The world's governments and top climate scientists will confirm for the first time tomorrow that global warming is drastically altering the face of the planet.

The world's governments and top climate scientists will confirm for the first time tomorrow that global warming is drastically altering the face of the planet.

The Intergovernmental Panel on Climate Change - which brings together the work of 3,000 top experts in the field - is putting the finishing touches to a huge report at a meeting in Geneva this weekend.

Scientists and government representatives on the panel were still negotiating the detailed wording of the report yesterday. But they have already agreed - after examining some 200 separate studies from around the world - that climate change is having a "discernible impact" on the earth.

Their conclusions - the result of three years' work - come after another report by the panel finalised last month which in effect ended two decades of debate about global warming by concluding that climate change posed twice as great a threat as had previously been believed and firmly pinned the blame on pollution, largely from the burning of fossil fuels.

While the first report focused on whether the world's climate was actually heating up, the new one concentrates on the effects it is having on the ground.

The panel has been particularly struck by dramatic evidence of melting ice in the Arctic and Antarctic, and in mountain glaciers. Research shows that the Arctic ice-cap is now little more than half as thick as it was a quarter of a century ago, and that its area is shrinking rapidly.

Earlier this month, the yachtsman and explorer Sir Peter Blake made a dramatic phone call from the Antarctic to ministers attending the governing body of the UN Environment Programme to announce that he had just sailed through 100 miles of sea that had been frozen solid for hundreds of thousands of years.

Three Antarctic ice-shelves melted away during the 1990s and two others are expected to break up soon, while glaciers in the world's mountains are now smaller than at any time in at least the last 5,000 years. Glaciers in the Alps and the Caucasus have lost half their ice over the past 100 to 150 years. A fifth of those in the eastern Himalayas have vanished altogether, along with two-thirds of those in Montana's Glacier National Park.

The scientists have also been impressed by evidence that spring is coming earlier, and autumn arriving later. Studies in Britain show that the onset of autumn is slipping back by two days every decade, while spring is beginning six days earlier.

Two islands in the Pacific Ocean's Kiribati archipelago have vanished beneath the rising seas, and 16 per cent of the world's coral reefs died in just nine months in 1998 when water temperatures in parts of the tropics exceeded all records.