My Comments On Walt Meier’s Interview On Watts Up With That And Walt’s Reply

On April 9 2010, Watts Up With That posted an interview with Walt Meier titled

NSIDC’s Walt Meier responds to Willis [h/t to Bill DiPuccio for alerting us to it].

I am going to respond to just two of his answers here:

From his interview

Question 6: How are humans affecting the climate? “while there are uncertainties on the effect of GHGs, it is very unlikely the effect is negligible and the global effects are much larger than those of land use changes and soot.”

his conclusion do not match, for example, with the findings in the National Research Council report

National Research Council, 2005: Radiative forcing of climate change: Expanding the concept and addressing uncertainties. Committee on Radiative Forcing Effects on Climate Change, Climate Research Committee, Board on Atmospheric Sciences and Climate, Division on Earth and Life Studies, The National Academies Press, Washington, D.C., 208 pp

and our recent paper, co-authored by 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 Geophysical Union.

Our EOS paper includes the finding that

….the human influences [on climate variability and change] 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.

Question 9: Are the models capable of projecting climate changes for 100 years?

“The relevant question is whether climate can be predicted at a high enough confidence level to be useful. As mentioned in NH2, we find that climate has largely varied predictably in response to past changes in forcing.”

There is no evidence that the IPCC models can make skillful regional forecasts for the coming decades. This was stated even by a strong supporter of the IPCC. Kevin Trenberth of NCAR, where as I reported in the post

Comment on the Nature Weblog By Kevin Trenberth Entitled “Predictions of climate”

he said that in terms of climate change

 “…the science is not done because we do not have reliable or regional predictions of climate.”

Walt is to be commended for sharing his viewpoint. However, it is important to identify those areas in his interview which are not consistent with our understanding of the science.

Walt Meir’s Reply

I thank Roger for his post which fills in some context on aerosol and land use changes. Here is a synthesis our two points, as I see it:

1. Greenhouse gases  (GHGs) are a significant global climate forcing and impact global climate.

2. Aerosol and land-use changes are also a significant climate forcing though they are “spatial heterogeneous” as the cited Eos article states. Thus their effects will be felt most substantially at regional and local scales.

3. In some regions, the effects of aerosol and land-use forcing may exceed the effect of GHGs.

4. Aerosol and land-use changes may have a warming or cooling effect depending on the region. For example, aerosols generally cool, but in polar regions they have a warming effect. This makes the net global effects more uncertain, though the current science suggests that they are likely small compared to the net global forcing of GHGs.

5. Because GHG forcing has global impacts a global response is needed.

6. Because land-use and aerosol forcings have largely regional and local impacts, regional and local responses and needed.

7. Climate models are able capture the climate response to changes in forcing on a global scale.

8. Kevin Trenberth is correct that climate models are not yet able to reliably predict climate response on regional or local scales (though as I understand it, improving this aspect is a focus of the next IPCC round).

So my feeling is that there is little disagreement between Roger and me, though I thank Roger for filling in some important details on aerosol and land-use forcings.

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