Come hell or high water

Current theory suggests that if the warming effect of the buildup of carbon dioxide and other greenhouse gases reaches the equivalent of twice the preindustrial level, the atmosphere will be committed to warm by 3 to 9 degrees Fahrenheit. At the rate we are now going, that symbolic set point will probably be reached before the middle of the twenty-first century, perhaps before 2030. If fossil fuel combustion were reduced and other complementary measures were taken, that day, of course, could be delayed. No matter what is done now, we can't avoid some future climate change. Even if they were to stop all greenhouse gas emissions tomorrow, we still face an accumulated buildup from the last century whose physical effects won't be fully known at least until the end of this century. A global warming will increase urban ozone levels and the frequency of smog alerts. This chapter explores some of the possible impacts of a rapid global warming. Not all will necessarily occur. Some may be inhibited or aggravated by others, and some may be less severe than the worst scenarios suggest. But the economic costs of even scaled-down damages to human societies and natural ecosystems - which we can do something about - are likely to be tremendous, and the rate of climate change will determine just how serious those damages are