I just read Ronald Bailey's article "Ugly Climate Models" to which co-blogger David Henderson linked below. From what I can gather, it looks like it's clear that the world is getting hotter and that human activity is contributing to it. Like David Friedman, I'm not convinced that it's going to be unambiguously bad.
I've been thinking over the last few days about ways in which people adjust to changes in climate and the like. As the climate warms, we might expect to see people reduce their demand for relatively resource-intensive warm clothing. Demand for heating oil will go down in exceptionally cold regions. The net effect on mortality will be ambiguous but likely positive: Indur Goklany argues that extreme cold kills far more people than extreme heat.
Norms will change. People are always coming up with new ways to solve problems, and with the global explosion in information technology I think we're just scratching the surface of what a truly global conversation will mean. In grad school, a friend told me his father's winter rule of thumb: if you're comfortable indoors without socks on, you have the heat on too high. Resources are needed to produce the socks, but I would be surprised if the net climate impact for extra socks is higher than the net climate impact of home heating.
As things get warmer, new types of vegetation will creep northward. Most of what I've seen has focused on bad flora and fauna, but again, this will be offset to at least some extent by the emergence of "good" flora and fauna. To use one example, we're doing an experiment with our kids in which we're going to learn why people don't grow avocados in central Alabama. We planted avocado pits, and they sprouted, but suffice it to say they don't do well in cold weather and will probably be dead before Spring. Changes in agricultural conditions will likely mean changes in the relative prices of meat and vegetable matter. Might climate change itself produce more climate-friendly diets?
I don't know. There are a lot of ways people will adjust to changing climate conditions. Some of them will be good, some of them will be bad, and in some ways ingenuity and markets mean that the system contains some of its own "automatic stabilizers" that will dampen the effects in either direction. I'll close with a quote from Friedman, who makes the most important (but most overlooked) point about the entire discussion in a post that is worth reading in its entirety (I'll even link to it again!):
The answer, I think, is that nobody knows if the net effects would be good or bad, and probably nobody can know. We are talking, after all, about effects across the world over a century. How accurately could somebody in 1900 have predicted what would matter to human life in 2000? What reason do we have to think we can do better?
Should we, for instance, assume that Bangladesh will still be a poor country a century hence, or that it will by then have followed the path blazed by South Korea, Taiwan, Singapore and Hong Kong--and so be in a position to dike its coast, as Holland did several centuries ago, or move housing some miles further inland, at a cost that can be paid out of petty change? Should we assume that population increase makes agricultural land more valuable and the expansion of the area over which crops can be grown more important, or that improvements in crop yield make it less? While there may be people who believe that they know the answer to such questions, the numbers required to justify such belief are at best educated guesses, in most cases closer to pure invention. Someone who wants to prove that global warming is bad can make high estimates for the costs, low estimates for the benefits, and so prove his case to his own satisfaction. Someone with the opposite agenda can reverse the process and prove his case equally well.