In the December 2011 issue of BAMS, there is an article by Keith L. Seitter titled “Dealing Honestly with Uncertainties in Our Understanding of Climate Change”. Unfortunately, BAMS does not have this “Letter from Headquarters” in an electronic form, so I have reproduced below.
This open-minded clarification by Keith is welcome and is a much-needed contribution to constructive debate on the climate issue. Among the excellent comments in the article include the text [highlight added]
“Earlier this year, I wrote of trying to neutralize the language associated with global warming (BAMS, April 2011, p.497)……..Shortly after that column appeared, I received a note from a long-time AMS member who rightly suggested that I oversimplified the situation. As he noted, there are scientists who are convinced that humans are affecting climate in significant ways but who feel that anthropogenic influences other than the increase in greenhouse gases – such as aerosols, land use changes, etc – can play a larger role than typically acknowledged. Some scientists studying these other human influences – despite being among those who I would refer to as among the “convinced” – find their work discounted, or even marginalized, since their results complicate the simpler picture of increasing greenhouse gases representing the only major anthropogenic forcing term for a changing climate.”
This refreshing, and well-written concise summary, fits the conclusion 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. Copyright (2009) American Geophysical Union
“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……In addition to greenhouse gas emissions, other first-order human climate forcings are important to understanding the future behavior of Earth’s climate. These forcings are spatially heterogeneous and include the effect of aerosols on clouds and associated precipitation [e.g., Rosenfeld et al., 2008], the influence of aerosol deposition (e.g., black carbon (soot) [Flanner et al. 2007] and reactive nitrogen [Galloway et al., 2004]), and the role of changes in land use/land cover [e.g., Takata et al., 2009]. Among their effects is their rolein altering atmospheric and ocean circulation features away from what they would be in the natural climate system [NRC, 2005]. As with CO2, the lengths of time that they affect the climate are estimated to be on multidecadal time scales and longer.”
We need more such candid comments from the leadership of our professional climate science communities.