Indian monsoon among risks from rapid climate change

Farmers work in their paddy field on the outskirts of Agartala, capital of India's northeastern state of Tripura, July 5, 2009.

SINGAPORE (Reuters) - Rising seas, a rapid weakening of the Indian monsoon and spiraling costs of adapting to a warmer, drier world are just some of the looming risks from rapid climate change, a report for the Australian government says.

The report, "Climate change 2009, faster change and more serious risks," examines the rapid progress of climate change science in recent years and the growing threats that face billions of people around the planet.

Rising temperatures, drought and long-term drying out of farmlands in Australia, Africa, the United States, acidifying oceans and rapid switches in weather patterns all threaten to undermine societies and cost billions in damage.

"Part of the reason for suggesting that the risks are higher than we thought is that the climate system appears to be changing faster than we thought likely a decade ago," the report's author Will Steffen told Reuters on Friday from Canberra, Australia.

The report was written for the Department of Climate Change and comes five months before a major U.N. meeting that aims to seal a broader pact to fight global warming.

(The report is available here)

Many scientists have revised upwards their projections for the pace of global warming since United Nation's Climate Panel issued a major report in 2007, underscoring the increased focus on understanding the risks from climate change.

Steffen, executive director of the Climate Change Institute at the Australian National University, said drought and long-term drying out of farmlands and water catchment areas will likely cause costs to spiral as societies try to adapt.

"I think there are risks that are potentially more important. One is drought and drying risk and not just in Australia but in other parts of the world where that appears to be linked to climate change. That's going to affect water resources, it's affecting it now," he said.

He said there was now evidence of climate change being linked to the drying trends in major agricultural regions of Victoria state and southern South Australia. Evidence was much stronger for the grain-growing area of south-west of Western Australia.

SEA LEVEL

Sea level was less of a risk in the medium-term.

"Whereas sea level rise, unless there is a really fast, catastrophic event in West Antarctica, we're not going to see huge changes till the second half of the century at least," he said referring to a major collapse of the West Antarctic ice sheet.

Potentially greater threats were abrupt changes to the ocean and atmosphere that led to irreversible switches in weather or ocean patterns, so-called "tipping points."

"An example is the Indian monsoon. According to some models, that could switch into a drier mode in a matter of years," he said. More than a billion people in South Asia rely on the monsoon for agriculture and water supplies.

Steffen pointed to the accumulation of carbon-dioxide, the main gas blamed for global warming, in the atmosphere that is now near the upper range of scenarios by the U.N.'s Intergovernmental Panel on Climate Change (IPCC) in its 2007 report.

Sea level rise of more than 3 millimeters per year was also tracking near the upper range of the panel's projections. The rate at which global ocean temperatures have been rising had also been revised up by 15 percent, he said.

"I think the reports coming out at various fora are clear the system seems to moving at the upper range of IPCC projections," he said.

"That in itself is a major change in thinking. What it says is there's a sense of urgency to getting on top of this issue."

(Editing by Sanjeev Miglani)