Would powerful volcanic eruptions really cause global cooling?

For decades, scientists have speculated about strong global cooling following a powerful volcanic eruption. Now, new studies provide more precise answers on this subject.

grande erupção vulcânica
If a major volcanic eruption were to occur again, what would happen to the atmosphere?

A new study by a team at NASA's Goddard Institute for Space Studies (GISS), published in the American Meteorological Society's (AMS) Journal of Climate, concluded that after a powerful volcanic eruption, global-scale cooling would not exceed 1.5ºC.

By using advanced computational modelling methods to simulate the effects of the presence of volcanic particles in the atmosphere, researchers observed that temperature changes would not be so drastic as to generate a large-scale catastrophe, endangering the human species and ecosystems. planetaries.

For modelling, they took into account the microscopic dimensions of sulphur particles that are ejected during a volcanic eruption and that reach the stratosphere (between 10 and 50 km high) during a large-scale eruption.

What are the effects of an eruption?

In the stratosphere, sulphur dioxide undergoes chemical reactions that condense it into liquid sulphate. In the presence of these particles, two phenomena with opposite effects can occur: the reflection of sunlight entering the atmosphere, which would cause cooling; or that the thermal energy that comes out is “trapped” producing the well-known greenhouse effect.

It has been shown that the smaller and denser the sulphate particles, the greater their ability to block sunlight. By simulating the presence of particles of different sizes, it was proven that they would not be able to drastically change the planet's temperature.

The big challenge continues to be recovering the physical evidence of aerosols from major eruptions that occurred in the past, to have a broad repertoire of data that allows us to reach conclusive results about what has happened so far and what to expect in the future.

Volcanic winter?

The term “volcanic winter” was coined in 1993 by scientific journalist Ann Gibbons, referring to the supposed effects on human evolution as a consequence of the eruption of the Lake Toba volcano, on the island of Sumatra (Indonesia), 74 thousand years ago.

The theory was later supported by scientist Stanley Ambrose of the University of Illinois, who theorised about an average temperature decrease on Earth of between 3 and 3.5 ºC during 6 years after the Toba eruption. This would be the cause of a drastic impact on the species, which in the case of Homo Sapiens could be reduced to the presence of just 10 thousand individuals across the planet.

In 2009, this theory was rejected, as multidisciplinary research demonstrated that the Toba eruption did not have catastrophic effects on the Earth's climate and human evolution, which had been attributed to it until then.

Can we cool the atmosphere?

The application of aerosols to the atmosphere to cause a cooling effect has been one of the unanswered questions in geoengineering. To date, it has not been possible to develop viable technologies that would allow us to apply what studies like this reveal.

News reference:
McGraw, Z. et al . Severe Global Cooling After Volcanic Super-Eruptions? The Answer Hinges on Unknown Aerosol Size. Journal of Climate, vol. 37, no. 4, 2024.