| By Brian K Sullivan Record-breaking temperatures seared the eastern US last month, leading to power emergencies across the region. The cause: an enormous ridge of high pressure that settled on the region, known as a heat dome. This phenomenon has also already struck Europe and China this summer, leading to the temporary closure of the Eiffel Tower and worries about wilting rice crops, respectively. But while heat domes are easy to identify once they strike, they remain difficult to forecast — a problematic prospect in a warming world. “There is a world of difference between normal summer heat and record or near-record breaking extreme heat,’’ said Scott Handel, lead forecaster at the US Climate Prediction Center. “While normal summer heat can be dangerous, extreme heat can be particularly life threatening.”  Power transmission lines during high temperatures in Columbia, South Carolina, in June. The Trump administration declared a power emergency in the US Southeast as a blistering heat wave strained grids across the country. Photographer: Sam Wolfe/Bloomberg Meteorologists are now trying to figure out where and when heat domes will next strike. “I don’t have the same ability to predict heat domes like cold air outbreaks, but there are some trends,’’ said Judah Cohen, director of seasonal forecasting at Atmospheric and Environmental Research Inc. Meteorologists know, for example, the jet stream — a river of fast-flowing air girdling the globe — naturally migrates northward in summer and they can measure how fast it moves. That metric is known as the Global Atmospheric Angular Momentum, and it’s among the best predictors for heat domes, said Matt Rogers, president of the Commodity Weather Group. When the value is low, as it is two weeks ago, “it can be a leading indicator of widespread, middle latitude heat ridges,’’ he said.  A water misting station in Paris on July 1. Photographer: Anita Pouchard Serra/Bloomberg Climate change has warmed the planet, particularly the high latitudes. That influences heat domes in two ways. The first is their northward migration. That phenomenon played out in 2023 as a large ridge of high pressure parked across western-to-central Canada and kicked off a record wildfire season. Read More: Wildfire Smoke Brings a Forgotten Danger to the Arctic The second is changes to the jet stream. The temperature gradient between the poles and the tropics helps keep the jet stream taut, allowing it to push weather patterns along after a few days, Zobel said. But as the Arctic warms faster than the rest of the planet, that gradient weakens and is akin to loosening the grip on a rope. The resulting slack can cause the jet stream to kink, bend and buckle. The river of air can also sometimes split, creating a “kind of a no-man’s land” that holds heat domes in place, Cohen said. Still, Arctic warming’s exact impact on the jet stream is an area of active research, Simpson said. Some papers haven't been able to show the impacts that adherents of the weakening theory suggest, and others have come up with opposite results. What is clear is that temperatures are rising everywhere, said Karen McKinnon, an associate professor at the Institute of the Environment and Sustainability at the University of California Los Angeles, and it doesn’t take that much of an increase on the hottest days to “make summers feel substantially more extreme.” Read the full story on Bloomberg.com. Extreme heat is killing European workers | By Laura Millan Montse Aguilar was a healthy 51-year-old woman when she started her shift cleaning streets in Barcelona at around 2:30 p.m. on June 28. The Spanish city was under alert for high temperatures amid a brutal heat wave that brought record temperatures for that time of the year across the country. She was responsible for sweeping one of the hottest, dirtiest and more touristic areas — the Raval district. At the end of the shift, at around 9:30 p.m., she walked back home and asked her elderly mother to prepare dinner because she wasn’t feeling well. She also messaged a friend and told him she felt cramps in her arms, chest and neck, her brother-in-law Manuel Ceacero told Bloomberg Green. Some time before 11 p.m., Aguilar dropped dead in her apartment. “She had called my wife that afternoon saying it was impossible to work with those levels of heat,” Ceacero said. “She was assigned the area around the cathedral, where streets are really narrow and hot, the stench made the air unbreathable, she wore plastic clothes and carried a heavy basket and a broom — it was inhuman.” People who work outside are among the most exposed to dangerous levels of heat and European countries are moving fast to protect them. Spain and Greece already limit work outside on hot days, while France and some Italian regions passed similar legislation this year. Yet even some of the world’s most advanced regulations are not enough, and the problem is getting worse as climate change makes heat waves more frequent and intense. On Wednesday, scientists released a first-of-its-kind rapid attribution study linking recent deaths in Europe to climate change-driven extreme heat, which killed an estimated 2,300 people in 12 European cities, including Barcelona, between June 23 and July 2. The research, led by a team at the Imperial College in London and the London School of Hygiene and Tropical Medicine, found climate change made Europe’s recent heat wave three times more fatal, with more people dying during the event than during floods in Valencia in 2024 and in northwestern Europe in 2021.  “These numbers represent real people who have lost their lives in the last days due to the extreme heat,” said Friederike Otto, a climate scientist at the Imperial College and a co-author of the report. “Heat deaths can increase rapidly when temperatures reach certain thresholds that push vulnerable people to the limit — an increase in heat wave temperature of just 2 or 4 degrees can mean the difference between life and death for thousands of people.” In Spain, Aguilar’s death sparked an outcry. The Barcelona city hall toughened heat protocols, including forcing workers to take five-minute breaks to hydrate every hour during heat waves. Authorities also launched an investigation into FCC SA, the company Aguilar worked for and one of four contracting companies performing street cleaning services for the city. FCC declined a request for comment. “The protocol was perverse because it left all the responsibility to workers — it was them who decided whether they drank water one, or a hundred times,” said Lluís Lampurlanes, a secretary of urban cleaning services at UGT union in Barcelona, which Aguilar was a member of. “We need more measures because we’re having more frequent and longer heat waves, and street rubbish needs to be picked up anyway.” In Italy, at least three people have died of extreme heat-related causes while working. Last week, Prime Minister Giorgia Meloni’s government set up nationwide protocols for businesses in order to shield workers from high temperatures. The new measures, backed by unions, include a potential reduction of working hours and the possibility of shutting down business activities if temperatures reach certain levels. In Greece, the Labor Ministry restricted outdoor work from 11 a.m. to 5 p.m. in some areas including Athens and the second-largest city Thessaloniki, as several regions posted temperatures above 40C this week. The Acropolis in Athens was shut due to the heat, and workers including delivery and couriers benefited from these protection measures, but not those working in areas that are deemed important and socially critical infrastructure, which includes health, transport and utilities.  Workers outside during high temperatures on Areopagus Hill in Athens on June 28, Photographer: Ioana Epure/Bloomberg While many heat strokes and heat deaths go undercounted, researchers are coming up with new ways to find out how many people die because of extreme temperatures. For their recent study, the Imperial College scientists used weather observations from the recent heat wave and analyzed how it impacted the 12 cities included in the research, determining what would have happened in a world without climate change. They found man-made global warming made the event between 1C and 4C hotter, depending on the location. Then, they used modeling and historical mortality data to estimate the number of people that died during the ten-day heat wave. By combining weather and mortality data they concluded that 1,500 fewer people would have died in a world without warming. Back in Barcelona, the Aguilar family awaits the results of the autopsy that will officially determine Montse’s cause of death. Whatever the conclusion, the family plans to take the issue to the courts, Ceacero said. “We’ll do it to honor her memory,” he said. “But also because I’ve been talking to so many of her colleagues this week and all they say is that they’re people, not animals — and they want to make it back home alive.” Read the full story on Bloomberg.com. | 
