A Greener World of Changing
The vegetation poles of the greenhouse debate are defined by the greener and the browner people. The former think that a world warmed by carbon dioxide is a greener place with more abundant food, while the latter worry about advancing deserts and starvation. On first principles, it seems pretty hard to side with the browns here. As noted in earlier chapters, the prime characteristic of greenhouse heating is a warming of the winters, and, in particular, of the coldest air of the winter.
During late fall, cold air masses in the Northern Hemisphere sometimes migrate southward and eastward from Siberia or northwestern Canada, bringing an abrupt end to the growing season with the first freezing temperatures. Similarly, the last of these in the spring initiate the beginning of the growing season with the final freezing temperature before summer. Warming these, which has occurred preferentially (see Chapter 2), will tend to lengthen the growing season.
Chapter 6 provided considerable evidence for an increase in rainfall in the world's most important agricultural zone, the United States. And, as also shown in that chapter, increases in temperature have been so small compared with the increases in rainfall that indeed the surface of the planet is wetter than it used to be. It's hard to imagine how, once started, this happy differential—where increasing rain more than compensates for increasing temperature— would suddenly reverse.
If the defining characteristics of greenhouse warming are warmer winters, more rain, and longer growing seasons, what's so bad about that? Plenty, apparently.
Sometimes, the killjoys at the New York Times just can't seem to leave warm enough alone. So, after a spate of wonderfully balmy