DOHA, Qatar — Rich countries are to blame for climate change and should take the lead in forging a global climate pact by 2015, a deadline that “must be met,” the head of the United Nations said today.

At the international climate talks in Qatar, U.N. Secretary-General Ban Ki-moon said it was “only fair and reasonable that the developed world should bear most of the responsibility” in fighting the gradual warming of the planet.

Ban’s comments echoed the concerns of China and other developing countries, which say rich nations have a historical responsibility for global warming because their factories released carbon emissions into the atmosphere long before the climate effects were known.