Why climate change is making extreme heat more likely

Scientists say the sweltering heat experienced in recent days across five continents is further evidence that man-made global warming is raising the normal temperature baseline and making once-unthinkable catastrophes commonplace.

These hardships come despite predictions that a year-long global heatwave would soon begin to abate. But in the past seven days alone, billions of people have experienced climate-change-induced heatwaves, with more than 1,000 temperature records broken around the world. Hundreds of records have been broken in the United States, with tens of millions of people in the Midwest and East Coast suffering in sweltering temperatures during the worst early-season heatwave in living memory.

“It’s clear that dangerous climate change is already on our doorstep,” said Michael Wehner, a climate scientist at the Lawrence Berkeley National Laboratory. “Humans will die today because of global warming.”

Much of this week’s heatwaves came after the El Niño weather pattern that normally drives up global temperatures disappeared, showing how greenhouse gas pollution has pushed the planet into frightening new territory, researchers said. Scientists had predicted that this summer may be somewhat cooler than 2023, which was the Northern Hemisphere’s hottest in at least the past 2,000 years.

But the summer of 2024 has only just begun, and there are ominous signs that even more scorching heat may be on the way.

June is almost certain to be the 13th consecutive month of record global average temperatures, said Zeke Hausfather, a climate scientist at payments company Stripe, adding that next month could see the global average temperature approach or surpass the highest ever recorded.

Scientists say it’s not yet clear whether the trend of record heat will ease soon as El Niño is expected to give way to the cooler La Niña weather system. Scientists are also continuing to analyze individual extreme weather events to determine the extent to which, or if, climate change has played a role.

What’s clear: How humans caused a spike in baseline temperatures.

“Greenhouse gas concentrations are higher than they’ve been in the last 3 million years. Carbon dioxide traps heat, so the Earth is getting warmer,” says Michael McFadden, a senior scientist at the National Oceanic and Atmospheric Administration. “It’s really simple physics.”

“Extremely” hot weather comes early and lasts long

While not all of the temperatures observed around the world this week were unprecedented, they did provide evidence that the climate is changing in a way that makes hot weather come earlier and last longer.

Last week’s heatwaves have become twice as likely for about 80 percent of the world’s population, or 6.5 billion people, as humans have started burning fossil fuels and releasing greenhouse gases into the atmosphere, according to data provided to The Washington Post by the nonprofit Climate Central.

Nearly half of those experienced what Climate Central considers to be “extremely hot” conditions, conditions that would be rare or even impossible in a world without climate change.

“What really stands out is [heat waves] “There are a number of events happening at once,” said Andrew Pershing, the nonprofit’s climate science director.

“Extreme” weather continued across much of Africa, the Middle East, Southern Europe and Southeast Asia this week. A surge in demand for air conditioning paralyzed the power grids of Albania and Kuwait. More than 1,400 maximum temperature records were broken around the world in the past week, according to the National Oceanic and Atmospheric Administration.

Since the beginning of the Industrial Revolution, human activities (primarily the burning of fossil fuels) have warmed the Earth by about 1.2 degrees Celsius (2.2 degrees Fahrenheit). Over the past 12 months, global temperatures have increased further, averaging about 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial levels.

To assess how much warming will increase the likelihood of certain heatwaves, Climate Central uses several global climate models to calculate how often those temperatures would have occurred in a pre-industrial climate and how often they are reached today. The methodology, which has been peer-reviewed and published in a journal, highlights how warming is increasing the likelihood of temperatures at the limits of human tolerance.

On Thursday, temperatures in Hartford, Connecticut, reached 98 degrees Fahrenheit, the hottest day on record. According to an analysis by Climate Central, such events are twice as likely at current levels of warming and will become more frequent as the world continues to warm.

Peter Fossek, secretary-treasurer of the Connecticut State Tenants Union, has been going door-to-door in sweltering buildings in recent days to check on low-income residents unaccustomed to long periods of sweltering heat. He recalled an East Hartford man coming through his door drenched in sweat, his apartment barely cooling because of an old air conditioner wheezing in the background.

“It’s really frightening to see these heat waves happening in an increasingly volatile climate,” Husek said.

Climate change won’t just make higher temperatures and other extreme weather events more likely, Wehner said — it will also make any disasters that do occur more severe.

According to Wehner’s research, heat waves like the one we’re experiencing now in the US are the result of human changes to the planet that have warmed it by about 2 to 3 degrees Celsius (3 to 5 degrees Fahrenheit). Powerful hurricanes will get at least 14 percent more rain because the warmer atmosphere can hold more moisture. And in areas where sea levels are more than a foot higher than they were half a century ago, storm surges are occurring, leading to unprecedented flooding.

“We’ve been predicting for at least the last 20 years that extreme weather events will become more dangerous as the planet warms,” ​​Wehner said. “This shouldn’t be a surprise.”

Early summer heat may signal further world records

Climate scientists say the global heatwave was expected after the strongest El Niño weather pattern on record developed this winter and dissipated earlier this month. That’s what happened in 2016, when the world was on track to become the hottest since at least the 1850s, but a year ago a surge in global heatwaves began breaking eight-year records.

But this time, with eight more years of greenhouse gas emissions that cause global warming, the natural increase in global warming is pushing the planet further into uncharted territory, McFadden said, despite the fact that the latest El Niño event is “not at the same level” as the unusual pattern of 2015-2016.

“The impact of this event was amplified by the warm background conditions,” McFadden said. “What was a severe El Niño rainfall event became an extreme El Niño rainfall event.”

El Niño, a phenomenon in which abnormally warm water in the Pacific Ocean rises to the surface and releases huge amounts of heat into the atmosphere, has left signatures around the world, including scorching heat in South and East Asia and torrential rains in East Africa. These signatures are particularly notable not because El Niño events were extremely strong, but because they occurred in a world where greenhouse gas emissions continue to rise, McFadden said.

“The impacts associated with a stronger-than-normal El Niño are much stronger this time because this El Niño occurred in a much warmer world,” he said. “It’s no longer just the temperature of the Pacific Ocean that matters. It’s what the global temperature baseline is that El Niño is developing at.”

Though El Niño has ended, its warming effects linger, making it increasingly likely that the annual average temperature in 2024 will surpass the 2023 record, Hausfather said.

Hausfather said global temperatures in June were likely to be slightly more than 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial levels.

Last July was the hottest global average temperature ever recorded by scientists, and is estimated to be the hottest month in more than 100,000 years. Hausfather said it’s almost certain that Earth could surpass that record next month, and come close.

Climate scientists predict that the end of the El Niño weather phenomenon will lead to a global cooling, but we’re not seeing any signs of that happening yet.

“If temperatures stay at their current high levels, we’ll be looking at roughly the same as we saw last July,” Hausfather said. “Either way, it’s going to be very hot. The question is, is it going to be hotter than we think?”

About a month ago, Hausfather predicted there was a relatively low chance of another record-high global temperature next month — the odds seem to be around 50/50 these days, he said — and that after witnessing a shocking rise in temperatures over the past year, he’d be “too humble” to bet on another record.

John Muyskens contributed to this report.