Global Geological And Climatic Events

Role of Volcanoes in global warming


From UPSC perspective, the following things are important :

Prelims level : Vulcanism, Deep Carbon Observatory (DCO)

Mains level : Role of Volcanoes in global warming

  • Human activity churns out up to 100 times more carbon each year as all the volcanoes on Earth, says a decade-long study Deep Carbon Observatory (DCO).

Deep Carbon Observatory (DCO)

  • DCO is a 10-year global research collaboration of more than 1,000 scientists to understand the quantities, movements, forms, and origins of carbon in Earth.
  • The findings are part of estimations by the DCO scientists of the Earth’s immense interior carbon reservoirs, and how much carbon the deep Earth naturally swallows and exhales.

Role of volcanoes

  • Scientists at the Deep Carbon Observatory (DCO) have found that even a handful of volcanic events have caused catastrophic releases of carbon, leading to a warmer atmosphere, acidified oceans, and mass extinctions.
  • Researchers from DCO’s DECADE (Deep Earth Carbon Degassing) subgroup found that volcanoes and volcanic regions outgassed an estimated 280-360 million tonnes of CO2 per year.
  • This includes the contribution from active volcanic vents, from the diffusing and widespread release of CO2 through soils, faults, and fractures in volcanic regions, volcanic lakes, and from the mid-ocean ridge system.

1. Particles of dust and ash

  • Volcanic ash or dust released into the atmosphere during an eruption shade sunlight and cause temporary cooling.
  • Larger particles of ash have little effect because they fall out of the air quickly. Small ash particles form a dark cloud in the troposphere that shades and cools the area directly below.
  • Most of these particles fall out of the atmosphere within rain a few hours or days after an eruption.
  • But the smallest particles of dust get into the stratosphere and are able to travel vast distances, often worldwide.
  • These tiny particles are so light that they can stay in the stratosphere for months, blocking sunlight and causing cooling over large areas of the Earth.

2. Sulfur

  • Often, erupting volcanoes emit sulfur dioxide into the atmosphere. Sulfur dioxide is much more effective than ash particles at cooling the climate.
  • The sulfur dioxide moves into the stratosphere and combines with water to form sulfuric acid aerosols.
  • The sulfuric acid makes a haze of tiny droplets in the stratosphere that reflects incoming solar radiation, causing cooling of the Earth’s surface.
  • The aerosols can stay in the stratosphere for up to three years, moved around by winds and causing significant cooling worldwide. Eventually, the droplets grow large enough to fall to Earth.

3. Greenhouse gases

  • Volcanoes also release large amounts of greenhouse gases such as water vapor and carbon dioxide.
  • The amounts put into the atmosphere from a large eruption doesn’t change the global amounts of these gases very much.
  • However, there have been times during Earth history when intense volcanism has significantly increased the amount of carbon dioxide in the atmosphere and caused global warming.

Contrasting to humans

  • For the past 100 years, humanity’s annual carbon emissions through the burning of fossil fuels and forests were 40 to 100 times greater than those from geologic sources such as all volcanic emissions, a/c to DECADE.


  • About 400 of the 1500 volcanoes active since the last Ice Age 11,700 years ago are venting CO2 today, said DECADE.
  • Another 670 could be producing diffuse emissions, with 102 already documented.
  • Of these, 22 ancient volcanoes that have not erupted since the Pleistocene Epoch (2.5 million years ago to the Ice Age) are outgassing.
  • DECADE also confirmed that more than 200 volcanic systems emitted measurable volumes of CO2 between 2005 and 2017. Of these, several regions of degassing have been documented.
  • These include Yellowstone in the United States, the East African Rift, and the Technong volcanic province in China.

A fine balance

  • The quantity of carbon released from Earth’s mantle has been in relative balance with the quantity returned through the downward subduction of tectonic plates and other processes.
  • Any imbalance to the carbon cycle could cause rapid global warming, changes to the silicate weathering rate, changes to the hydrologic cycle, and overall rapid habitat changes that could cause mass extinction as the earth rebalanced itself.

Total carbon

  • The scientists also calculated that just two-tenths of one per cent of Earth’s total carbon — about 43,500 Gt — is above surface in the oceans, on land, and in the atmosphere.
  • The rest is subsurface, including the crust, mantle and core — an estimated 1.85 billion Gt in all.
  • While around 37,000 gt carbon (85.1 per cent) is in the deep ocean, 3,000 gt (6.9 per cent) lies in marine sediments.
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