THE TRANSIENT-RESPONSE OF TERRESTRIAL CARBON STORAGE TO A PERTURBED CLIMATE

MODEL simulations suggest that at equilibrium, global warming driven by higher atmospheric concentrations of greenhouse gases will lead to increased terrestrial carbon storage1,2, implying a negative feedback between the global vegetation/soil system and the atmospheric CO2 Concentration. But changes in vegetation and soil type that result in a net release of CO2 to the atmosphere (such as those caused by wildfires) could be more rapid than changes that result in a net increase in terrestrial carbon storage (such as species immigration and soil formation), so that in its transient response to climate change, the terrestrial vegetation/soil system could be a net source of carbon to the atmosphere. Here we use two general circulation models3,4 to estimate the transient response of the terrestrial surface to a step doubling of atmospheric CO2. We find that vegetation and soil changes could prove to be a significant source of CO2 in the first 50-100 years following a climate warming, increasing the atmospheric CO2 concentration by up to a third of the present level.