The Greenland ice sheet melted at a record rate this year, the largest ever since satellite measurements began in 1979, a top climate scientist reported on Monday.

“The amount of ice lost by Greenland over the last year is the equivalent of two times all the ice in the Alps, or a layer of water more than one-half mile (800 meters) deep covering Washington DC,” said Konrad Steffen of the University of Colorado at Boulder.

A report released by the World Wide Fund for Nature is warning that more than half of the Amazon rainforest could be gone by 2030 as a result of increased logging and decreased rainfall.

That in turn would release some 90 billion tons of carbon dioxide into the atmosphere, accelerating global warming and affecting rainfall over the world’s major agricultural areas.

The latest international update on climate change says global warming is turning oceans acidic and threatening marine life but offers new hope - the cost of tackling carbon emissions is modest and the means to do it are already available.

The UN’s Intergovernmental Panel on Climate Change yesterday delivered its strongest warning yet, calling the rise in global temperatures “unequivocal” and its effects potentially irreversible and laying blame - with at least 90 per cent probability - on humans.

Satellite imaging has revealed that Hurricanes Katrina and Rita produced the largest single forestry disaster on record in America, an essentially unreported ecological catastrophe that killed or severely damaged some 320 million trees in Mississippi and Louisiana.

The die-off, caused by wind and later by weeks-long pooling of stagnant water, was so massive researchers say it will add significantly to the greenhouse gas buildup - ultimately putting as much carbon from dying vegetation into the air as the rest of the U.S. forest takes out in a year of photosynthesis. Also, the downing of so many trees has opened vast and sometimes fragile tracts of land to several aggressive and fast-growing exotic species that are squeezing out far more environmentally productive native species.

For scientists, global warming is a disaster movie, its opening scenes set at the poles of Earth. The epic already has started. And it’s not fiction.

The scenes are playing, at the start, in slow motion: The relentless grip of the Arctic Ocean that defied man for centuries is melting away. The sea ice reaches only half as far as it did 50 years ago. In the summer of 2006, it shrank to a record low; this summer the ice pulled back even more, by an area nearly the size of Alaska.