From the beginning of time and on up through the advent of humankind, the concentration of carbon dioxide in the Earth’s atmosphere was balanced between the amount released by the respiration of animals and plants or from warm ocean water, and the amount absorbed by plants or the colder ocean water.
It wasn’t until humans came along and started burning fossil fuels that the balance was thrown out of whack and carbon dioxide levels in the atmosphere started to increase. But while CO2 levels were not like the post-industrial levels seen today, there were fluctuations in temperature and in the climate.
The fluctuations in CO2 levels in the Earth’s past have fascinated scientists and led to a number of studies. Just about all of them have come to the conclusion that it was volcanic activity related to plate tectonics that changed the Earth’s temperatures and caused changes in the climate, often on a worldwide scale.
Volcanism and changes in climate
While Benjamin Franklin was stationed in Paris as the first diplomatic representative of the U.S. in 1784, he made an important connection between volcanic eruptions and their impact on the Earth’s climate. He observed that in the summer of 1873, the climate was “abnormally cold,” both in the U.S. and in Europe.
Scientific American reports that Franklin is said to have written, the ground froze early and the first snow stayed on the ground. Winter was more severe than usual and there seemed to be “a constant fog over all of Europe, and [a] great part of North America.”
Indeed, the climate conditions Franklin had observed was the result of volcanic activity. In 1783, the Laki fissure system, southwest of the Vatnajokull glacier in Iceland, produced one on the largest lava flows in historic times. The Laki fissure system is a chain of volcanoes in which lava erupts through a crack in the ground instead of a single point.
The eruptions lasted from May 1783 to May 1785. At least 15 cubic kilometers (3.6 cubic miles) of basaltic magma erupted from 140 vents along the 27 kilometer (17 mile) long fissure. The resulting lava flow ended up covering two churches and partially or completely destroying 30 farms.
During peak episodes of the Laki event, large portions of Iceland were covered in a fine volcanic ash and an obnoxious haze of gas and aerosols. Fish catches were dramatically decreased and at least 50 percent of Iceland’s livestock were lost and there was a 25 percent decline in the human population.
While the Laki eruptions were astonishing, we must not forget that another eruption was taking place in Iceland during that same period of time. Nearby Grímvötn volcano was also erupting, possibly as many as eight times between May 1783 and May 1785. The devastation caused by the Laki and Grímvötn eruptions on Iceland was profound, but the events also had an impact worldwide.
More recently, the eruption of Mt. Pinatubo in the Philippines on June 15, 1991, blasted an estimated 20 million tons of sulfur dioxide and ash 12 miles into the atmosphere. This eruption also caused a great loss of life and widespread destruction. And even more recently, the volcanic eruptions in Japan and Ecuador also have their role to play.
How volcanic eruptions can change the climate
While volcanic eruptions might last a few days or even longer, the huge amount of gasses and ash that are spewed into the atmosphere can last for several years, altering the climate patterns and temperatures worldwide sometimes. The sulfuric gasses convert to tiny sulfate aerosols containing 75 percent sulfuric acid, and they can hang around in the stratosphere for as long as four or five years.
Correlating volcanic activity with tectonic plate movements, scientists have found that “Volcanic eruptions cause short-term climate changes and contribute to natural climate variability,” says Georgiy Stenchikov, a research professor with the Department of Environmental Sciences at Rutgers University.
But man-made, or “anthropogenic” emissions can make the consequences of volcanic eruptions on the global climate system more severe, Stenchikov says. This is because the actual amount of carbon dioxide added to the atmosphere by volcanic eruptions is trivial, compared to what is added by anthropogenic emissions. Volcanoes produce about 110 million tons of CO2 each year while humans contribute almost 10,000 times that amount.
While climate change is here to stay, don’t be surprised if the weather gets cooler again, and it may last for a number of years. But it doesn’t mean global warming is taking a hiatus, it just means we have experienced a lot of volcanic activity recently.
