Monday, April 28, 2008

Fact or belief?

Two complimentary or contrasting articles on climate change from the same journal are here and here. The first suggests that global warming is real and based on the best science we have. The second suggests the science is becoming more precise but is no more accurate and that global warming remains a belief.
The first is a well-written and accessible account of how we know global warming is real. It also contains these caveats:
  • While there are uncertainties in climate projections, it is important to realize that the climate projections are based on sound scientific principles...
  • However, climate models are not empirical, based on correlations in such records, but incorporate our best understanding of the physical, chemical, and biological processes being modeled.
And it is these aspects that the second article focuses upon. Rejection of global warming is not premised upon a denial of science, but, rather, on an adherence to scientific principles:
  • ...uncertainties in the energetic responses of Earth climate systems are more than 10 times larger than the entire energetic effect of increased CO2. If the uncertainty is larger than the effect, the effect itself becomes moot.
  • ...68% of the time (one standard deviation), the projections of the models will fall within the shaded regions. It's not saying that the shaded regions display the physical reliability of the projections. The shaded regions aren't telling us anything about the physical uncertainty of temperature predictions. They're telling us about the numerical instability of climate models. The message of the Legend is that climate models won't produce exactly the same trend twice.
  • ...the shaded regions are about the calculational imprecision of the computer models. They are not about the physical accuracy of the projections. They don't tell us anything about physical accuracy. But physical accuracy — reliability — is always what we're looking for in a prediction about future real-world events.
  • somehow the complex quintillion-watt feedbacks from the oceans, the atmosphere, the albedo, and the clouds all average out to approximately zero in the General Circulation Models. Apart from low intensity wiggles, the GCMs all predict little more than passive global warming.
  • the physical model of Earth climate in GCMs says that as CO2 increases, Earth surface temperature does little else except passively respond in a linear way to greenhouse gas forcing.
  • From clouds alone, all the IPCC projections have uncertainties that are very much larger than the projected greenhouse temperature increase. What is credible about a prediction that sports an uncertainty 20–40 times greater than itself? After only a few years, a GCM global temperature prediction is no more reliable than a random guess. That means the effect of greenhouse gasses on Earth climate is unpredictable, and therefore undetectable. And therefore moot.
  • Direct tests of climate models tell the same tale. In 2002, Matthew Collins of the UK Hadley Centre used the HadCM3 GCM to generate an artificial climate, and then tested how the HadCM3 fared predicting the very same climate it had generated. It fared poorly, even though it was the perfect model. The problem was that tiny uncertainties in the inputs — the starting conditions — rapidly expanded and quickly drove the GCM into incoherence.
  • The rapid growth of uncertainty means that GCMs cannot discern an ice age from a hothouse from 5 years away, much less 100 years away. So far as GCMs are concerned, Earth may be a winter wonderland by 2100 or a tropical paradise. No one knows.
  • So the bottom line is this: When it comes to future climate, no one knows what they're talking about. No one. Not the IPCC nor its scientists, not the US National Academy of Sciences, not the NRDC or National Geographic, not the US Congressional House leadership, not me, not you, and certainly not Mr. Albert Gore. Earth's climate is warming and no one knows exactly why. But there is no falsifiable scientific basis whatever to assert this warming is caused by human-produced greenhouse gasses because current physical theory is too grossly inadequate to establish any cause at all.
So this the heart of the matter. The best science we have uses scientific principles to develop models, that despite our best efforts, are woefully imprecise. They are not empirically based and are not physical models but mathematical ones, subject to the values that are inputted into them. In this instance, those values are both arithmetic, moral and political in form.

The results have uncertainties that compromise any predictive value of those models and should invalidate them as tools for policy development. Prudence suggests are far different response than ideological dogma:
  • correlation is not causation, and cause can't be assigned by an insistent ignorance.
  • The proper response to adamant certainty in the face of complete ignorance is rational skepticism.
  • And aren't we much better off accumulating resources to meet urgent needs than expending resources to service ignorant fears?