Our understanding of climate and how it changes is advanced enough to make reasonable decisions, using computer models, about activities such as future energy use and food production. However, for the last four decades, some have been using these models to project catastrophes in the event that governments fail to act. Although many of these projections have been wrong, the doomsayers continue to warn that humanity has 12, 10, or even fewer years left to save society.

These models represent our best current understanding of how the climate works. They have been positively evaluated by the World Climate Research Programme. Yet they are not necessarily correct. For example, a group of scientists at the University of Alabama in Huntsville found that the forecast temperature trends were twice those observed for the tropical upper atmosphere. Other published studies have shown that these same models overestimate global mean surface temperatures, such that observed global temperature trends are often in the lower part of the range of the models’ predictions.