Climate scientists warn of looming disaster

By Fiona Harvey, Environment Correspondent
Published: April 29 2009 18:59

Scientists have worked out how much greenhouse gas the world can emit in total without tipping climate change towards catastrophic levels of warming and have warned the world is on course for disaster.
Even the most drastic emissions cuts currently being discussed stand little chance of limiting global warming to safe levels, two studies by scientists in Oxford and Germany have found, prompting calls for a radical rethink on how to tackle climate change.

The findings, to be published on Thursday in the peer review journal Nature, mean that less than a quarter of the world’s proven and economically recoverable fossil fuel reserves can be burnt between now and 2050 to avoid a jump of more than 2ºC above pre-industrial levels, widely regarded by scientists as the limit of safety.
To remain on track with this “carbon budget” Canada would have to leave its oil sands untapped and Saudi Arabia would need to leave most of its oil reserves in the ground to avert disaster.
“If we continue burning fossil fuels as we do, will have exhausted the carbon budget in merely 20 years and global warming will go well beyond 2ºC,” said Malte Meinshausen, of the Potsdam Institute and lead author of one of the studies.
At more than 2ºC of warming, climate change becomes irreversible and in many cases catastrophic, according to the Intergovernmental Panel on Climate Change. Sea level rises, droughts, floods, heatwaves and more intense storms would result, and large swaths of land, including parts of southern Europe, would become unsuitable for agriculture.
The conclusion has led to calls for governments to consider more drastic measures than emissions cuts, including ways to “geo engineer” the world’s climate through untried and exotic methods such as erecting mirrors in space.
“This changes the way we think about climate change,” said Myles Allen of Oxford University, one of the lead authors. “It’s something for policymakers to chew on.”
More than 100 governments have committed to halving global emissions by 2050, and many developed countries to reducing their emissions by 80 per cent by 2050, compared with 1990 levels. But the authors of Thursday’s studies said this was unlikely to be enough.
“In theory we could just make it,” said Martin Parry, of Imperial College London. “But this is the real world, not scientific theory – and who would bet on this, given our experience with the pace of [progress] in the past?”
Once the carbon budget, which the studies put at about 1,000bn tonnes of carbon, has been used up then the world will be committed to more than 2ºC of warming unless drastic alternative action is taken.
Another danger of reaching 2ºC of warming is that the climate might surpass some “tipping points” which amplify the warming effect, resulting in much more rapid rises in temperature. Tipping points result from feedback mechanisms in the climate – for instance, as permafrost melts in Siberia it uncovers marshes which release methane, a powerful greenhouse gas, adding to the warming.
Drastic actions such as “seeding clouds” to lighten their colour and reflect more sunlight could help to cool the earth by reflecting sunlight. Other suggestions including putting a sunshield or mirror in space to deflect some of the sun’s rays.
Prominent scientists including John Holdren, President Barack Obama’s chief science adviser, have mooted such methods recently. But these would have to be carried out alongside deep emissions cuts to have an effect.
We must also adapt the world’s infrastructure – through flood barriers, improving health services and other measures – to prepare for warming far above 2ºC, according to Professor Parry and colleagues, also writing in Nature. “We should be planning to adapt to at least 4ºC of warming,” they said.
Copyright The Financial Times Limited 2009