Saturday, June 28, 2008

Study predicts amount of CO2 emissions that could lead to Greenland melting


melting water greenland
Image from Bart de Haan

The chorus of bad news for Greenland's fate has been growing louder in recent months. I've written at length about numerous studies suggesting that Greenland may not last much longer in light of rapidly increasing carbon emissions. A new study published in the latest issue of Geophysical Research Letters (sub. required) predicts under which CO2 emissions scenarios Greenland will "irreversibly" undergo total melting.

In short, the team of researchers from France's Laboratoire des Sciences du Climat et de l'Environnement, estimates that if the level of atmospheric CO2 emissions surpasses 3,000 GtC (GtC = gigaton of carbon), total melting will be inevitable. If, however, it remains below 2,500 GtC, Greenland will experience a partial melting followed by a re-growth phase. For some context, the current level of CO2 emissions lies slightly above 350 GtC.

melting scenarios

To reach their findings, the scientists combined realistic long-term CO2 emission scenarios with a model capable of capturing future climate-ice sheet interactions. They used two series of experiments -- one (EXP1) in which CO2 is released to the atmosphere over a longer period than the other (EXP2) though total levels remain constant -- to perform their simulations. Therefore, while the maximum content of CO2 in the atmosphere is lower for EXP2 than that obtained in EXP1 -- and only reached several centuries later -- there is a longer period of high level atmospheric CO2.

The researchers found that the primary factor responsible for the complete melting Greenland's ice sheet was the cumulative amount of CO2 released -- and not the maximum atmospheric CO2 content. This would therefore suggest that an EXP1 scenario, under which CO2 is released to the atmosphere more quickly (causing temperatures to rise faster as well), would be more detrimental to Greenland's fate.

Even if carbon capture and sequestration (CCS) schemes like ocean storage or geological storage prove effective, they would only help delay emission increases for a few centuries or millenia, they explain. The rate of emissions growth over the next century, they conclude, will likely determine Greenland's eventual fate and that of future sea-level rises.

They acknowledge that their models may underplay the impact of the ice sheet's dynamics, which could accelerate melting, but stress that, over the long term, their predictions will probably ring true. They recommend focusing climate policy around the goal of limiting emissions over the next centuries to below 2,150 GtC to avoid the worst possible outcomes.

For a less number-heavy take on Greenland's melting, check out the following posts from Real Climate and Nature's Alexandra Witze. This is only one study, of course, so we'll have to wait and see how CO2 emission scenarios and models change (and improve) over the coming years. Either way, Greenland's future looks pretty dire at the moment.

Via ::Geophysical Research Letters: Amount of CO2 emissions irreversibly leading to the total melting of Greenland (journal)

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