Simulating the Planet

Climate models are mathematical representations of Earth's climate system — atmosphere, oceans, land surfaces, ice sheets, and biosphere — encoded in millions of lines of computer code. They divide the planet into three-dimensional grid cells and calculate how energy, water, and chemicals move between cells based on the laws of physics.

A common objection is that weather forecasts fail after a week, so how can climate be projected decades ahead? The answer is the difference between weather and climate — predicting tomorrow's temperature is hard, but predicting average seasonal temperature is straightforward.