The evidence is clear — the long - term trend in global temperatures is rising, and humans are largely responsible for this rise. (dotearth.blogs.nytimes.com)
The idea that we might be entering another ice age was put forward in the 1970s by some scientists who noted a cooling trend in global temperatures from the 1940s to the 1970s. (discovermagazine.com)
As can be seen from your graph there had been a slight falling trend in global temperatures between 1950 and 1976. (realclimate.org)