Calbuco Eruption and Climate

volcano-image
After laying dormant for more than 40 years, the Calbuco volcano in southern Chile erupted violently twice last week, once at about 6pm local time on April 22 and the second time just after midnight on the early morning hours of April 23. The eruptions produced many spectacular photo and video images—including the one here, taken by Tori Cooper and used by permission.

Tori writes the food blog “Gringalicious” (http://gringalicious.com/) and only lives about 20 miles from the volcano, so she had a front row seat and took many wonderful photos and videos that you can see on her website.

The Calbuco volcano is part of the Andes chain of volcanic mountains. Plate tectonics tells us that these types of volcanoes are formed when a denser oceanic plate partially melts as it’s descending underneath a lighter continental plate. In this case the Nazca oceanic plate is being subducted under the South American Plate. Although the material that creates the volcanoes originates with the relatively heavy basalts and gabbros that make up the oceanic plate (like what is found in Hawaii and Iceland), it gets “distilled” by the melting process and the result are lighter igneous rocks, such as the granite that comprises much of the continents. Most of the material that makes up the continents is believed to have initially formed in this manner.

Volcanoes formed in subduction processes, such as Calbuco, have lava that is much less fluid and they erupt much more violently than “hotspot” volcanoes like Hawaii or at mid-ocean ridges like Iceland. Because of their violent nature, they have the possibility of injecting aerosols high in the stratosphere and affecting climate worldwide. Whenever a spectacular eruption like the Calbuco eruption occurs, a natural question to ask is whether climate will be affected. The spectacular clouds that you see are mixtures of volcanic ash and various gases: mostly water vapor, but also carbon dioxide, sulfur dioxide and various other gases in small concentrations.

Perhaps surprisingly, the carbon dioxide emitted by volcanoes has little effect on world climate, even though it is an important greenhouse gas. The total emissions of carbon dioxide from ALL volcanic eruptions worldwide are less than 1% of anthropogenic emissions each year, so volcanic carbon dioxide is a relatively small factor in climate change.

While volcanoes don’t contribute significantly to global warming, they can cause temporary global cooling. Volcanoes can put large quantities of aerosols into the stratosphere, where they can reflect some of the sunlight back into space before it has a chance to warm the Earth’s surface. Global temperatures dropped for three years after the eruption of Mt. Pinatubo in 1991, and it is believed that the 19th century eruptions of Krakatau and Tambora caused even larger declines. In the northern hemisphere, the year after the Tambora eruption was called the “year without a summer.”

While you might expect that it is the volcanic ash that is the culprit, it is heavy and tends to fall out relatively quickly. In contrast, sulfur dioxide in the volcanic cloud can combine with fine water droplets to make droplets of sulfuric acid that can remain in the atmosphere for years. It is these sulfuric acid droplets that reflect the sunlight and cool the planet.

