3 february 2009

Effects of Climate Change Now "Irreversible"
New Scientist, January 28, 2009

WHAT would happen if in 50 years' time the world suddenly stopped burning fossil fuels? Surprisingly little as far as the climate is concerned.

Of course, it's not actually possible to halt CO2 emissions overnight, but envisaging such a scenario helped Susan Solomon of the US National Center for Atmospheric Research (NCAR) in Boulder, Colorado, get a better grip on our climate's future.

In her model, CO2 concentrations were double pre-industrial levels - which could easily happen by mid-century - when emissions were stopped. The team found that while levels would fall as the oceans absorb CO2, the overall change would be slow.

By 2200, only a quarter of the CO2 in the atmosphere would have dissolved into the oceans. Then air and sea CO2 concentrations would reach equilibrium, preventing further significant quantities of CO2 being mopped up by the ocean. Even by the year 3000, CO2 would still be about a third higher than pre-industrial levels (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0812721106).

Solomon estimates that in this scenario, average global temperatures would cool by just a few tenths of a degree over the next 1000 years. Areas including north Africa and southern Europe would suffer regular droughts, and sea levels would rise by up to a metre.

Kevin Trenberth, a colleague of Solomon's at NCAR who was not involved in the study, believes we need to act before CO2 levels rise that far: "By the time the public and policy-makers realise the changes are here, it will be far too late to do anything."

Solomon says that carbon-trading schemes that estimate the impact of greenhouse gases on the basis of the warming over a century "neglect CO2's unique long-term effects".

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