The 18th United Nations climate change conference (COP18) has opened in Doha, the Qatari capital.
For the next fortnight, up to 17,000 people will attend the conference. Delegates will be negotiating a new global deal on climate, but there are ongoing tensions between rich and poor countries.
A central issue at the summit is the the problem of "hot air" carbon permits.
The term refers to attempts by some wealthy countries to carry over unused carbon permits so they can be offset against future cuts.
Developing nations say this is unfair and reduces the value of any commitment to reduce carbon dioxide.
South African foreign minister Maite Nkoana-Mashabane officially handed over the COP presidency to Qatar’s Abdullah Al-Attiyah here at the Qatar National Convention Centre.
After brief speeches by both, UNFCCC executive secretary Christiana Figueres pointed out the "unique" location of this year’s COP.
"Each COP is unique - and this is no exception," she said.
"This is the first time the COP is being held in the Gulf region. On this historic occasion, the Gulf region has an unequaled world stage to showcase the contributions being made to reduce the Gulf’s food and water vulnerabilities, to put regional energy growth on a more sustainable path and to build a safer, stronger and more resilient energy future for all countries."
As Qatar welcomes world leaders to the conference, its own environmental record has come under criticism as a major contributor to greenhouse gases.
The climate talks have placed a spotlight on the Gulf Arab state, which produces nearly 50 tonnes a year of carbon dioxide for each of its 1.6 million residents.
Environmentalists question whether Qatar has the diplomatic muscle - and, more importantly, the political will to play a positive role in the critical two-week negotiations.