The cooling effect of volcanoes on the environment is often underestimated. Volcanic eruptions produce high-temperature lava that can cause severe damage to surrounding areas, but they can also introduce large amounts of sulfur dioxide gas into the atmosphere due to the large amounts of volatiles and ash ejected into the atmosphere. In particular, sulfur dioxide enters the upper atmosphere (the stratosphere) and is converted into extremely small droplets of sulfuric acid, effectively increasing the Earth’s albedo and acting as a stratospheric mirror.These tiny droplets of sulfuric acid reflect the sun’s energy into outer space, and this solar reflection causes an overall decrease in Earth’s surface temperature over the years due to the parasol effect. Examples of these long-lasting cooling effects can be seen in volcanic events throughout our planet’s history, such as the 1991 eruption of Mount Pinatubo, because that eruption taught scientists the importance of understanding how natural aerosols help maintain Earth’s complex thermal balance.
Volcanoes could cool the earth
The injection of large amounts of sulfur dioxide into the atmosphere during volcanic eruptions is a major contributor to global cooling. Because volcanic ash is much heavier than sulfur dioxide and settles to the ground quickly within days or weeks, it does not have the same long-term impact on the climate as sulfur dioxide does.Once sulfur dioxide is injected into the atmosphere, it reacts with water vapor to produce very small sulfuric acid particles (micron size) in the form of aerosols. These aerosols can remain suspended in the atmosphere for years and form a haze that causes the Earth’s surface to become more reflective of incoming solar radiation. By reflecting and refracting incident solar radiation through the aerosol layer, aerosols will cause a significant decrease in global average temperature.
How 20 million tons of gas cool the Earth
The 1991 eruption of Mount Pinatubo in the Philippines greatly improved scientists’ understanding of how volcanic eruptions interact with atmospheric materials. About 15-20 million tons of sulfur dioxide are injected into the stratosphere, which diffuses around the world and forms an effective blocker of solar radiation. According to NASA’s Earth Observatory, the global average temperature dropped by about 0.5 degrees Celsius from 1992 to 1993. The researchers used the case to illustrate how volcanoes affect climate and how scientists can use satellite data to quantify how much solar energy is blocked by volcanic activity.
Lessons from the Tambora eruption
The April 1815 eruption of Mount Tambora in Indonesia is the most dramatic example of volcanic cooling in Earth’s history. The National Oceanic and Atmospheric Administration (NOAA) noted that the amount of aerosols produced during this eruption was enough to cause a “volcanic winter” worldwide, leading to the “year without summer” in the Northern Hemisphere in 1816. The climate in the Northern Hemisphere also changed dramatically during this period, with frost and even snowfall in July in New England and rain in the form of ice in Europe. The resulting drop in temperatures caused crop failures and livestock deaths across North America and Europe; so while this cooling effect is scientifically interesting, it also had devastating effects on human civilization and agriculture.
Why volcanic cooling cannot offset the greenhouse effect
It is important to be able to determine the impact of volcanoes on Earth’s temperature compared to that caused by human activity. Volcanoes do produce carbon dioxide; however, the amount produced is far less than that emitted by humans and their activities. This is clear when comparing the tons of carbon dioxide emitted by volcanoes to the amount emitted by man-made sources in just a few days. According to a study published in the journal Climate, the total annual carbon dioxide emissions from global volcanoes is 0.13-0.44 billion tons of carbon dioxide, while humans’ annual industrial carbon dioxide emissions are significantly higher than volcanic emissions, and the emissions last from days to weeks. In addition, the cooling effects of sulfate aerosols emitted by volcanoes last only 1-3 years on average before being returned to the lower atmosphere via precipitation, so these cooling effects do not offset the long-term warming of the Earth due to the accumulation of greenhouse gas emissions in the atmosphere.
