Petro-Canada’s Edmonton Refinery and Distribution Centre glows at dusk in Edmonton in this photo from February 15, 2009.
The world can burn only a quarter of proven reserves of oil, gas and coal to be confident of staying within safer climate limits, unless untested carbon fixes work, experts said on Wednesday.
In two studies published in the journal Nature, scientists honed the basis for urgent climate action as the world tries to map by the end of this year agreement on a new treaty to replace the Kyoto Protocol.
People could burn no more oil, gas and coal in their homes, cars and factories after 2024, at current rates, to limit to one in five the chance of exceeding 2 degrees Celsius warming worldwide, one article found.
“It really casts doubt on whether any investment into more fossil fuel exploration is really a good investment,” said the Potsdam Institute’s Malte Meinshausen, who led the study.
“It makes a bet on technologies which at the moment are pretty uncertain still, or otherwise just leads us on a path to 3 or 4 degrees (Celsius) warming,” he said, referring to untested climate fixes which trap carbon from the flue gas of power plants or else sucks it out of the air.
Both articles tallied total global emissions with warming by a certain date, in a novel “carbon budget” approach that could aid U.N.-led climate talks by showing negotiators the climate impacts of any agreement in Copenhagen in December.
A key concern was uncertainty — meeting even the most ambitious carbon-cutting targets could still result in climate change which inflicted water shortages on billions of people and risked coastal flooding for millions more.
“We won’t know, won’t resolve that uncertainty for sure until after we’ve made major reductions in emissions,” said Oxford University’s Myles Allen, who led the second study.
IMPACT
Carbon emissions are rising at about 3 percent a year, although that rate is expected to fall temporarily as a result of the recession.
Without urgent action the climate problem could get out of hand, becoming very difficult or impossible to contain within safer limits, both studies found.
Even at 2 degrees warming above pre-industrial levels there is a risk of serious impacts, for example that the Greenland ice sheet melts over centuries, adding 7 meters sea level rise, and worse droughts ensue in dry areas such as Australia, southern Europe and south-west United States.
Fighting climate change will be expensive, for example to replace cheap fossil fuels with more costly renewable energy.
Both Nature studies recommended that global emissions peak by 2020 or sooner. Japan advocated on Tuesday that they peak “in the next ten to twenty years.
“Late and rapid reductions are risky, expensive and disruptive, and hence potentially politically infeasible,” both researchers said in a joint commentary in Nature.
The second study said that people could only emit another 500 billion tonnes of carbon for all time, which they would do in the next 40 years at current rates. That implied a 50 percent chance of exceeding 2 degrees.
A safer target may be to limit emissions to 200 billion tonnes from 2009-2050, the first study estimated, for a one in four chance of exceeding 2 degrees.
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Full article and photo: http://www.reuters.com/article/environmentNews/idUSTRE53S69C20090429?feedType=RSS&feedName=environmentNews&sp=true
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See also:
‘Safe’ climate means ‘no to coal’
 Coal must either modernise or become obsolete, the research implies
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About three-quarters of the world’s fossil fuel reserves must be left unused if society is to avoid dangerous climate change, scientists warn.
More than 100 nations support the goal of keeping temperature rise below 2C.
But the scientists say that without major curbs on fossil fuel use, 2C will probably be reached by 2050.
Writing in Nature, they say politicians should focus on limiting humanity’s total output of CO2 rather than setting a “safe” level for annual emissions.
The UN climate process focuses on stabilising annual emissions at a level that would avoid major climate impacts.
But this group of scientists says that the cumulative total provides a better measure of the likely temperature rise, and may present an easier target for policymakers.
“To avoid dangerous climate change, we will have to limit the total amount of carbon we inject into the atmosphere, not just the emission rate in any given year,” said Myles Allen from the physics department at Oxford University.
“Climate policy needs an exit strategy; as well as reducing carbon emissions now, we need a plan for phasing out net emissions entirely.”
Forty years
The UN climate convention, agreed at the 1992 Rio Earth Summit, commits countries to avoiding “dangerous” climate change, without defining what that is.
