“If you’re younger than 26, you have never seen a month where the global mean was as cold as the 161 year average,” observes Robert Grumbine. In contrast, “there are no periods as long as even 20 years of continual below reference temperatures.” He finds that the period 1880-1940 seems to best represent a stable long-term average for global temperatures. If that’s the case, then the “last time the global mean was below the climate normal was March, 1976. If you’re 35 or younger, you have never seen a global mean below climate’s real normal.”
Cumulative deviations from the 1850-1940 global mean temperature.