The heat is on, in the world's warmest year

British scientists warn that by 2050, 100 million more people could be facing extreme drought due to mankind altering the climate. And this year is set to be the world's warmest, according to a Met Office report released yesterday. Nicholas Schoon and Colin Brown report on a grim forecast.

With three days left before the UN Climate Treaty summit starts in Kyoto, Japan, the British Government stepped up the international pressure for cuts in greenhouse gas emissions with a grim report on the changes in store for the next century.

Tropical forests, already under pressure, will shrink in a warmer world and their ability to soak up the extra carbon dioxide humanity is putting in the atmosphere will be diminished - tending to accelerate the warming.

Huge sums will have to be spent on new coastal defences as sea levels gradually rise. If not, by 2080 about 200 million people will be seriously endangered by flooding. By then, the climate change will also increase the risks of starvation for 50 million people in the tropics, particularly in Africa.

The report uses the latest supercomputer simulations of climate change up to 2100 from the Met Office's Hadley Centre in Bracknell, a world leader in this specialised and arcane science.

Then it farmed out these predictions to Britain's leading university and government scientists in the fields of water resources, coastline dynamics, crop growing and plant ecology to find out what pressures the rainfall and temperature changes would bring to bear on a global population of about 10 billion people.

Thousands of copies of the report will be distributed among the delegates from 160 nations who begin gathering in Kyoto next Monday. Their task is to negotiate what action needs to be taken to slow down the change in climate caused by humanity's intervention in the atmosphere.

The Hadley Centre's best estimate for the average temperature rise over the next century of between 2.5 and 3C, if countries carry on burning more and more coal, oil and gas in a ``business as usual'' scenario. By 2080, the concentration of carbon dioxide in the atmosphere will have doubled from today's level; this is the most important of the heat-trapping greenhouse gases which fossil fuel use, forest clearing, cement manufacture and farming are pouring into the air.

Overall, there will be 3 per cent more rainfall around the world by 2050 - but it will be unevenly distributed. Much of the tropics and subtropics will become substantially drier. Mexico, North Africa, southern Europe and India are all forecast to have less water available, although China and the US are predicted to have more.

The Met Office said that, with a month of 1997 still left to go, this year was almost certain to be the world's warmest in a global temperature record stretching back to 1860.

Partly this is due to this year's particularly powerful El Nino event, a warming of the sea and air in the tropical east Pacific which occurs every few years and causes huge disruption and destruction.

But the five warmest years since global records began have all been in the 1990s. Overall, temperatures have risen 0.6C this century, and are expected to carry on rising - but more quickly.

Deputy Executive Director of Greenpeace UK, Chris Rose, said: ``All the evidence points to the fact that climate change is already happening ... the sky does indeed have a limit.''

Yesterday, in Canberra, Australia, Britain's Deputy Prime Minister, John Prescott, pleaded with that country's government to change its stance on global warming.

Australia has taken the most extreme position of any developed country, saying it wants to be allowed to raise its greenhouse gas emissions by 18 per cent between 1990 and 2010.

The European Union, which Mr Prescott is representing in a world tour of last minute climate diplomacy, says the wealthy nations must commit to a 15 per cent cut over this period. The US, the biggest polluter in absolute and per capita terms, is holding out for a stabilisation of emissions at the 1990 level by 2010.

It seems increasingly likely that the notion of greenhouse gas emission quotas which can be traded between countries will feature in any final agreement at the Kyoto talks, which last 10 days.