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CLIMATE CHANGE: Two-Degree Rise Ever More Likely, Scientists Warn

Stephen Leahy

ANCHORAGE, Alaska, Apr 30 2009 (IPS) - Climate scientists are calling for a phase-out of fossil fuels because humans are now pumping so much carbon dioxide (CO2) into the atmosphere that the ‘2-degree-C climate balloon’ will burst otherwise, new studies show.

That 2-degree C climate balloon has a maximum capacity of less than 1,400 gigatonnes of CO2 total emissions from the year 2000 to 2050, Malte Meinshausen and colleagues report in the current issue of Nature. The European Union and others consider a global temperature rise of more than 2 degrees C as dangerous and potentially catastrophic. Temperatures are already 0.8 C warmer than the pre-industrial period.

The reality is that global emissions for the last seven years amounted to almost 250 gigatonnes of these long-lived greenhouse gases, meaning that the current and growing rates of fossil fuel emissions would burst the balloon in about 20 years – or less. Even if emissions are held to 1,400 gigatonnes maximum for the next 40 years, there is still a 50-percent probability of exceeding 2 degrees C, said Meinshausen, lead author of the study and climate researcher at the Potsdam Institute for Climate Impact Research.

Indigenous peoples from around the world also called for a phase-out of fossil fuels at the conclusion of the first Indigenous Peoples’ Global Summit on Climate Change in Anchorage, Alaska, that concluded last week.

“That call is well-supported by the evidence in this study,” Meinshausen told IPS.

However, the world’s future global carbon budget is likely less than 1,400 gigagtonnes. When other short-term warming gases like methane are included, then the total ‘forcing’, i.e. warming, could be 10 to 40 percent greater by the year 2100, said Meinshausen.

And some climate feedbacks – changes that will amplify or accelerate the warming – are absent from computer models. “Our modeling cannot account for emissions in methane from melting permafrost,” he said.

Permafrost – permanently frozen bog and peatland – contains enormous amounts of organic carbon, perhaps enough to triple the amount currently in the atmosphere.

“Only a fast switch away from fossil fuels will give us a reasonable chance to avoid considerable warming,” said Meinshausen. “We shouldn’t forget that a 2-degree C global mean warming would take us far beyond the natural temperature variations that life on Earth has experienced since we humans have been around.”

This will be a serious challenge, he said, because there is plenty of carbon left in the ground. Proven reserves of oil, gas and coal represent four times the amount of carbon that would burst the 2-degree climate balloon. Burning just one quarter of what’s left in the ground will bring humanity to the 50-50 point of tipping into dangerous climate change.

Delay is not an option when it comes to the fossil fuel phase-out, scientists stress. Even though a tonne of carbon is a tonne of carbon, whether released today or in 50 years’ time, there is only so much the atmosphere can take before a 2-degree rise or more is inevitable, Meinshausen, Myles Allen of the University of Oxford and others write in a Nature Reports Climate Change commentary.

“Emitting CO2 more slowly buys time, perhaps vital time, but it will only achieve our ultimate goal in the context of a strategy for phasing out net CO2 emissions altogether,” they conclude.

“Climate policy needs an exit strategy: as well as reducing carbon emissions now, we need a plan for phasing out net emissions entirely,” Allen said in a release.

So what are the targets for the negotiators United Nations Framework Convention on Climate Change (UNFCCC) in the Copenhagen this December?

If negotiators heed the scientific evidence, then a new global agreement’s goal will be to reduce global emissions by 50 percent compared to 1990 and do that by 2050. To achieve this, the current three-percent annual growth in carbon emissions must flatline by 2015 and start the decline by 3 percent per year, reports Martin Parry of the Grantham Institute for Climate Change and Centre for Environmental Policy, Imperial College London in another Nature study.

“If we do this it leaves an even chance of exceeding 2-degree C of warming,” Parry and colleagues write.

If mitigation efforts are not substantial enough and emissions peak in the year 2025, then a 3-degree C rise in temperatures will likely occur. The damage from this level of warming could be substantial, placing billions more people at risk of water shortage and millions more at risk of coastal flooding. To avoid such damage will require massive investment in adaptation, such as improving water supply and storage, and protecting low-lying settlements from rising seas.

A final cautionary note: “The true sensitivity of the Earth system may well be higher, implying that any temperature-based target will become progressively harder to maintain as slower feedbacks kick in,” write Gavin Schmidt, of the NASA Goddard Institute for Space Studies, and David Archer of the University of Chicago in short article in Nature Wednesday.

“The bottom line? Dangerous change, even loosely defined, is going to be hard to avoid,” they said.

Like an oil spill, it is far better and cheaper to avoid making the mess in the first place, they conclude.