Climate Change Thinking, Then and Now

I decided to take a day off from Charles Adams’s school days today. Instead, here’s a repeat of some comments from eighteenth-century Boston‘s leading scientists on anthropogenic climate change.

Many Americans of that period were anxious to refute the European perception that North America’s climate was too extreme—too cold in winter and too hot in summer—to be healthy. Winter was changing, they declared, as the European population spread. For example, the Rev. Cotton Mather wrote in The Christian Philosopher in 1721:

our Cold is much moderated since the opening and clearing of our Woods, and the Winds do not blow such Razours, as in the Days of our Fathers, when Water, cast up into the Air, would commonly be turned into Ice e’er it came to the Ground.

Benjamin Franklin was more scientific in his approach, telling the Rev. Dr. Ezra Stiles in 1763 that Mather’s belief needed to be tested with systematic measurements over a range of time and space:

I doubt with you, that Observations have not been made with sufficient Accuracy, to ascertain the Truth of the common Opinion, that the Winters in America are grown milder; and yet I cannot but think that in time they may be so. Snow lying on the Earth must contribute to cool and keep cold the Wind blowing over it. When a Country is clear’d of Woods, the Sun acts more strongly on the Face of the Earth. It warms the Earth more before Snows fall, and small Snows may often be soon melted by that Warmth. It melts great Snows sooner than they could be melted if they were shaded by the Trees. And when the Snows are gone, the Air moving over the Earth is not so much chilled; &c. But whether enough of the Country is yet cleared to produce any sensible Effect, may yet be a Question: And I think it would require a regular and steady Course of Observations on a Number of Winters in the different Parts of the Country you mention, to obtain full Satisfaction on the Point.

Mather, Franklin, and their contemporaries inherited the seventeenth-century Scientific Revolution, but their view of time and space were still limited. Scientists of the nineteenth century made the crucial breakthrough of conceiving of Earth’s age in millions and then billions of years, not just thousands. We have the benefit of a much broader perspective and a whole lot more data. We should listen to the scientists of today.