Scientists already understood in theory the sunshade effect of airborne particles, but in later years it was factored into climate models, and global warming forecasts were revised slightly downward. Models, in effect, are a statement of our understanding of the physical processes that lie behind climate and influence it. Models are collections of theories so they can t exactly prove theories. They are smarter than people in the sense that they can do more calculations more quickly. But if the theories and principles underlying the calculations are wrong, then the models too will be wrong.
Computer models represent the atmosphere by dividing it into boxes.
The boxes might typically be about 150 miles on a side and mile deep spread like tiles across the surface of the earth and stacked a dozen or more high. For every step forward in time, complete calculations are done for each box. The size of the boxes limits the resolution of the model just as the size of the dots in a newspaper photo limits the amount of detail the photo can represent. The problem is that making the boxes smaller requires more calculations, pushing even today s best computers to their limits. This is why climate scientists have more confidence in what models say about the broad global picture than about what the climate will be in a particular city.