Mark Boslough: Ben Franklin, Climate Science, and National Security
That summer  was the hottest on record, and a mysterious "dry fog" had settled across Europe. The combination of heat and air pollution was too much for the weak and elderly. Mortality spiked among farm workers and laborers across the continent.
...The heat was so intense that meat went bad the day after it was butchered, and swarms of flies made life miserable.
The seeds of climate science in America were very possibly being planted as Franklin observed the changes 200+ years ago. Conditions went from bad to worse as Europe and North America were plunged into a deep freeze that winter. In its first peacetime year as an independent nation, the United States had to contend with more extreme weather than the colonies had ever experienced.
Other parts of the world were also in trouble. Monsoons in Africa and India were extremely weak, and rain barely moistened the African Sahel. Agriculture collapsed in the Nile Valley leading to mass starvation. Volney, the French historian, wrote, "Soon after the end of November , the famine carried off, at Cairo, nearly as many as the plague; the streets, which before were full of beggars, now afforded not a single one: all had perished or deserted the city." Within a year, Egypt had lost a sixth of its population.
Franklin watched this extreme weather with great interest and concern.
Recent computer models have shown that the Laki eruption cooled the northern hemisphere's land masses by about 2° to 6° F. This led to the extreme harsh winter, diminished the land-sea temperature contrast, weakened the Asian and African monsoons, and reduced water and food supplies in the most vulnerable parts of the world.