The record-breaking heat wave in the Pacific Northwest last week would have been "virtually impossible" without the effects of climate change, according to an analysis from an international group of climate researchers published Wednesday.
The team of American, Canadian, British, Dutch, French, German and Swiss scientists analyzed historically observed temperatures in the affected region. They found that the temperatures in the area were statistically a once-in-a-millennium event.
The results were published by World Weather Attribution, an international research organization that works to identify the role of climate change in extreme weather.
The two possible explanations for such a spike, they wrote, are a low-probability event that is “the statistical equivalent of really bad luck.”
“The second option is that nonlinear interactions in the climate have substantially increased the probability of such extreme heat, much beyond the gradual increase in heat extremes that has been observed up to now,” they wrote.
Combined results from a climate model and weather observation analysis suggest that the heat would have been at least 150 times rarer without the presence of human-caused climate change, according to researchers.
If climate change were to cause another 2 degrees Celsius of warming, the Northwestern heat would have been one degree hotter, according to the analysis. With that degree of warming, the event in question would occur one to two times every decade.
“Our results provide a strong warning: our rapidly warming climate is bringing us into uncharted territory that has significant consequences for health, well-being, and livelihoods. Adaptation and mitigation are urgently needed to prepare societies for a very different future,” researchers wrote.
“Adaptation measures need to be much more ambitious and take account of the rising risk of heatwaves around the world, including surprises such as this unexpected extreme,” they wrote.
The researchers went on to describe steps that could mitigate deaths from extreme heat, such as action plans that feature early warning systems. However, they warn long-term plans are also necessary to ensure preparation for more common periods of extreme heat. Any plans for reduced greenhouse gas emissions should incorporate the risks posed by such heat conditions, they added.