"Global cooling was a conjecture during the 1970s of imminent cooling of the Earth's surface and atmosphere culminating in a period of extensive glaciation. This hypothesis had little support in the scientific community, but gained temporary popular attention due to a combination of a slight downward trend of temperatures from the 1940s to the early 1970s and press reports that did not accurately reflect the full scope of the scientific climate literature, i.e., a larger and faster-growing body of literature projecting future warming due to greenhouse gas emissions."
But this is so easy to find that I suspect the details don't really matter to you. Perhaps another wikipedia article might help: http://en.wikipedia.org/wiki/Motivated_reasoning