Climate Change Research Spotlight

Volcanic Eruptions Stir an Already Complex Atmosphere

A study of Earth's atmospheric response to major volcanic eruptions seeks to reconcile contradictions between observations and climate models.

Source: Geophysical Research Letters

By

Volcanic eruptions can have an enormous influence on global climate from year to year. Most notably, the sulfuric acid particles from eruptions reflect sunlight and absorb energy radiating from Earth, warming the lower stratosphere while cooling the troposphere. Despite its importance, the atmospheric response to volcanic eruptions is not well characterized. Only two large tropical eruptions have occurred since the beginning of the satellite era in 1979, and climate models often seem to contradict observations of those eruptions. In a new study, McGraw et al. work to explain this apparent discrepancy.

After the eruptions of El Chichón in 1982 and Mount Pinatubo in 1991, the belt of westerly winds surrounding Antarctica expanded toward the equator. Because of the sample size of only two events, previous studies were unable to conclude whether there was a causal relationship between the eruptions and the atmospheric changes (called a negative Southern Annular Mode, or SAM) that followed.

By analyzing observations of the Mount Pinatubo and El Chichón eruptions alongside 207 model simulations, the team found that the atmospheric response to volcanic eruptions is a positive SAM and that the concurrent El Niño during both eruptions may be to blame for why a negative SAM was observed. Their research also shows that the positive SAM response to volcanic eruptions is stronger during La Niña, when the equatorial Pacific Ocean is cooler than usual.

The statistical significance of the scientists’ results relies upon their use of many different simulations. Because internal climate variability is large, the Southern Hemisphere’s atmospheric response to volcanic eruptions could be obscured in any single simulation. Between internal variability and the effects of El Niño and La Niña, the discrepancies between climate models and observations can be accounted for. Earth’s atmosphere is a complicated system, and the response to major tropical volcanic eruptions like Pinatubo, although significant, does not overwhelm its other complexities. (Geophysical Research Letters, doi:10.1002/2016GL069835, 2016)

—Leah Crane, Freelance Writer

Citation: Crane, L. (2016), Volcanic eruptions stir an already complex atmosphere, Eos, 97, doi:10.1029/2016EO056249. Published on 25 July 2016.
© 2016. The authors. CC BY-NC-ND 3.0
  • ROO2

    Your car crash understanding of even the most fundamental science that schoolchildren can grasp is astonishing.

    Yet you are the one that also claims that the moon landings were faked.

    You are lacking in so many areas. Not evidence free assertions or lying about going to University though.

    Keep up the lying dross though, this is fun.

    • maltow

      Ohhhh! Those arms flap much more you’ll take off Sparky?
      Totally lost it haven’t you. Poor Dan.

      Ahhhh!

  • ROO2

    ‘the rate of change of Co2 levels actually DROPS after a volcanic eruption, DUE TO THE COOLING EFFECT OF AEROSOLS’

    Wow, the rate of change drops.

    So what are the anticipated lifetimes of the CO2 and aerosols of which you speak?

  • maltow

    “Any trying to attribute that Maxwell claimed that gravity supplies a perpetual source of heat….” ?WHAT? And who came up with that drivelled tosh then Dan? You did! And ONLY you did. In atrocious English as your signature tune.

    So there are not far greater quantities of Co2 at the Earths surface present in the lower crust and mantle of the Earth than in the atmosphere then? I see you want it both ways Dannyboy. Sure, I can play that game if you like:
    http://www.skepticalscience.com/volcanoes-and-global-warming.htm
    ‘In contrast, humans are currently emiting around 29 billion tonnes of CO2 per year (EIA). Human CO2 emissions are over 100 times greater than volcanic CO2 emissions. This is apparent when comparing atmospheric CO2 levels to volcanic activity since 1960. Even strong volcanic eruptions such as Pinatubo have little discernable impact on CO2 levels. In fact, the rate of change of CO2 levels actually DROPS slightly after a volcanic eruption, possibly DUE TO THE COOLING EFFECT OF AEROSOLS.’
    So – this site at least (albeit entirely witlessly) recognises that CO2 levels follow temperatures, and NOT the other way round, something that entirely tramples the alarmist memes though, obviously. Certainly this fact, supported as it is by the entire historical record, has been CONTINUOUSLY and vociferously denied by you and ‘yours’ for decades now.
    Join-up much thinking then Dannyboy? EVER?

    The ideologically driven position is all yours Dan, just as ever it was, and just as you are salaried to trumpet.

    • ROO2

      And who came up with that drivelled tosh then Dan?

      You posted a link within which it stated that to be the case. Do you not even bother to read the scientifically illiterate links you post?

      Then you take to posting a rebuttal of the claims you previously posted by Plimer, and you show them to be wrong.

      You really are not all there maltow.

  • BlueScreenOfDeath

    “climate models often seem to contradict observations of those eruptions”

    Shouldn’t that read “observations of those eruptions seem to contradict climate models”?

    Oops, I forgot!

    “The data doesn’t matter. We’re not basing our recommendations on the data. We’re basing them on the climate models.”

    ~ Prof. Chris Folland ~ (Hadley Centre for Climate Prediction and Research)

    I’ll never make a climate scientist!

  • Wyss Yim

    My experience following volcanic clouds of selected VEI 3 or higher eruptions penetrating the lower stratosphere shows a connection with regional rainfall variability. For example, the 2010 Iceland eruption was responsible for the wettest year on record in Slovakia since record began in 1881. Surely rainfall is just as important as temperature in climatic variability.
    Volcanic eruption clouds provides a natural chemical experiment to enable us for study. Exciting times ahead!

  • davidlaing

    Working with the GISP2 ice cores from Greenland over the last several years, Peter L. Ward has found that not all volcanic eruptions are created equal, and some may, in fact, cause global warming. Subaerial, non-explosive, basaltic volcanism, such as is common in Iceland, produces significant quantities of HCl and HBr, which can deplete the ozone layer, thereby letting more solar UV-B radiation through to warm Earth’s surface, particularly to the oceans, where it is absorbed. Explosive volcanism, on the other hand, like Pinatubo and El Chichon, introduces long-lasting aerosols into the stratosphere, which has the opposite effect, that is, global cooling. Ward found that these two effects prevail throughout the Phanerozoic record, thus affording explanations for several hitherto poorly understood phenomena.