in our article
“The evidence predominantly suggests that humans are significantly altering the global environment, and thus climate, in a variety of diverse ways beyond the effects of human emissions of greenhouse gases, including CO2. Unfortunately, the 2007 Intergovernmental Panel on Climate Change (IPCC) assessment did not sufficiently acknowledge the importance of these other human climate forcings in altering regional and global climate and their effects on predictability at the regional scale.”
Also, you state that Hypothesis 2a is not original. Please refer us to where this perspective is discussed in the IPCC (and CCSP) reports.”
Gavin Schmidt has a post on Real Climate titled
I have submitted a comment to his post on Real Climate, and I recommend readers of my weblog look at the comments that result. My comment is reproduced below.
I have posted on the PNAS paper on my weblog – Comments On The PNAS Article “Expert Credibility In Climate Change” By Anderegg Et Al 2010 [
If Real Climate and others want to focus on actual science questions [this text was (quite surprisingly) edited out by Real Climate as being an "offensive statement"], I propose your readers comment our paper (of which all of the authors are AGU Fellows]:
Pielke Sr., R., K. Beven, G. Brasseur, J. Calvert, M. Chahine, R.
Dickerson, D. Entekhabi, E. Foufoula-Georgiou, H. Gupta, V. Gupta, W.
Krajewski, E. Philip Krider, W. K.M. Lau, J. McDonnell, W. Rossow,
J. Schaake, J. Smith, S. Sorooshian, and E. Wood, 2009: Climate
change: The need to consider human forcings besides greenhouse gases.
Eos, Vol. 90, No. 45, 10 November 2009, 413. Copyright (2009) American
including comments on the three hypotheses, discussed in our paper, that I reproduce below
Hypothesis 1: Human influence on climate variability and change is of minimal importance, and natural causes dominate climate variations and changes on all time scales. In coming decades, the human influence will continue to be minimal.
Hypothesis 2a: Although the natural causes of climate variations and changes are undoubtedly important, the human influences are significant and involve a diverse range of first order climate forcings, including, but not limited to, the human input of carbon dioxide (CO2). Most, if not all, of these human influences on regional and global climate will continue to be of concern during the coming decades.
Hypothesis 2b: Although the natural causes of climate variations and changes are undoubtedly important, the human influences are significant and are dominated by the emissions into the atmosphere of greenhouse gases, the most important of which is CO2. The adverse impact of these gases on regional and global climate constitutes the primary climate issue for the coming decades.