there might be politics in there. tell me if i'm right or wrong and why. >> no. scientists are very careful in looking at this important question to determine how much of the warning, which is approaching about it degrees fahrenheit is due to human activity. their confidence is improving. originally we thought there was a discernible influence, then we had likely, then very likely. in the latest report it's extremely likely. that means a 95% chance. this isn't politics. this is scientific calibration. >> marshal, what are we doing that's causing this? >> clearly since we figured out how to burn fossil fuels, that's increasing carbon dioxide, but we're changing the land cover, we're urbanizing our landscape. it's important to note that the 95% is very important, because