- Related Topics:
- Climate change
- volcanism
- sulfur dioxide
- Winter
- volcanic ash
volcanic winter
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What is a volcanic winter?
A volcanic winter refers to the cooling of the Earth's surface caused by large quantities of volcanic ash and sulfur aerosols deposited in the stratosphere following explosive volcanic eruptions. These sulfur aerosols reflect incoming solar radiation and absorb terrestrial radiation, which cools the troposphere below.
Significant sulfur aerosol loading can cause global climate changes for years, resulting in cooler temperatures, crop failures, and unusual weather patterns. For example, the eruption of Mount Tambora in 1815 led to the "year without a summer" in North America and Europe. The eruption of Mount Pinatubo cooled the world’s climate by about 0.5 °C (0.9 °F) for a few years after it erupted in 1991.
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How do volcanic eruptions cause volcanic winter?
Volcanic eruptions can cause a volcanic winter by injecting massive amounts of volcanic ash and sulfur aerosols into the stratosphere. These sulfur aerosols reflect incoming solar radiation and absorb terrestrial radiation, which cools the troposphere below.
The concentration of sulfur aerosols in the stratosphere increases reflection, which results in a decline in surface heating and cooler temperatures on Earth. Because the stratosphere has little atmospheric turbulence, the aerosols can remain for years before settling. The cooling effect can last for one to three years after the eruption.
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What changes happen to Earth's climate during a volcanic winter?
During a volcanic winter, the Earth's surface cools due to volcanic ash and sulfur aerosols deposited in the stratosphere. These aerosols reflect incoming solar radiation and absorb terrestrial radiation, cooling the troposphere and causing global climate changes for years. Significant sulfur aerosol loading leads to cooler temperatures, crop failures, and atypical weather. For example, the eruption of Mount Tambora in 1815 led to a reduction of the average global temperature by as much as 3 °C (5.4 °F) in 1816, causing the "year without a summer" in parts of North America and Europe. The major haze-forming agent from volcanic eruptions is an aerosol of tiny sulfuric acid droplets.
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How do volcanoes block sunlight during a volcanic winter?
Volcanic eruptions can cause a volcanic winter by releasing volcanic ash and sulfur aerosols into the stratosphere. These sulfur aerosols then reflect incoming solar radiation and absorb terrestrial radiation. The increased concentration of sulfur aerosols leads to greater reflection, which causes surface heating to decline and cooler temperatures to predominate at the Earth’s surface. The injection of volcanic matter into the atmosphere can lower average world temperatures for one to three years.
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What are some historical examples of volcanic winter events?
Volcanic winters are cooling events caused by large quantities of volcanic ash and sulfur aerosols entering the stratosphere. These aerosols reflect incoming solar radiation, which leads to cooler temperatures, crop failures, and unusual weather.
Examples include:
* Mount Toba Between 71,000 and 74,000 years ago, this Sumatran volcano ejected 2,800 cubic km of ash, potentially dropping global temperatures 3–5 °C.
* Laki fissure The 1783 eruption in Iceland released enormous amounts of volcanic gas, causing a conspicuous haze over Europe and possibly contributing to the severe winter of 1783–84.
* Mount Tambora The 1815 eruption in Indonesia led to a global temperature decrease of as much as 3 °C in 1816, resulting in the "year without a summer" in North America and Europe.
* Krakatoa The 1883 eruption discharged nearly 21 cubic km of rock fragments, causing spectacular sunsets and potentially disrupting weather patterns for years.
* Mount Pinatubo Gases and ash from this Philippine volcano cooled the world’s climate by about 0.5 °C for a few years after its 1991 eruption.3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How does volcanic winter affect plants, animals, and humans?
Volcanic winter is a period of cooling on Earth's surface caused by large quantities of volcanic ash and sulfur aerosols deposited in the stratosphere following explosive volcanic eruptions. The consequences of volcanic winter can be severe for plants, animals, and humans:
- Plants Crop failure can occur over large areas downwind from major ash eruptions, and widespread famine and disease may result, especially in poorly developed countries. However, in the long run, the decomposition of nutrient-rich volcanic fallout is responsible for some of the world’s best soils.
