U.S. defends warming record

The U.N. process is often criticized, even ridiculed, both by climate activists who say the talks are too slow and by those who challenge the scientific near-consensus that the global temperature rise is at least partly caused by human activity, primarily the burning of fossil fuels like coal and oil.

The concentration of greenhouse gases such as carbon dioxide has jumped 20 percent since 2000, according to a U.N. report released last week. The report also showed that there is a growing gap between what governments are doing to curb emissions and what needs to be done to protect the world from potentially dangerous levels of warming.

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