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The effect of the Agung volcano in Bali, on global temperatures

Analysis: How could the Agung volcano in Bali affect global temperatures? Carbon Brief, ZEKE HAUSFATHER 25.10.2017  While human activity has been the dominant driver of climate change over the past century, natural factors can influence short-term variations in global temperature.

Major volcanic eruptions, in particular, can have a sizable cooling impact on the climate lasting for five years or so.

The Mount Agung volcano in Bali, Indonesia has been showing signs that an eruption is likely to occur this year. Last time Agung erupted, back in 1963, it had a noticeable cooling effect on the Earth’s climate.

Here, Carbon Brief examines how volcanoes influence the climate, and suggests that a new Agung eruption would likely only result in a modest and temporary cooling of global temperatures.

Volcanoes and climate changeVolcanoes generally have a cooling influence on the Earth’s surface.Eruptions send a cloud of ash and dust high into the atmosphere. The sulphur dioxidereleased combines with water to form sulfuric acid aerosols, which reflect incoming sunlight and influence cloud formation. When eruptions are powerful enough to reach the stratosphere (18 km or more above the surface at the equator), these sulphate aerosols can stay aloft for a number of years and have a strong cooling effect on the climate.

Volcanic eruptions also release CO2 into the atmosphere, meaning they contribute to warming by strengthening the greenhouse effect. But this influence is very small, and is outweighed by the cooling impact of the dust and ash.

The location of volcanoes also matter. Major volcanic eruptions near the equator are more likely to have a big effect on global temperatures, while high-latitude eruptions (like Laki) will have their effects more limited to the one hemisphere. Sulphate aerosols from high-latitude volcanoes generally will not cross the equator, while tropical volcanoes tend to cool both hemispheres………

This projection, which is based on the historical relationship between volcanic eruptions and temperature, suggests that an Agung eruption would reduce global temperatures between 0.1C to 0.2C in period from 2018 to 2020, with temperatures mostly recovering back to where they otherwise would be by 2023.

There is no guarantee that an eruption of Agung today would be the same size as the one in 1963, however. A small volcanic eruption that doesn’t reach the stratosphere would have a relatively minor climate impact, as sulphur dioxide from the volcano would quickly fall out of the atmosphere.

On the flip side, we have records of much larger volcanic eruptions, such as Tambora in 1815 that may have cooled the globe by 0.6C or more and led to the “year without a summer”. Even in large eruptions this cooling only lasts a few years, however, as once sulphate aerosols eventually fall back to earth the climate quickly returns to normal.

This projection, which is based on the historical relationship between volcanic eruptions and temperature, suggests that an Agung eruption would reduce global temperatures between 0.1C to 0.2C in period from 2018 to 2020, with temperatures mostly recovering back to where they otherwise would be by 2023.

There is no guarantee that an eruption of Agung today would be the same size as the one in 1963, however. A small volcanic eruption that doesn’t reach the stratosphere would have a relatively minor climate impact, as sulphur dioxide from the volcano would quickly fall out of the atmosphere.

On the flip side, we have records of much larger volcanic eruptions, such as Tambora in 1815 that may have cooled the globe by 0.6C or more and led to the “year without a summer”. Even in large eruptions this cooling only lasts a few years, however, as once sulphate aerosols eventually fall back to earth the climate quickly returns to normal……..https://www.carbonbrief.org/analysis-how-could-agung-volcano-bali-affect-global-temperature

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December 1, 2017 - Posted by | climate change, Indonesia

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