In 1981, James Hansen was the Director of the NASA Goddard Institute for Space Studies. He was also the lead author of a seminal paper published in the prestigious journal Science entitled “Climate Impact of Increasing Atmospheric Carbon Dioxide“.
In the paper, Hansen and his colleagues reported (and illustrated with multiple graphs) the widely accepted 100-year (~1880-1980) record of hemispheric and global temperature changes. At the time, most climate scientists were reporting that the Northern Hemisphere’s (NH) temperatures had undergone a rapid warming of between +0.8 and +1.0¬∞C between the 1880s and 1940. Then, after 1940 and through 1970, NH temperatures were reported to have dropped by about -0.5 to -0.6¬∞C, a decades-long cooling trend which at the time had fomented widespread debate about global cooling in the scientific community.
Like their peers, NASA’s Hansen and his co-authors indicated that the Northern Hemisphere had warmed by ~0.8¬∞C between the 1880s and 1940, and then cooled by ~0.5¬∞C between 1940 and 1970.
A graph of “observed temperature” for the Northern Hemisphere was included in the paper to illustrate these climatic trends.
Today, NASA’s Goddard Institute for Space Studies is directed by Dr. Gavin Schmidt, a trained mathematician. (James Hansen retired from the position in 2013.) Schmidt’s version of the Northern Hemisphere’s temperature record for 1880-1980 looks vastly different than what his predecessor had illustrated in 1981. Instead of leaving the historically observed temperatures alone, NASA has invented new ways to portray the pre-1981 temperature history of the Northern Hemisphere.