This has been the subject of many Free Republic posts.
Newsweek:The Cooling World April 28, 1975 Text of Newsweeks 1975 story on the trend toward global cooling.
It may look foolish today, but in fact world temperatures had been
falling since about 1940. It was around 1979 that they reversed
direction and resumed the general rise that had begun in the 1880s,
bringing us today back to around 1940 levels.
A fine short history of warming and cooling scares has recently
been produced and is available here.
PDF:Newsweek Global Cooling