Raising the Climate Stakes

Consider the case closed on global warming. The assessment released on Feb. 2 by the U.N.'s Intergovernmental Panel on Climate Change (IPCC) concluded for the first time that evidence of the earth's rising temperatures was "unequivocal"—and that this warming was more than 90% likely the result of human activity. We are locked into some amount of climate change: the IPCC reported that even if we managed to end all greenhouse-gas emissions today, the earth would continue to warm through the rest of the century because of the amount of carbon we have already added to the atmosphere. But if the 600 international scientists who authored the assessment have fingered the culprits behind global warming, the question now becomes how the world will respond. The policy debate will be even more contentious than the scientific one. China, which could become the world's largest carbon emitter by 2010, reiterated on Feb. 6 that it wants First World polluters to take primary responsibility for cutting emissions—a stance that doesn't sit well with the U.S., which refuses to give large developing countries like China a pass. But as the IPCC report shows, the price of inaction will be enormous for all of us.

Temperatures
Depending on greenhouse-gas emissions, global temperatures will rise between 1.1°C and 6.4°C by 2100. If carbon levels double from the pre-industrial norm—something many experts say is a lock—the IPCC believes the mercury will rise by about 3°C, accompanied by longer and more intense heat waves.

Sea Levels
The IPCC predicts a rise in sea levels of 18-59 cm. But the assessment doesn't account for the possibility of accelerated glacial melting posited in a recent Science study, which estimated that seas could rise as much as 1.4 m by the end of the century—enough to swamp low-lying coastal cities.

Hurricanes
The IPCC said it's "more likely than not" that man-made factors are responsible for tropical storms' increased intensities—a much stronger statement than in the past. The World Meteorological Organization said last November that it could not link stronger storms to global warming.

Air Pollution
Surprisingly, the report suggests that by reflecting solar energy, visible airborne particles like sulfates from coal-burning power plants could actually have a cooling effect. But while better filters are reducing visible air pollution around the world, invisible—and harmful—carbon emissions are on the rise.

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