杏吧原创

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

Of course, it鈥檚 not actually possible to halt CO₂ emissions overnight, but envisaging such a scenario helped Susan Solomon of the National Oceanic and Atmospheric Administration鈥檚 Laboratory in Boulder, Colorado, get a better grip on our climate鈥檚 future.

In her model, CO₂ concentrations were double pre-industrial levels 鈥� which could easily happen by mid-century 鈥� 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, ).

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.

, a colleague of Solomon鈥檚 at the US National Center for Atmospheric Research who was not involved in the study, believes we need to act before CO₂ levels rise that far: 鈥淏y the time the public and policy-makers realise the changes are here, it will be far too late to do anything.鈥�

Solomon says that carbon-trading schemes that estimate the impact of greenhouse gases on the basis of the warming over a century 鈥渘eglect CO₂鈥榮 unique long-term effects鈥�.