Over the last month or so, there have been several volcanic eruptions across the globe. After weeks of earthquake swarming around the Bardarbunga Volcano in Iceland, an area northeast of the sub-glacial hot spot began a small eruption on August 29th. Interestingly, on the same day, Mount Tavurvur in Papua New Guinea erupted explosively, sending ash 50,000 feet into the air (see the moment of the eruption here). With the recent activity and continuing concern over a larger eruption in Bardarbunga, let's investigate the climatic impact of volcanic events.
The reason meteorologists are concerned with volcanoes is their potentially explosive nature and the ability to hurl excessive amounts of ash and gas into the upper atmosphere. Although ash typically falls back to the Earth on the order of days or weeks, the gas emission is a bigger problem. In particular, the large amounts of carbon dioxide (CO2) and sulfur dioxide (SO2) volcanoes produce can affect global temperature for 1 - 3 years! We all know carbon dioxide can produce global warming, but warming effects of volcanic carbon dioxide are rather minimal. The main reason warming is not detected is generally due to the vast quantities of CO2 we are putting into the atmosphere each year. In fact, maximum volcanic CO2 emission is typically 0.26 gigatons/year, while our cars, power plants, and other infrastructure produce an immense 35 gigatons/year. It's no wonder scientists can't detect volcanic warming (but that's an issue to discuss in future blogs).
On the other hand, sulfur dioxide injected into the stratosphere can produce sulfate aerosols which reflect the Sun's incoming radiation. Typically, volcanic activity and its subsequent sulfates can cool the lower atmosphere by a global average of 0.5°F. However, past large events, like Pinatubo in 1991 (the largest eruption in the 20th century) has lowered the average global temperature by as much as 1.3°F and Tambora in 1815 helped create "the year without a summer" in 1816. While the current volcanic activity is likely not large enough to produce substantial cooling, it is certainly something to keep an eye on this winter. In addition, if Iceland's Bardarbunga were to erupt under the glacier, it would likely do so explosively potentially cooling the northern hemisphere some. To follow Bardarbunga's activity, visit the news feed from the Icelandic Met Office here.
References:
USGS: http://volcanoes.usgs.gov/hazards/gas/climate.php
