[Illustrations, footnotes and references available in PDF version]
Recently we shared a story in the Wall Street Pit how NASA has gradually reduced the warm middle 20th century blip and created a more continuous warming. You can see in this 1976 National Geographic graph, a rather significant warm period starting in the 1920s and peaking during the dust bowl era in the United States in the 1930s and only slowly declining heading into the 1950s. It showed more significant cooling in the 1960s and 1970s. The story questioned where to from there.