Tuesday, June 24, 2014

Klyuchevskaya Sopka


Hell yeah, that’s a volcanic eruption as seen from space.

To be more precise, it is the eruption of Klyuchevskaya Sopka taken by the Space Shuttle Endeavour on the 30th of September 1994.

Impressive, isn’t it eh?

This particular eruption expelled ash and gases upwards of 18,300 metres above sea level and the winds carried the ash as far as 1,030 km. Looking at this image and reading just how enormous the eruption was, it is easy to understand why some people link current climate change with events like volcanic eruptions. But, what role do volcanoes actually play?

As we can see, during major volcanic eruptions huge amounts of volcanic gas, aerosols and ash are injected into the stratosphere. The ash tends to fall fairly rapidly from the stratosphere; a matter of days or weeks and has little implication on the climate. However, volcanic gases like sulphur dioxide can cause global cooling and volcanic carbon dioxide, the infamous greenhouse gas, has the potential to promote global warming.

Perhaps contrary to belief, the most significant climate impacts of volcanic activity are as a result of sulphur dioxide. Sulphur dioxide gas is converted to droplets of sulphuric acid in the stratosphere over the course of a week to several months after the eruption. Winds in the stratosphere spread the aerosols until they practically cover the globe. As the droplets have a high albedo, they reflect sunlight reducing the amount of energy reaching the lower atmosphere and the Earth's surface; cooling them. (NASA,1996)

Once formed, these aerosols stay in the stratosphere for around 2 years, although data from NASA’s stratospheric Aerosol and Gas Experiment (SAGE II) showed the effects of the eruption of Mt. Pinatubo in 1991 lingered for up to 10 years.

As mentioned previously, carbon dioxide is also emitted during volcanic eruption and a question that has commonly been asked is “Don’t volcanoes contribute much more CO2 emissions than human activities?

Unfortunately the answer to that question is a clear and unequivocal “No”.

Published reviews of the scientific literature by Kerrick et al (2001) report a minimum-maximum range of emission of 65 to 319 million tonnes of CO2 per year from subaerial and submarine volcanoes.

This seems like a huge amount, and it is. That is, until we compare it to anthropogenic emissions.

According to an International Energy Agency some 30. 6 billion tonnes of carbon dioxide were released into the atmosphere as a result of human activity in 2010.To say that another way, assuming the highest estimates of volcanic CO2 emissions (319 million tonnes), human-emitted carbon dioxide levels were more than 95 times higher.

The Mount Pinatubo eruption in 1991 emitted 42 million tonnes of CO2 (Gerlach et al 1996). Now, compare this to human emissions in 1991 which were a total of 23 billion tonnes of CO2 (CDIAC). The strongest eruption over the last half-century amounted to 0.2% of human CO2 emissions in that year. 0.2%.

Image courtesy of NASA

References:

Carbon Dioxide Information Analysis Centre:http://cdiac.ornl.gov/trends/emis/overview_2006.html

Kerrick, D. M. (2001). "Present and past nonanthropogenic CO2 degassing from the solid earth." Rev. Geophys. 39(4): 565-585.

NASA,1996; “Atmospheric Aerosols: What Are They, and Why Are They So Important?”

Terrence M. Gerlach(1996) Pre-Eruption Vapor in Magma of the Climactic Mount Pinatubo Eruption: Source of the Giant Stratospheric Sulfur Dioxide Cloud . http://vulcan.wr.usgs.gov/Projects/Emissions/Reports/Pinatubo/pinatubo.html

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