Featured video: temperature rises across North America by 2100

A new short video predicts temperature changes across North America depending on the future of greenhouse gas emissions. Produced by NASA, the first series shows average temperatures changes (relative to 1970-1999) based on carbon dioxide levels hitting 550 parts per million (ppm) in the atmosphere by 2100. The second, even more dramatic series, shows changes if levels hit 800 ppm by the end of the century. Earlier this year, carbon dioxide levels hit 400 ppm for the first time in around 5 million years, which is longer than humans have been around.