Connecting the Global Warming Dots
By ANDREW C. REVKIN (see graph at end)
If thought of as a painting, the scientific picture of a growing and potentially calamitous human influence on the climate has moved from being abstract a century ago to impressionistic 30 years ago to pointillist today.
The impact of a buildup of carbon dioxide and other greenhouse gases is now largely undisputed. Almost everyone in the field says the consequences can essentially be reduced to a formula: More CO2 = warmer world = less ice = higher seas. (Throw in a lot of climate shifts and acidifying oceans for good measure.)
But the prognosis — and the proof that people are driving much of the warming — still lacks the sharpness and detail of a modern-day photograph, which makes it hard to get people to change their behavior.
Indeed, the closer one gets to a particular pixel, be it hurricane strength, or the rate at which seas could rise, the harder it is to be precise. So what is the basis for the ever-stronger scientific agreement on the planet’s warming even in the face of blurry details?
As in a pointillist painting, the meaning emerges from the broadest view, from the “balance of evidence,” as the scientific case is described in the periodic reports issued by an enormous international network of experts: the Intergovernmental Panel on Climate Change, http://www.ipcc.ch/. The main findings of the panel’s fourth assessment since 1990 will be released in Paris on Feb. 2.
In the panel’s last report, ...full text