The five warmest years over the last century occurred in the last eight years.

Hansen's development and use of global climate models has contributed to the further understanding of the Earth's climate. 6–5. The linear polarization data obtained from the same mission confirmed that the low- and mid-level clouds were sulfuric acid with radius of about 1 micrometer.

Hansen retired from NASA in April 2013 saying he planned to take a more active role in the political and legal efforts to limit greenhouse gases. From 1981 to 2013 he was the head of the NASA Goddard Institute for Space Studies in New York City a part of the Goddard Space Flight Center in Greenbelt Maryland. In recent years Hansen has become an activist for action to mitigate the effects of climate change which on a few occasions has led to his arrest.