In DepthClimate Change

UV radiation blamed in ancient mass extinction

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Science  29 May 2020:
Vol. 368, Issue 6494, pp. 926
DOI: 10.1126/science.368.6494.926

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Summary

It has long been thought that, before the rise of humanity, there were two ways to cause a mass extinction of life on Earth: a giant impact or massive volcanic eruptions. Scientists have now found evidence, in the shape of malformed spores from fernlike trees, that one of the planet's greatest extinctions, 359 million years ago, was instead triggered by a mass depletion of the ozone layer. A rock core taken from Greenland suggests a rapidly warming climate triggered this ozone loss, perhaps causing an increase in powerful convective storms capable of injecting water vapor and ozone-destroying salts into the stratosphere. It's unclear, however, whether this mechanism can truly deplete ozone in significant quantities. If it can, then Earth's fate during the end-Devonian extinction could be a warning for the warming present.

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