Burning Issues: Climate change made heat wave more likely

One week later, they know by how much. Global warming made the hottest day of the North American heat wave 150 times more likely and 2 degrees Celsius (3.6 Fahrenheit) hotter, according to a rapid attribution study released Thursday by an international team of 27 scientists from the World Weather Attribution initiative (WWA). Temperatures broke records in Oregon and Washington, in the US, and in British Columbia, in Canada. They reached a high of 49.6 C (121 F) that researchers say would have been “virtually impossible” without climate change.

The study, which has not yet been published in a peer-reviewed journal, is the latest example of scientists using models to swiftly assess the role of greenhouse gas emissions in exacerbating extreme weather. Its findings dispel a myth prevalent in rich countries that climate change only hurts people far away from them or in the distant future. “We are entering uncharted territory,” said study co-author Sonia Seneviratne, from the Institute for Atmospheric and Climate Science at ETH Zurich in Switzerland. “Much higher temperature records will be reached if we don’t manage to stop greenhouse gas emissions and halt global warming.”The temperatures  which authorities estimate have killed hundreds of people  were so much higher than historical records that researchers struggled to work out exactly how often such a heat wave could be expected. Their best guess is that such temperatures would occur once every thousand years in today’s climate. And they found two theories for how it got so hot.

One explanation is that a combination of pre-existing drought and unusual atmospheric conditions  a heat dome of warm air trapped in place by a bend in the jet stream — combined with climate change to drastically raise temperatures. “The statistical equivalent of really bad luck, albeit aggravated by climate change,” the authors summarised. An alternative, more troubling possibility is that the climate system may have already crossed a threshold where small amounts of warming push up temperatures up faster than previously observed. If true, it would mean such record-breaking heat waves have already become more likely to happen than climate models predict.

“What we are seeing is unprecedented,” said study co-author Friederike Otto, from the Environmental Change Institute at the University of Oxford. “This is such an exceptional event that we can’t rule out the possibility that we’re experiencing heat extremes today that we only expected to come at higher levels of global warming.” Previous heat records were “pulverised” by such large margins that “something else must be going on,” said Stefan Rahmstorf, head of Earth System Analysis at the Potsdam Institute for Climate Impact Research in Germany, who was not involved in the study. “The study is valid and state of the art.”Climate change has made heat waves hotter, longer and more common. By burning fossil fuels  which release gases that trap the sun’s heat like a greenhouse humans have warmed the planet by about 1.1 C above pre-industrial levels. This raises the chance of record-breaking temperatures. Lytton, a village in the Canadian province of British Columbia, broke the country’s heat record on July 2 when temperatures shot almost 5 C above the previous record of 45 C.

The next day it was destroyed by a wildfire. “We are a small, rural, Indigenous, low-income community and we are at the spearpoint of climate change,” Gordon Murray, a resident who escaped Lytton, said in an interview Friday with public broadcaster CBC News. “But it’s coming for everybody. We’re the canary in the coal mine.” Heat waves, which have been among the deadliest disasters in the past few years, stress the human body. Hot weather exacerbates existing health conditions like heart, lung and kidney disease, as well as diabetes. It is particularly harmful to elderly people, young children, construction workers and homeless people.

This article was provided by Deutsche Welle