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Carbon dioxide climate sensitivity overestimated

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Global temperatures could be less sensitive to changing atmospheric carbon dioxide (CO2) levels than previously thought, a study suggests.

Researchers say people should still expect to see “drastic changes” in climate worldwide, but that the risk was a little less imminent, the BBC reported November 25, 2011.

Previous climate models have tended to used meteorological measurements from the past 150 years to estimate the climate’s sensitivity to rising carbon dioxide.

From these models, scientists find it difficult to narrow their projections down to a single figure with any certainty, and instead project a range of temperatures that they expect, given a doubling of atmospheric CO2 from pre-industrial levels.

The new analysis, which incorporates palaeoclimate data into existing models, attempts to project future temperatures with a little more certainty, the publication disclosed.

The publication’s Lead author Andreas Schmittner from Oregon State University, US, explained that by looking at surface temperatures during the most recent ice age – 21,000 years ago – when humans were having no impact on global temperatures, he, and his colleagues show that this period was not as cold as previous estimates suggest.

“This implies that the effect of CO2 on climate is less than previously thought,” the BBC quoted Scmitter as saying.

By incorporating this newly discovered “climate insensitivity” into their models, the international team was able to reduce uncertainty in its future climate projections.

The new models predict that given a doubling in CO2 levels from pre-industrial levels, the Earth’s surface temperatures will rise by 1.7oC to 2.6oC (3.1oF to 4.7oF).
That is a much tighter range than the one produced by the Intergovernmental Panel on Climate Change’s (IPCC) 2007 report, which suggested a rise of between 2.0oC to 4.5oC.

The new analysis also reduces the expected rise in average surface temperatures to just over 2oC, from 3oC.

The authors according to the publication, stress the results do not mean threat from human-induced climate change should be treated any less seriously, explained palaeoclimatologist Antoni Rosell-Mele from the Autonomous University of Barcelona, who is a member of the team that came up with the new estimates.

But it does mean that to induce large-scale warming of the planet, leading to widespread catastrophic consequences, we would have to increase CO2 more than we are going to do in the near future, he said.

“But we don’t want that to happen at any time, right?”

Dr Rosell-Mele is quoted by the BBC as remarking that, “at least, given that no one is doing very much around the planet [about] mitigating Carbon Dioxide emissions, we have a bit more time,”.

Whether these results mean that the global temperatures will be less responsive to falling Carbon Dioxide is unclear. “I don’t think we know that, to be honest,” the BBC quoted Dr Rosell-Mele.

“There is evidence the relationship between Carbon Dioxide and surface temperatures is likely to be different [during] very cold periods than warmer”, Climatologist Andrey Ganopolski is quoted by BBC as saying.

Meanwhile, Mr Edward Nsenkyire, Chairman of the National Climate Change Committee has stated that, Ghana needs collaborative efforts from all stakeholders to find local solutions to the climate change menace .

By Pascal Kelvin Kudiabor

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