A: Climate models are mathematical representations of the interactions between the various aspects of the climate system including the atmosphere, oceans, land surface, ice, and the Sun. The complex task of simulating Earth’s climate is carried out by computer programs designed to detect long-term climate trends based on large-scale forces. Unlike weather prediction models, climate models are not intended to predict individual storms systems.
Climate models are tested against what we know happened in the past and they do accurately map past climate changes. Climate models have also been proven to make accurate predictions. For example, the eruption of Mt. Pinatubo provided an opportunity for such a test. The models successfully predicted the climatic response after the eruption, a cooling influence that lasted a couple of years.
Models have also been applied to the question of how the climate system will react to additional greenhouse gases. These models have correctly predicted effects subsequently confirmed by observation, including greater warming in the Arctic and over land, greater warming at night, and stratospheric cooling. Far from overestimating future climate change, climate models are more likely to be conservative in their predictions. For example, model predictions of how fast Arctic sea ice would decline and how fast sea level would rise have proven to be considerably less than the changes actually observed.