Fire simulation models that consider the complex dynamics of weather, fuels, and terrain are essential to forecasting fire behavior. A growing number of such models are available, so understanding the differences in their predictions and sensitivity to drivers of fire behavior is critically important. Geoffrey Cary and colleagues made an extensive comparison of five fire simulation models used in different parts of the world. They studied the sensitivity of predicted area burned to variation in terrain, fuel pattern, climate and weather. Sensitivity was measured as the variance in area burned explained by each of these four drivers of fire behavior.