Earth’s jet streams — currents of air that wrap around the planet — are worrying some climate scientists, who this week described the pattern as “chaotic,” “insane” and looking like a van Gogh painting.
They say the stream appears more broken and wavy than usual, and that the irregular pattern is tied to human-caused climate change.
The jet stream over North America has broken apart, and meteorologists link this to an extreme heat dome — when hot air is trapped under a swath of high pressure — over Mexico and some parts of the U.S. including Texas and Florida.
This blistering weather comes two years after a similar heat dome in B.C., which caused the deaths of 619 people. The June 2021 heat wave led to a record 49.6 C in Lytton, one day before the village burned down from wildfire.
Climate scientists agree greenhouse gas emissions are making the heat waves more intense, but more data is needed to determine whether the emissions are the direct cause of these more wavy jet streams. However some say the heat dome and Canada’s wildfires are tied to these chaotic streams.
Prof. Michael E. Mann, the director of the Center for Science, Sustainability and the Media at the University of Pennsylvania, says the pattern of human-caused warming (in particular, the amplified warming of the Arctic) is altering the summer jet stream, causing it to get “stuck” in very persistent, wavy patterns.
He said that means extreme weather systems stay in place for weeks at a time, leading to the extreme droughts, heat waves, wildfires and floods.
“Climate models have long predicted we would see a rise in these sorts of extreme weather events from human-caused warming, and we are seeing it now very clearly,” he told Postmedia, in an email.
“Some of the mechanisms are pretty simple — a warmest planet is obviously going to produce more frequent and intense heat waves. But warming of the land in summer causes drying, and the heat and drought combine to give us larger and more damaging wildfires. And warmer oceans means there’s more moisture in the air, so when we get storm systems, they contain more moisture and produce worse flooding.”
Rachel White, a professor of atmospheric science at UBC’s department of earth, ocean and atmospheric sciences, is more cautious when linking the wavy jet streams and climate change.
She emphasized that climate change is causing more extreme heat waves — that’s not in dispute — but said when it comes to the jet streams there just isn’t enough years of data to link it all together with confidence. She said, however, this is something atmospheric scientists around the world are studying.
She said on average the jet streams look like relatively straight lines around the world but right now there are “some pretty big waves” and they are causing some extreme weather.
“There’s not a clear consensus yet that climate change is definitely making these things more wavy, but we do know that that climate change is making heat events more intense and more frequent,” said White.
“My opinion is while we don’t have scientific consensus that climate change is also making the jet wavier, and so further amplifying the increasing probability of heat waves, it’s a real concerning possibility.”
White said this phenomenon could be a chicken and egg scenario, where the warming of the Arctic is causing the lines or the other way around.
“It could be that there’s also some feedback from the waviness back into the Arctic. It gets very complicated very quickly,” she said.
Nathan Gillett, a research scientist with Environment and Climate Change Canada, agreed with White that there’s a low certainty that climate change is affecting these blocking events in the jet streams.
“Climate change, greenhouse gas increases are warming the climate. We’ve observed an increase in hot extremes, generally across the globe, and we know that climate change is increasing the odds of heat waves,” he said
“So, even if the circulation and everything stayed the same, there’s a background warming which is only going to increase the risk or the intensity of heat waves when they do occur.”
Do these wavy jet streams affect B. C.?
White said looking at the streams over the Pacific, the circles are really strong.
“The wave is pretty lined up with B.C. So there are some big weather systems ahead, but whether they become stationary and cause an extreme heat wave we don’t know. We have to watch the weather forecast.”
B.C. is not under any heat warnings but much of neighbouring Alberta is, according to Environment and Climate Change Canada. In B.C. the temperature is expected to spike again next week.
Gillett added that while it’s difficult to predict whether another intense heat dome could hit B.C. this year, if there is one it probably won’t be as severe as in 2021.
“It was made much more likely by climate change, but even so it was still a very rare event. So, based on the work that we’ve done so far it’s unlikely to happen again in the next few years,” he said.
However, Gillett also said it’s a good idea to be prepared because the seasonal prediction for this summer is warmer than normal across Canada, which increases the risk of heat waves.
Earlier this year, the world Meteorological Organization warned the likelihood of El Nio was increasing, and hot weather records are expected around the globe.
‘Like a van Gogh’
Mann said these persistent summer extreme weather events are exceeding what the models predicted, which may suggest the consequences of carbon pollution and human-caused warming have been underestimated.
Mann compared the jet stream’s appearance to the swirling painting style of Post-Impressionist artist Vincent van Gogh.
“I’m honestly at a loss to even characterize the current large-scale planetary wave pattern,” Mann wrote on Twitter. “Frankly, it looks like a van Gogh.”
Jeff Berardelli, a meteorologist and climate specialist at Cornell University, called the jet streams “insane” and said it’s astonishing that this is happening so early in June.