The problem is that only the European Union and a handful of other countries — that together are responsible for than 15 percent of global emissions — are willing to set emissions targets for a second commitment period of Kyoto.
The U.S. rejected the Kyoto accord because it didn't impose binding commitments on major developing countries such as India and China, which is now the world's top carbon emitter.
China and other developing countries want to maintain a clear division, saying climate change is mainly a legacy of Western industrialization and that their own emissions must be allowed to grow as their economies expand, lifting millions of people out of poverty.
That discord scuttled attempts to forge a climate deal in Copenhagen in 2009 and risks a recurrence in Doha, as talks begin on a new global deal that is supposed to be adopted in 2015 and implemented in 2020.
Environmentalists found the choice of Qatar as host of the two-week conference ironic. The tiny Persian Gulf emirate owes its wealth to large deposits of gas and oil, and it emits more greenhouse gases per capita than any other nation.
Qatar has not even announced any climate action in the U.N. process, and former Qatari oil minister Abdullah Bin Hamad al-Attiyah didn't do so when he opened the conference Monday.
"We should not concentrate on the per capita (emissions). We should concentrate on the amount from each country," al-Attiyah told reporters. "I think Qatar is the right place to host" the conference, he said.
AP Environment Writer Michael Casey contributed to this report.
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