Climatologist's Toolbox


Mount Pinatubo
© Philippine Institute of Volcanology and Seismology.
poof!Pass the Tums
What do volcanoes have to do with climate? Plenty. Explosive volcanoes, says ice core expert Ellen Mosley-Thompson, can have a significant, although short-lived, effect on global climate. Significant eruptions, she says, are those that propel tons of material -- pulverized rock and, more importantly, gases -- into the stratosphere (defined). The gases in particular, Mosley-Thompson tells The Why Files, can exert a major influence on the Earth's radiation balance because the gases are converted to sulfuric acid aerosols which can stay in the atmosphere for years. The volcanic dust particles, on the other hand, settle back to Earth within six months or so.

These materials can blanket the Earth and influence climate, at least on the short term, by blocking sunlight. The Tambora eruption of 1815, for instance, is easily discerned in ice cores from both Antarctica and Greenland. It neatly coincides with the fact that the decade between 1810 and 1820 was the coldest on record. That could be attributed, too, says Mosley-Thompson, to a mysterious eruption in 1809. While that eruption shows up in ice cores, it was apparently recorded by no human at the time. More recently, in 1991 to be precise, a sun-reflecting haze cast aloft by the eruption of Mount Pinatubo in the Philippines cooled the Earth for about two years.

If the ice masses from which Mosley-Thompson's cores are drawn are carefully chosen, they can provide neat annual records of climate and weather. That's because ice caps and other long-lived bodies of ice tend to accumulate in layers. If properly preserved and measured, the ice cores read like books.

One chapter of interest is how human influences are recorded in the ice, and from her cores it is possible to see such things as the advent of the Industrial Revolution as sulfuric acid from fossil fuels and nitrates from fertilizers begin to appear in the icy record. Like the gaseous aerosols from volcanoes, these tracers settle on distant ice and are there to be read by anyone bold enough to retrieve the record.

And speaking of records, how can a sample of sediment tell us things that even Thoreau didn't know about Walden Pond?

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