Reversible and irreversible impacts of greenhouse gas emissions in multi-century projections with a comprehensive climate-carbon model

Currently, about a quarter of the anthropogenic CO2 emitted into the atmosphere is absorbed by the surface ocean and causes a reduction in pH, thus, ocean acidification leads to an alteration in the calcium carbonate precipitation equilibrium.
We assess the long-term impacts of 21st century greenhouse gas emissions on climate and ocean acidification with the NCAR CSM1.4-carbon model on both the global and the regional scale. Emission commitment scenarios with zero emissions after 2100 AD and 21st century emissions of 1800 (High case), 900 (Low), and 0 gigatons of carbon (Hist) are run up to the year 2500 AD. In the High case, atmospheric CO2 remains above 580 ppm and 30% of carbon emissions are still airborne by 2500. Consequently, the perturbations in carbonate chemistry persist. Undersaturation of the Arctic surface ocean with respect to aragonite, a mineral form of calcium carbonate secreted by marine organisms, is imminent and remains widespread for centuries. System time lags and physical-biogeochemical coupling often cause largest impacts to accrue after emissions have been stopped. The volume of supersaturated water providing habitat to calcifying organisms is reduced from preindustrial 40% to 25% in 2100 and to 10% in 2300.
The precautionary principle requires to reduce carbon emissions to keep atmospheric CO2 below about 450 ppm, thereby avoiding the risk of large-scale ecosystem disruption. We conclude that emission trading schemes, related to the Kyoto Process, should not permit trading between emissions of relatively short-lived agents and CO2 given the irreversible impacts of anthropogenic carbon emissions.



Frölicher, T. & Joos, F., 2009. Reversible and irreversible impacts of greenhouse gas emissions in multi-century projections with a comprehensive climate-carbon model. Awards Ceremony Speeches and Abstracts of the 19th Annual V.M. Goldschmidt Conference, V.M. Goldschmidt Conference. Geochimica et Cosmochimica Acta 73(13)-1: A399. Supplement.

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