The era of Runaway Heat records is here

Las Vegas set a heat record of 117 degrees Fahrenheit (47.2 C) in 1942, and for 82 years no weather system could change it. Thermometers have recorded the same temperature four times before, all since 2005, without setting a new high. Then 2024 happened.

The heat record has been broken – and not just by a little. On July 7, the temperature at Harry Reid Airport in Paradise, Nevada, soared to 120F.

Records are breaking around the world this summer, following a 13-month streak of the warmest average monthly temperatures worldwide. At least two major science agencies recently determined that July set another record high temperature, also recording the two hottest days worldwide in recorded history. There is now a better than 95% chance that this year will surpass 2023, making it the hottest since record keeping began.

But it’s not just that heat records are being set more often than before. Many of these temperature peaks beat local records by noticeably wide margins. And that’s fueling renewed interest among scientists modeling future warming as the planet continues to warm rapidly.

Record extreme heat has become an expected consequence of the pace of climate change among scientists studying it. Climate scientists usually frame the dangers by talking about the level of warming, comparing the conditions that would develop after average temperatures rise by 2C or 3C. But when it comes to the magnitude of new heat records in the coming decades, the rate of warming may take precedence.

It is a fundamental question raised by the research of Erich Fischer, a climate specialist at ETH Zurich. Fischer began to wonder a few years ago if the world had seen records fall more dramatically. The simulation of extreme heat waves in the US led him to such an unusual conclusion that he initially rejected it. He saw in his data the possibility in the coming decades of “record-breaking extremes, almost impossible in the absence of warming,” he and other researchers wrote in a 2021 paper.

This analysis has stood up to real-world events. Four weeks after a journal accepted his paper, western North America experienced an abnormal heat wave on the scale he projected. A village in British Columbia broke Canada’s 84-year-old heat record of 45C (113F) three days in a row, reaching 49.6C (121.3F). The next day, a fire ravaged much of the city, killing two people. A team of scientists later declared it among the six most intense heat waves ever recorded.

“The climate is currently acting like a guy who would come in and jump a meter further than anyone before,” Fischer said. “You’d think he was an athlete on steroids.”

Fischer found that such extreme jumps could be up to seven times more common by 2050 compared to the past 30 years if the world continues high levels of greenhouse gas emissions. This aligns with other findings about the major role climate change plays in these very large peaks. July’s Las Vegas heat was made 22 times more likely by climate warming, according to research by nonprofit Climate Central, while a spring heat wave in Vietnam was 38 times more likely to be due to climate factors. Mali’s capital, Bamako, set four daily record highs in April during a month of heat made 90 times more likely by climate change.

As new extremes arrive, Fischer predicts that previously rare extreme temperatures will become more common. A 1-in-1,000-year heat wave anytime between 1951 and 2019 will have changed to a 1-in-100-year event by around 2020, according to his study. This not-so-unusual heat wave will move again to a 1-in-40-year event in the mid-2020s.

A small number of scientists are working on the problem of heat records. Fischer and others expect, based on their understanding of climate physics, to see examples piling up over the coming decades.

It’s no trivial task to monitor the margins of new heat records, in part because there are so many ways to define a heat event. Maximum temperature for a day? An average value over three days? And how big is an area? Even in well-monitored regions, including the US and Europe, data are inconclusive.

Take the UK as an example. Temperatures hit 40C (104F) for the first time in 2022 and the number of days above 30C (86F) tripled. However, the amount of data scientists would need to determine climate change is causing a jump in margins is huge, said Mike Kendon of Britain’s Met Office.

So far, there are not enough anomalous weather episodes for the phenomenon to be conclusively observed in real-world data rather than projected in scientific models. But examples from just the past year focus the imagination: Africa’s hottest June temperature of 50.9 C (123.6 F) descended on Aswan in Egypt, breaking the 63-year-old national record by 0, 6 C. Costa Rica reached 41.5 °C (106.7 °F) in March, 1.1 °C higher than its 2010 mark.

It all adds up to big jumps in global heat. Last September it broke the world record by such a wide margin that one American climatologist memorably called it “absolutely bananas.”

Mingfang Ting, a climate professor at Columbia University, is among the researchers who expect future data to show a shift in margins. “My personal feeling is that I think we’re seeing it, but we don’t have a long enough record to prove it yet,” she said.

Photo: A dry pond in Bac Lieu province, Vietnam. The country experienced a spring heat wave, which was much more likely due to climate change. Photo credit: Linh Pham/Bloomberg

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