Climate change doesn’t happen in a vacuum. Many factors contribute to it, not the least of which is volcanic activity. And while you probably think of a volcano in terms of the heat produced, the gas and dust it emits actually affect climate change a lot more than you might think.

In a study published Tuesday in Nature Communications, scientists at the National Center for Atmospheric Research report that major volcanic eruptions could cause more disruption to the global climate than they have in the past. By examining the conditions that followed the eruption of the Indonesian volcano Mount Tambora in 1815, the Boulder, Colorado scientists predict what would happen if this type of major eruption occurred in 2085.

The potential alterations to the climate will not be in the Earth’s favor. While the scientists predict that the cooling that will follow a future eruption of that scale would be even more extreme, it will not offset the effects of a warming climate. Furthermore, they predict that the eruption will disrupt the water cycle, decreasing global precipitation.

Mount Tambora erupted in 1815, causing a year of global temperature declines. Scientists predict this type of phenomenon would play out differently in the future.

The effects of a “volcanic winter” occur as the ash and smoke from an eruption obscure rays from the sun, decreasing their ability to heat the Earth. When Mount Tambora erupted in 1815, thousands of people died instantly, and it is considered the most destructive eruption on Earth in 10,000 years. The dust and gas it emitted into the atmosphere altered global climate for a year afterward, which is why 1816 is known as “The Year Without a Summer.” Global temperatures dipped so severely that crops failed, even in places far away from the volcano. Farms in the northern United States suffered frost damage in August, as did farms in Europe. The massive volcanic eruption triggered a global subsistence crisis, which is estimated to have killed an additional 10,000 people.

Using computer climate models, the researchers of the new study concluded that, if an eruption like Mount Tambora’s happens in 2085, the Earth will cool up to 40 percent more than the 1815 eruption, assuming current rates of climate change continue. However, they also predict that the cooling will be spread out over several years.

ywsa in 1990s
This figure shows two different predictions of what the temperature decreases in 1816 would have been like under climate conditions present in the 1990s.

The reason the temperature change will so drawn out, they explain, is because ocean temperature is becoming increasingly stratified — that is, separated into layers based on temperature. As this happens, the surface water in the ocean will be increasingly less able to moderate the cooling effects of the eruption, causing a longer and more severe cooling event. Because the cooling in 1815-1816 occurred at a time when ocean temperature was not as stratified, it was absorbed to some degree by the water.

“As a consequence of increased ocean stratification, temperature anomalies in the upper ocean do not penetrate to depth as efficiently as in 1815,” write the study’s authors. In other words, the cooler water would be trapped at the ocean’s surface instead of circulating to deeper levels. This, in turn, would mean that land masses would bear more of the brunt of the cooling event. Unfortunately, the scientists predict that this cooling event won’t be enough to offset the long-term human-induced warming caused by climate change.

Furthermore, the scientists predict that rainfall patterns will be severely affected by a major volcanic event. Increasing ocean stratification plays a role here, too: Cooler ocean surface temperatures resulting from a volcanic winter prevent evaporation, which is necessary for precipitation. This means that in addition to drastic temperature decreases, people could also face severe drought in the years following a major volcanic eruption.

“The response of the climate system to the 1815 eruption of Indonesia’s Mount Tambora gives us a perspective on potential surprises for the future, but with the twist that our climate system may respond much differently,” said study co-author Otto-Bliesner in a statement.

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