Astronauts aboard the International Space Station photographed this large eruption from Sarychev volcano in the Kuril Islands of Russia in June 2009. PHOTO/ NASA
- There is a 95% chance that the time-averaged 2015–2100 volcanic SO2 flux from explosive eruptions exceeds the time-averaged 1850–2014 flux
- Standard climate projections very likely underestimate the 2015–2100 stratospheric aerosol optical depth and volcanic climate effects
- Small-magnitude eruptions (<3 Tg SO2) contribute 30%–50% of the volcanic climate effects in a median future eruption scenario
By SPECIAL CORRESPONDENT
When volcanoes erupt, they often spew large amounts of sulfur dioxide into the atmosphere.
This toxic, foul-smelling gas may then form tiny sulfate particles that particularly in the stratosphere, can influence Earth’s climate for months to many decades.
Using the latest ice-core and satellite records, scientists from American Geophysical Union (AGU) have found that explosive eruptions could emit more sulfur dioxide into the upper atmosphere for the period of 2015–2100 than standard climate projections.
Climate projections are the simulations of Earth’s climate in the future using complex climate models. Standard climate projections, as in Intergovernmental Panel on Climate Change Sixth Assessment Report, assume that explosive volcanic activity over 2015–2100 are of the same level as the 1850–2014 period.
“Our climate model simulations show that the impacts of volcanic eruptions on climate, including global surface temperature, sea level and sea ice extent, are underestimated because current climate projections do not fully account for the recurrent frequency of volcanic eruptions,” the researchers say.
“We also find that small-magnitude eruptions occur frequently and can contribute a significant effect on future climate,” the researchers add.
In modeling future climate change, scientists have therefore incorporated the effects of volcanic eruptions. However, Chim et al. now show that there is a 95% chance that volcanic eruptions between 2015 and 2100 will release more sulfur dioxide into the atmosphere than standard climate models currently assume.
A report by AGU Advances says the challenge of predicting future sulfur dioxide release arises because eruptions cannot be precisely forecasted. So standard climate models have typically relied on averaged historical sulfur dioxide release data from 1850 to 2014, under the assumption that future releases will be similar.
However, this approach does not account for large variation in releases that can occur from century to century, nor does it account for small-magnitude but frequent eruptions that are not captured in historical records.
To address these shortcomings, the researchers used updated data sets from satellites and ice cores, which provide a glimpse into eruptions over the past 11,500 years, to simulate the effects of future volcanic sulfur dioxide releases.
They also applied a mathematical modeling method that more adequately represents eruptions of all magnitudes, and they developed a new modeling framework that better simulates plumes of gases and other materials ejected in eruptions.
Their analysis suggests that existing climate projections most likely underestimate the effects of volcanic sulfur dioxide on Earth’s climate, including on global surface temperature, sea level, and sea ice extent.
It also indicates that existing models appear to inadequately account for the effects of smaller-scale eruptions that add up over time to influence climate significantly.
The researchers recommend that standard climate models—in particular, those produced as part of the Coupled Model Intercomparison Project—be updated accordingly.