Climate change has already arrived

We don't have to wait for climate change - it has already arrived. It can be seen in the plants and animals around us as they adjust to the gradual rise in temperatures. "Almost all sets of data we are looking at are showing a clear signal of climate change," said Prof Chris Thomas of the University of Leeds.

He was addressing a session on the ecological impact of climate change yesterday at the British Association for the Advancement of Science's annual Festival of Science, which is being held in Glasgow.

Rising temperatures are melting away many of the world's great glaciers and mountain ice. The ice caps are also under pressure. Closer to home, however, are the small indications of change provided by fauna and flora. Literally hundreds of species of butterflies, birds and plants are either changing the way they grow or where they live in response to higher average temperatures, Prof Thomas said. "It is happening now and it is going to happen more and more."

One of the most dramatic changes will occur in the oceans with the rapid extinction of tropical corals, according to Dr Rupert Ormond of the University of Glasgow's and the University of London's marine research station on the Isle of Cumbrae. He predicated that within decades, rising ocean temperatures will destroy the corals.

"I find it very hard to avoid the conclusion that most coral will be lost in 30 to 50 years," he said. "The evidence that it is temperature is overwhelming." The result is "bleaching", where warm water and sunlight break down the symbiotic relationship between corals and photosynthesising algae, eventually wiping out the coral.

Dr Noranne Ellis of Scottish National Heritage said beech trees were leafing about two-and-a-half weeks earlier than they did in the 1940s, a response to temperature. Species in the uplands, such as the snow bunting, might be driven from their habitat and out of Scotland entirely.

Climate change, she said, was even beginning to have an effect on the chemistry of both soil and water. Heavier winter rainfalls were also disturbing river beds, in the process interfering with breeding patterns of fish and other species.

Prof Thomas, who specialises in butterflies, said species such as the speckled wood and silver spotted skipper were colonising new areas, extending their range northward.

The skipper, which in the past only occupied the southern slopes of hills near south coasts, can now be found even on north-facing slopes.

"The big concern is not in Britain," he said, but in those countries with clouded forests and rainforests. Warming temperatures have driven the golden toad out of the Monteverde rainforest in Costa Rica, he said. There will be nowhere for the rainforest species to go if climates change in these habitats.

Prof Andrew Watkinson of the University of East Anglia painted a picture of what our climate might be like in a few decades' time. "What we are predicting is more rainfall in the winter and less in the summer." He said there would be far fewer winter days with temperatures below zero by the end of the century. "This will have consequences for organisms," he said.