Could Global Warming be Efficient?

I’ve come across some people with no scientific inclinations nor training who are worried about global warming, due mainly to Al Gore’s premonitions.  Leaving aside for the moment the debate over the science behind global warming (I’ll even concede that Al Gore is right about temperature changes), my inner economist asks, why is this necessarily bad?  Sure, I know those who see global warming as a big problem cite things like rising sea level/ coastal flooding, depredation of ozone layer (which could lead to higher incidence of skin cancers?), increased volatility and ferocity of the weather, etc., as some major costs of global warming.  But what about the potential benefits that might arise from global warming?  Some things come to mind: longer growing seasons in temperate zones leading to greater crop yields, ability to do more outside work in winter (e.g. more construction can be done due to less frozen soil),  fewer resources spent heating homes and buildings in the milder winters, better year-round ocean shipping due to less sea ice, etc.   Has anyone, to your knowledge, discussed the potential benefits of warming?  I’m not suggesting the benefits would outweigh the costs, but I’m suggesting that they might, and we as economists should get busy doing some careful studies to see if they do or don’t.  Who knows, perhaps, if Al Gore is right, the money I save on firewood, heating oil, cheaper food, etc., might just outweigh my higher air conditioning bill and the need to wear long sleeves and broad hats in August (which I do anyway ;).  Also, if the ice caps do melt away, sure, Miamians might have to move inland, but think of all that prime pasture that will open up in Greenland! 

I think that most environmentalists are undisciplined by economics.  They see changes that they perceive as bad, and then cry out for these changes to be halted.  They often don’t consider the potential benefits of the changes for other folks, nor the costs or even the feasibility of halting the changes.  Finally, they take it for granted that their values are supreme.  As for me, I would gladly trade the extinction of Polar Bears (which I have never seen except in a zoo and neither think about or care about much) for, say, a 10% increase in my real income, if that’s what global warming wrought. 

If you know of any studies about the benefits of global warming, please tell me about them!