UN Secretary-General Ban Ki-moon, right, and chairman of the Intergovernmental Panel on Climate Change, Rajendra Pachauri, show the Synthesis Report of the IPCC, 17 Nov 2007

U.N. Secretary-General Ban Ki-moon has urged the international community to do more to fight global warming, following a new report that warns human activities may lead to abrupt and irreversible climate changes.

Mr. Ban told delegates at a United Nations conference in Valencia, Spain, there is no time to waste to address threats from climate change.

He said the U.N. report, released Saturday by the Nobel-prize-winning Intergovernmental Panel on Climate Change, shows there are concrete and affordable ways to deal with the problem.

The U.N. chief said the report also sets the stage for a breakthrough during upcoming talks on climate change in Indonesia.

The European Union's environment commissioner, Stavros Dimas, says the report's findings amount to a "stark" warning that the world must act fast to slash greenhouse gas emissions to prevent climate change from reaching devastating levels.

The report says global warming and other changes could lead to heat waves, droughts, tropical cyclones, and food and water shortages.

British Prime Minister Gordon Brown reacted to the report by pledging that Britain will lead the world in reducing carbon dioxide emissions.

He called for a plan leading to a 50 percent global cut in carbon dioxide emissions when environment ministers discuss climate change again next month at a meeting in Indonesia, on the island of Bali.

This week's five-day conference in Spain was sponsored by the International Panel on Climate Change, which shared this year's Nobel Peace Prize for its work on the global-warming problem.

Some information for this report was provided by AFP, AP and Reuters.