The world’s first empire began 4,300 years ago and was located between the Tigris and Euphrates rivers. King Sargon united the Babylonian cities, and his family ruled for three generations until, suddenly, Akkad collapsed. The “Curse of Akkad” was presumed fictional until Yale archaeologist Harvey Weiss discovered the ancient city of Tell Leilan in 1978. Weiss surmised that severe drought had caused the fall of the great city. Other ancient empires afflicted by climate change include the classic Mayan, Andean Tiwanaku and the Old Kingdom of Egypt. Scientists in the 1980s and 1990s postulated shifting precipitation patterns as the cause of crop failure. These climate changes predate industrialization.

In the 1980s, the Goddard Institute for Space Studies (GISS) produced a climate model that showed global warming. Climate modelers refer to anything that alters the energy of the system as “forcings.” Adding carbon dioxide to the atmosphere is an anthropogenic forcing. Since preindustrial times, carbon dioxide concentration in the atmosphere has risen by a third, and methane has doubled. It takes several decades for the impacts of a forcing to be felt, which is both fortuitous and disastrous.