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 Wednesday.

On the sidelines of international climate talks in Qatar, UN 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.

"The climate change phenomenon has been caused by the industrialisation of the developed world," Ban said. "It's only fair and reasonable that the developed world should bear most of the responsibility."

Many rich nations including the US and European Union say the firewall between developed and developing countries that has guided the two-decade-old climate process in the past no longer reflects the world today and isn't helpful in dealing with the problem.

Most of the emissions now come from the developing world, and China has overtaken the US to become the world's top carbon polluter.

Lord Nicholas Stern, author of the landmark Stern review of the economics of climate change, told the Guardian this week that poorer countries including China and India must step up to their responsibilities. "It's a brutal arithmetic – the changing structure of the world's economy has been dramatic. That is something developing countries will have to face up to." He added that the historic emissions of developing countries will overtake those of developed countries within a few years.

How to divide the burden of emissions cuts is at the core of discussions to create a new global climate treaty that would apply to all nations. The only binding pact so far, the Kyoto protocol, only covers the emissions of industrialised countries.

Last year, governments decided that the new treaty should be adopted in 2015 and enter force five years later. The Doha meeting is supposed to produce a work plan to ensure that the treaty is ready by 2015.

"This deadline must be met. There is no time to waste, no time to lose for us," Ban said.

"Climate change is happening much, much faster than one would understand," he added. "The science has plainly made it clear: it is the human beings' behavior which caused climate change, therefore the solution must come from us."

Ban came to the negotiations in Doha in an attempt to "accelerate the process" of shifting the world to a clean-energy pathway, and helping the most vulnerable countries adapt to inevitable warming.

Governments represented at the talks in Qatar are also discussing a second commitment period for the Kyoto protocol, whose first commitment period ends this year , as a stopgap measure until the new deal takes effect.

The United States never ratified the Kyoto protocol, partly because it didn't cover emerging economies such as China and India. For similar reasons, Canada, New Zealand and Japan don't want to be part of the extension, meaning it would only cover Europe and Australia, who account for less than 15% of global emissions.

Nevertheless, Ban said it is "imperative" that the treaty is extended, because it is "the only existing legally binding commitment when it comes to climate change."