1816: The Year Without a Summer
Volcanoes erupt all over the world, particularly in the "Ring of Fire". The ring refers to a circle of volcanoes that surrounds the Pacific Ocean. There are many active volcanoes in this perimeter zone and they have a big influence on the climate of the world.
Tambora, when it erupted in April of 1815, was perhaps the most dramatic example of that in human history. In the local area of the volcano alone, an estimated 92,000 people were killed either directly in the eruption or indirectly in the famine and epidemic triggered by it. Its worldwide impacts are beyond calculation.
Tambora is a volcano that forms the Sanggar Peninsula of Sumbawa Island. Sumbawa is one of the Lesser Sunda Islands of Indonesia and is a few islands east of Java. Today, the volcano is 33 NM (61 km) across at sea level and 9,348 feet (2,850 meters) high. Its caldera is 3.5 NM (6 km) across and 3,640 feet (1,110 meters) deep.
Prior to its eruption in 1815, the volcano may have been more than 13,000 feet (4,000 meters) tall. When it blew, Tambora spewed roughly 22 cubic NM (about 150 times the Mount St. Helen eruption) of ash and debris into the atmosphere. The ash from Mount St. Helen was only about 5 percent of the total Tambora produced. The eruption reduced the height of Tambora by more than 3,600 feet or 1,100 meters (some scientists estimate the volcano lost as much as 4,200 feet).
Ash fell as far as 700 NM (1,300 km) from the volcano and the eruptive column reached 24 NM (45 km) into the atmosphere. On Java, over 260 NM (480 km) away, the explosive eruption was heard "like the sound of cannon fire." It was so loud, the British navy put out to sea from Java under the impression they were under attack!
The sky went dark for days as far away as eastern Sumatra (west of Java) and ash piled several feet deep within 50 NM (93 km) of Tambora. The volcano ejected rafts of pumice so large, they were mistaken for new islands by ships that encountered them as much as four years later. Some were documented to be over 2.3 NM (4.8 km) long and proved to be a significant navigation hazard around Sanggar (what was left of Tambora’s peninsula).
It was the column of ash, gas and dust that cooled the Northern Hemisphere climate the most. The fine particles ejected into the upper atmosphere quickly circled the globe on the wind and shadowed the higher latitudes. This shadowing cooled the lower atmosphere noticeably within just a few months. Sulfur aerosols, halogens, chlorine, etc, in the eruptive column also contributed to the problem.
Interestingly, the upper atmosphere warmed quite a bit even as the lower atmosphere cooled. As the lower atmosphere experienced a maximum cooling of roughly 2-5 Fahrenheit (1-2 Celsius) degrees within 6 months of the eruption, the upper atmosphere warmed by up to 26 Fahrenheit (15 Celsius) degrees at 14 NM (25 km) above the surface.
In both cases, the temperature change was caused by a rise in the Earth’s albedo (reflectivity), which cooled the lower atmosphere, and increased absorption of solar energy in the upper atmosphere, which heated the upper atmosphere. Because the upper atmosphere is thin, it only takes a small change in radiational energy to effect a large change in temperature, which is why it heated so much.
A third element contributed to the ensuing cold period. The Tambora eruption coincided with a sunspot minimum (1790-1830) known as the Dalton Minimum (or Little Maunder Minimum). Sunspot minimums have been linked to colder than normal spells and the climate was already cooling before Tambora blew its top.
How much the Northern Hemisphere cooled is both a matter of debate and of location. It is a matter of debate because scientists can not agree on how much of the climate change could be attributed to Tambora’s eruption and how much could have been caused by other effects such as El Niño or sunspots. Sunspots were at a minimum in that period and a mild El Niño appears to have occurred a year after the eruption which might have offset the worst effects. I could get into all the tedious little details of the arguments, but I’ll spare you and just leave it that what caused how much of the cooling is still being debated.
In New England, eastern Canada, and western Europe, the late spring through early fall of 1816 was extraordinarily cold, an estimated 4-7 Fahrenheit (1.5 to 2.5 Celsius) degrees cooler than normal. In New England alone, wintry weather continued through the summer; snow fell with strong, frigid storms in every summer month and severe frosts destroyed crops repeatedly all season. In Canada, conditions were even worse. Small lakes remained frozen through the middle of July and even the cold-hardy wheat crop failed. The Lancashire Plain of England reported its coldest and wettest July in written history and Geneva, Switzerland had its coldest summer in the span of 1753 to 1960.
Elsewhere, the effects were milder or undocumented. Remember when this occurred; record-keeping was very limited west of the Mississippi River and not everyone in Europe (or anywhere else) was sufficiently educated to do any reporting either, even if they could spare the time from trying to survive. The disastrous summer of 1816 is the reason many of us are Americans today. Our ancestors came to America when crops failed and hunger drove them from their homes in Europe. The rest, as they say, is history.
Impacts of Tambora’s eruption expanded all over the Northern Hemisphere but were generally milder than those felt in New England, eastern Canada, and western Europe. It has however been argued (there go those scientists again) that the first worldwide epidemic of cholera was at least partly caused by Tambora’s eruption and the subsequent famine it spread across the world.
Over 92,000 people died in Tambora immediate area and uncounted thousands more died of starvation or disease it triggered around the world. Tambora proved conclusively that volcanic eruptions strongly affect the climate so we would do well to work to understand them so we may better predict and prepare for the impact of the next volcano that blows its top.