Climate change is ‘game-changing’ when it comes to heatwaves

(ORDO NEWS) — All of today’s heatwaves bear the unmistakable and measurable signature of global warming, leading experts in quantifying the impact of climate change on extreme weather said Wednesday.

The burning of fossil fuels and the destruction of forests have released enough greenhouse gases into the atmosphere to increase the frequency and intensity of many floods, droughts, wildfires and tropical storms, according to a state of the art report.

“There is no doubt that climate change is a huge game changer when it comes to extreme heat,” Friederike Otto, a scientist at Imperial College London’s Grantham Institute, told AFP.

Extreme heat waves like those that gripped South Asia in March and April are already the deadliest of extremes, she added.

“Every heat wave in the world is now intensifying and becoming more likely due to anthropogenic climate change,” said Otto and co-author Ben Clark of the University of Oxford in a report presented as a media briefing paper.

Evidence of the impact of global warming on extreme weather has been accumulating for decades, but only recently has it become possible to answer the most obvious question: To what extent was this or that event caused by climate change?

Previously, scientists could only say that an unusually strong hurricane, flood, or heat wave was in line with common predictions about how global warming would eventually affect the weather.

At the same time, the media sometimes ignored climate change altogether or, in extreme cases, misattributed weather disasters solely to rising temperatures.

However, with more data and better tools, Otto and other pioneers in what is known as the science of event attribution have been able to calculate sometimes almost in real time how much more likely or intense a given storm or hot spell has become due to global warming.

Otto and his colleagues at the World Weather Attribution (WWA) consortium, for example, have concluded that the heat wave that swept western North America last June, which sent temperatures in Canada to a record 49.6 ºC (121 ºF), would be “virtually impossible” without anthropogenic climate change.

Otto told AFP that the heat wave that scorched India and Pakistan last month is still under review, but the overall picture is eerily clear.

“What we’re seeing right now in terms of extreme heat is going to be quite normal, if not chilly, in a 2 to 3 degree Celsius world,” she said, referring to average global temperatures above pre-industrial levels.

To date, the world has warmed by almost 1.2 degrees Celsius.

This increase has made record rains and floods last July in Germany and Belgium, which killed more than 200 people, nine times more likely, according to WWA.

But global warming is not always to blame.

A two-year near-starvation drought in southern Madagascar that the UN attributed to climate change was actually the result of natural weather variability, experts say.

Quantifying the impact of global warming on extreme weather events using peer-reviewed methods has real policy implications.

For example, attribution studies have been used as evidence in landmark climate lawsuits in the US, Australia and Europe.

In one case due to reopen later this month, Saul Luciano Llluya v. RWE AG, a Peruvian farmer has filed a lawsuit against the German energy giant for the cost of preventing harmful flooding from a glacial lake destabilized by climate change.

A scientific assessment presented as evidence concluded that human-caused global warming is directly responsible for creating a “critical threat” of a devastating outbreak that would put a city of about 120,000 people in the path of potential floodwaters.

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