Quantifying the effect of vegetation dynamics on the climate of the Last Glacial Maximum

[摘要] The importance of the biogeophysical atmosphere-vegetationfeedback in comparison with the radiative effect of loweratmospheric CO₂ concentrations and the presence of ice sheetsat the last glacial maximum (LGM) is investigated with the climatesystem model CLIMBER-2. Equilibrium experiments reveal that mostof the global cooling at the LGM (-5.1°C) relativeto (natural) present-day conditions is caused by the introductionof ice sheets into the model (-3.0°C), followed bythe effect of lower atmospheric CO₂ levels at the LGM(-1.5°C), while a synergy between these two factorsappears to be very small on global average. The biogeophysicaleffects of changes in vegetation cover are found to cool the global LGMclimate by 0.6°C. The latter are most pronounced inthe northern high latitudes, where the taiga-tundra feedbackcauses annually averaged temperature changes of up to-2.0°C, while the radiative effect of loweratmospheric CO₂ in this region only produces a cooling of1.5°C. Hence, in this region, the temperaturechanges caused by vegetation dynamics at the LGM exceed thecooling due to lower atmospheric CO₂ concentrations.

[学科分类] 大气科学