Re: [asa] Creation Care

Thanks for pointing to Hansen's presentation. Lots of interesting pictures and graphs.

I acknowledge my ignorance of climate modeling, but I've been involved in one way or another with geophysical modeling for most of my career as a scientist. This experience makes me skeptical of climate modeling.

Geophysical modeling as I knew it concerned primarily the evaluation of seismic wave behavior in sedimentary rocks. Geophysicists are usually able to come up with impressive models of subsurface rocks from seismic data; but when you look closely at the details, you often find they did a little stretching here, a little bending there, and a little tweaking over here. The scientists of course had perfectly "reasonable" explanations for all their manipulations, but still the manipulations were necessary to make the fit impressive. If you look even more closely, you find cases where the fits really aren't good at all. Sometimes the impressive models turn out to correspond well with reality, sometimes poorly. Earth is messy.

Is climate less messy than subsurface rocks? Superficially it seems likely to be rather messier.

Seismologists fit literally thousands of different models to thousands of different data sets involving millions of seismic traces. Climatologists really have only a single data set to fit: the historical record. I suspect many geophysical modelers of seismic data would consider the task of fitting such a single trace to be relatively straightforward: You just tweak what you think are all the relevant parameters until you get a good match. This doesn't mean that your calculations have considered all the relevant parameters, it just means that, for the parameters you chose, you could get an impressive match. If the history had been different, the match might not have been as good. The good match also does not necessarily mean your model can give good predictions.

Were I to seriously investigate climate modeling, one of the first things I'd want to do is invite the graduate students who're doing the work to the local bar long enough to get them to tell me how they work and what they think!

Many of Janice's posts on this topic seem to go over poorly with the majority, but I think it's important when dealing with Earth science predictions for someone to vociferously take the minority view. With something so messy, there are many ways to go wrong. It's good to be a bit skeptical of "beautiful fits to data." Earth science is not physics.

Getting back to seismology: Everyone in the West bases seismic models on acoustic impedance changes. There's essentially complete consensus. Halfway through my career a Russian scientist (aided by his beautiful and intelligent daughter, who's fluent in English) came on the scene with models based on radically different assumptions. We were unable to find fault with his assumptions or models. I eventually concluded that both kinds of models may be relevant, some more so in certain environments than others; and some of our unexplained results might be better explained in terms of the Russian's model. Recently his daughter (now married to Werner Herzog) informed me that her father had been given a lifetime achievement award by Vladimir Putin. Yet to this day he's had very little influence in the West.

How about having two radically different models that can explain your data? Who would have guessed?

Don

  ----- Original Message -----
  From: Randy Isaac<mailto:randyisaac@comcast.net>
  To: asa@calvin.edu<mailto:asa@calvin.edu>
  Sent: Tuesday, January 23, 2007 8:09 AM
  Subject: 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<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<mailto:dfwinterstein@msn.com>
    To: asa@calvin.edu<mailto:asa@calvin.edu> ; Randy Isaac<mailto:randyisaac@adelphia.net>
    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 Wed Jan 24 05:06:09 2007