Top graph is slope of a linear trend line for the 15 years prior to each indicated year. Bottom graph is the underlying temperature data.
For 30 of the 15-year blocks the trend was negative; for 88 the trend was positive. The last year in which there was a linear cooling trend for the 15 years prior was 1977.
http://imgur.com/CYc5G5A
Top graph is slope of a linear trend line for the 15 years prior to each indicated year. Bottom graph is the underlying temperature data.
For 30 of the 15-year blocks the trend was negative; for 88 the trend was positive. The last year in which there was a linear cooling trend for the 15 years prior was 1977.