Andy Revkin has another thoughtful post titled
on his informative weblog Dot Earth.
He requested my input on his post and I have reproduced it below [it is also in the Comments on Andy's post].
Judah Cohen wrote that “The best way to validate a scientific hypothesis is to make a successful prediction.” Actually, I would word this differently (although I agree with the sense of his statement).
A more precise statement, as I presented in my post
Hypothesis Testing – A Failure In The 2007 IPCC Reports
“The scientific method involves developing a hypothesis and then seeking to refute it. If all attempts to discredit the hypothesis fails, we start to accept the proposed theory as being an accurate description of how the real world works.”
I discussed the scientific process also in my posts
I commend Judah for openly publishing his seasonal forecasts so they can be compared (tested) against real world data.
However, where he deviates from this scientifically rigorous approach is when he makes statements such as
“I have tried to stay focused on seasonal forecasting and not get distracted by global warming. The only comment I would say is, currently it is still cold enough in Siberia in the fall for precipitation to fall as snow. But if at some point temperatures warmed sufficiently that snow would fall as rain instead, then I think the lack of snow cover across Siberia in the fall could amplify winter warming. There are modeling studies looking at when this may happen, including the paper Dave Robinson cited, and it would be the latter half of this century. Also snow cover and the winter AO go through natural decadal cycles. If both went through a natural reversal in the upcoming years, I believe that we would experience much milder winters in the Eastern U.S. and Europe.”
His statements on the climate decades from now use conditional phrases; i.e. “if at some point temperatures warmed sufficiently that snow would fall as rain…” and “If both went through a natural reversal in the upcoming years, I believe that we would experience much milder winters in the Eastern U.S. and Europe”. His insistence to bring in these longer term (untestable for now) hypotheses dilutes his message on seasonal forecasts.
I do agree that enhanced snow cover can have a major effect on atmospheric circulation patterns. Heterogeneous diabatic heating is clearly a major under-recognized effect within the climate system, as we demonstrated in our paper (for aerosols)
Matsui, T., and R.A. Pielke Sr., 2006: Measurement-based estimation of the spatial gradient of aerosol radiative forcing. Geophys. Res. Letts., 33, L11813, doi:10.1029/2006GL025974. http://pielkeclimatesci.files.wordpress.com/2009/10/r-312.pdf.
The importance of these regional heating patterns was also reported in
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
where it is written
“regional variations in radiative forcing may have important regional and global climate implications that are not resolved by the concept of global mean radiative forcing.”
“Regional diabatic heating can cause atmospheric teleconnections that influence regional climate thousands of kilometers away from the point of forcing.”
This regional diabatic heating produces temperature increases or decreases in the layer-averaged regional troposphere. This necessarily alters the regional pressure fields and thus the wind pattern. This pressure and wind pattern then affects the pressure and wind patterns at large distances from the region of the forcing which we refer to as teleconnections.
The seasonal work by Judah Cohen, based on Siberian snow cover, could be an an important new addition to our understanding of teleconnections in the climate system associated with regional variations in diabatic heating and cooling.