Global average sea level has risen and ocean heat content has increased. Changes have also occurred in other important aspects of climate. Some important aspects of climate appear not to have changed. Emissions of greenhouse gases and aerosols due to human activities continue to alter the atmosphere in ways that are expected to affect climate. Concentrations of atmospheric greenhouse gases and their radiative forcing have continued to increase as a result of human activities.
Antropogenic aerosols are short-lived and mostly produce negative radiative forcing.
Natural factors have made small contributions to radiative forcing over the past century. Confidence in the ability of models to project future climate has increased. Modeling of water vapor, sea-ice dynamics, and ocean heat transport has improved. Simulations that include both natural and anthropogenic forcing reproduce observed large-scale changes in surface temperature over the 20th century. Some aspects of model simulation of El Nino, monsoons, and other well known phenomena have improved.