Yes, people like to bring up the "global cooling" scare of the 1970's. Do you know the story behind that?

Between 1940 and 1970, scientist reported that there was a cooling trend. In 1975, Newsweek picked up the story and warned that we where heading into another ice age (this is what most people quote).

The funny thing is, the 1974 report this was based on goes on to state that: "the present time of high temperatures should be drawing to an end" but "human interference has already altered the environment so much that the climatic pattern of the near future will follow a different path".

In short, the earth should be cooling but it isn't because of human involvement. We've stopped an ice-age and now we're over correcting.