Today I experienced perhaps the coolest thing that’s ever happened to me since I became a historian: in the reading room of the Massachusetts Historical Society, I was handed the one and only original of a journal book written by Thomas Jefferson. Not a copy–not a microfilm, facsimile or digitized version–but the real one, written by Jefferson’s own hand. This may not sound quite so momentous, given that there are approximately (I checked) 50,000 original documents attributed to Jefferson in various archives; but this volume was his “Weather Book,” the text of which has never been published. It’s not that it’s a big secret, but it’s just that the many cataloguing, archiving and publishing projects that have been going on since Jefferson’s death in 1826 simply haven’t gotten around to it yet. The “Weather Book” is not considered as important as, say, the Declaration of Independence, or his famous correspondence with John Adams; yet, as I discovered today, there are some fascinating and momentous things contained in its ancient pages.

I got to see the book because, as you may know if you read this blog, I’m researching a period of global climate change called the “Cold Decade” (1810-1820), and Jefferson, having lived through it and left documents behind, is a key source in this story. You may recall that back in June I found some letters (published) from Jefferson that established the fact that his post-presidency was quite a trying period, mainly because he was broke and the environmental problems at Monticello–many of them connected to the Cold Decade–seriously hampered his income and livelihood. Not only does the Weather Book completely corroborate this thesis, but it demonstrates that Jefferson was far more concerned with climate–and climate change–than has generally been let on.


Monticello, Jefferson’s Virginia plantation, was the main place where the records in his Weather Book were gathered.

First, I should tell you that the Weather Book itself (that’s a title come up with by archivists) consists mostly of a record of weather observations–temperature, wind direction and conditions during the day, including precipitation–over a period of 14 years, from November 1802 to December 1816. This period encompasses most of Jefferson’s presidency and part of his retirement. The first entry, on November 1, 1802, reports that it was 34° in Washington and they were experiencing the first ice of the season. In addition to weather, he would also record various other environmental details, such as when particular trees bloomed or when in the year various items of produce became available for the first time. For example, on June 5, 1803, Jefferson writes, “Crabs came to market. we have heard of them in Alexa [Alexandria] a fortnight.” Noteworthy weather events occurring away from where he was also sometimes made it into the journal. In 1816, the “Year Without Summer,” Jefferson records the news of bizarre snowfalls in Canada and Vermont in June, and unseasonable frosts in August.

In a journal like this it’s tempting to look for particular historic days, and see them recorded in the long list of readings just like any other. April 30, 1803 was the day the treaty concluding the Louisiana Purchase was signed. Jefferson mentions nothing of that, but he does record that the temperature at Monticello was 59 degrees in his bedroom at sunrise. The sun that day rose for the first time on an America that was suddenly twice as larger. The day Lewis and Clark left on their expedition, the day Jefferson’s Vice-President Alexander Hamilton was murdered by Aaron Burr, even the day of Jefferson’s re-election–all pass without comment other than the usual temperature and wind readings.

Even from this collection of raw data you can learn something about what the Presidency was like in the early 1800s. Because he has to record where his readings were taken, the Weather Book is a chronicle of Jefferson’s comings and goings during his term in office. It’s surprising how little of it he spent in Washington. Most 19th century presidents hated Washington and were only in town when Congress was in session, but Jefferson didn’t even do that. He was, for example, at Monticello from March 8 to May 14, 1804, then in Washington only until July 22, and after that returned to Monticello and evidently remained there until after the beginning of 1805. Nowadays Barack Obama can’t take an afternoon off to play a round of golf without Republicans pillorying him for neglecting the people’s business. Jefferson was on vacation nearly 70% of a full year–a year during which he was running, ultimately successfully, for re-election!


Jefferson might not have imagined a future world blighted by global warming, but the Weather Book proves that he was curious and concerned about manmade climate change.

But the most amazing part of the Weather Book comes at the end. Over the course of three pages of tiny writing–Jefferson’s handwriting was so small I needed a magnifying glass to see it–he explains, in a passage evidently written in December 1816 or January 1817, why he kept all these meticulous readings. He kept them in the hopes that some scientist (a “physician,” as Jefferson refers to them) could someday synthesize all his data into a discernible pattern to explain the long-term behavior of climate. Even more specific than that, Jefferson was seeking the answer to a great debate that was going on at that time: was the Earth’s climate gradually growing warmer or colder, and if so, why? In 1785, in Notes on the State of Virginia, Jefferson had come out firmly as a global warming theorist; he believed (correctly, it turns out) that human activity, mainly deforestation, development and alteration of waterways, was making the seasons more moderate. This was a century before the greenhouse effect was discovered (and there were few greenhouse gas emissions anyway until the mid-19th century), but he clearly had the right idea. The Weather Book proves that he still held this idea in 1816, and he had devoted 14 years of painstaking record-keeping so that somebody, somewhere could eventually use his data to prove it. Now, of course, we know that manmade climate change is an undeniable fact, and Jefferson’s data was small issue to that discovery, but he did come to the right conclusion.

I couldn’t be more gratified by what I found in the Weather Book. Not only was it thrilling to read something actually written on the page by one of my great heroes in history–and something not very many others, comparatively speaking, have read–but it was as if Jefferson was talking directly to me. He was deeply interested in climate change, something I’d previously suspected but had never been able to prove. Today, in Jefferson’s own tiny handwriting, I found the proof.

My thanks to the Massachusetts Historical Society for giving me the opportunity to see this incredible piece of living history. This is one of my favorite things I’ve ever done as a historian. It was truly a wonderful day!