The EU proposed some years ago that restricting the rise to 2C from pre-industrial times was a reasonable threshold, and it has since been adopted by many other countries, although some – particularly small islands – argue that even 2C would result in dangerous impacts.
Temperatures have already risen by about 0.7C during the industrial age.
Dr Allen’s analysis suggests that if humanity’s CO2 emissions total more than about one trillion tonnes of carbon, the 2C threshold is likely to be breached; and that could come within a lifetime.
“It took us 250 years to burn the first half trillion,” he said, “and on current projections we’ll burn the next half trillion in less than 40 years.”
Inherent uncertainties in the modelling mean the temperature rise from the trillion tonnes could be between 1.3C and 3.9C, Dr Allen’s team calculates, although the most likely value would be 2C.
Oil change
The “trillion tonnes” analysis is one of two studies published in Nature by a pool of researchers that includes the Oxford group and scientists from the Potsdam Institute for Climate Change Impact Research in Germany.
 Impacts such as droughts would increase above 2C, the IPCC believes
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The second study, led by Potsdam’s Malte Mainshausen, attempted to work backwards from the 2C goal, to find out what achieving it might mean in practice.
It suggests that the G8 target of halving global emissions by 2050 (from 1990 levels) would leave a significant risk of breaching the 2C figure.
“Only a fast switch away from fossil fuels will give us a reasonable chance to avoid considerable warming,” said Dr Mainshausen.
“If we continue burning fossil fuels as we do, we will have exhausted the carbon budget in merely 20 years, and global warming will go well beyond 2C.”
If policymakers decided they were happy to accept a 25% chance of exceeding 2C by 2050, he said, they must also accept that this meant cutting emissions by more than 50%.
That would mean only burning about a quarter of the carbon in the world’s known, economically-recoverable fossil fuel reserves. This is likely to consist mainly of oil and natural gas, leaving coal as a redundant fuel unless its emissions could be captured and stored.
Both analyses support the view of the Stern Review and the Intergovernmental Panel on Climate Change (IPCC) in suggesting that making reductions earlier would be easier and cheaper than delaying.
But according to Potsdam’s Bill Hare, a co-author on the second paper, some key governments appear to favour pledging milder cuts in the near term in return for more drastic ones in decades to come.
“We have a number of countries – the US, Japan, Brazil – saying ‘we will emit higher through to 2020 and then go down faster’,” he said.
“That might be true geophysically, but we cannot find any economic model where emissions can fall in the range that this work shows would be necessary – around 6% per year.”
Major intervention
Myles Allen’s group has made the argument before that focussing on humanity’s entire carbon dioxide output makes more scientific and political sense than aiming to define a particular “safe” level of emissions, or to plot a pathway assigning various ceilings to various years.
Some greenhouse gases, such as methane, have a definable lifetime in the atmosphere, meaning that stabilising emissions makes sense; but, said Dr Allen, CO2 “doesn’t behave like that”.
“There are multiple levers acting on its concentration and it does tend to accumulate; also models have to represent the possibility of some feedback between rising temperatures and emissions, such as parts of the land turning from carbon sinks into sources, for example.”
The Nature papers emerge in a week that has seen the inaugural meeting of President Obama’s Major Economies Forum on Energy and Climate, a new version of a body created under President Bush that brings together 17 of the world’s highest-emitting countries for discussion and dialogue.
During the opening segment, Secretary of State Hillary Clinton re-affirmed the administration’s aim of cutting US emissions by 80% from 1990 levels by 2050 – a target espoused by some other developed countries.
But according to Malte Meinshausen’s analysis, even this reduction may not be enough to keep the average global temperature rise within 2C, assuming less developed nations made less stringent cuts in order to aid their development.
“If the US does 80%, that equates to about 60% globally, and that offers only a modest chance of meeting the 2C target,” he said.
Last week saw the publication of data showing that industrialised countries’ collective emissions rose by about 1% during 2007.
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Full article and photos: http://news.bbc.co.uk/2/hi/science/nature/8023072.stm
