Larry O’Neill knew a heatwave was coming, but he still couldn’t believe what the climate models were telling him.
The temperatures projected for this week were so unusually high – between 115 and 120 degrees Fahrenheit in parts of the Pacific Northwest – that O’Neill, the Oregon state climatologist, felt something must be wrong. not work.
“The predictions sounded completely out of the ordinary,” said O’Neill, associate professor at Oregon State University. “They were so crazy that professional forecasters and people like me thought something was wrong with the models.”
The forecast turned out to be good.
With global warming making heatwaves and other extreme weather events both more likely and more severe, this week’s scorching temperatures could herald a climate reality that scientists believed to be decades in the future.
“We are already seeing evidence of climate change in the data, but in the Pacific Northwest we might have thought that by mid-century we would start to see some really substantial and impactful events,” O ‘said. Neill. “But we see them now.”
In the western United States, more than 35 cities matched or set temperature records on Monday, with several locations shattering their historic highs. Seattle set a new high of 108 degrees, 5 degrees higher than the city’s previous all-time high, and Portland, Oregon, hit 116 degrees, surpassing the city’s previous milestone by 8 degrees.
The intensity of the heat, especially in an area of the country known for its mild conditions, has been shocking, said Nicholas Bond, a University of Washington researcher and Washington state climatologist.
“The extent to which records are broken – not by a degree or more but 5 degrees and in some cases more – is truly astounding,” Bond said. “I didn’t really expect something like this until further into the future.”
What caused the sweltering heat was a ridge of high pressure parked over the Pacific Northwest that Bond said was “exquisitely poised to provide hot temperatures.”
These giant heat domes have been linked to tropical cyclone activity in the western Pacific Ocean, which can affect airflow in the northern hemisphere and generate unusual weather conditions.
“Tropical cyclones tend to disrupt the jet stream throughout the Pacific Ocean,” O’Neill said, adding that they can affect high and low pressure systems. “If we get a tropical cyclone, we’re three times more likely to have a high pressure ridge installed near where we see it.”
It is not yet clear how climate change affects the jet stream and the resulting weather systems, but the consequences of these complex atmospheric disturbances that occur in the context of global warming are well understood.
Average temperatures in the Pacific Northwest have warmed by about 1.3 degrees since 1895, according to the University of Washington’s Climate Impacts Group, and most cities in the region feel more than 2 degrees warmer. hot in summer than in 1970.
“Along with this warming, we have seen an increase in episodes of extreme heat, and these events are becoming more frequent, more intense and of longer duration,” said Meade Krosby, senior researcher at the Climate Impacts Group.
It is a trend that is playing out across the country. A national climate assessment carried out in 2018 found that heat waves in the United States occurred an average of six times a year in the 2010s, compared to an average of twice a year five decades earlier.
The effects of extreme heat are also being felt all over the world. Parts of Eastern Europe and Russia are currently baking at record highs, with some Bulgarian cities expected to reach 104 degrees and temperatures in Siberia reaching nearly 90 degrees.
While attributing a specific event to climate change is tricky, scientists say the overall effect of global warming is undeniable, creating conditions conducive to heat waves and other extreme weather events.
“The question is no longer whether climate change caused a specific heat event, but by how much,” Krosby said.
Temperatures in parts of Oregon and Washington are likely to have peaked, but warmer-than-usual conditions are expected to persist throughout the weekend.
Experts said it was baffling to see such a crippling heat wave so early in the summer, adding that the implications could be dire for this year’s wildfire season.
For O’Neill, he hopes recent events will act as a red flag on the immediate impacts of global warming.
“All of this adds to the danger and risk we face,” he said. “Climate change absolutely sets the dice for more extreme events.”