Volcanic eruptions can have an impact on global climate as they release significant amounts of ash, gas, and particles into the atmosphere, which can lead to temporary cooling by reflecting sunlight and blocking some of its radiation. These particles can remain suspended for months, affecting temperatures on a global scale.
When a volcano erupts, it hurls tons of gases into the air, primarily sulfur dioxide (SO₂), but also carbon dioxide (CO₂), water vapor, and other less pleasant compounds. The real culprit of rapid climate change is sulfur dioxide. Once in the atmosphere, it transforms into tiny particles called sulfate aerosols, which can cool the Earth by reflecting some of the solar radiation back into space. And this can last for months, even years if the eruption is powerful enough. In contrast, the released CO₂ has a warming effect, but over a very long term. The short-term impact on the climate mainly comes from the cooling caused by these aerosols, which simply filter out a portion of the sunlight.
When a volcano erupts, enormous amounts of ash and aerosols (small solid or liquid particles suspended in the air) are thrown into the atmosphere. If the eruption is violent enough, these particles rise very high, sometimes reaching the stratosphere, an atmospheric layer located between about 10 and 50 kilometers in altitude. At this level, aerosols can be transported thousands of kilometers by the prevailing winds, remaining suspended for months or even years. Unlike heavier ash, which falls back relatively quickly, aerosols form a persistent veil around the Earth, altering sunlight and impacting the climate all over the planet.
During a major eruption, volcanoes eject large quantities of aerosols into the atmosphere, mainly sulfur compounds. These tiny particles remain suspended around the globe, reflecting some of the solar radiation back into space. The result is that less solar energy reaches the Earth's surface, temporarily causing global cooling. For instance, after the eruption of Mount Pinatubo in 1991, the average temperature of the planet dropped by about 0.5 °C for nearly two years. However, this cooling effect is generally short-lived: the atmosphere gradually regains its balance once the particles have dissipated. Volcanic greenhouse gases, such as CO₂, could conversely contribute to warming, but the amount released by volcanoes remains too low compared to human emissions to significantly influence the short-term balance.
Intense volcanic eruptions inject particles and aerosols into the atmosphere that disrupt precipitation cycles. Less solar energy reaching the surface often means reduced evaporation, and less evaporation means less moisture available for rainfall. As a result, some regions may experience unusual drought for months or even years. Conversely, other areas see increased precipitation, as eruptions also disrupt the usual movements of air masses and change local climate patterns. Monsoons, in particular, which are very sensitive to temperature variations, can be particularly disrupted, making their arrival and intensity more unpredictable than ever.
A major volcanic eruption can disrupt the dominant winds and atmospheric circulation on a large scale. By releasing large amounts of aerosols, temperature differences between regions are altered, which can shift or slow down certain traditional air currents like the jet stream. These disturbances in the atmospheric currents will even influence the ocean circulation, particularly by locally cooling some ocean areas, which in turn affects key currents, such as the Gulf Stream. In short, a major eruption disrupts the atmosphere-ocean balance and disturbs the climate in various places for several months, if not years.
Volcanic eruptions can enrich the surrounding soils with essential minerals such as potassium, magnesium, and phosphorus, making these areas particularly fertile after a few years.
Volcanic aerosols, particularly the sulfur particles released into the atmosphere, can remain suspended for up to two or three years, significantly disrupting the global radiative balance and temporarily cooling the climate.
A single large volcanic eruption can release more sulfur dioxide (SO₂) in a few days than all human activities combined over an entire year, immediately and significantly affecting the chemical composition of the stratosphere.
The climate impact of large volcanic eruptions can sometimes influence global phenomena such as the jet stream, monsoons, or even the El Niño phenomenon, thereby causing changes in weather conditions across the planet.
Volcanic ash contains fine abrasive particles that can damage aircraft engines and drastically reduce visibility. The encounter between an airplane and an ash cloud can therefore pose a real danger, forcing airlines to avoid these areas.
No, only explosive eruptions that are powerful enough to send a large volume of aerosols and ash into the stratosphere generally have a significant impact on the global climate. Smaller eruptions are usually limited to a local or regional effect.
The effects of a major volcanic eruption on the climate can last from a few months to several years. For example, the eruption of Mount Pinatubo in 1991 led to a global temperature drop for about one to three years following the eruption.
Significant volcanic eruptions can temporarily cool the planet in the short term. However, this effect is temporary and does not offset the overall trend of global warming associated with human activities in the medium and long term.
Sulfur dioxide (SO₂) is the most notable volcanic gas influencing the climate, as it can form sulfate aerosols that reflect sunlight and globally cool surface temperatures. Carbon dioxide (CO₂), on the other hand, can influence the climate over the very long term, but its volcanic emissions remain modest compared to those from human activities.
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