http://denisdutton.com/newsweek_coolingworld.pdf
Published 1975, with a great graphic of the nation w/ cooling temps

An excerpt:

"There are ominous signs that the earth's weather patterns have begun to change dramatically and that these changes may protend a drastic decline in food production - with serious political implications for just about every nation on earth.  The drop in food output could begin quite soon, perhaps only ten years from now.  The regions destined to feel its impact are the great wheat-producing land of Canada and the U.S.S.R. in the north, along with a number of marginally self-sufficient tropical areas - parts of India, Pakistan, Bangladesh, Indochina and Indonesia - where the growing season is dependant upon the rains brought on the monsoon.

The evidence in support of these predictions has now begun to accumulate so massively that meteorologists are hard pressed to keep up with it.  In England, farms have seen their growing season decline by about two weeks since 1950, with a result over-all loss in grain production estimated at up to 100,000 tons annually.  During the same time, the average temperature around teh equator has risen by a fraction of a degree - a fraction that in some areas can mean drought and desolution.  Last April, in the most devastating outbreak of tornadoes ever recorded, 148 twisters killed more than 300 people and caused half a billion dollars worth of damage in 13 US states."