The truth is, evidence of man's impact on climate remains maddeningly elusive, in part because man's impact on climate is so small as to be hard to disentangle from natural variability. This is not Mr. Gore's position, of course. If anything, however, the case for action has become less closed since he pronounced it closed in 1989, if only because of the huge sums and manpower poured into the subject to little avail.
In retrospect, a significant moment was the falling apart or debunking of two key attempts seemingly well-suited to clinch matters for a scientifically literate public. One, the famous hockey stick graph, which suggested the temperature rise of the past 100 years was unprecedentedly steep, was convincingly challenged. The other, a mining of the geological record to show past episodes of warming were sharply coupled with rising CO2 levels, fell victim to a closer look that revealed that past warmings had preceded rather than followed higher CO2 levels.
These episodes from a decade ago testified to one important thing: Even climate activists recognized a need for evidence from the real world. The endless invocation of computer models wasn't cutting it. Yet today the same circles are more dependent than ever on predictions made by models, whose forecasts lie far enough in the future that those who rely on them to make policy prescriptions are in no danger of being held accountable for their reliability.
For a while the media could patch over the scientific shortfall by reporting evidence of warming as if it were evidence of what causes warming. Inconveniently, however, just as temperature-measuring has become more standardized and disciplined and less reliant on flaky records from the past (massaged to the Nth degree), the warming trend seems to have faded from the recent record.
We could go on. But from our first column on this subject, we have been convinced that the scientific questions are interesting and irrelevant, since it was never in the cards that Western societies (or Brazil or India or China) would sacrifice economic growth for the uncertain benefits of fighting climate change. Unable to do anything meaningful about climate change, policy would therefore default to satisfying the demand of organized interests for climate pork.
Isn't that, however much he may be distracted by feelings of sincerity, exactly the economic function of Mr. Gore today?
The Wall Street Journal November 12,2009