Little doubt that global warming ‘human-caused’

February 1, 2016

A new report has said the chances that global warming is caused by random weather swings are virtually zero, and that the Earth is hotting up as a result of human activity. The report comes as separate research shows that sea levels are rising at a faster rate than previously thought, increasing the probability of more severe storms.

The journal Scientific Reports published a study by a team of experts led by Michael Mann, a professor of meteorology from Pennsylvania State University. It looked at average global temperatures and the likelihood that they could be the result of random climate variations, as climate change sceptics claim. As 13 of the 15 hottest years on record occurred between 2000 and 2013, the experts concluded that the chances of natural factors explaining such trends were one in 770 at best, and one in 13,000 at worst.

‘Climate change is real, human-caused and no longer subtle,’ Prof Mann told the Reuters news agency. ‘We’re seeing it play out before our eyes. Natural climate variations just can’t explain the observed global heat records, but man-made global warming can.’

The conclusions were reached before figures on 2015 temperature data were released. These showed that 2015 was by far the hottest year on record, which means the conclusions are likely to be an understatement.

In addition, the impact of global warming could be greater than previously thought following a German report which says rising sea levels caused by warming have been underestimated. Up to now, sea levels have been thought to be rising by 0.7-1.0mm per year, but an analysis of satellite data for the period 2002-14 suggests they are rising by 1.4mm per year because the thermal expansion of water has been underestimated. The result could be increasingly severe storm surges.

The findings are published in the US journal Proceedings of the National Academy of Sciences.

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