Their unpredictability adds a touch of mystery. Volcanic eruptions are a significant natural forcing factor in climate change, and accurately predicting the climate response within two years of a volcanic eruption is of great social value.
Atmospheric Effects
Long-Term Climate Effects of Volcanic Eruptions
The atmospheric effect is a climate phenomenon in which volcanic ash and aerosols released after a volcanic eruption enter the stratosphere, causing a global temperature drop through a parasol effect. Typical examples include the "Year Without a Summer" caused by the 1815 eruption of Mount Tambora, the two-year global cooling caused by the 1991 eruption of Mount Pinatubo, and the prolonged cold temperatures in Europe caused by the 2010 Icelandic eruption. The intensity of this effect is closely related to the volcano's geographic location (more pronounced at lower latitudes), the height of the eruption column (more than 35 kilometers), and the composition of the magma (intermediate-acidic volcanoes are more likely to form aerosols). In addition to direct cooling, it will also enhance secondary disasters such as regional precipitation anomalies and ozone layer depletion.
Factors affecting the intensity of the effect
- Geographic latitude: Eruption materials from low-latitude volcanoes (such as Mount Pinatubo in the Philippines) are more likely to spread globally through atmospheric circulation, and their impact range is 3-5 times larger than that of mid- and high-latitude volcanoes (such as Eyjafjallajokull in Iceland).
- Eruption column height: Eruptions that break through the tropopause (about 10 kilometers) can extend the retention time of aerosols from several weeks to several years. In 1991, aerosols from Mount Pinatubo spread to an altitude of 50 kilometers .
- Magma composition: Intermediate-acidic magma (SiO₂ content ≥58%) is more likely to produce sulfur-rich gases. The volcanic ash formed by basaltic magma has a larger particle size and a faster settling speed.
Volcanic eruptions and the atmosphere and climate
Atmospheric impact mechanism
When a volcano erupts, it is not only accompanied by the raging of magma, but also releases a large amount of volcanic ash. Volcanic ash is composed of debris such as rock, minerals, and volcanic glass fragments. Its size and weight vary, resulting in uneven distribution in the atmosphere and a significant blocking effect on solar radiation.
Volcanic Ash and Climate Impacts
Volcanic ash, these larger particles, primarily remain in the troposphere. They gradually settle with precipitation, and their impact on climate is relatively short-lived. However, the truly profound impact on climate is the sulfur-containing gases released during volcanic eruptions. These gases enter the stratosphere in large quantities, where they oxidize to form sulfate aerosols.
Regional and Global Impacts
The Impact of Temperature Changes
So, do volcanic eruptions worldwide have a significant impact on climate? In reality, this is not the case. The intensity of a volcanic eruption is typically measured using the Volcanic Eruption Index (VEI), which ranges from 0 to 8, with higher values indicating greater intensity. For example, the 1815 eruption of Mount Tambora in Indonesia achieved a staggering VEI of 7, ejecting 150-170 cubic kilometers of volcanic ash. The eruption had profound impacts on the global climate, particularly in Europe and North America.
Impact of Precipitation Changes
Volcanic activity not only alters temperatures but also directly affects precipitation. Following an eruption, near-surface temperatures drop, reducing evaporation and leading to a decrease in atmospheric water vapor. These changes ultimately lead to a significant decrease in average global precipitation.
