Explosive volcanic eruptions can influence climate far beyond the areas surrounding the volcano. When sulfur dioxide reaches the stratosphere, it reacts with water vapor and oxygen to form sulfuric acid aerosols. These particles reflect some incoming sunlight back into space, reducing the energy that reaches Earth’s surface for months or even years.

A new study led by Dr. Zachary McGraw of Columbia University examines whether a volcano’s latitude affects the amount of cooling experienced in the Northern Hemisphere. The research, published in Geophysical Research Letters, challenges earlier findings that eruptions in the extratropics—between 30° and 70° latitude—could cause up to 7.5 times more Northern Hemisphere cooling than tropical eruptions of similar size.

Using a NASA climate model, the researchers compared tropical and extratropical eruptions that released different quantities of sulfur during both summer and winter. Their simulations found no clear evidence of such a large difference. At most, an extratropical eruption produced twice as much cooling as a comparable tropical event.

The team identified one mechanism that could increase the effect of extratropical eruptions: aerosols may remain concentrated in the Northern Hemisphere, while aerosols from tropical eruptions are distributed between both hemispheres by atmospheric circulation. However, the researchers found no known process capable of producing the 7.5-fold increase reported in earlier studies.

The researchers also compared their simulations with paleoclimate evidence, including tree-ring records. They examined historical extratropical eruptions in Iceland in 1783, the mid-latitudes in 536 CE and Alaska in 43 BCE, then compared them with numerous tropical eruptions recorded after 750 CE. Tree rings can reflect the effects of cold, dry or otherwise stressful growing conditions through changes in their annual width.

The analysis showed that Northern Hemisphere cooling more often followed tropical eruptions. The researchers also found that aerosols from extratropical eruptions generally lasted for up to nine months, compared with as long as three years after tropical eruptions. They linked the shorter lifespan to lower-altitude sulfur emissions, removal by rain and snow, and the movement of aerosols toward the poles.

The findings may help scientists improve climate modeling and evaluate the effects of volcanic aerosols on agriculture, food security and competition over resources. The study also provides a clearer basis for separating the temporary cooling caused by eruptions from longer-term climate trends associated with human-made greenhouse gas emissions.

The study is titled “No evidence for strongly enhanced Northern Hemisphere cooling from extratropical versus tropical eruptions” and was published in Geophysical Research Letters in 2026. Its DOI is 10.1029/2026GL122071.

Sources: Phys.org.