Re: [asa] Creation Care

Yes, Don, there's been a lot of progress lately. See the correlations of models, temperature, and sea level in http://www.columbia.edu/~jeh1/SierraStorm.09Jan2007.pdf

I also wanted to follow up on a comment someone made recently but I can't find that post right now. I think it was Rich, but I'm not sure, who mentioned the few thousand year mismatch in temperature cycles between climate models and historical data. Last week Jim Hansen told me a story about how this was recently resolved. One of the inputs to the model is the Mankovitch cycle and the 21,000 year cycle of the perihelion vs the direction of tilt of the earth's axis. The assumption in the model was reasonable, it seemed, that the maximum solar energy absorbed in the northern hemisphere coincided with the time when the perihelion occurred in summer (for the northern hemisphere). For a long time, the paleoclimatologists puzzled over the timelag of the models with respect to the data. Finally, they realized that the maximum solar energy absorption was actually when the perihelion occurred in the springtime. That shortened the snowcover, changed the albedo, and maximized the solar energy flux for the entire season until the next winter. This was confirmed with more detailed modeling of that specific effect. When the modified assumption was changed in the global model, the discrepancy disappeared and the match is now remarkable!

Beautiful example of science at work.

Randy
  ----- Original Message -----
  From: Don Winterstein
  To: asa@calvin.edu ; Randy Isaac
  Sent: Tuesday, January 23, 2007 4:19 AM
  Subject: Re: [asa] Creation Care

  Randy wrote: "I learned that there were no competing models and that the basic climate model, complex though it was, fit the data well enough to be considered the right model. That is, the community is not in the uncertainty phase since there is a framework of understanding that explains the key features of climate for the last 420,000 years."

  I need clarification on this. Wikipedia says, "The causes of ice ages remain controversial for both the large-scale ice age periods and the smaller ebb and flow of glacial/interglacial periods within an ice age." This Wikipedia statement is consistent what I heard throughout my 25-year career as an Earth scientist. Ice ages are certainly key features of climate, they've occurred within 420 000 years, and there is no agreement on causes despite multiple possible or likely mechanisms. This implies there are competing models.

  Don

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Received on Tue Jan 23 11:10:15 2007