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• Find out what 3 degrees really means.
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Targets debate: George Monbiot and Clive Hamilton

Are we getting the third degree?

by David Spratt

"Dissent" magazine #24, Spring 2007

For subscriptions to "Dissent" magazine: www.dissent.com.au

The climate change policy goal posts are being shifted, but do we understand the new game? It's all a matter of degree.

Climate scientists generally agree global temperatures should not rise more than 2 degrees above pre-industrial levels to prevent catastrophic effects. So do the UN and the European Union, on paper. James Hansen, the Director of NASA's Goddard Institute for Space Studies, warns that 2-3 degrees would produce a planet without Arctic sea ice, a catastrophic sea level rise in the pipeline, and super-drought in the American west, southern Europe, the Middle East and parts of Africa: "Such a scenario threatens even greater calamity, because it could unleash positive feedbacks such as melting of frozen methane in the Arctic, as occurred 55 million years ago, when more than ninety per cent of species on Earth went extinct".

Despite this, 3 degrees is fast being adopted as the new target, the relative safety of the 2-degree limit put aside. In his 2006 report to the British government, Sir Nicholas Stern declared keeping the rise to two degrees as "already nearly out of reach" because it meant emissions "peaking in the next five years or so and dropping fast", which he judged to be neither politically likely nor economically desirable. Three degrees was a more practical target, and Stern nominated the appropriate emissions reduction plan as 60 per cent by 2050. In his footsteps file Kevin Rudd and Ross Garnaut (appointed by Rudd to do a Stern report for Australia) but saddled with the answer before he has researched the question.

This view is shared by Dr Brian Fisher, Australia's lead delegate to the May 2007 International Panel on Climate Change (IPCC) meeting, who says the 2-degree target, with emissions peaking by 2015, "is exceedingly unlikely to occur... global emissions are growing very strongly... On the current trajectories you would have to say plus 3 degrees is looking more likely."

The shift is plain in the most recent IPCC report. Of the 177 research scenarios assessed for future emissions profiles, only six dealt with limiting the rise to the range of 2-2.4 degrees. By contrast, 118 covered the range of 3.2-4 degrees, which suggest that the IPCC researchers have also largely shifted focus from 2 degrees.

So what does 3 degrees mean?

Britain's Hadley Centre calculates a 1-degree increase would in the long run eliminate fresh water from a third of the world's land surface. In Australia now we are witness to this event. Today, at less than 1 degree, the Barrier Reef is doomed; the floating ice covering the north pole is disappearing fast, likely to be gone within a few decades; and we are close to the tipping point when the Greenland ice sheet starts the irreversible melting that will lift sea levels by five to seven metres, in as little as a 100 years, according to Hansen.

An increase of 2 degrees is far from safe. It will be too late for Greenland, and over a third of species will be committed to extinction. Europe will be hit regularly by heatwaves like the one in 2003 which killed up to 35,000 people, caused $12b in crop losses, and resulted in a 30 per cent drop in plant growth, adding half a billion tonnes of carbon to the atmosphere that year.

Peer-reviewed research says that in a 3-degree world vast amounts of dead vegetation stored in the soil – more than double the entire carbon content of the atmosphere – will be broken down by bacteria as soil warms. The carbon cycle will be thrown into reverse so that vegetation and soils start to release carbon dioxide instead of absorbing it, boosting global warming by another 1.5 degrees. In this context 3 degrees becomes 4-5.

Between 2 and 3 degrees the Amazon rainforest, whose plants produce 10 per cent of the world's photosynthesis, will turn to savannah, as drought and mega-fires first destroy the rainforest, turning trees back into carbon dioxide as they rot and decompose. It is suggested than in human terms the effect on the planet will be like cutting off oxygen during an asthma attack.

The prime minister thinks it "crazy and irresponsible.... to commit to a target when you don't know the impact ". Modelling for the IPCC suggests a 3-degree, "60/2050" target would only marginally reduce annual growth – from 2.3 to 2.2 per cent to 2050. Both miss the point. We have no reliable research on the economic cost of severe climate change because we cannot quantify losing the Amazon, reversing the carbon cycle or tipping the climate system towards 5 degrees. Past 2 degrees, adding up the dollar costs and benefits no longer tells the story.

A 2-degree target means an 80 percent global emissions cut, and a reduction 95 per cent below 2000 levels by 2050 for countries such as Australia, according to Oslo's Centre for International Climate and Environmental Research. Such a crash programme, including new national infrastructure projects for renewable solar-thermal and geo-thermal power and a low-carbon national rail network, is good and necessary value compared to the bleak vista of a 4 or 5 degree world.

It's time to talk not only about the costs of mitigation, but also of the unquantifiable cost of acting too late. Between 2 and 3 degrees, there may be a world of economic difference.