Is GDP impact the best way to measure global warming's effects?

Roger Pielke (from the science policy blog Prometheus) has an interesting point to make about the relative weight the IPCC is placing on mitigation as the best way to deal with global warming. Roger points out that if you use GDP as the primary measure of the effect of global warming, which both Nicholas Stern and the IPCC do, then the inescapable conclusion from the IPCC's own report, is that how the world chooses to develop has a much greater effect on global GDP than global warming, making the mitigation of global warming a relatively poor investment compared to investing in better development solutions.

“To put this another way, from the standpoint of global GDP decisions that the world makes that make one storyline more likely to occur than another are between 19 and 74 times more important than decisions that are made about greenhouse gas emissions, under the assumptions provided by the IPCC!”

It begs the question, is global GDP the best way to measure the impact of global warming? Given that this is the primary 'stick' that the Stern Report used to ensure we all got the message about global warming, it would seem that global warming alarmists would think it must be ... yet the IPCC themselves believe that making better development decisions can have a much greater impact on this figure than global warming!

Roger's not the first person to point this out, Arnold Kling at the economics blog EconLog has made a similar point. He also find the statistical basis for global warming more than a little suspect:

“These statistical projections are highly uncertain. In fact, I do not think that the climate modelers have anywhere near enough data to make usable predictions.

99 percent of the people who knowingly tell you that global warming is real and that the science is conclusive have no clue about statistical modeling. The statistical challenges of climate modeling that scientists understand among themselves are quite different from the popular conceptions that imagine some concrete certainty. To paraphrase Winston Churchill, never before in the field of public policy have so many had such confidence in model forecasts based on so few meaningful observations.”

Finally, the real reason why human caused global warming has been pursued so vigorously may well be more political than environmental (or even religious), with some similarity to the way eugenics obtained the status of 'settled science'*:

“One must ask, "How in the world did university researchers come to conclusions that defended this outrageous affront to society?" A look back at the research concluded that the researchers adjusted their outcomes to support the theory of those paying for the research. This is not unusual. It is very easy to believe that the settled science regarding climate change is just as suspicious, and indeed may be another example of pseudo-science capturing the imagination of politicians, actors and the media elite who have a desperate need to embrace some "science" which may force us to change the way we live our lives. H. L. Mencken once wrote, "The urge to save humanity is almost always a false front for the urge to rule it." We see pictures of huge blocks of ice crashing into the sea from the Antarctic Peninsula, which comprises about 2 percent of the continent. The fact that the remaining 98 percent of Antarctica is growing by 26.8 gigatons of ice per year is ignored.”

* This is perilously close to equating it with the Nazis, a dead giveaway of an uncertain argument, however the point is well made by Rep. John Linder.