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Volcanic eruptions help combat global warming

Ian Sample— © Guardian Newspapers Limited 2004

Discharges have a cooling effect on the planet's atmosphere

London: Violent volcanic eruptions help to combat some of the effects of global warming by cooling the Earth and keeping a check on rises in sea level, scientists have discovered.

Eruptions are known to have a cooling effect on the planet's atmosphere because the fine particles thrown up by the volcanoes linger in the air at high altitudes and reflect sunlight and warming infrared radiation before it can hit the Earth's surface.

But the effect of atmospheric ash on sea temperatures had not been properly investigated.

In a study reported in the journal Nature on Thursday, John Church at the Australian Government's CSIRO research facility and scientists at the U.S. National Centre for Atmospheric Research in Colorado found that the huge eruption of Mount Pinatubo in the Philippines in 1991 led to a vast cloud of fine particles that triggered a dramatic cooling of ocean waters, equivalent to losing the amount of energy contained in more than 700 million tonnes of oil.

The rises in sea level observed in recent decades are caused by a mixture of land ice melting into the seas and the expansion of water with increasing global temperatures.

The researchers calculated that the sea cooling brought about by the Mount Pinatubo eruption lowered sea levels around the globe by an estimated 5 millimetre. According to Dr. Church, the cooling effect of eruptions on the atmosphere lasts for two years, but large bodies of water take around a decade to warm up again.

The knock-on effect is a rapid rise in sea levels in the years immediately after a big eruption.

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