July 6. Products of volcanic eruptions that do not reach the stratosphere once, after a while there is still carried by atmospheric currents and begin to reflect the sun's rays.
Scientists have shown that even small volcanic eruptions have a significant impact on the climate, saturating the upper layers of the atmosphere of their emissions. The study is published in the journal Science.
Previously it was thought that only large volcanoes that could throw ash particles directly into the stratosphere affect climate in the long term. Sulphur dioxide (SO2), one of the main products of volcanic activity, forms in the stratosphere, aerosol, which is held in it for months and years, reflecting the sun's rays, thereby lowering the temperature of the Earth. So, after a powerful eruption of Mount Pinatubo in the Philippines in 1991, the annual average temperature of the Earth has fallen by half a degree.
Volcanic slurry during smaller eruptions reaches the limits of the troposphere, the lower layer of the Earth's atmosphere, where rain clouds are formed, so the researchers believed that the impact on the climate of small volcanoes minimal. "Aerosol does not stay in the lower layers of the atmosphere, and the slightest change in the weather immediately lowers it down" — said Adam Bourassa, one of the authors of the work.
Vulcan Nebro helped the Asian monsoon
To prove that small eruptions still have an impact on the climate, the researchers studied the effects of Dialled eruption in Eritrea (North East Africa), which happened in 2011. Then the volcano threw in the upper troposphere, at the height of 9-14 kilometers, about 1.9 million tons of sulfur dioxide. In these latitudes, the stratosphere begins at a height of only 17-kilometers, therefore, according to generally accepted ideas, the emissions of the volcano Dialled had to quickly settle.
In fact, it was found that the aerosol formed sulfur dioxide yet penetrated into the stratosphere. Its fixed by the Swedish meteorological satellite "One", on board of which are sensors of the OSIRIS, which allows to analyze the composition of the upper atmosphere. The content of SO2 in the atmosphere after the eruption Dialled was the highest in all the ten years of observation.
Scientists have concluded that sulfur dioxide fell from the upper troposphere to the lower stratosphere by a powerful anticyclone, which is observed during the monsoon season in Asia and the Middle East, next to whom, and erupted. From this the researchers concluded that even small volcanic emissions can rise atmospheric flows and form a stable suspension in the stratosphere, cooling the Earth. According to the authors, this fact must be taken into account in the construction of climate models.