Searing effect

Forget volcanic eruptions and El Nino, global warming continues to worsen

Published: Wednesday 31 January 2001

Even after removing the effects of volcanic eruptions and El Nio events on global mean temperature record reveals a gradual yet stronger global warming trend over the last century. This was stated in a new analysis done by Tom Wigley, a climate expert at the National Centre for Atmospheric Research (ncar), Colorado, usa . "Once the volcanic and El Nio influences have been removed, the findings are more consistent with the current view which suggests that global warming can be attributed to both natural and anthropogenic factors and human activities have more substantial effect on global warming," says Wigley. Volcanic emissions cool the planet by blocking sunlight, while El Nio events raise global temperatures through warmer ocean waters. Sometimes the two occur simultaneously, muddying evidence of any underlying warming trend.

Wigley quantified the effects of major volcanic eruptions and El Nio episodes on global mean temperatures. He found an overall cooling effect from volcanic emissions was slightly stronger than the warming effect of El Nios. He then removed both from the temperature record. This indicated an intensified warming trend over the past century.

"When the El Nio and volcanic effects are removed, the recent warming trend increases from 0.18c to 0.25c per decade. This is highly significant," asserts Wigley. The overall result is a long-term warming trend that intensifies by century-end due to increasing emissions of greenhouse gases, Wigley added.

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