Global heatwaves show climate change and El Nio are a bad combination

Outdoor workers are vulnerable to sustained heatwaves like the one hitting Texas, which climate scientists warn are becoming more common.

David J. Philip/AP


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David J. Philip/AP


Outdoor workers are vulnerable to sustained heatwaves like the one hitting Texas, which climate scientists warn are becoming more common.

David J. Philip/AP

If there’s one type of extreme weather that scientists clearly link to climate change, it’s worsening heat waves.

“They’re getting hotter,” says Kai Kornhuber, an adjunct scientist at Columbia University and a scientist at Climate Analytics, a climate think tank. “They occur at a higher frequency, so the likelihood of sequential heat waves also increases.”

In Texas, the southern United States and Mexico, a three-week heat wave has gripped the region with temperature records dropping for consecutive days. The extreme heat has also hit India, China and Canada, where widespread wildfires are burning.

“Most of the world’s population has experienced record-breaking heat in recent days,” says Daniel Swain, a climate scientist at the University of California, Los Angeles.

This year, something else is adding fuel to the fire: the El Nio climate model. This seasonal shift causes global temperatures to warmer, which could make 2023 the hottest year on record.

Longer heat waves are more dangerous

Heatwaves Already Deadliest Weather Disaster in U.S. Not only do extreme temperatures cause heat exhaustion and severe dehydration, they also increase the risk of having a heart attack or stroke. Those risks are even higher in low-income neighborhoods and communities of color, where research has found temperatures are warmer than in white neighborhoods.

Even the temperatures in the weather report don’t tell the whole story of danger. With higher humidity, the toll that heat takes on the human body is much more taxing. Meteorologists try to capture that with a heat index alert, which shows what the temperature actually feels like. But that’s only calculated for someone sitting in the shade, underestimating the risk to outdoor workers and others in the sun.

In recent years, scientists have made rapid assessments to determine how heat waves are affected by climate change. In several, they found that extreme temperatures were nearly impossible without climate change, such as in the Mediterranean in April, the Pacific Northwest in 2021 and the UK in 2022.

El Nio is the exclamation point

This year, the planet also made a seasonal shift towards an El Nio pattern. It begins as the ocean in the central and eastern Pacific warms. That extra heat alters weather patterns, raising temperatures globally.

“That’s its role in the global climate system: to move some of the energy from deep inside and dump it into the atmosphere,” says Swain.

With El Nio just starting this year, the full effect is likely not yet to be felt in heatwaves or precipitation. Typically, the southern US gets wetter and the northern US gets drier.

“That lag is because it takes some time for that extra heat near the ocean’s surface to actually get into the atmosphere and be displaced by wind currents,” Swain says.

Climate experts say signs point to a strong El Nio this year, which could break global temperature records. The past eight years have already been the warmest since records began, and 2016, the warmest on record, was also a year with a powerful El Nio.

“While it won’t be the hottest on record, we are definitely seeing the warmest decade yet,” says Kornhuber. “That alone should be worrying enough.”

If the world continues to emit fossil fuels, these types of heat events are expected to become much more likely. Even if the world does manage to meet the goal of limiting warming to 1.5 degrees Celsius (2.7 Fahrenheit), extreme heatwaves are still likely to be eight times more common than they once were.

“The long-term driver is human-caused climate change, where we’re climbing the ladders along that inexorable upward trend,” Swain says. “El Nio represents the exclamation point of this trend.”

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