Scientists worry record hot streak might be sign of new climate reality
The heat fell upon Mali’s capital like a thick, smothering blanket — chasing people from the streets, stifling them inside their homes. For nearly a week at the beginning of April, the temperature in Bamako hovered above 110 degrees Fahrenheit. The cost of ice spiked to 10 times its normal price, an overtaxed electrical grid sputtered and shut down.
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 Jan. 1. Each of the last 10 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.”
Mysterious heat
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.