Evidence of a warmer world is all around

Some are of enormous scale, others are tiny ­ but there is no doubt that changes in nature that can be attributed only to a warming world are now becoming increasingly visible across the earth.

Some are of enormous scale, others are tiny ­ but there is no doubt that changes in nature that can be attributed only to a warming world are now becoming increasingly visible across the earth.

The rejection this week by the American President, George Bush, of the argument that climate change is happening not only flies in the face of a growing consensus among scientists ­ it ignores what is taking place before our eyes.

From the melting of large areas of ice in both polar regions to alterations in the behaviour of insects, birds, plants and fish, there are now many unfamiliar events happening in the natural world, which, if they cannot yet be directly linked to climate change caused by human action, can certainly only be explained by the steadily rising ambient temperatures. Most of these happenings have only started to become noticeable in the past 10 years, although they may have begun earlier.

The melting of the ice-caps in the polar regions is perhaps the most spectacular. In the Arctic, the sea-ice has lost 40 per cent of its depth in less than three decades, and has lost 14 per cent of its volume since 1978 ­ an area the size of Texas.

An area the size of Wales is disappearing every year; Britain's climate research institute, the Met Office's Hadley Centre, predicts it will all have gone by 2080, if not before.

Wildlife is already becoming affected: body weights of polar bears in Hudson Bay are declining as their hunting season shortens with the longer periods of open water; they feed on ringed seals, which they can catch only on ice.

In the Antarctic, where the great mass of ice is sitting on land, there have recently been several collapses of the ice shelves that jut out into the sea. The death of the Larsen A shelf was spectacular ­ in a few days in January 1995, 1,300 square kilometres broke up.

Two months ago, the explorer and yachtsman Sir Peter Blake called ministers attending the governing council of the United Nations Environment Programme to say that he had just sailed 100 miles through open water that had been frozen for hundreds of thousands of years. The King George VI ice shelf at the base of the Antarctic peninsula was breaking up, he told them.

But significant changes that only warming can explain can be seen closer to home. Britain's spring is starting earlier, as records kept by nature lovers and amateur observers haveproved.

The orange-tip butterfly, for example, is now emerging about 11 days earlier than it was 20 years ago and the leaves on oak trees at a monitored site in Surrey are emerging about three weeks earlier than when records began in 1947. Spring's harbinger, the swallow, is arriving at eight different bird observatories that keep records an average of six days earlier than in the 1970s.

Mobile types of wildlife such as butterflies are also extending their range northwards within Britain, and increasingly, species whose range had previously ended south of the UK in continental Europe are being seen here: they include dragonflies, bats and birds.

This phenomenon is most clearly visible in fish catches: species from southerly latitudes that until recently were rarely or never seen in British waters are now increasingly turning up in fishing nets. Sunfish, triggerfish, torpedo rays and sea horses from the Mediterranean or further south in the Atlantic are now regularly taken off south-west Britain, and our list of sharks is steadily growing. Sharp-nosed seven-gill sharks normally found in the Caribbean and the Mediterranean were seen off the Isles of Scilly in August 1999 and in the same summer a great white shark, the model for Jaws, was seen off the coast of Cornwall.

Ute Collier, climate change campaigner for the World Wide Fund for Nature, said: "Climate change is real and there is plenty of evidence that it is already happening."

Matthew Spencer, climate campaigner for Greenpeace, said: "You'd have to be blind to miss the changes that are already occurring. Some people will continue to bury their heads in the sand, but farmers, fishermen and hunters have been reporting dramatic changes to our weather for many years now."

There are further, massive weather events affecting people's lives, such as Hurricane Mitch, which devastated Honduras, or last autumn's record rainfall in Britain, which led to the most widespread flooding for centuries. While they cannot directly be attributed to climate change, they are entirely consistent with predictions of the more extreme weather global warming may bring.

And of course, there are temperatures. The 1990s were the hottest decade in the global temperature record that goes back to 1860, and an analysis of tree-rings and ice-cores over the past 1,000 years indicates that 1998 was the hottest year of the last millennium.

Don't bet on it being a record for the next one.