The period 1812-1817 was one of exceptional volcanic activity, and the sheer volume of volcanic dust pumped into the atmosphere by these volcanic eruptions caused a general, temporary cooling in the earth’s climate around this time.
This temporary climatic cooling peaked during the summer of 1816 was the peak of this cooling and the reason the peak fell in the summer of 1816 is almost certainly die to the eruption of the Tamboro volcano east of Java in April 1815 (believed to be one of the most explosive eruptions of the last 10,000 years). At the time sunspots were blamed for the unseasonable weather (Laskin 1996). Anyway, this eruption put more than 150 million tonnes of dust in the atmosphere which gradually spread around the globe acting as a veil reflecting incoming solar radiation back into space and cooling the earth (temporarily) which in turn caused a change in the world’s, and in particular the northern hemisphere’s, weather patterns. Some dust from volcanic eruptions in the West Indies in 1812 and Philippines in 1814 was also probably still the atmosphere (Lamb 1995) and this will have helped the global cooling process too.
So if Tamboro erupted in 1815 why wasn’t the summer of 1815 rather than the summer of 1816 the year without a summer? Well, the answer is that there is a time lag between a volcanic eruption and a change in weather patterns caused by the length of time needed for stratospheric winds to distribute the volcanic dust particles around the world.
It should at this stage be pointed out that not all volcanic eruptions affect the climate - whether an eruption will affect the climate or not depends on how powerful the eruption is and what part of the atmosphere the dust from the eruption reaches. When volcanoes erupt lots of gas and dust is injected into the atmosphere. Depending on how the volcano erupts (eg vertically or horizontally) and where the volcano is a large eruption can have a cooling effect on the atmosphere which can last for 1-3 years or so. The dust and gases need to reach the Stratosphere (more than 10km above sea level) where winds at that level in the atmosphere can blow the dust and gas around the world. The dust and gas then reflect energy from the sun which would otherwise reach the earth back into space this cooling the earth and altering its weather patterns. This sort of thing has happened from time to time through the earth’s history and most recently in the early 1990’s when the eruption of Mount Pinatubo in the Philippines in 1991 cooled global temperatures in 1992 by around half a degree.
Now, here some of the highlights of the year without a summer:
Between May and September southern Quebec was affected by a series of cold waves which killed crop and led to near famine conditions in some parts. During one such cold spell between June 6th and 10th 30-36cms snow lay on the ground in Quebec City. Meanwhile on June 6th and 8th it snowed in Montreal (Neil Davids 1976). Sub-zero temperatures during June blackened crops and froze ponds killing wildfowl.
Some mornings in July and August were decidedly chilly and probably frosty, whilst hard frosts on 11th, 12th and 27th September ended the already shortened growing season.
In New England the summer of 1816 included some early June snow, cold nights in both July and August, for example the widespread frost at low level sites around New England on the 8-9th July and the damaging frosts on the 22nd August from interior New England right the way south into North Carolina (Ludlum 1989). There were droughts too and finally killing frosts in September, such as that of the 27th in New England (Ludlum 1976, 1989). This all led to crop failures and food shortages and helped stimulate a move westwards the following year. In both Connecticut and parts of New York State frosts after April are rare, but in 1816 frosts were recorded every month of the year (Lamb 1816, Neil Davids).
Summer temperatures were between slightly below average and 3-5 degrees below average, depending on which source you choose to believe. The most severe cold snap came in early June and killed the vegetable crop in parts of New England, ruining some farmers. This, and a couple of other cold snaps, each just a few days long, has made the summer of 1816 notorious and infamous, hadly surprising given the far reaching consequences of the unseasonable weather. The worst of the weather and of the effects of the poor weather was in northern New England. However, conditions during the summer were also, well, summer-like at times. For example, a late June heatwave saw temperatures top 32C between the 22nd and 24th June and temperatures were near normal for much of the first two-thirds of August (Ludlum 1985). It should also be pointed out that since 1816 it has been just as cold or even colder in each of the summer months but never in consecutive months.
The most notorious part of the infamous summer of '16 was the cold snap in early June. Juen began promising enough and on the 5th temperatures in New England climbed into the low 30's Celsius, for example Salem, Mass., reached 32C. However, during the afternoon of the 5th thundery showers broke out over New England and later in the day a cold front swept across the region, dragging cold air down from Canada in its wake. The next day, the 6th, was much colder. Some places were as much as 27 degrees colder than the day before (Ludlum 1989), and in parts of Vermont and in Boston temperatures reached little more than 7C (Ludlum 1985, Laskin 1996). Conditions turned colder during the next 2 or 3 days and precipitation that fell became increasingly wintry in nature. On the 7th snow fell over the northern highlands of New England, snow flurries fell in parts of Connecticut and Massachusetts (Ludlum 1976), in Salem and Boston for example, and away from the coast, snow fell in June as far south as 42 degrees north (Lamb 1995). Near Danville, Vermont snowdrifts just over 50cms high were reported (Ludlum 1985). Contemporary reports spoke of prolonged falls of snow, snow settling and lying for a couple of days and very windy weather at times (Ludlum 1985). However, by the 10th and 11th conditions began to improve, although mornings were still frosty.
