According to a new quick scientific analysis, the deadly heat wave that roasted the Pacific Northwest
and western Canada
would have been nearly impossible to avoid if not for human-caused climate change
, which added a few degrees to the record-breaking temperatures.
An international team of 27 scientists calculated that climate change increased the likelihood of extreme heat
by at least 150 times, but most likely much more.
The study, which has not yet been peer reviewed, stated that the region's late June triple-digit heat would not have occurred in human civilization prior to the industrial era, and that the heat was a once-in-a-millennium event even in today
's warming world.
However, once the world warms another 1.4 degrees (0.8 degrees Celsius), that once-in-a-millennium event would likely occur every five to ten years, according to a study published on Wednesday by World Weather Attribution. However, that much warming could be 40 or 50 years away if carbon pollution continues at its current rate, according to one study author.
This kind of extreme heat “would go from essentially virtually impossible to relatively commonplace,” according to study co-author and Princeton University climate scientist Gabriel Vecchi.
According to study co-author Kristie Ebi, a professor at the University of Washington
's Center for Health
and the Global Environment
, climate change is responsible for about 3.6 degrees (2 degrees Celsius) of the heat shock in the Pacific Northwest and Canada. "Those few degrees make a big difference in human health," she said.
“This study tells us that climate change is killing people
,” said Ebi, who endured the blistering heat in Seattle
, adding that it will be many months before a death toll
from June’s blast of heat can be calculated, but it is likely to be hundreds or thousands.
The state medical examiner in Oregon
alone reported 116 heat-related deaths on Wednesday.
According to the National Academy of Sciences, the team of scientists used a well-established and credible method to search for climate change's role in extreme weather
. They logged observations of what happened and fed them into 21 computer models and ran numerous simulations before simulating a world without greenhouse gases
from the combustion of coal, oil
, and natural gas
“Without climate change, this event would not have occurred,” said Friederike Otto, a climate scientist at the University of Oxford
and study senior author.
The Northwest heat wave was notable because it was significantly hotter than previous records and climate models predicted, implying that a larger climate shift may be at work
— and in unexpected places.
“Everyone is really concerned about the implications of this event,” said study co-author Geert Jan van Oldenborgh, a Dutch climate scientist. “This is something that nobody saw coming, that nobody thought possible, and we feel that we do not understand heat waves
as well as we thought we did. The big question for many people is: Could this happen in a lot of places?”
The World Weather Attribution team conducts these quick analyses, which are later published in peer-reviewed journals. In the past, they have discovered similar large climate change effects in many heat waves, including those in Europe
. However, sometimes the team discovers that climate change was not a factor, as they did in a Brazilian drought
and an Indian heat wave.
Six outside scientists agreed that the quick study made sense, but that it likely underestimated the extent to which climate change was responsible for the heat wave.
According to Pennsylvania
State University climate scientist Michael Mann, this is because climate models used in simulations typically underestimate how climate change alters the jet stream, which parks “heat domes” over regions and causes some heat waves.
According to Daniel Swain, a climate scientist at UCLA and the Nature
Conservancy, the models also understate how dry soil worsens heat because there is less water
to evaporate, feeding a vicious cycle of drought.
The study struck a chord with Andrew Weaver, a climate scientist at the University of Victoria who was not on the research
“Victoria, which is known for its mild climate, felt more like Death Valley
last week,” Weaver said, adding, “I've been in a lot of hot places around the world, and this was the worst I've ever been in.”
“But you ain't seen nothing yet,” he added, “and it's only going to get a lot worse.”