Changing climate: 'Compost effect' may cause global warming to reach crisis point in 2050

The world faces a catastrophic rise in global warming in 2050 unless urgent action is taken to cut human-induced carbon emissions, a leading academic warned yesterday.

Professor Peter Cox, of Exeter University, told the Royal Geographical Society annual conference that temperatures could rise 8C by 2100 because of a "compost effect" which could see carbon dioxide levels increase 50 per cent faster than previously estimated.

Currently, around one quarter of carbon emissions are absorbed by the soil and one quarter by the oceans. It had previously been assumed that these proportions would remain the same. But Professor Cox said that global warming is damaging the soil's ability to absorb carbon emissions.

He said this vicious circle would reach crisis point in 2050 when a key threshold would be passed. After this point the land would begin to release carbon into the atmosphere. He predicted that this "compost effect" would lead to carbon dioxide levels rising from the current 380 parts per million to more than 1,000 parts per million by 2100.

Professor Cox warned that the Amazonian rainforest would be lost unless urgent action was taken to keep carbon dioxide levels below 500 parts per million. Higher levels of CO2 would see rainfall move away from the Amazon basin causing its lush vegetation to die.

In a separate report, the growing threat of climate change to Britain was highlighted yesterday with an urgent call for the reintroduction of salt marshes along the country's coasts and estuaries.

A leading academic said that action was needed to stop flooding of coastal areas as global warming produced higher sea levels.