Saturday, February 03, 2007

Grim Climate Change Report

The Intergovernmental Panel on Climate Change report which was presented yesterday is quite grim indeed.

Declaring that "warming of the climate system is unequivocal," the authors said in their "Summary for Policymakers" that even in the best-case scenario, temperatures are on track to cross a threshold to an unsustainable level. A rise of more than 3.6 degrees Fahrenheit above pre-industrial levels would cause global effects -- such as massive species extinctions and melting of ice sheets -- that could be irreversible within a human lifetime. Under the most conservative IPCC scenario, the increase will be 4.5 degrees by 2100. ...

While the summary did not produce any groundbreaking observations -- it reflects a massive distillation of the peer-reviewed literature through the middle of 2006 -- it represents the definitive international scientific and political consensus on climate science. It provides much more definitive conclusions than the panel's previous report in 2001, which said only that it was "likely" -- meaning between 66 and 90 percent probability on a scale the panel adopted -- that human activity accounted for the warming recorded over the past 50 years.

Many energy and environment experts see such a doubling, or worse, as a foregone conclusion after 2050 unless there is a prompt and sustained shift away from the 20th-century pattern of unfettered burning of coal and oil, the main sources of carbon dioxide, and an aggressive expansion of nonpolluting sources of energy.

And the report says there is a more than a 1-in-10 chance of much greater warming, a risk that many experts say is far too high to ignore. ...

The panel said there was no solid scientific understanding of how rapidly the vast stores of ice in polar regions will melt, so their estimates on new sea levels were based mainly on how much the warmed oceans will expand, and not on contributions from the melting of ice now on land.

Other scientists have recently reported evidence that the glaciers and ice sheets in the Arctic and Antarctic could flow seaward far more quickly than estimated in the past, and they have proposed that the risks to coastal areas could be much more imminent. But the climate change panel is forbidden by its charter to enter into speculation, and so could not include such possible instabilities in its assessment.

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