This year, China has endured by far the worst heatwave ever recorded. Many other parts of the world have also seen extreme heat, with numerous records smashed and devastating consequences including many deaths. We have long been warned that ever more extreme heatwaves will occur as the planet heats up, but some events this year far exceeded predictions. So what is going on?
This year began with heatwaves in many parts of the southern hemisphere. In January, Paraguay set maximum temperature of 45.6掳C (114掳F), for instance.
There were even heatwaves in Antarctica, relatively speaking. In March, the temperature on top of the ice sheet at a place called Dome C, which is 3 kilometres above sea level, reached -10掳C (14掳F). That might be cold, but it is a whopping 38.5掳C (69掳F) above the average high temperature at Dome C at that time of year.
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鈥淚n terms of the temperature excess above normal, the Antarctic heatwave appears to have been the most extreme that humans have ever directly observed, anywhere,鈥� at the non-profit organisation Berkeley Earth.
Another major heat event occurred in India during March and April, with weeks of unseasonably early extreme heat making it hard for people to work.
Over summer in the northern hemisphere there were many more heatwaves. In Europe, the heat led to wildfires and exacerbated a severe drought, affecting food production, energy generation and river transport.
In July, the UK recorded a temperature of more than 40掳C (104掳F) for the first time, with an extraordinary than the previous record of 38.7掳C (102掳F). One team recently warned that the were rising, but the researchers .
Meanwhile, China was enduring by far the worst heatwave recorded in human history. It lasted more than two months with hundreds of places repeatedly exceeding 40掳C and once more exacerbating a severe drought.
鈥淭here is nothing in world climatic history which is even minimally comparable to what鈥檚 happening in China,鈥� weather historian Maximiliano Herrera told 快猫短视频 in August.
In the city of Chongqing, for instance, (95.5掳F), the highest on record in China and nearly 3掳C (5掳F) hotter than the previous hottest August in the city.
Even in September, the heatwaves aren鈥檛 over, with extreme temperatures across parts of North America, north Africa, Asia and Greenland at the time of writing. Fairfield in the San Francisco Bay region just set a heat record of 47.2掳C (117掳F).
There is no doubt that the main underlying reason for this extreme heat is climate change. When the planet is getting hotter, temperatures will exceed whatever is regarded locally as a heatwave level more often and for longer periods overall.
鈥溾�楿nprecedented鈥� is unfortunately a term we will have to use summer after summer as long as the warming of the planet continues,鈥� says at Pennsylvania State University. 鈥淲e can expect worse heatwaves, droughts, wildfires and floods until human carbon emissions drop to zero.鈥�
However, there is more to this year鈥檚 extreme heat than warming alone. After all, so far 2022 isn鈥檛 even the hottest year on record, notes Herrera.
What鈥檚 more, while the average global temperature is increasing in line with climate model projections, some of the extremes this year, such as the UK passing 40掳C, are happening much sooner than expected. It appears that warming is making extremes more extreme.
鈥淧ersistent weather extremes are increasing beyond what climate models have predicted, in substantial part because they are not fully capturing the jet stream dynamics behind many of these extremes,鈥� says Mann.
The jet streams are bands of strong winds high in the atmosphere that circle each pole. Their positions and strength affect the weather at the surface. The streams are powered by temperature difference between the equator and poles, so the rapid warming in the Arctic is having a major effect on the northern jet stream, especially in summer.
One of the results is that the jet stream is splitting into two over Europe and Asia more often, says at the Free University Amsterdam. The resulting double jets are also persisting longer. Between the double jets, high pressure systems that bring dry and potentially hot conditions are more likely to form and persist. Last year, her team reported that this phenomenon explains in Europe.
鈥淭his summer there was a double jet configuration, starting end of June and coinciding with the heatwaves in Europe, exactly as described in our recent paper,鈥� says team member Efi Rousi, who did the work while at the Potsdam Institute for Climate Impact Research in Germany.
The behaviour of the northern jet stream might also explain why we are seeing so many extremes. The jet stream can develop big kinks known as Rossby waves. South of where the jet stream bends north, there will be high pressure, while north of southward loops, there will be low pressure and rain.
When the Rossby waves stall and remain in the same place for weeks, this leads to weather on repeat and extremes such as the 2010 Russian heatwaves and floods in Pakistan, says Luo. 鈥淭his is why a lot of extreme events co-occur.鈥�
In 2019, it was reported that two patterns of Rossby waves consisting of either five or seven waves around the northern hemisphere and can lead to simultaneous heatwaves around the world. This year, Luo reported that while climate models do reproduce these upper atmosphere wave patterns, they .
In other words, this could at least in part explain why climate models are underestimating heat extremes. Unlike with the double jets, however, it isn鈥檛 yet known how warming is affecting the odds of the five and seven-wave Rossby patterns.
What is clear is that as long as we keep emitting more carbon dioxide, even the extraordinary and unprecedented heat events of 2022 will be surpassed, with ever more severe consequences.
鈥淚t鈥檚 very scary, actually,鈥� says Luo.
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