By the 12th June 1816 temperatures were rather more normal and in the 20's Celsius, and there they stayed until the 22nd to the 24th when something of a heatwave developed; during these 3 days temperatures around New England widely topped 32C. On the 23rd a high of 37C was recorded at Waltham, Massachusetts (Ludlum 1976) whilst on 24th June Salem, Massachusettes also reached 37C (Ludlum 1989). The Boston area also reached the high 30's Celsius during this time (Ludlum 1985).
July 1816 was notable for a lack of warm nights, which, it turns out, are necessary in allowing corn to grow and ripen. Some of the coldest nights were on the 8th and 9th when a light ground frost affected some areas, such as the Upper Connecticut Valley and at Middlebury, Windsor and Williamstown in Vermont (Ludlum 1985). July 1816 was also a very dry month and drought began to affect the harvest in some parts of New England. Moving into August, temperatures were normal for the first two-thirds of the month, and peaked in the low 30's Celsius on the 18th and 19th, whilst connditions remained dry. The passage of an active cold front on the 20th led to a cooling down and a couple of spells of frosty nights during the last third of the month which wiped out crops in some northern parts of New England (Ludlum 1985). Contemporary reports mentioned snow covered mountains in August and the dry, cool conditions of late August persisted through September which ended with a series of crop killing frosts (Ludlum 1985).
Europe was worse affected than the USA (possibly something to do with the relative sizes of population rather than weather conditions themselves). Either way, cold weather and rain caused crop failures and famine.
During the summer the northern hemisphere's most unsettled weather is usually concentrated in the sub-Arctic region. However, during the summer of 1816 some of the northern hemisphere most unsettled weather was to be found in an area extending from Newfoundland eastwards across the Atlantic Ocean and England into the southern Baltic.
With this in mind it's perhaps to suprise to find that it rained on 142 out of 153 days during the May-September period in Ireland. In England the Central England Temperature Series value for the summer of 1816 is 13.37C, the third coldest summer on record (records began in 1659) behind those of 1725 (13.17C) and 1695 (13.1C) which occured during the Little Ice Age. A few Mays, plenty of Septembers and a couple of Octobers in England have been warmer than any of the three summer months in the summer of 1816. Low temperatures and prolonged rain caused crop failures in some western parts of Britain whilst to the south-east parts of Switzerland experience famine due to crop failures (Lamb 1995).
Away from Britain, there were food riots in France and Switzerland and at least 200,000 died from hunger and a typhus epidemic in Europe whilst in Germany there was a sharp peak in rye prices in 1816 and 1817 and around Europe wheat prices also rose at that time. Meanwhile, near Iceland sea ice persisted into June. The unusual weather patterns of the summer of 1816 have also been blamed for causing or adding to the severity of a number of plagues and epidemics, including the 1816-1819 European typhus epidemic which was among the severest ever, a plague which affected south-eastern Europe and the Mediterranean between 1816 and 1819 (Lamb 1995).
So far we’ve focused on where weather patterns were negatively altered, but whenever there are unusually cold and wet weather patterns in one part of the world the opposite weather pattern will occur somewhere else in the world to compensate. And so it was in the summer of 1816 when Ukraine had a hot summer and northern Scotland and the Shetland Islands were fine (Lamb 1995).
The Asian summer monsoon didn’t go unaffected; the far east and Korea had some heavy rains whilst summer rainfall over India was concentrated in the south of the country and a huge cholrea epidemic which began in 1816-17 may also have been linked to the adverse weather conditions during the summer of 1816 (Lamb 1995).
Consequences and Final Remarks
The near destruction of the harvest in New England led to the first mass migration out of New England to the mid-west which in turn led to a shift of farming away from eastern USA. In other words, a few days of bad weather one summer nearly 200 years changed farming in the USA for ever! The summer of 1816 and the fact that in England other summers at this time were cooler and wetter than in the 18th century may have led to the practice of irrigation being abandoned, particularly from the 1820's onwards (Lamb 1995). In the far east climatic cooling in the early 19th century led to crop failures in the Yantze Valley in China and in parts of Japan. Globally, the period 1820-1850 was one of social upheaval, international migration, disease epidemics and various crises and some writers have suggested that this might not be entirely unconnected to the climatic events during the 1810's.
Some of these consequences are perhaps not directly attributable to the summer of 1816, but certainly to the general climate of the time, but one definite consequence of the summer of 1816 is that the bad summer weather over central Europe inspired Mary Shelley to write her novel Frankenstein.
CHANG, G. (1999): 1816: The Year Without a Summer, www.exn.ca/volcanoes/weather.cfm
LAMB, H. H. (1995): Climate, History and the Modern World, Routledge, p.433
LASKIN, D. (1996): Braving the Elements, The Stormy History of American Weather, Anchor Books, p.241
LUDLUM, D. (1976): The Country Journal New England Weather Book, Houghton Mifflin Company, p.147
LUDLUM, D. (1985): The Vermont Weather Book, The Vermont Historical Meteorological Society, p.300
LUDLUM, D. (1989): The American Weather Book, The American Meteorological Society, p.296
NEIL DAVIDS, T. (1976): 1816 The Year Without a Summer, www.gi.alaska.edu/ScienceForum/ASF0/098.html
PHILLIPS, D. (1990): The Climates of Canada, Minister of Supply and Services Canada, p.176
Many of these books are out of print. However, they can be bought from second hand book dealers. The best place I've found to buy old books on the 'net is Abebooks.com, who I can thoroughly recommend. The search engine is dead easy to use and I've never had a purchase that's gone wrong!
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Dan Suri, 27 January 2002