analysis

Analysis: Climate-induced extreme weather is running amok

Sattelite image capturing the Californian wildfires and Hurricane Laura. Photo credit: NOAA.

By Anders Lorenzen

As California continues to burn, torrential rains hit Africa, freak hot temperatures are measured on the surface of tropical oceans, extreme heatwaves are experienced from the Siberian Arctic to California. And yet another bout of powerful hurricanes making landfall in the US, the extreme climate-induced weather that the world is experiencing in 2020 is having catastrophic impacts.

This bout of extreme weather which scientists have for years warned us to expect is consistent with climate change. It will only intensify as emissions pour into the atmosphere and the planet continues to heat up. Though previously some scientists have been very conservative about the link to particular extreme weather events and climate change, they are now starting to up the ante. Sonia Seneviratne, a climate scientist at ETH Zurich, a Swiss university explained that we would not be experiencing such severity of extreme   weather events were it not for climate change:  “We are seeing the emergence of some signals that would have had almost no chance of happening without human-induced climate change.”

Easier to make the link to climate change

In scientific terms, a new field known as ‘event attribution’ has emerged which means that researchers can now assess how big a role climate change might have played in individual weather events. This new breakthrough will allow scientists to view simulations predicting how the weather systems would have behaved if humans had not started pumping CO2 into the atmosphere at the beginning of the industrial revolution, and they can compare it with today. They can also factor in weather observations made over the last century or more. What was once the reality that you could not attribute specific weather events to climate change is becoming less and less true.

Heatwaves

That model is already being used, for example, in the growing frequency and intensity of heatwaves worldwide. In this year’s Siberian heatwave scientists needed only days to confirm climate change as the main culprit. Climate links have also been identified in a series of summer heatwaves which hit Europe, Japan and North America in 2018. Studies concluded that the chance of these events happening simultaneously without the industrial-era rise in CO2 emissions would have been near zero. 

One example would be the heatwave that hit the US West Coast last month, resulting in a possible new global heat record with an air temperature in Death Valley of 54.4 degrees Celcius. Two weeks later the heatwave was still operating, with the Mercury recording a new all-time high in Los Angeles County of 49 degrees Celcius. 

Daniel Swain, a climate scientist at the University of California, explained that it is not so much that climate change is destabilising historical weather patterns but that it in many cases amplifying them. Warmer temperatures drain the air of humidity which dries out forest and brush on land. Therefore they create prime conditions for wildfires. Swain added that in California the fires are larger and faster-moving than would historically have been expected.

However, there are still some events that attribution science cannot explain. For example, researchers still do not fully understand Europe’s heatwaves, which are much stronger than the models predict and puzzle researchers.

Storms

But what about an increase in more violent storms? As the planet on average has warmed by around 1 degree Celcius since pre-industrial times, the changes in the atmosphere and oceans is the perfect recipe for more intense storms.

Overall, the hurricanes are getting stronger and are moving more slowly, both factors that make them able to inflict far more damage. A report published by the University of Bristol, England, last month came to the conclusion that climate change could make extreme hurricane rainfall in the Caribbean five times more likely without rapid cuts to emissions. And the more recent Category 4 Hurricane to make landfall in Louisiana was a result of warm waters in the Gulf of Mexico. The weather event has been described as the most powerful hurricane to have ever hit the state.

In the Indian Ocean tropical cyclones have shown similar patterns. In recent history, the region which has long been considered a hot spot for cyclones has seen some of the deadliest cyclones coming through the Bay of Bengal before slamming into India or Bangladesh. The high surface temperatures in the Indian Ocean which have been connected with climate change in May contributed, according to scientists, to Cyclone Amphan growing into a Category 5.

And just the following month Cyclone Nisarga made landfall 100 kilometres (km) south of Mumbai with wind gusts of 120 kph. According to Roxy Mathew Kroll, a climate scientist at the Indian Institute of Tropical Meteorology, both cyclones were unprecedented: “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.” 

Rainfall

In addition, those warm ocean temperatures likely contributed to the extreme rainfall and flooding in China which this summer suffered one of its worst flood seasons in decades.

Also the African continent has suffered from torrential rains and severe flooding. Tens of thousands have been left homeless by flooding from the Nile in Sudan. And 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 reported.

It appears that with the advance in scientific methods scientists can more quickly and with greater precision determine the role of climate change in extreme weather events.  This should make it easier to determine what climate change is doing right here and right now making it much harder for governments to delay action.

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