Twenty-first-century climate change commitment from a multi-model ensemble

Climate change commitment in the 21st - century due to human activity in the 20th century is quantified using output from 16 global coupled general circulation models. With the atmospheric composition held constant at year 2000 values, the global annual mean surface temperature anomaly stabilizes with an additional warming over and above what already occurred in the 20th century of + 0.5 degrees +/- 0.2 degrees C by the end of the 21st century. The magnitude is about 0.1 degrees C warmer in the models with the 20th century volcanic aerosol than those models without. The multimodel ensemble ( from 6 models) globally averaged sea level rises + 10 +/- 3cm by 2100 and does not show signs of leveling off. The committed winter warming pattern is characterized by polar amplification due in part to ice albedo feedback, with a further committed warming of above 1.0 degrees C and 0.6 degrees C in the Arctic and Antarctic regions, respectively. The tropical surface temperature pattern shows an El Nino-like response, with consequent changes in precipitation over the tropics. Thus, even after GHGs are stabilized, the multi-model results show that the climate continues to change with similar patterns to those when GHGs are continuously increasing, but these changes are due to the thermal inertia of the climate system reacting to the radiative forcing from the atmospheric composition changes applied during the 20th century.