Ric Werme writing at Watt Up With That has an interesting weather story that takes place during the Dalton Minimum. The article is quite long and he provides this Executive Summary:
- The proximate cause of the cold weather in 1816 is the explosion of Mt Tambora in April 1815. This may have been the largest volcanic explosion in recorded human history and lofted a lot of sulfuric acid aerosols into the stratosphere. However, 1816 is just one of several cold years blamed on volcanoes, solar activity, and other causes.
- There were warm days, even a few hot days. There were even some warm months mixed in with the cold ones, so the result was that the annual average temperature wasn’t very far from average. In this and other cases, small deviations can add up to a major impact on the length of the growing season, number of growing degree days, etc.
- I think the weather pattern was most affected by high latitude cooling and the polar jet stream (the storm track) shifting southward. South of the storm track there was less cooling, but they were still affected by weather systems from the north. There are signs that the jet stream had a “meridional” flow which allows polar air to surge south and tropical air to surge north.The effect of volcanic aerosols is poorly documented, likely because its poorly understood. Pretty much all of the sources talk about the amount of aerosol and the effect on global temperatures. However, I think the effects vary with latitude and that had a major effect on temperatures at different latitudes and the intensity of various weather events.
- What set 1816 apart from other years were two freeze events. If frosts in June and August hadn’t happened, the harvest would have been very different, and few people would write about the weather of 1816. There was plenty of other cold weather in 1816, so this essay is way too long and needs this executive summary
- A claim that snow or frosts occurred in every month of the year does not hold for parts of New Hampshire in July. There may have been such events in western Connecticut or Massachusetts, or even Virginia, but some descriptions may be exaggerated. It doesn’t affect the outcome of the year, as most everything that made it through July was killed in August.
- 1816 set into motion changes in New Hampshire that probably would have happened later, but traces of them still exist today.
The full article is HERE.
I found the comments on the article equally interesting. My grandmother Thomas was an avid gardener and had a kitchen garden all of her adult life. She kept a record of the last spring frost and the first fall frost in Nevada County CA and adjusted her planting and harvesting based on the record of the past. An 1812 summer with late and early frosts would have thrown her for a loop.