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Wednesday, May 14, 2008

Natural changes pinned to warming

by Richard Black, Environment correspondent, BBC News website,

Emperor penguins. Image: BBC
A decline in some Emperor penguin populations is blamed on warming

Major changes in the Earth's natural systems are being driven by global warming, according to a vast analysis.

Glacier and permafrost melting, earlier spring-time, coastal erosion and animal migrations are among the observations laid at the door of man-made warming.

The research, in the journal Nature, involves many scientists who took part in last year's Intergovernmental Panel on Climate Change (IPCC) report.

It links warming and natural impacts on a tighter regional scale.

We need to get our act together, both for adaptation to changes that are happening now, and for mitigation to reduce long term risk
Cynthia Rosenzweig

Changes in the Earth's physical and biological systems since at least 1970 are seen in regions which are known to be warming, it concludes.

The researchers assembled a database including more than 29,500 records that documented changes seen across a wide range of natural phenomena, such as:

  • the earlier arrival of migratory birds in Australia
  • declining krill stocks around Antarctica
  • earlier break-up of river ice in Mongolia
  • genetic shift in the pitcher plant mosquito in North America
  • declining productivity of Lake Tanganyika
  • melting Patagonian ice-fields

"Since 1970, there's been about 0.5C, 0.6C of warming - that's the global average," said Cynthia Rosenzweig from Nasa's Goddard Institute for Space Studies (Giss) in New York.

"And look at all the effects this relatively low amount of warming has had.

"It reveals the sensitivity to relatively low amounts of warming in many physical and biological systems," she told BBC News.

Deeper look

Dr Rosenzweig was one of the scientists who played a leading role in compiling the section of last year's IPCC report dealing with climate impacts.

This analysis uses more sets of data, and different techniques for attributing the root cause of the observed changes.

Francis Zwiers from Environment Canada and Gabriele Hegerl from the University of Edinburgh, who reviewed the work for Nature, commented: "(This) is the first (study) to formally link observed global changes in physical and biological systems to human-induced climate change, predominantly from increasing greenhouse gases".

About 90% of the changes documented were consistent with rising temperatures at regional scales, the researchers found.

Great tit chick. Image: TA Wilkin

And in virtually all cases, global warming was the primary driver of change, as opposed to natural variability or other human impacts such as deforestation or water pollution.

Not all of the changes observed in nature are damaging to all creatures - for example, last week researchers showed that some British birds are able to handle the earlier arrival of spring pretty well.

But others, such as the loss of Arctic sea ice, will clearly have a detrimental effect on parts of the living world.

And phenomena such as the melting of mountain glaciers are likely to have major impacts on societies that depend on them for drinking water.

"This provides up-to-the-minute impetus that climate change is changing how the world works," said Dr Rosenzweig.

"We need to get our act together, both for adaptation to these changes that are happening now, and for mitigation to reduce long-term risk."

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