Volcanoes, Weather, and Climate

A lot of the viewer questions we receive in the weather center are forecast related and pretty easy to answer; things like "what time will it rain on Saturday?", "how much snow fell at my house?", and "when will the humidity go away?!".  A recent question, though, sent me down a rabbit hole of research -- EXCITING! -- and I wanted to share what I found with you.

Marvin poses a good question -- have the recent eruptions of Kilauea in Hawaii and Fuego in Guatemala had an impact on the weather?

The science

Volcanic eruptions spew more than just lava; they also release ash and varying amounts of poisonous gasses like carbon dioxide (CO2), sulfur dioxide (SO2), hydrogen fluouride (HF) and hydrochloric acid (HCl).  Each of these byproducts interact differently with earth's atmosphere and can have differing impacts on weather and climate.

Ash suspended in the air, for example, can block sunlight and have a cooling effect... but only for several days to several weeks, until it falls out of the sky.  Ash, then, can contribute to weather changes, and sometimes even seasonal changes, but is a little too heavy to remain in the atmosphere long enough to have a significant impact on long-term climate change.

The most significant cooling can come from lighter sulfur dioxide molecules injected into the atmosphere, where they convert into sulfuric acid.  The U.S. Geologic Survey has an excellent overview of how this takes place:

"... sulfuric acid [...] condenses rapidly in the stratosphere to form fine sulfate aerosols. The aerosols increase the reflection of radiation from the sun back into space, cooling the earth's lower atmosphere or troposphere." 

The stratosphere is a stable layer of the atmosphere that begins at 6 to 12 miles in altitude (depending on the geographic location and season), and extends up to about 30 miles in altitude.  An explosive volcanic eruption is needed to send contaminants like SO2 into the stratosphere, where they can stay there for months or years, encircle the globe, and have the biggest impact.  This has occurred in the past, including in the eruption of Mount Pinatubo on June 1991 (which cooled the earth's surface for three years), Krakatau in 1883, and Tambora in 1815.

Oh, and if you're wondering about the carbon dioxide emitted by volcanic eruptions, know this: Poland's 2015 CO2 emissions outrank even the highest estimate of annual volcanic CO2 emissions; in 2015 the U.S. emitted 10 times more CO2 this estimate; and, worldwide human activity in 2015 accounted for about 130 times more CO2 than this estimate.  To quote the U.S. Geologic Survey again:

"There is no question that very large volcanic eruptions can inject significant amounts of carbon dioxide into the atmosphere. The 1980 eruption of Mount St. Helens vented approximately 10 million tons of CO2 into the atmosphere in only 9 hours. However, it currently takes humanity only 2.5 hours to put out the same amount. While large explosive eruptions like this are rare and only occur globally every 10 years or so, humanity's emissions are ceaseless and increasing every year."

Pyrocumulus clouds seen toward Kilauea from Seaview Estates, about 4 miles away from the lava vent, on June 26, 2018. Credit: WCCO viewer Charlie Luke.

The 2018 Kilauea Impact

The most recent eruption of Kilauea began on May 3, 2018, and continues as of this writing.  In nearly two months of continuous eruption (and counting) it has produced a lot of lava, a lot of dramatic images, and vented a lot of harmful gasses; but it has not produced an explosive eruption -- and likely never will.

All Hawaiian volcanoes are "shield volcanoes" that produce thin, fluid lava flows. This type of molten rock allows gas to vent more easily from the volcano, which tends to prevent the buildup of gases that can lead to explosive eruptions.

Kilauea continues to vent thousands of tons of sulfur dioxide into the atmosphere which, as we saw earlier, can lead to some cooling effects.  Without an explosive eruption that injects ash and SO2 high into the atmosphere, however, the prospect of long-term climate impacts just doesn't exist.

Kilauea's continuing eruption is having a localized impact on weather, though.  One National Weather Service meteorologist who is working with FEMA on the Big Island shared her (unofficial, but helpful) weather report:

  • Vog [volcanic air polution that resembles smog] from the volcano reached Guam and the Marinara Islands on multiple occasions. This resulted in reduced visibility and even some respiratory issues to folks who are sensitive

  • Heat from the fissures along the East Rift impacted the winds (both speed and direction); but this was very localized to just the Lower Puna area

  • There was a Winter Weather Advisory issued for portions of Mauna Loa due to freezing vog (this was the beginning of June)

Low-altitude satellite imagery from the MODIS satellite also shows a volcanic ash plume extending downwind (west of) the easterly Trade Winds, as well. This plume is likely lowering temperatures slightly, but its effects are over open ocean, and in a very small area.  Given the effusive nature of this eruption (as opposed to explosive) the ash is at a relatively low altitude, and falls out of the sky much more quickly than if it were suspended in the stratosphere.

Credit: NOAA

The 2018 Fuego Impact

Credit NASA/NOAA/US Department of Defense

The eruption of Fuego in Guatemala on June 2, 2018 was much more violent and explosive than the Kilauea eruption.  A high-resolution view of the area, taken by the Suomi NPP satellite just after the eruption, shows the volcanic ash and gas cloud piercing through the surrounding cloud deck. Additional data from Suomi NPP's Ozone Mapping Profiler Suite (OMPS) measured elevated amounts of SO2 in the middle of the boundary between the troposphere and the stratosphere.

All of this indicates that contaminants from the volcano may have been injected into the stratosphere and, therefore, could reside in the atmosphere long enough to create a cooling effect.

As in the case of Kilauea, the prevailing east-to-west wind over Guatemala will tend to blow any ash and gas out over the ocean, making it difficult to directly measure any long-term temperature changes that may occur.  Looking at the strength and duration of the eruption, though, it seems like a safe bet that the effects of the June 2nd eruption alone will not be enough have a significant long-term weather or climate impact.

Tremendous thanks to the scientists who contributed information that was the basis of this blog, via the University at Albany Department Atmospheric and Environmental Sciences mailing listserv:

  • Paquita Zuidema - Department of Atmospheric Sciences, University of Miami
  • Dr. Steven Lazarus - Ocean Engineering and Marine Sciences, Florida Institute of Technology
  • George Kiladis - NOAA
  • Brandon Smith - NOAA
  • Sheldon Kusselson - NOAA/NESDIS (Retired)