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Old 06-02-2013, 04:29 PM
Michael Reach Michael Reach is offline
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Join Date: Apr 2013
Location: Baltimore, Maryland, USA
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Default Re: Data snooping and science

Sorry, I hadn't noticed your earlier response. If I understood Silver right (it's been a few months), he suggested that there may have been enough random variation in the last decades of the twentieth century, say from 1970-2000 when they were building the models - and tweaking the parameters to get them right - to cause the models to run "hot". That was the training data, so to speak. Hansen's original predictions preceded the hot spell (that is, the rapid growth of temperature anomaly) at the end of the century, so his estimates were naturally somewhat lower. Now that there hasn't been the same rapid growth for a decade or so, his estimates are looking better and better.
If Silver is right, that's a classic case of overfitting.
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