The summer of 2024 was the hottest ever in the Northern Hemisphere, putting the Earth on track for another record-breaking year. The European Union’s Copernicus Climate Change Service reported that for June to August, global temperatures were 0.69°C above historical averages, beating the previous high set last year. The record for the world’s highest average temperature was broken on a number of days over the summer.
Climate change is increasing the frequency and intensity of heat waves, triggering extreme weather events from droughts and wildfires to violent storms and flooding. Over the past 12 months, the global average temperature was 1.64°C higher than pre-industrial levels, above the 1.5°C threshold that policymakers and scientists say threatens life on the planet.
In Europe, the heat over the June to August period was 1.54°C above the 1991-2020 average, according to Copernicus. The most extreme conditions were recorded in the Mediterranean region and Eastern Europe, while the U.K., Iceland, parts of Ireland, the west coast of Portugal and southern Norway were cooler than the norm.
Across the world, soaring temperatures are testing the limits of the human body, posing threats and even causing deaths at outdoor activities such as concerts, sports events, and religious gatherings. More than 1,300 people died during the Hajj pilgrimage in Saudi Arabia in June after temperatures reached 52°C (126°F). There were heat-related fatalities in nations including the U.S., Thailand, India, and Mexico this year.
China’s weather authority said the nation had its hottest summer since records began in 1961, with heat scorching crops from rice to corn. U.S. cities also experienced historically high temperatures, and New York canceled commuter trains as rails overheated. And parts of the Southern Hemisphere just had a very mild winter, with Australia experiencing the hottest August since data started in 1910 and looking forward to a warmer-than-average spring.
This summer the effects of a strong El Niño weather pattern, which causes warming in the Pacific Ocean, started giving way to the La Niña phenomenon. This shift usually means less extreme heat, but it can also bring droughts in some areas and produces flooding and hurricanes elsewhere.
Record-Breaking Heat
Summer 2024 sweltered to Earth’s hottest on record, making it even more likely that this year will end up as the warmest humanity has measured, the European climate service Copernicus reported on Friday.
And if this sounds familiar, that’s because the records the globe shattered were set just last year as human-caused climate change, with a temporary boost from an El Niño, keeps dialing up temperatures and extreme weather, scientists said.
The northern meteorological summer – June, July and August – averaged 16.8C (62.24F), according to Copernicus. That’s 0.03C (0.05F) warmer than the old record in 2023.
Copernicus records go back to 1940, but American, British and Japanese records, which start in the mid-19th century, show the last decade has been the hottest since regular measurements were taken and probably in about 120,000 years, according to some scientists.
The Augusts of both 2024 and 2023 tied for the hottest Augusts globally at 16.82C. July was the first time in more than a year that the world did not set a record, a tad behind 2023, but because June 2024 was so much hotter than June 2023, this summer as a whole was the hottest, the Copernicus director, Carlo Buontempo, said.
“What those sober numbers indicate is how the climate crisis is tightening its grip on us,” said Stefan Rahmstorf, a climate scientist at the Potsdam Institute for Climate Research, who was not part of the research.
Extreme Heat and Its Impacts
It’s a sweaty grip because with the high temperatures, the dew point – one of several ways to measure the air’s humidity – probably was at or near record high this summer for much of the world, Buontempo said.
Until last month Buontempo, like some other climate scientists, was on the fence over whether 2024 would smash the hottest year record set last year, mostly because August 2023 was so enormously hotter than average. But then this August 2024 matched 2023, making Buontempo “pretty certain” that this year will end up hottest on record.
“In order for 2024 not to become the warmest on record, we need to see very significant landscape cooling for the remaining few months, which doesn’t look likely at this stage,” Buontempo said.
With a forecasted La Niña – a temporary natural cooling of parts of the central Pacific – the last four months of the year may no longer be record-setters like most of the past year and a half. But it is probably not cool enough to keep 2024 from breaking the annual record, Buontempo said.
These are not just numbers in a record book, but weather that hurts people, climate scientists said.
“This all translates to more misery around the world as places like Phoenix start to feel like a barbecue locked on high for longer and longer stretches of the year,” said the University of Michigan environment dean and climate scientist Jonathan Overpeck.
The Arizona city has had more than 100 days of 100F weather this year. “With longer and more severe heatwaves come more severe droughts in some places, and more intense rains and flooding in others. Climate change is becoming too obvious, and too costly, to ignore.”
Jennifer Francis, a climate scientist at the Woodwell Climate Research Center in Cape Cod, said there had been a deluge of extreme weather of heat, floods, wildfires and high winds that are violent and dangerous.
“Like people living in a war zone with the constant thumping of bombs and clatter of guns, we are becoming deaf to what should be alarm bells and air-raid sirens,” Francis said in an email.
While a portion of last year’s record heat was driven by an El Niño – a temporary natural warming of parts of the central Pacific that alters weather worldwide – that effect is gone, and it shows the main driver is long-term human-caused climate change from the burning of coal, oil and natural gas, Buontempo said.
“It’s really not surprising that we see this, this heatwave, that we see these temperature extremes,” Buontempo said. “We are bound to see more.”
A Global Trend
As Southern California swelters under its most punishing heat wave of the year, international climate officials have confirmed that summer 2024 was Earth’s hottest on record.
The global average temperature in June, July and August — known as the boreal summer in the Northern hemisphere — was a record-breaking 62.24 degrees, according to the European Union’s Copernicus Climate Change Service. The season was marked by explosive wildfires, sizzling heat waves and heat-related deaths in California and many other parts of the world.
