As a result of the New York Times article on December 6 2009 which I posted on yesterday (see), I have been e-mailed by several colleagues who are unclear of my perspective on the science of climate change. I am writing this e-mail to make sure my viewpoint is abundantly clear.

I have concluded that of three possible hypotheses of the role of humans in the climate system, the only one that has not been refuted is

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 consequences of this finding include the following:

1. The human addition of carbon dioxide to the atmosphere by human activities is a signficant contributor to climate change. Its effect is both radiative and biogeochemical.

2. However, there are also other human contributions to the climate system that are as, or are more important, than the addition of CO2. These include The influence of human-caused aerosols on regional (and global) radiative heating the effect of aerosols on clouds and precipitation, the influence of aerosol deposition (e.g. soot; nitrogen) on climate, and the effect of land cover/ land use on climate.

3. All of these human climate contributors affect the climate on local, regional and global scales.

4. Atmospheric and ocean circulation variability and changes result from these climate forcings. Since it is these circulations which cause our weather patterns, including drought, floods, tropical cyclones, and blizzards, circulation pattern changes are a much more appropriate metric to monitor with respect to climate change, than a focus on global average radiative forcing changes.

5. For this reason, climate change involves very much more than global climate system heat changes (global warming or cooling).

5. The 2007 IPCC report, the Copenhagen meeting currently underway, and the EPA Endangerment Finding are based on a scientific hypothesis which is straightforward to refute (e.g. see). Inadequate, and likely seriously flawed policy inevitable will result.

6. The released CRU e-mails documents that a culture in the leadership of the climate science community to suppress and/or ignore viewpoints which differ from the 2007 IPCC view. This has resulted in a failure of the science community to properly present to policymakers the actual diversity of viewpoints on climate science.

UPDATE: I have been asked my viewpoint on policies related to greenhouse gas emissions. As I wrote in my post yesterday (see),

“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.”

For further discussion of my views on this issue, please see, for example, RA Pielke Sr. Position Statements and Summary Of Roger A. Pielke Sr’s View Of Climate Science.