The Year with No Summer was a Brutal Shock for Half the World in 1816

Jefferson as he appeared following the crippling blow to his finances suffered from the failed harvests of 1816. Wikimedia

2. Jefferson was likely aware of the volcanic eruption which caused the weather event, though he did not recognize it as such

Thomas Jefferson’s extensive correspondence – most of which is retained at Monticello and the University of Virginia – makes it likely that he was aware that a major volcanic event occurred in April, 1815, half a world away from the Blue Ridge of Virginia. On April 10 Mount Tambora erupted, with the immediate effect of killing approximately 100,000 Pacific islanders and launching into the atmosphere the largest amount of volcanic ash and toxic gases ever recorded as coming from a single source. No volcanic eruption in human history threw more damaging gases and particulates into the atmosphere. The massive cloud of volcanic ash, which was actually particles of many substances, spread across the Pacific, filling the atmosphere with a cloud which blocked the warming solar radiation, or at least a significant portion.

Thomas Jefferson did not just look out of his window and record his weather observations, along with temperatures. He was a collector of the finest weather instruments available in his day, and he used them with a scientific mind. Yet Jefferson was not possessed of the knowledge necessary to connect the Tambora disaster with the disastrous summer he and his fellow agriculturalists were to suffer that year. Nonetheless, much of what is known about the disaster, is from the observations he dutifully recorded daily, and are still the primary source of weather impact studies by those who analyze the Tambora disaster, and predict the potential damage of a similar or worse such event today.