Den stora tråden om global uppvärmning/växthuseffekten

Leading international scientists have issued a clarion call for urgent political action to curb climate change so the world does not plunge into decades of upheaval and war.

More than 2,500 experts have agreed a tough statement demanding that governments move fast as worst-case predictions of global warming start to come true.

The message to politicians, issued at an emergency climate conference in Copenhagen, warns that the world now faces 'dangerous climate change' which would be irreversible and there is 'no excuse for inaction'
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The results of failure were spelled out by former World Bank chief economist Lord Stern, whose Stern Review two years ago enumerated the cost of climate change.

'What would be the implication? Hundreds of millions of people would have to move, probably billions,' he told the conference.

'What would be the implication of that? Extended conflict, social disruption, war essentially, over much of the world for many decades.'

Speaking after giving a keynote speech, Stern said he feared that politicians had not grasped the seriousness of the crisis. "Do the politicians understand just how difficult it could be? Just how devastating four, five, six degrees centigrade would be? I think not yet. Looking back, the Stern review underestimated the risks and underestimated the damage from inaction."

In the conference centre that will also host the December UN negotiations, experts at this week's meeting presented a string of new studies that suggested global warming could strike harder and sooner than expected.

They said carbon emissions have risen more in recent years than anyone thought possible, and the world's natural carbon stores could be losing the ability to soak up human pollution.

The conference also heard that:

· A 4C rise could turn swaths of southern Europe to desert.

· Sea levels will rise twice as fast as official estimates predict.

· Modest warming could unleash a carbon "time bomb" from Arctic soils.

· A failure to cut emissions could render half of the world uninhabitable.

· Rising temperatures could kill off 85% of the Amazon rainforest.

Several experts at the conference warned that temperatures are likely to soar beyond the 2C target set by European politicians. "The 2C target is gone and 3C is difficult. I think we're heading for 4C at least," one said. Oxford University yesterday announced that it would hold a conference in September to discuss the implications of a rise of 4C or more.