A British experts report on climate change warns that failure to curb global warming could trigger worldwide economic devastation, with poor countries hit first and hardest.  Prime Minister Tony Blair called for urgent international action.

Prime Minister Blair said the scientific data is overwhelming - the world is getting warmer and greenhouse gas emissions are largely to blame and that if the trend goes unchecked the consequences could prove disastrous.

"This disaster is not set to happen in some science fiction future many years ahead, but in our lifetime," reminded Mr. Blair. "Unless we act now, not some time distant, but now, these consequences, disastrous as they are, will be irreversible."

Mr. Blair spoke at the launch of the Stern Report - a 700-page review of climate change and its economic impact. The report's author, Nicholas Stern is a senior government economic advisor and former chief economist for The World Bank.

Stern warns that unchecked global warming could push world temperatures up by five degrees Celsius over the next 100 to 150 years, causing an increase in severe droughts, heavy flooding and potentially displacing hundreds of millions of people.

Stern points out that even a slight temperature shift will have dramatic consequences on where and how we live.

"Further, the impacts are inequitable, poor countries will be hit hardest and earliest when it is the rich countries which are responsible for three-quarters of greenhouse gases currently in the atmosphere," he said.

But, Stern predicts no one will be spared and failure to act now could disrupt world economic and social activity - in a way comparable to the world wars and great depression of the last century.

Stern says that taking "bold and decisive" action now to cut greenhouse gases would cost about one percent of gross domestic product, or GDP.

"This is equivalent to paying on average, one percent more for what we buy. That's manageable," added Nicholas Stern. "We can grow and be green."

Thirty-five industrialized nations have signed the Kyoto Protocol, which obliges them to cut carbon emissions. However, the United States did not sign on with the Bush administration arguing it would negatively impact jobs and economic growth. The United States remains the biggest producer of greenhouse gases, but emissions from emerging economic powers such as China and India are also dangerously on the rise.

Britain is among a handful of industrialized nations to have cut its greenhouse gas emissions. Prime Minister Blair said while Britain could lead by example, the effort must be global.

"This issue is the definition of global interdependence. We have to act together," urged Mr. Blair. "This is an international challenge and in the end only an international solution will meet it and overcome it."

The Kyoto Protocol expires in 2012. United Nations-sponsored climate talks begin in Nairobi next week to focus on a successor. But, experts point out that any successful future agreement must include the major greenhouse gas producers.

Britain is considering new so-called "green taxes" on high emission vehicles and budget airline fares and Finance Minister Gordon Brown has proposed new European Union emission cuts of 30 percent by 2020. Brown also announced that former U.S. Vice President Al Gore will serve as a special advisor to the British government on environmental issues. Mr. Gore is an ardent environmental activist and recently produced a documentary, An Inconvenient Truth, which focuses on climate change.