Wild weather shows growing effect of climate change

A warning sign alerts visitors of the extreme heat dangers at Badwater Basin, the lowest point in North America, in California's Death Valley National Park in the US.
A warning sign alerts visitors of the extreme heat dangers at Badwater Basin, the lowest point in North America, in California's Death Valley National Park in the US.
Image: REUTERS/ DAVID BECKER

In recent weeks, the world has seen ferocious wildfires in the US West, torrential rains in Africa, weirdly warm temperatures on the surface of tropical oceans and record heatwaves from California to the Siberian Arctic.

This spate of wild weather is consistent with climate change, scientists say, and the world can expect even more extreme weather and higher risks from natural disasters as global emissions of greenhouse gases continue.

“We are seeing the emergence of some signals that would have had almost no chance of happening without human-induced climate change,” Sonia Seneviratne, a climate scientist at Swiss university ETH Zurich, said.

For decades, scientists have warned of such events — but previously had been wary of saying a particular storm or heatwave was a direct result of climate change.

But advances in a relatively new field known as “event attribution science” have enabled researchers to assess how big a role climate change might have played in a specific case.

Scientists assess simulations of how weather systems might behave if humans had never started pumping carbon dioxide into the air, and compare that with what is happening today. They also factor in weather observations made over the last century or more.

Scientists needed only days to identify climate change as the key culprit in 2020’s record temperatures in Siberia, with extreme heat drying out forests and peat across the Russian tundra, leading to massive wildfires.

Climate change links have also been found in the summer heatwaves that hit Europe, Japan and North America in 2018. Studies found the chances of these events happening together would have been near zero without planet-warming carbon emissions.

As a heatwave hit the US West Coast in August, Earth saw a new record high temperature of 54.4°C in Death Valley in California’s Mojave Desert. On Sunday, the mercury soared to a new record of 49°C for nearby Los Angeles County.

Researchers do not yet fully understand Europe’s heatwaves.

“In Western Europe, the increase in heatwaves is much stronger than the models predict, and we have no clue why,” Geert Jan van Oldenborgh, an attribution science expert at the Royal Netherlands Meteorological Institute, said.

As average global temperatures have risen by about 1°C since pre-industrial times, changes in the atmosphere and oceans are leading to more intense storms.

Hurricanes are getting stronger and spinning slower as they pick up energy from heat in the oceans.

Warm waters in the Gulf of Mexico boosted Hurricane Laura to a category 4 storm before it slammed into Louisiana with 240km/h winds, surpassing Katrina in 2005.

Some of the deadliest Indian Ocean storms have churned through the Bay of Bengal before slamming into India or Bangladesh.

If we go back to what led to these kinds of extreme events, what we see is that very warm ocean temperatures have played a major role

Exceptionally high surface temperatures in the Indian Ocean helped Cyclone Amphan grow into a Category 5 storm in just 18 hours before it tore into West Bengal in May.

In June, Cyclone Nisarga, initially forecast to be the first to batter Mumbai since 1948, made landfall 100km south of the city.

“If we go back to what led to these kinds of extreme events, what we see is that very warm ocean temperatures have played a major role,” Roxy Mathew Koll, of the Indian Institute of Tropical Meteorology, said.

This also likely contributed to extreme rainfall and flooding in China this summer.

In Africa, tens of thousands have been left homeless by flooding from the Nile in Sudan. In Senegal, more rain fell on a single day on Saturday than the country would usually see during three months of the rainy season, the government said. — Reuters



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