Climate change is perhaps the most important issue of the 21st century. It was also a topic of profound interest to the Founding Fathers of the United States. Thomas Jefferson had an interest that bordered on the obsessive. Indeed, on the morning of July 4, the day that America’s independence from Britain was declared, Jefferson visited Sparhawk’s stationery store in Philadelphia to buy himself a new thermometer. We know from his diary that as the Declaration was being delivered to Congress, Jefferson was busy recording that the ambient temperature was 72.5°F.

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