Monday, February 12, 2007

Accepting Climate Change

Sunday's Times had an essay on the recent IPCC report and the changes that the author has observed in reactions to climate change since he first began covering the subject. For one thing, the climate science supporting warming has grown in certainty:

  • In 1990, in its first report, the panel found evidence of global warming but said its cause could be natural as easily as human.
  • In a landmark 1995 report, the panel altered its judgment, saying that “the balance of evidence suggests a discernible human influence on global climate.”
  • In 2001, it placed the probability that human activity caused most of the warming of the previous half century at 66 percent to 90 percent — a “likely” rating.

The author also points out the diverse types of evidence cited by the review: rising temperatures, more droughts, more violent precipitation events, and fewer frosts, for example. We also now have a much longer climate record for comparison. The endpoint for warming is sobering.

Some experts believe that no matter what humans do to try to rein in greenhouse gas emissions, a doubling is all but inevitable by 2100. In this view, the urgent task ahead is to keep them from rising even higher.

If the concentrations were to triple, and even if they just double, there is no telling at this point what the world will really be like as a result, except to speculate that on balance, most of its inhabitants probably won’t like it much. If James E. Hansen, one of the bolder climate scientists of the last two decades, is right, they will be living on a different planet.

I will probably have some more to say about the report in a future post when I have a chance to review it thoroughly. In the mean time, take a look at the linked essay.