Volcanoes and Climate

The Earth’s Energy (Radiation) Budget

Pinatubo 1963 Agung 1982 El Chichon Santa Maria 1902

Atmospheric Stability Many things can cause air to rise As it rises, the pressure falls and the air cools If the air is then warmer than the surrounding air, it carries on rising – unstable. If the air is colder than the surrounding air, it sinks back to where is came from – stable. The stratosphere is always very stable – but explosive volcanic eruptions can blast material up into the stratosphere. Once in the stratosphere, the stability means that the volcanic materials tends to stay there for several years.

Explosive volcanoes and latitude Stratospheric circulation Tropospheric circulation

For maximum effect a volcano should be… -Explosive -Low latitude -Effects are greater over land than over sea -Northern hemisphere summer season -Lots of Sulphur dioxide emitted.

Volcanic forcing of climate over the past 1500 years: An improved ice core- based index for climate models 2008, Chaochao Gao, Alan Robock, and Caspar Ammann

Effusive or small volcanoes - e.g. Bárðabunga, Explosive volcanoes Super volcanoes or intense volcanic activity -Snowball Earth (pre-Cambrian) -Super volcanoes - any volcano capable of producing a volcanic eruption with an ejecta mass greater than kg -Toba, Sumatra (74,000 years ago), preceded major glaciation -Yellowstone (640,000 years ago), 5°C global cooling

Laki & Grímsvötn, Lasted for eight months during 1783 to 1784, and produced one of the largest basaltic lava flows in historic times The release of sulphur gases during fountaining produced an acid haze (aerosol) which spread widely and had a considerable environmental, and possibly climatic, impact on the Northern Hemisphere. Troposphere, not stratosphere Fire-fountains of magma reached 1.4km, ash reached 9-13km The quantity of SO 2 released was comparable to the total annual present-day anthropogenic input to the atmosphere

Laki & Grímsvötn, During the explosive phases, the atmosphere over Iceland became loaded with fine ash and sulphuric acid droplets. Grass growth was stunted, 50% of grazing livestock died and 22% of Icelanders died. Haze or dry fog was reported over much of the Northern Hemisphere, blood red sunsets – affected vegetation, animals and people Summer of 1783 was warm, was colder than usual, but was it due to the volcano? Linked to famine and plague in middle east, virtual dying out of Inuit in NW Alaska Did the aerosol reach the stratosphere? Food poverty was a major factor in the build-up to the French revolution of 1789

Eyjafjallajökull, 2010

Volcanoes and Climate Change? Climate Change Less Ice Less Pressure More magma generation c.org/2015/11/icelands- volcanic-activity-to- increase-from-climate- change/