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Water vapour from volcanic eruptions could impact climate change – University of Reading

Research by meteorologists at the University of Reading has shown that large volcanic eruptions – which can affect global weather patterns by adding tiny particles of liquid called aerosols to the atmosphere – also add water vapour to the Earth's stratosphere, and potentially affect climate change. Dr Manoj Joshi and Professor Keith Shine, from the University's Department of Meteorology, simulated the effect of the 1991 eruption of Mount Pinatubo in the Philippines on atmospheric temperature using a model designed to study weather and climate. They found a significant increase in stratospheric water amount in the years following the eruption in their model. 'Observations show that water vapour in the stratosphere has increased by 1% per decade since the 1960s,' said Dr Joshi, whose research was published in the November issue of the American Meteorological Society's Journal of Climate. 'There is a need to fully explain this trend, because stratospheric water vapour is potentially a significant factor in climate change because it can force surface temperatures to rise in the same way as carbon dioxide does.' The aerosol clouds from volcanic eruptions typically disappear after one or two years, but the water vapour increases could typically take between five and 10 years to dissipate, according to Dr Joshi. If large volcanic eruptions took place frequently enough, the water vapour pulse from one eruption would add to the decaying pulse from the previous one, thus 'ratcheting' water vapour amounts upwards. Between 1960 and 2000, five volcanoes have erupted with sufficient strength to significantly alter the water vapour level in the stratosphere, so Dr Joshi and Professor Shine suggest that these eruptions could make a large contribution to the observed increase in stratospheric water vapour amounts. 'The long-term results would include stratospheric cooling, stratospheric humidification and surface warming,' said Dr Manoj. 'It is important to understand that adding tiny amounts of water vapour in that region can play a significant role in increasing surface temperatures on Earth. If we have more frequent volcanic eruptions in the future, this could become an even larger issue.' end Note to Editors and Assignment Desks: For more information, contact Dr Joshi on (0044) 118 378 6507 or e-mail: m.m.joshi@reading.ac.uk Or contact Craig Hillsley, Press Officer at the University of Reading on (0118) 378 8005 or e-mail: c.hillsley@reading.ac.uk PDF or faxed copies of the paper, "A GCM Study of Volcanic Eruptions as a Cause of Increased Stratospheric Water Vapor," are available to journalists from Stephanie Kenitzer, AMS press office at (425) 432-2192, or kenitzer@dc.ametsoc.org. Craig Hillsley Press Officer Department of Communications, Room 301 Whiteknights House University of Reading PO Box 217 Reading RG6 6AH tel: 0118 378 8005 fax: 0118 378 8924 e-mail: c.hillsley@reading.ac.uk