volcano graph
Simulation of a volcanic eruption. The shading shows where the volcanic aerosols are and the cone shows the approximate location of the volcano itself.

How does the climate system respond to volcanic eruptions? Volcanoes inject vast amounts of small particles – aerosols – high into the atmosphere. These particles act like a mirror in the sky, reflecting sunlight back into space and causing a cooling that lasts between 1–2 years. Understanding this process can say something about the response to human-made emissions such as CO2 and aerosols. In this way, volcanoes are natural experiments we can examine to better understand climate change caused by human activities.

The new study, published in the journal Science Advances, describes how a simulated volcano eruption affects the El Niño phenomenon. The researchers modelled the effects of a Tambora-size volcanic eruption occurring in the tropics but far from the equator. Conventional theories focus on the local, equatorial effects of the volcanic cooling. Contrary to this, they found that the cooling occurred mostly in the region outside the tropics. This distant cooling leads to a shift in winds along the equator favouring the onset of an El Niño event.

Why are the results important?
“It’s a fascinating example of the complex global linkages that control climate change. El Niño has societal impacts in large parts of the world. If we have a volcano eruption now, we would have an enhanced chance of an El Niño event: this may help forecast those impacts”, says co-author Rodrigo Caballero.

The study shows the effects of volcanic aerosols. What can be said about anthropogenic emissions, in connection to the study?
“Human aerosol emissions are concentrated in the Northern Hemisphere, just like the volcanic aerosols in our simulations. Our study provides insight into how anthropogenic emissions may affect El Niño in the long term”.

The article “ITCZ shift and extratropical teleconnections drive ENSO response to volcanic eruptions” by Francesco S. R. Pausata, Davide Zanchettin, Christina Karamperidou, Rodrigo Caballero, and David S. Battisti is published in the journal Science Advances.