CO2 proposals and their effects

In Copenhagen last week, policymakers pledged to keep global temperatures from rising more than 3.6 degrees Fahrenheit above pre-industrial levels. If the world's biggest greenhouse gas emitters pursue the high end of their current climate targets, by 2020 they will be 65 percent of the way toward meeting this goal. But if they stick to the lower end, they will be only a third of the way there.

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