Thursday, September 29, 2005

Hurricanes, global warming, and global politics

Dáithí Stone and Dave Frame

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The devastation wrought by hurricane Katrina and the subsequent development of hurricane Rita have invited speculation about the role of greenhouse warming in the frequency and intensity of hurricanes.

Over the last decade many scientific studies have attempted to examine the links between the two.

This index is plausibly linked with observed climate signals, including multi-decadal cycles in the north Atlantic and north Pacific, and global warming.

The results suggest that continued warming may lead to an increase in hurricane destructiveness, which, combined with the accumulation of coastal risk that has resulted from urbanisation along vulnerable coasts, may lead to a substantial increase in socio-economic damage over the coming century.

New techniques available to researchers which exploit the probabilistic turn in climate science can, in some instances, allow us to examine the degree to which an event becomes more or less common in a world with increased greenhouse gases.

Peter Stott and co-workers applied this technique to the European summer 2003 heatwave and concluded that the risk of such a heatwave was strongly amplified in our 2003 (378 parts per million [ppm] CO2) world, when compared to a non-industrial world (278ppm).

This is a softer sort of causal link than the sort of deterministic cause-effect chain that people customarily associate with science, but the complexity which characterises the earth system make such determinism elusive.

The most literal sense of global greenhouse warming is that the Earth's average surface temperature is expected to rise by a few degrees over the coming century because of increasing atmospheric abundances of greenhouse gases.

But climate impacts are felt on a range of scales beneath this: El Niño affects much of the Pacific region; the heatwave that beset Europe in 2003 was pretty much continent-wide; and hurricane Katrina affected one large city and the surrounding regions.

Where risks remain constant we can continue as before; when risks change, we need to try to quantify the magnitude of those changes and adapt accordingly by figuring out what the new odds are.

Summarized by Copernic Summarizer

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