Wednesday, June 18, 2008

Fun with model trains and climate models

When I was a lad I got an electric train for Christmas. This was a big deal back in the 1950s. Retailers simply did not have the plethora of different toys now seen in the stores. The problem with the toy train was that it got boring after about 10 times circling its track. You could expand the track and build little villages around it to make it more interesting, but that involved skills I did not possess and money that my parents lacked.

I was reminded of that train when I read this article in the National Post concerning climate models. They seem to be going somewhere but never reach their destination.

The writer, Roger Pielke, Jr., a professor in the environmental studies program at the University of Colorado and a former director of its Center for Science and Technology Policy Research, makes several incisive comments.

According to Pielke, past events are not a satisfactory guide to future events, and climate models are designed to predict climate changes 20 to 30 years out and are unreliable to account for weather patterns of less than this time period. He points out that the climate models that informed the opinion of the IPCC in 1990 have now had 17 years to demonstrate that they did not accurately predict temperature change or ocean levels.

The first IPCC projections of future climate were issued in 1990, and with more than 17 years of observations since that prediction we can confidently state that the IPCC’s 1990 “best guess” overstated the global temperature increase as well as sea level rise for the subsequent two decades. But such retrospective evaluations are typically dismissed because those predictions were made using outdated models based on earlier understandings. The IPCC issues predictions for 20- to 30-year periods into the future, and updates them every 6-7 years, so in practice its current predictive capabilities can never be evaluated against real world data. As Tebaldi and Knutti observe, “climate projections, decades or longer in the future by definition, cannot be validated directly through observed changes.”

In short, climate models are interesting but perhaps useless as a tool to inform public policy regarding climate change.

On the issue of why worry if climate models are iffy instruments since it is more important to get action on climate change, Pielke says,

I have been asked by some of my colleagues why I raise these points, since action on climate change is a good thing and those questioning climate models typically are opposed to action. So what, I am told, if action on climate change is based on some exaggerations and false claims to certainty, isn’t the end goal important enough to justify bending the truth just a bit? After all, those opposed to action often show no hesitation toward exaggeration and hyperbole.

My short answer to such questions is that false claims to certainty were exactly what got us into the Iraq war. A somewhat longer reply involves explaining how both science and democracy flourish when we are open and honest about what science can actually deliver. Effective action on climate change is more likely when we fully appreciate what science can, and cannot, do. We should expect more from our scientific community.

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