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Transcript
Volcanoes and Climate The Earth’s Energy (Radiation) Budget Santa Maria 1902 1963 Agung 1982 El Chichon 0 1992 Pinatubo 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 Tropospheric circulation Stratospheric 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 corebased index for climate models 2008, Chaochao Gao, Alan Robock, and Caspar Ammann Volcanoes and their effect on climate David Viner & Phil Jones • • • • - Effusive or small volcanoes - e.g. Bárðabunga, 2014-15 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 1015 kg - Toba, Sumatra (74,000 years ago), preceded major glaciation - Yellowstone (640,000 years ago), 5°C global cooling Laki & Grímsvötn, 1783-84 • 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 SO2 released was comparable to the total annual present-day anthropogenic input to the atmosphere Laki & Grímsvötn, 1783-84 • 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, 1784-1786 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 http://www.yalescientifi c.org/2015/11/icelandsvolcanic-activity-toincrease-from-climatechange/ Additional Sources: https://www.wunderground.com/climate/volcanoes.asp