With much of the majority-Muslim country fasting for the holy month of Ramadan, dehydration and heat stroke became epidemic. As their body temperatures climbed, people’s blood pressure lowered. Their vision went fuzzy, their kidneys and livers malfunctioned, their brains began to swell. At the city’s main hospital, doctors recorded a month’s worth of deaths in just four days. Local cemeteries were overwhelmed.
The historic heat wave that besieged Mali and other parts of West Africa this month — which scientists say would have been “virtually impossible” in a world without human-caused climate change — is just the latest manifestation of a sudden and worrying surge in global temperatures. Fueled by decades of uncontrolled fossil fuel burning and an El Niño climate pattern that emerged last June, the planet this year breached a feared warming threshold of 1.5 degrees Celsius above preindustrial levels. Nearly 19,000 weather stations have notched record high temperatures since January 1. Each of the last ten months has been the hottest of its kind.
The scale and intensity of this hot streak is extraordinary even considering the unprecedented amount of greenhouse gases in the atmosphere, researchers say. Scientists are still struggling to explain how the planet could have exceeded previous temperature records by as much as half a degree Celsius (0.9 degrees Fahrenheit) last fall.
What happens in the next few months, said Gavin Schmidt, director of the NASA Goddard Institute for Space Studies, could indicate whether Earth’s climate has undergone a fundamental shift — a quantum leap in warming that is confounding climate models and stoking ever more dangerous weather extremes.
But even if the world returns to a more predictable warming trajectory, it will only be a temporary reprieve from the conditions that humanity must soon confront, Schmidt said. “Global warming continues apace.”
As soon as the planet entered an El Niño climate pattern — a naturally occurring phenomenon associated with warming in the Pacific Ocean — scientists knew it would start breaking records. El Niños are associated with spikes in Earth’s overall temperature, and this one was unfolding on a planet that has already warmed 1.2 degrees Celsius (2.2 degrees Fahrenheit) from preindustrial levels.
Yet this El Niño didn’t just break records; it obliterated them. Four consecutive days in July became the hottest days in history. The Northern Hemisphere saw its warmest summer — and then its warmest winter — known to science.
By the end of 2023, Earth’s average temperature was nearly 1.5 degrees Celsius (2.7 degrees Fahrenheit) higher than the preindustrial average — and about 0.2 degrees Celsius (0.36 degrees Fahrenheit) hotter than climate modelers predicted it would be, even taking El Niño into account.
Researchers have spent the past several months investigating possible explanations for that 0.2 C discrepancy: a volcanic eruption that spewed heat-trapping water vapor into the atmosphere, changes in shipping fuel that affected the formation of clouds that block the sun. So far, those factors can only account for a small fraction of the anomaly, raising fears that scientists’ models may have failed to capture a longer-lasting change in the climate system.
“What if the statistical connections that we are basing our predictions on are no longer valid?” Schmidt said. “It’s niggling at the back of my brain that it could be that the past is no longer a guide to the future.”
This possibility has preoccupied the climate community, sparking multipart explainers in science magazines and special breakout sessions at academic meetings. But Schmidt says it’s too soon to know how worried the world should be. New data from a recently launched NASA satellite could show that changes in shipping emissions did in fact contribute to the extra warming. Studies might find that an accumulation of seemingly small shifts in the atmosphere and oceans were enough to push the planet to such extremes.
Another test will come over the next few months, as the planet shifts out of an El Niño and into its opposite pattern, La Niña — something that the National Weather Service predicts will happen by the summer. Because La Niña is typically associated with cooler global temperatures, scientists expect it will bring an end to Earth’s record hot streak.
There are hints that may be happening, said Zeke Hausfather, a climate scientist at Berkeley Earth and the payments company Stripe. Even though last month was the hottest March in history, it broke the previous record by a mere 0.1 degree Celsius — not the whopping 0.5 C margin seen last September.
“I hope we’re going to return to a predictable regime,” Hausfather said. “But if we keep setting records, then we have to revisit some of our assumptions, because it may be there is some new persistent forcing that is not being accounted for.”
A whole new kind of weather
Even if global average temperatures do return to a more predictable trajectory, the effects of warming on people and ecosystems have already entered uncharted territory.
Sea ice around Antarctica shrank to its smallest extent ever last year. The mighty Amazon River has reached its lowest level since measurements began. Researchers this week declared a global coral bleaching event — just the fourth in history — and warned that the crisis in the oceans is on track to set a record.
“The climate is warming at such a rate that we’re now pushing beyond the bounds of what would have been not even normal weather but feasible weather in the past,” said Clair Barnes, a researcher at the Grantham Institute at Imperial College London.
In the analysis published Thursday, Barnes and her colleagues reported that the recent heat wave in West Africa could not have occurred on a cooler, preindustrial planet. In one Malian city, the mercury hit 48.5 degrees Celsius (119.3 degrees Fahrenheit) — likely the hottest temperature ever reliably recorded in Africa, the researchers said.
Nights offered little relief, with temperatures often staying above 90 degrees. Studies show that high nighttime temperatures are especially dangerous, because they deny the body a chance to recover.
Kiswendsida Guigma, a climate scientist and adviser for the Red Cross Climate Center based in Burkina Faso who contributed to the new analysis, said he barely slept during the heat wave. Frequent power outages prevented him from even using a fan to cool off.
Few people in the region have access to air conditioning, he said. And the architecture of many poorer neighborhoods — where buildings are often constructed with heat-trapping bricks and metal roofs — exacerbates the danger.
“We are used to heat, but this level of extreme we have never experienced,” Guigma said. “We will soon be at the very edge, the very limit of what human beings can actually tolerate.”
The heat wave analysis was just the latest report from World Weather Attribution — a global network of researchers who study the influence of climate change on extreme events — to find that previously unthinkable events are becoming commonplace as the world continues to warm. An October heat wave in Madagascar, where record-breaking heat persisted for 10 unbearable days, “would not have occurred” without human-induced warming, the group said. The heavy rainfall in Libya that contributed to a catastrophic dam failure, killing thousands of people, was made 50 times more likely because of climate change.
The West African heat wave might have been unprecedented today, Barnes said. But if the world warms to 2 degrees Celsius (3.6 degrees Fahrenheit) — something that could happen by the middle of the century without rapid action to tackle climate change — a heat wave of that magnitude would be expected to occur every 10 years.
“If we keep putting carbon dioxide and other greenhouse gases into the atmosphere, we’re just going to keep warming … and this is going to continue to get worse,” Barnes said. “The sad truth is this is not the new normal. This is on the way to the unknown.”
