Volcanic eruptions play an overlooked role in Earth's climate

New research has discovered that the cooling effect produced by volcanic eruptions on Earth’s surface temperature is likely underestimated by a factor of two, and potentially up to four, in standard climate models. 

This revelation, while not significant enough to counteract human-induced global warming, alters our understanding of the complex global climate system.

Focus of the study

Led by the University of Cambridge, the research delves into small-scale volcanic eruptions, stating that they account for almost half of all the sulfur gases spewed into the upper atmosphere. These eruptions may lack the drama of their large-scale counterparts, but their cumulative impact is undeniable.

The results of the study, which are published in the journal Geophysical Research Letters, highlight the need for a more comprehensive representation of volcanic eruptions, regardless of their magnitude, in climate projections. This could enhance the reliability of these models, shedding a more accurate light on potential future scenarios.

Volcanic eruptions and climate

The course of volcanic eruptions – both their location and timing – remains beyond human control. Yet, the role they play in the global climate system is undeniably important. Upon eruption, volcanoes emit sulfur gases into the upper atmosphere, which subsequently form tiny aerosol particles capable of reflecting sunlight back into space. 

Major eruptions, such as the Mount Pinatubo incident in 1991, spew such a vast volume of volcanic aerosols that they single-handedly trigger a dip in global temperatures. But these large eruptions are relatively rare, occurring only a few times per century. On the other hand, small-scale eruptions occur every one to two years.

“Compared with the greenhouse gases emitted by human activity, the effect that volcanoes have on the global climate is relatively minor, but it’s important that we include them in climate models, in order to accurately assess temperature changes in future,” said study first author May Chim.

Current climate projections, such as those outlined in the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report, base their assumptions on calculations of past volcanic activity (from 1850-2014) and estimates of future activity (from 2015-2100). This approach largely overlooks the impacts of small-scale eruptions. 

“These projections mostly rely on ice cores to estimate how volcanoes might affect the climate, but smaller eruptions are too small to be detected in ice-core records,” explained Chim.

To address this gap, Chim and her team set out to analyze satellite data to develop a more comprehensive picture. Alongside collaborators from the University of Exeter, the German Aerospace Center (DLR), the Ludwig-Maximilians University of Munich, Durham University, and the UK Met Office, the team generated a thousand different scenarios of future volcanic activity using state-of-the-art ice-core and satellite records.

What the researchers learned 

Through a series of simulations run on the UK Earth System Model, the experts discovered that current climate projections largely underestimate the plausible future level of volcanic activity, leading to a significant underestimation of the impact of volcanic eruptions on factors like global surface temperature, sea level, and sea ice extent.

“Volcanic aerosols in the upper atmosphere typically stay in the atmosphere for a year or two, whereas carbon dioxide stays in the atmosphere for much, much longer,” said Chim. “Even if we had a period of extraordinarily high volcanic activity, our simulations show that it wouldn’t be enough to stop global warming. It’s like a passing cloud on a hot, sunny day: the cooling effect is only temporary.”

Despite the underestimation of volcanic activity in climate projections, it’s important to note that the cooling effect of volcanoes does not compare to the warming effect of anthropogenic carbon emissions. However, the study underlines the importance of fully accounting for the role of volcanoes in our climate models to ensure their reliability.

Future research

Moving forward, the team plans to apply the insights gained from these simulations to investigate potential threats to the recovery of the Antarctic ozone hole. They aim to understand whether future volcanic activities could impede the healing process of this critical atmospheric layer and thus maintain a relatively high level of harmful ultraviolet radiation at the Earth’s surface. 

This work underscores the complexities of Earth’s climatic systems and highlights the critical role that every element, no matter how minor it seems, plays in shaping our future environment.

In conclusion, while volcanic eruptions may be dwarfed by the scale of human activity in terms of their climate impact, their role is far from insignificant. This study is a powerful reminder that our planet operates on a complex web of interconnected systems, where even the seemingly minor players can exert a profound influence. 

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