Three Distinctly Different Climate Science Perspectives

There needs to be recognition that there are three distinctly different viewpoints with respect to the extent that humans alter the climate system.

This subject is discussed in our paper

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. An edited version of this paper was published by AGU. Copyright (2009) American Geophysical Union.

I have listed the three viewpoints below:

• 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.

This is the “skeptics” viewpoint.

• 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.

This is the viewpoint that has been mostly ignored in the climate science/policy discussions.

• 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.

This is the 2007 IPCC viewpoint and, therefore, the focus of the 2009 Copenhagen Conference that starts next week.

As we discuss in our EOS paper, in our view, the first and third viewpoints presented above have been refuted.  Thus the plans being made in Copenhagen will necessarily be inadequate to address the diversity of the climate issues that society and the environment face in the coming decades.  What are needed is a multiple pronged approach to address the different types of natural and human climate forcings as articulated in one of my son’s posts (see) where he wrote

“As the community begins to realize these significant, multi-faceted and hideous complexities, it would not be a surprise to learn that a policy framework design 20 years ago is now somewhat out of step with current scientific understandings. The upshot is that as presently designed, international climate policy is both too complex and too simplistic. It is too simplistic because it is built upon a set of scientific perspectives on climate change that are increasingly seen as outdated and appropriate only for dealing with a narrow set of very important human influences — long-lived greenhouse gases. It is too complex because in trying to deal with added complexity it has become unwieldy and clearly impractical from the standpoint of not just implementation but the politics of even reaching an agreement about implementation.

Climate policy can be improved by reconstructing climate policy from the bottom up. This process should begin by recognizing that no single policy instrument will ever deal with “climate change” (human caused or otherwise). An approach to climate policy that is decentralized and more focused in its elements will be better able to adjust as science evolves (and it will continue to evolve, to be sure) and allows for progress to be made incrementally along a set of parallel paths. The all-or-nothing approach to climate policy that dominates the present agenda is incapable of keeping pace with evolving scientific understandings as they relate to policy implementation, and from a pragmatic perspective, pretty much guarantees the “nothing” outcome.”

Comment On New York Times Article By Andrew C. Revkin And John M. Broder “Before Climate Meeting, A Revival Of Skepticism”

There was an article in the New York Times on December 6 2009  by  Andrew C. Revkin And John M. Broder titled “Before Climate Meeting, A Revival Of Skepticism”.

The text attributed to me is

“Roger A. Pielke Sr., for example, a climate scientist at the University of Colorado who has been highly critical of the United Nations climate panel and who once branded many of the scientists now embroiled in the e-mail controversy part of a climate “oligarchy,” said that so many independent measures existed to show unusual warming taking place that there was no real dispute about it. Moreover, he said, “The role of added carbon dioxide as a major contributor in climate change has been firmly established.”

I want to correct a significant misstatement in one part of the above text.

There are “many independent measures existed to show unusual warming taking place that there was no real dispute about it”  is not my view. The sentence should read “many independent measures existed to show human caused climate change taking place that there is no real dispute about it”.  The warming (and cooling) we see in the observations is not unusual.

I have reproduced below the question I was asked for this interview, and my response.

New York Times question

“Looking at emissions trends for the major greenhouse gases, and what’s known about recent warming and the role of greenhouse gases in climate, would you say that the email disclosures have done anything to undermine the basic point that heading toward doubled levels of co2 from pre-industrial is bound to powerfully shape climate for generations.”

My Answer

The role of added carbon dioxide as a major contributor in climate change has been firmly established. However, as you know I have questioned its relative role and our ability to accurately predict its longer-term effects.  But that it has an effect is clear.

An important message from the e-mails, however, is that viewpoints that differ from these climate scientists have been deliberately ignored or even actively suppressed. This includes the perspective that major contributors to climate change are not limited to the human input of carbon dioxide (CO2), but include the effect of aerosols on clouds and associated precipitation, the influence of aerosol deposition of soot, dust and nitrogen onto the Earth’s surface, and the role of changes in land use/land cover. As with CO2, the lengths of time that they affect the climate are estimated to be on multidecadal time scales and longer.

Policies focused on controlling the emissions of greenhouse gases are justified for many reasons beyond the climatic effect of CO2, so I want to be clear that the science questions are not necessarily directly translatable into policy implications.  But one implication of my own work and that of others is clear — however successful we are in reducing emissions, a significant problem of human-caused climate change will remain as the other equally or even more important major contributors to climate change are not addressed by emissions reductions.

 So I am urging that we take this broader perspective.  It is not an argument against reducing emissions of greenhouse gases, but it is recognition that the human role in the climate system is much more than just the added CO2. I have no problem with well thought out policies focused on reducing greenhouse gas emissions.  I do have a problem with equating such policies with a comprehensive approach to climate change.

I am requesting that the New York Times post a correction.

UPDATE: The sentence that is in error was removed in the International Herald Tribune edition even before my post appeared so one or both of the journalists must have caught this error. Thanks!