In 1815, the volcano Mount Tambora exploded in what was probably the largest eruption of the last 1,500 years. The event has often been suspected of causing Europe's so-called “year without a summer” as ash and sulfur-dioxide blocked out the sunlight. However, atmospheric scientists have not been certain how much the explosion contributed to the chilly, wet conditions the following year. Now, climate models have been used to show Tambora indeed caused the record-breaking cold and possibly the damp.
For the people of Indonesia, the enormous eruption of April 10 meant a tsunami that killed between 40,000 and 60,000 individuals, depending on your source. However, with the history of the era primarily having been written in Europe and North America, attention has focused on a possible delayed effect in those places.
Average temperatures worldwide in 1816 were 0.4º-0.7ºC (0.7º-1.3ºF) cooler than preceding years. The rainy conditions have been credited for giving Mary Shelley the time to write Frankenstein, thus launching the entire Science Fiction genre.
Dr Andrew Schurer of the University of Edinburgh has modeled what the year 1816 would have been like without the volcano, using what we know of the conditions prior to the eruption and the solar input. He reports in Environmental Research Letters that eruption or no eruption, 1816 Europe might have experienced an unusually wet year, but it was the volcano that made it so cold.
"Including volcanic forcing in climate models can account for the cooling, and we estimate it increases the likelihood of the extremely cold temperatures by up to 100 times,” Schurer said in a statement. “Without volcanic forcing, it is less likely to have been as wet and highly unlikely to have been as cold."
When the year without a summer was underway, people had no idea of the causes. The possibility a volcano on the other side of the world affecting the climate only first became discussed after the similar cooling caused by Krakatoa's eruption of 1883. Tambora was first connected to the year without a summer in 1913, and over the century since the link has become widely accepted.
Nevertheless, it has also been noted that 1816 lay at the end of a period of unusually low solar activity, causing debate about whether Tambora represented the whole story. It's only now, with advanced global climate models and the collection of proxies from around the world, that we can answer this in more detail.
Tambora occurred when food supplies were unusually vulnerable from a combination of the disruption of the Napoleonic wars and several summers cooled by smaller eruptions. Hundreds of thousands of people died in the subsequent famines.