burden of proof

It's curious that economists, planners, politicians and mad hatters are prepared to accept the outcomes of  imperfect forecasting models as justification for substantial investment of public money in roads and other infrastructure needed to keep cities ticking over, while some of the same people won't accept action on climate change on the grounds that climate models are flawed.

Time and again transport models have been wrong in predicting how many people will drive on a new road, park in a public garage or take the bus. We transport planners know the limitations of the data that goes into the models, and we know that past trends can't always be translated into future patterns. We also know that the models are crude tools that in many cases don't tell us anything about how best to achieve policy objectives. We know all this, yet we are happy to give the decision-makers our numbers as a basis for deciding where to put your money. And they take comfort in recieving our numbers. Weigh up the costs and benefits, and make the call.

Why is it, then, that we are told not to risk damaging the economy with strategies to reduce carbon emissions on the grounds that science hasn’t proven beyond a shadow of doubt that carbon is the primary cause of anthropogenic climate change, and that global warming will damage the economy and human support systems if we don't do something about it? As pointed out in this article in LiveScience, science is never expected to "prove" a theory before the theory is acted upon:

Science simply arrives at the best explanation of how the world works. Global warming can no more be “proven” than the theory of continental drift, the theory of evolution or the concept that germs carry diseases.

We have to rely on the accumulation of miscellaneous bits of evidence - some of it circumstantial, some of it of debatable integrity - and at some point, make a call. It seems that this year, that point has been reached. Most of the world has moved on from debating the science and is focusing on response strategies. Which is not to say that the science no longer matters, as some have suggested. We need to improve our understanding of climate change cause and effect as we continue to refine our responses. But global public opinion has shifted from "no way" to "how". That's one giant leap for mankind.