- Animals Animals may face habitat loss and food scarcity, potentially leading to population declines. Some animals hibernate to conserve energy.
- Humans Humans may experience cooler temperatures, crop failures, and atypical weather conditions, which can lead to famine and disease.
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volcanic winter, cooling at Earth’s surface resulting from the deposition of massive amounts of volcanic ash and sulfur aerosols in the stratosphere. Sulfur aerosols reflect incoming solar radiation and absorb terrestrial radiation. Together these processes cool the troposphere below. If sulfur aerosol loading is significant enough, it can result in climate changes at the global scale for years after the event, causing crop failures, cooler temperatures, and atypical weather conditions across the planet.
Explosive volcanic eruptions are capable of sending pulverized rock, sulfur dioxide (SO2), and hydrogen sulfide (H2S) into the stratosphere. Although volcanic ash can decrease regional visibility for a few months after the eruption, sulfur compounds injected into the stratosphere form sulfur aerosols that can reflect a portion of incoming sunlight for several years. As the concentration of sulfur aerosols increases in this region of the atmosphere, greater reflection occurs. Surface heating declines as a result, and thus cooler temperatures predominate at Earth’s surface. Compared with the underlying troposphere, the stratosphere is relatively devoid of atmospheric turbulence, and thus these aerosols may remain in the stratosphere for several years before settling out.
There is evidence that volcanic winters have occurred several times throughout Earth’s history, with varying degrees of severity. One of the more severe episodes of volcanic winter occurred sometime between 71,000 and 74,000 years ago when Mount Toba, a volcano on the island of Sumatra, expelled possibly as much as 2,800 cubic km (about 670 cubic miles) of ash into the stratosphere. Ice-core evidence suggests that average air temperatures worldwide plunged by 3–5 °C (5.4–9.0 °F) for years after the eruption. (Some model simulations estimate that this temperature decline may have been as much as 10 °C [18 °F] in the Northern Hemisphere in the first year after the eruption.) Some scientists maintain that this event sent the planet into a severe ice age that nearly caused the extinction of modern humans. A study of a contemporaneous human settlement in southern Africa suggests that some areas of Earth with a plentiful food supply may have served as refuges for human beings in the years after the eruption.
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From June 1783 to February 1784 the Laki fissure in Iceland extruded about 12.5 cubic km (3 cubic miles) of lava that covered about 565 square km (220 square miles)—considered the greatest lava eruption on Earth in historical times. The enormous quantity of volcanic gas that was released caused a conspicuous haze over most of continental Europe. Some scientists link the presence of this haze over the region to the severity of the winter of 1783–84 in the Northern Hemisphere.
During the 19th century two volcanoes in the Indonesian archipelago were associated with volcanic winters. The first event was caused by the eruption of Mount Tambora, a volcano on the island of Sumbawa. It expelled about 100 cubic km (24 cubic miles) of ash into the atmosphere in 1815. This event had the effect of reducing the average global temperature by as much as 3 °C (5.4 °F) in 1816, causing the “year without a summer” in parts of North America and Europe.
The second event was caused by the eruption of Krakatoa in 1883. This eruption discharged nearly 21 cubic km (5 cubic miles) of rock fragments, destroying much of the island of Krakatoa, and the surrounding region was plunged into darkness for two and a half days because of ash in the air. The fine dust drifted several times around the Earth, causing spectacular red and orange sunsets throughout the following year. Some scientists contend that this eruption upset weather patterns for years afterward. In 1928, after a period of renewed volcanic activity, a new island called Anak Krakatau (“Child of Krakatoa”) emerged from the ocean in the spot where the original volcano once existed.
More recently, gases and ash from Mount Pinatubo, a volcano located on the island of Luzon in the Philippines, cooled the world’s climate by about 0.5 °C (0.9 °F) for a few years after the volcano erupted in 1991.
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