Should we wake up volcanoes to reverse climate change? Some scientists are seriously advocating it. But should the devastation caused this weekend make them think again?
Tonga turned into moonscape by volcanic ash
Should we wake up volcanoes to reverse climate change? Some scientists are seriously advocating it. But should the devastation caused this weekend make them think again?
The first sign that something was wrong was a series of explosions. Mere Taufa thought bombs were going off in the city of Nuku'alofa - until water started pouring into her home. The afternoon sky darkened as a cloud of smoke and ash rose 12 miles into the sky. "You could just hear screams everywhere," says Mere. "People screaming for safety, for everyone to get to higher ground."
Last week, the Hunga-Tonga-Hunga-Ha'apai volcano erupted in the South Pacific. It only happens once a millenniumA period of 1,000 years. People born at the end of the 20th Century are referred to as millennials because the oldest of them became adults in 2000. - but anyone living nearby knows to expect a tsunamiA Japanese word describing a succession of waves caused when an earthquake or volcano displaces a large body of water..
In Tonga, the closest inhabited island, the effects were the worst. Fifteen minutes after the first explosion, huge waves hit the coast. Tragically, not everyone survived. One woman, Angela Glover, was swept away and drowned. Her husband survived by clinging to a tree.
But effects were also felt much further away. Waves flooded car parks on the coast of California. In Japan 230,000 people were told to evacuate their homes.
Warnings were issued in New Zealand, Australia, Hawaii and Alaska. Shock waves were even registered 10,000 miles away in Britain.
Tonga is by no means the only country where volcanoes pose a threat.
Last September an eruption in the Canary Islands destroyed 200 homes. On Wednesday the Wolf Volcano in the Galapagos Islands started spewing lava and sending clouds of ash into the air.
The after-effects of eruptions can be felt long afterwards. In 1815, Mount Tambora in Indonesia threw so much debris into the atmosphere that it blotted out the sun. Temperatures fell and crops failed around the world. In New England, 1816 was known as "The Year Without a Summer". In Germany, 1817 was "The Year of the Beggar".
But some scientists believe this phenomenon could help us combat climate change.
In 1991, the eruption of Mount Pinatubo in the Philippines released between 6 and 22 million tons of sulphur dioxideA toxic chemical compound used in making sulphuric acid. into the atmosphere. There, it combined with moisture to create droplets known as aerosols. These scatter the sun's rays and reflect some of them back. As a result, the Earth's average temperature fell by 0.5C the following year.
Hunga-Tonga-Hunga-Ha'apai is unlikely to have the same effect. But it is possible that other volcanoes could - and it might be possible to make them eruptThis could be done by removing rock from the top so that there is no longer enough resistance to magma pushing up from beneath..
This could have a big impact. Brentan Alexander notes: "Geoengineering would allow mankind to avoid the worst impacts of climate change by adding planet-wide cooling technology to our toolset."
The drawback is that sulphur aerosols can damage the ozone layerA layer of gas around 10 kilometres above the Earth's surface which absorbs ultraviolet radiation (a type of heat that reaches the planet from the sun). The layer has a very important role as exposure to too much ultraviolet can be bad for living things., and return to the surface as acid rainRain caused by sulphur dioxide and nitrogen dioxide combining with water molecules in the atmosphere. It can be harmful to plants and animals. . And if too many were released, we could experience another "Year Without a Summer".
But, says Brentan Alexander, as climate problems grow more severe, it could become our "least bad" option.
<h5 class=" eplus-wrapper"><strong>Should we wake up volcanoes to reverse climate change?</strong></h5>
Yes: Climate change is a critical problem and anything that might halt it is worth trying. If one volcano can lower Earth's temperature by 1C, a few eruptions could solve all our problems.
No: Volcanoes are incredibly dangerous, in terms of both the lava and ash they produce and the tsunamis they can trigger. Causing an eruption could have terrible consequences across the world.
Or... We should try to mimic the effects of a volcanic explosion without actually causing one. We could disperse sulphur dioxide high up in the stratosphere just as Mount Pinatubo did.
Millennium - A period of 1,000 years. People born at the end of the 20th Century are referred to as millennials because the oldest of them became adults in 2000.
Tsunami - A Japanese word describing a succession of waves caused when an earthquake or volcano displaces a large body of water.
Sulphur dioxide - A toxic chemical compound used in making sulphuric acid.
Make them erupt - This could be done by removing rock from the top so that there is no longer enough resistance to magma pushing up from beneath.
Ozone layer - A layer of gas around 10 kilometres above the Earth's surface which absorbs ultraviolet radiation (a type of heat that reaches the planet from the sun). The layer has a very important role as exposure to too much ultraviolet can be bad for living things.
Acid rain - Rain caused by sulphur dioxide and nitrogen dioxide combining with water molecules in the atmosphere. It can be harmful to plants and animals.
Tonga turned into moonscape by volcanic ash

Glossary
Millennium - A period of 1,000 years. People born at the end of the 20th Century are referred to as millennials because the oldest of them became adults in 2000.
Tsunami - A Japanese word describing a succession of waves caused when an earthquake or volcano displaces a large body of water.
Sulphur dioxide - A toxic chemical compound used in making sulphuric acid.
Make them erupt - This could be done by removing rock from the top so that there is no longer enough resistance to magma pushing up from beneath.
Ozone layer - A layer of gas around 10 kilometres above the Earth’s surface which absorbs ultraviolet radiation (a type of heat that reaches the planet from the sun). The layer has a very important role as exposure to too much ultraviolet can be bad for living things.
Acid rain - Rain caused by sulphur dioxide and nitrogen dioxide combining with water molecules in the atmosphere. It can be harmful to plants and animals.