Volcanic eruptions in tropical regions could have a significant influence on Earth’s climate by temporarily lowering global temperatures, according to new research published in the journal Geophysical Research Letters. Scientists have found that tropical eruptions may contribute more consistently to cooling the Northern Hemisphere than previously understood.
When powerful volcanoes erupt, they release large quantities of sulphur dioxide into the stratosphere. The gas reacts with water vapour and oxygen to form tiny sulphuric acid aerosol particles. These particles reflect sunlight back into space reducing the solar energy reaching Earth’s surface and cooling the atmosphere for months or even years.
One of the most famous examples was the 1815 eruption of Mount Tambora in Indonesia, which contributed to the unusually cold conditions of 1816, widely known as the “Year Without a Summer”.
Scientists Re-examine the Cooling Impact of Volcanic Eruptions
A research team led by Dr Zachary McGraw of Columbia University investigated whether a volcano’s geographical location determines how strongly an eruption affects temperatures in the Northern Hemisphere.
Earlier studies suggested that eruptions between 30 and 70 degrees latitude, known as extratropical eruptions could produce up to 7.5 times more cooling than tropical eruptions of similar magnitude.
However, researchers used a NASA climate model to compare eruptions across different seasons and found no evidence of such an enormous difference. Their results suggested that extratropical eruptions could produce, at most, around twice as much cooling.
Scientists explained that aerosols released by tropical eruptions can spread across both hemispheres through atmospheric circulation. In contrast, particles from extratropical eruptions tend to remain concentrated in the Northern Hemisphere, potentially producing a stronger regional cooling effect.
Tree Rings Reveal Clues From Ancient Volcanic Eruptions
To verify their findings researchers examined historical climate records and tree ring evidence. Tree growth patterns provide valuable information about past environmental conditions, as rings generally become narrower during colder or drier periods.
The team analysed evidence associated with historical eruptions, including the 1783 Icelandic eruption, an eruption around 536 CE and another in Alaska in 43 BCE. They also compared these records with climate simulations and evidence from numerous tropical eruptions dating back to 750 CE.
The findings indicated that cooling in the Northern Hemisphere was more frequently associated with tropical volcanic eruptions. Such eruptions can influence atmospheric temperatures for longer periods because their aerosols remain suspended in the atmosphere for up to three years.
By comparison, aerosols from extratropical eruptions often remain for around nine months. Researchers attributed this shorter lifespan to lower altitude gas releases, removal of particles through rain and snow, and atmospheric circulation that transports aerosols towards the poles.
Findings Could Improve Global Climate Predictions
The study offers important insights into how volcanic activity influences short term climate fluctuations alongside longer term global warming driven by human greenhouse gas emissions.
Understanding the movement and lifespan of volcanic aerosols could help scientists improve climate forecasting and assess potential impacts on agriculture, food production and global food security.
Researchers also believe that better predictions of volcanic cooling events could help governments prepare for possible resource shortages and related geopolitical challenges.
The findings highlight the important role tropical volcanoes play in Earth’s natural temperature regulation and provide valuable information for understanding the complex relationship between volcanic activity and the global climate system.