“During the past three months of 2024, the globe has experienced the hottest June and August, the hottest day on record, and the hottest boreal summer on record,” read a statement from Samantha Burgess, Copernicus’ deputy director. “The temperature-related extreme events witnessed this summer will only become more intense, with more devastating consequences for people and the planet unless we take urgent action to reduce greenhouse gas emissions.”
Not only was it a hot summer, but August effectively tied 2023 as the planet’s hottest August on record with a global average temperature of about 62.28 degrees, the agency said.
In fact, the entire year to date has been so warm that even with four months to go, 2024 is now nearly certain to surpass 2023 as Earth’s hottest year on record.
That’s because the global average temperature anomaly from January to August was the highest on record for the period — and 0.41 degrees warmer than the same period last year.
The average anomaly would need to drop by more than half a degree for 2024 to not be warmer than 2023, which has never happened in the entire Copernicus data set, the agency said.
A Call to Action
The near-relentless string of record-hot months has left climate scientists and officials concerned as the planet hurtles toward a dangerous tipping point.
“We are playing Russian roulette with our planet, and we need an exit ramp off the highway to climate hell,” António Guterres, secretary-general of the United Nations, said during a speech at the start of the record-hot summer in June.
While Earth’s rising temperatures are somewhat consistent with the higher end of climate model projections, the heat has also defied some expectations, according to Zeke Hausfather, a climate scientist with Berkeley Earth.
“The heat in 2024 has persisted longer than many of us expected, with the past few months tying the extremes we saw in the latter half of 2023,” Hausfather said in an email.
This is particularly perplexing because El Niño — a climate pattern associated with warmer global temperatures — dissipated toward the end of May but did not lead to an anticipated decline in global temperatures. Typically, there is a three-month lag between peak El Niño conditions and the global surface temperature response, “but even with that we should have already started cooling off a bit,” Hausfather said.
That conditions have remained steadily warm without El Niño may be an indication that additional factors are at work, he said. Some theories include a change in aerosol shipping regulations that allowed more sunlight to reach Earth; an uptick in the 11-year solar cycle; and the 2022 eruption of the Hunga Tonga-Hunga Ha‘apai volcano, which may have trapped some heat in the atmosphere.
But even those factors “don’t seem to completely add up to what we are seeing,” Hausfather said.
Also concerning is the steady climb of temperatures beyond the international limit of 2.7 degrees, or 1.5 degrees Celsius, which was established by nearly 200 nations under the 2015 Paris climate accord in an effort to prevent the worst effects of global warming.
The limit is measured against the pre-industrial era, or the period before humans began to meaningfully alter the planet’s climate through greenhouse gases and other fossil fuel emissions, and generally uses temperature data from between 1850 and 1900.
August 2024 was the 13th month in a 14-month period to exceed that benchmark, with the global average temperature measuring roughly 2.72 degrees — or 1.51 degrees Celsius — above pre-industrial levels, according to Copernicus. The streak was broken only by the month of July, which came in just shy of the limit for the first time in a year.
Experts say a single year of warming over the limit does not mean humanity has officially exceeded the boundary, but it is a concerning trend that is moving in the wrong direction.
“It’s certainly a worrying sign that global temperatures have been persistently above 1.5 degrees Celsius for so long,” Hausfather said. He placed the probability of 2024 exceeding 2023 as the hottest year on record at greater than 95%, and said it is also very likely to be the first year above 1.5 degrees Celsius in the Copernicus data set, although other data sets may disagree due to slight differences in measurements.
And while summer was marked by sweltering heat on land, the planet’s oceans also simmered. Record-warm ocean waters contributed to a violent start to the Atlantic hurricane season this year, with Hurricane Beryl becoming the basin’s earliest Category 5 hurricane on record when it formed in late June.
August also saw Arctic sea ice extent dip to 17% below average — the fourth-lowest for the month in the satellite record and “distinctly further below average than the same month for the previous three years,” Copernicus officials said.
Antarctic sea ice extent was 7% below average, the second-lowest extent for August in the satellite data record.
A Warning For The Future
The report comes as Southern California endures several consecutive days of triple-digit temperatures, including highs over 110 degrees in some parts of Los Angeles County.
In fact, the summer was notably warm across nearly all of the Golden State, where July went down as California’s hottest month on record.
Officials in Death Valley National Park — where two people died of heat-related illness — confirmed that the park saw its hottest-ever summer with nine consecutive days of 125 degrees or hotter. The park’s average 24-hour temperature in June, July and August was 104.5 degrees, beating the previous record of 104.2 degrees set in 2021 and 2018.
Daniel Swain, a climate scientist with UCLA, said the current heat wave is likely to break some daily records in Southern California, which has largely fared better than the rest of the state during this year’s hot summer.
“It will almost certainly [bring] the hottest day of the year in a lot of Southern California, and perhaps even the hottest day in several years in some parts of Southern California,” Swain said during a briefing on Wednesday. “This is a significant heat event.”
Large swaths of the the region are also likely to see some of their warmest nights on record for the time of year, he said.
“It may not sound as dramatic as, say, the hottest days on record or the hottest afternoon peak temperatures, but those nighttime temperatures are quite consequential from a human health impact perspective, an ecosystem health perspective and also a wildfire perspective,” he said.
Indeed, heat is the deadliest of all climate hazards, and a recent study confirmed that heat-related deaths are on the rise in the United States.
The latest seasonal outlooks from the National Oceanic and Atmospheric Administration indicate that above-normal temperatures may persist across nearly all of the country through at least November.
Already, residents in Phoenix, Arizona, have endured more than 100 consecutive days of temperatures over 100 degrees, shattering the previous record of 76 days set in 1993, according to the National Weather Service.
