Monday, May 5, 2008

Predictive Power Of Computer Climate Models Proving To Be Nil......

Computer models of anything are fine, for what they are.....good entertainment. But when it comes to predicting actual climate change, they are falling far short of providing the confidence needed for making policy decisions. See the following article by an expert on the subject. GP

May 01, 2008
Global Cooling Consistent With Global Warming
By Roger Pielke Jr., Prometheus
If global cooling over the next few decades is consistent with model predictions, then so too is pretty much anything and everything under the sun.

This means that from a practical standpoint climate models are of no practical use beyond providing some intellectual authority in the promotional battle over global climate policy. I am sure that some model somewhere has foretold how the next 20 years will evolve (and please ask me in 20 years which one!). And if none get it right, it won’t mean that any were actually wrong. If there is no future over the next few decades that models rule out, then anything is possible. And of course, no one needed a model to know that.

Don’t get me wrong, models are great tools for probing our understanding and exploring various assumptions about how nature works. But scientists think they know with certainty that carbon dioxide leads to bad outcomes for the planet, so future modeling will only refine that fact. I am focused on the predictive value of the models, which appears to be nil. So models have plenty of scientific value left in them, but tools to use in planning or policy? Forget about it.
Read more here.

Icecap Note: This relates of course to the paper in Nature that suggest cooling may occur til around 2020 due to ocean changes, something we have talked about here on Icecap for many months. Recall recently Smith et al from UK Met Office & Hadley Center in Nature 2007 made a bold prediction that in the next decade half the years after 2009 will be warmer than the ‘hottest year’ which is 1998 based on models. Models recently were rerun at NASA Goddard to try and explain why the ozone hole wasn’t vanishing and to no surprise they found with better modeling they now see the light and that the hole won’t start shrinking til 2018 and disappear til 2068.

The modelers can find a way to show anything. As the famous mathematical physicst von Neumann said “If you allow me four free parameters I can build a mathematical model that describes exactly everything that an elephant can do. If you allow me a fifth free parameter, the model I build will forecast that the elephant will fly.” That is by the way why many of us more senior climatologists and meteorologists prefer to work with real data and correlate factors with real data than depend on models.

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