GREENLAND ICE-SHEET OVER THE NEXT 5000 YEARS

The two-dimensional climate model developed by Gallee et al. [1991, 1992] in Louvain-la-Neuve (2-D-LLN climate model) has been used to test the long-term response of the climate system to carbon dioxide (CO2) concentration changes induced by fossil fuel energy consumption. Three scenarios of future atmospheric CO2 concentration have been designed: in the first two, the concentration is kept constant over the next 5000 years (5 ka), first to the pre-industrial value (280 parts per million volume, 280 ppmv) and second, to the double of the present-day value (710 ppmv). In a third scenario, it has been assumed that the pre-industrial CO2 concentration will rise from 280 to 710 ppmv within the next 500 years and then decrease progressively to reach 450 ppmv and 350 ppmv, respectively 1000 years and 1500 years from now. In such a scenario, the mean annual and hemispheric temperature is shown to increase by about 3-degrees-C due to the increase in the atmospheric CO2 concentration from 280 ppmv to 710 ppmv. High latitudes are more sensitive than low latitudes, this being related to important albedo changes over these regions. While the Greenland ice sheet does not change significantly if the pre-industrial CO2 concentration is assumed to remain constant, it rapidly collapses with a CO2 concentration of 710 ppmv kept constant over the next 5 ka. Even in the third scenario where the CO2 concentration progressively returns to the present-day value at the end of the simulation (5 ka after present (5 ka AP)), the Greenland ice sheet disappears also.