Socrtease
Verified User
This site http://earthobservatory.nasa.gov/Library/GlobalWarmingUpdate/global_warming_update4.html is a good site for an overview from NASA on global warming. In the information presented there some things of note were:
By experimenting with the models—removing greenhouse gases emitted by the burning of fossil fuels or changing the intensity of the Sun to see how each influences the climate— scientists can use the models to explain Earth’s current climate and predict its future climate. So far, the only way scientists can get the models to match the rise in temperature seen over the past century is to include the greenhouse gases that humans have put into the atmosphere. This means that, according to the models, humans are responsible for most of the warming observed during the second half of the twentieth century.
But why do scientists trust results from climate models when models seem to have so much trouble forecasting the weather? It turns out that trends are easier to predict than specific events. Weather is a short-term, small-scale set of measurements of environmental conditions, while climate is the average of those conditions over a large area for a long time. The difference between predicting weather and climate is similar to the difference between predicting when a particular person will die versus calculating the average life span of an entire population. Given the large number of variables that influence conditions in Earth’s lower atmosphere, and given that chaos also plays a larger role on shorter and smaller scales of time and space, weather is much harder to predict than the averages that make up climate.