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.
Environmentalists found the choice of Qatar as host of the two-week conference ironic. The tiny Persian Gulf emirate owes its wealth to large resources of gas and oil and emits more greenhouse gases per capita than any other nation.
Yet it hasn't 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 added.
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.
The goal of the U.N. talks is to keep the global temperature rise under 2 degrees C (3.6 F), compared to pre-industrial times.