KEY climate change measures are tracking near or beyond worse-case scenarios predicted just two years ago, according to a science update drawing on more than 200 recently published studies.
Co-authored by 26 climate scientists, The Copenhagen Diagnosis reports that melting of summer Arctic sea ice, loss of the Greenland and Antarctic ice sheets, and projections of the rise in sea levels have accelerated dramatically since 2007.
It finds the statistical global warming trend has continued over the past decade, contradicting assessments by some scientists - including Copenhagen Climate Council chairman Tim Flannery - that there has been a recent cooling.
The review cites NASA data that shows a trend of a 0.19-degree increase over the past decade despite short-term fluctuations due to El Nino, solar variability and volcanic eruptions.
Matthew England, co-director of the University of NSW Climate Change Research Centre, said the world's three leading climate data series showed claims of temperatures cooling were "patently untrue".
"These are the data set even the sceptics go to, and they show that the last 10 years has been one of warming even if you start in [the particularly hot] 1998," Professor England said.
"Since 2001, every year has been among the top-10 warmest on record. I don't think that is cooling."
The diagnosis is billed as a supplement to the 2007 report by the UN's Intergovernmental Panel on Climate Change and aimed at influencing debate at next month's Copenhagen climate summit. Most of the scientists behind it are intergovernmental panel authors.
Its major findings include:
■ Greenhouse gas emissions from fossil fuel burning and cement production were nearly 40 per cent higher in 2008 than in 1990.
■ Global air temperature, humidity and rainfall patterns cannot be explained without factoring in greenhouse gas emissions.
■ Satellite and ice measurements show the Greenland and Antarctic ice sheets are increasingly losing mass. Each adds up to 0.7 millimetres a year to sea level rise.
■ The recent rate of summer Arctic see ice melting is unprecedented in at least 2000 years and about 40 per cent greater than average IPCC predictions.
■ Sea-level rise by 2100 is likely to be much greater than the 18-59 centimetres predicted by the UN panel. Failure to cut emissions could lead to a rise of more than a metre. The worse-case scenario is roughly two metres (though unlikely).
■ Localised tipping points, where changes happen abruptly, are possible this century at some sites. But despite talk of "runaway climate change", there is no strong evidence that the entire planet is near that threshold.
The report estimates global temperatures could rise by seven degrees by 2100. Emissions would need to peak in the next five to 10 years to limit warming to two degrees.
It comes at a charged time in the climate debate. Emails stolen from a leading climate research centre have prompted claims its scientists tried to massage unfavourable data and destroy scientific material sought under Freedom of Information. Professor England said the scandal was a diversion:
"A few loose email comments by a couple of researchers does not bring down the central science of climate change."
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