So, will the planet cool significantly from the Calbuco eruption? At the present time we don’t believe so. While the eruption did inject large amounts of material as high as 17 km (56,000 feet) into the stratosphere, it doesn’t look like there was enough sulfur dioxide emitted to cause a noticeable cooling. Preliminary estimates from satellite observations put the sulfur dioxide emitted by the Calbuco eruptions at 0.2-0.4 million tonnes, and while that is a very big number, it is small in comparison to that emitted by the climactic eruption of Mt. Pinatubo, which injected an estimated 20 million tonnes. The eruption of Pinatubo also reached about twice as high in the atmosphere as the Calbuco eruptions. Additionally, for various reasons associated with atmospheric dynamics, volcanoes in the tropics (e.g. Pinatubo, Krakatau, Tambora) have more effect on climate than those at higher latitudes, such as Calbuco or those in Iceland.
Even though we don’t expect to see climate significantly affected, there were many interesting meteorological effects. Time lapse videos are all over the internet that show the volcanic cloud pushing high into the stratosphere and bearing some resemblance to a supercell thunderstorm, and the nighttime eruption produced a spectacular lightning show. More hardcore weather nerds will be interested in the gravity waves (similar to the ripples you see if you drop a rock in a pond) caused by the volcanic explosion. The University of Wisconsin Space Science and Engineering Center (SSEC) has a page showing images of the gravity waves high in the Earth’s mesosphere (http://gringalicious.com/) and only lives about 20 miles from the volcano, so she had a front row seat and took many wonderful photos and videos that you can see on her website. The Calbuco volcano is part of the Andes chain of volcanic mountains. Plate tectonics tells us that these types of volcanoes are formed when a denser oceanic plate partially melts as it’s descending underneath a lighter continental plate. In this case the Nazca oceanic plate is being subducted under the South American Plate. Although the material that creates the volcanoes originates with the relatively heavy basalts and gabbros that make up the oceanic plate (like what is found in Hawaii and Iceland), it gets “distilled” by the melting process and the result are lighter igneous rocks, such as the granite that comprises much of the continents. Most of the material that makes up the continents is believed to have initially formed in this manner. Volcanoes formed in subduction processes, such as Calbuco, have lava that is much less fluid and they erupt much more violently than “hotspot” volcanoes like Hawaii or at mid-ocean ridges like Iceland. Because of their violent nature, they have the possibility of injecting aerosols high in the stratosphere and affecting climate worldwide. Whenever a spectacular eruption like the Calbuco eruption occurs, a natural question to ask is whether climate will be affected. The spectacular clouds that you see are mixtures of volcanic ash and various gases: mostly water vapor, but also carbon dioxide, sulfur dioxide and various other gases in small concentrations. Perhaps surprisingly, the carbon dioxide emitted by volcanoes has little effect on world climate, even though it is an important greenhouse gas. The total emissions of carbon dioxide from ALL volcanic eruptions worldwide are less than 1% of anthropogenic emissions each year, so volcanic carbon dioxide is a relatively small factor in climate change. While volcanoes don’t contribute significantly to global warming, they can cause temporary global cooling. Volcanoes can put large quantities of aerosols into the stratosphere, where they can reflect some of the sunlight back into space before it has a chance to warm the Earth’s surface. Global temperatures dropped for three years after the eruption of Mt. Pinatubo in 1991, and it is believed that the 19th century eruptions of Krakatau and Tambora caused even larger declines. In the northern hemisphere, the year after the Tambora eruption was called the “year without a summer.” While you might expect that it is the volcanic ash that is the culprit, it is heavy and tends to fall out relatively quickly. In contrast, sulfur dioxide in the volcanic cloud can combine with fine water droplets to make droplets of sulfuric acid that can remain in the atmosphere for years. It is these sulfuric acid droplets that reflect the sunlight and cool the planet. So, will the planet cool significantly from the Calbuco eruption? At the present time we don’t believe so. While the eruption did inject large amounts of material as high as 17 km (56,000 feet) into the stratosphere, it doesn’t look like there was enough sulfur dioxide emitted to cause a noticeable cooling. Preliminary estimates from satellite observations put the sulfur dioxide emitted by the Calbuco eruptions at 0.2-0.4 million tonnes, and while that is a very big number, it is small in comparison to that emitted by the climactic eruption of Mt. Pinatubo, which injected an estimated 20 million tonnes. The eruption of Pinatubo also reached about twice as high in the atmosphere as the Calbuco eruptions. (http://cimss.ssec.wisc.edu/goes/blog/archives/18174).

Late season, cold storm brings snow to the Sierras, rain to San Diego

W.E Weather Depiction 4-7-15 1610Z

A cold storm that seems more like winter than early spring is moving through the Lake Tahoe area toward San Diego.

Snowfall of 3 to 5 inches can be expected in the Incline Village area today, with a dusting of flurries tonight. At the highest peaks of the Sierras 6 to 12 inches of snow can be expected.

To the south a band of light rain and showers along a weak cold front will move from Ventura and San Luis Obispo Counties southeast into southwest California, affecting San Diego tonight. Rainfall amounts will be mostly a tenth of an inch or less. (See satellite picture as of 9:10 am this morning.)

As the storm system exits look for a bit of a warming trend with high temperatures rising to the 40’s at Incline Village, and into the upper 60’s to low 70’s across the San Diego County Valleys.