The recent drought in the Panama Canal was driven not by global warming but by below-normal rainfall linked to the natural climate cycle El Niño, an international team of scientists has concluded.
Low reservoir levels have slowed cargo traffic in the canal for most of the past year. Without enough water to raise and lower ships, officials last summer had to slash the number of vessels they allowed through, creating expensive headaches for shipping companies worldwide. Only in recent months have crossings started to pick up again.
The area’s water worries could still deepen in the coming decades, the researchers said in their analysis of the drought. As Panama’s population grows and seaborne trade expands, water demand is expected to be a much larger share of available supply by 2050, according to the government. That means future El Niño years could bring even wider disruptions, not just to global shipping, but also to water supplies for local residents.
“Even small changes in precipitation can bring disproportionate impacts,” said Maja Vahlberg, a risk consultant for the Red Cross Red Crescent Climate Center who contributed to the new analysis, which was published on Wednesday.
Panama, in general, is one of the wettest places on Earth. On average, the area around the canal gets more than eight feet of rain a year, almost all of it in the May-to-December wet season. That rain is essential both for canal operations and for the drinking water consumed by around half of the country’s 4.5 million people.
Last year, though, rainfall came in at about a quarter below normal, making it the nation’s third-driest year in nearly a century and a half of records. The dry spell occurred not long after two others that also hampered canal traffic: one in 1997-98, the other in 2015-16. All three coincided with El Niño conditions.
“We’ve never had a grouping of so many really intense events in such a short time,” said Steven Paton, director of the Smithsonian Tropical Research Institute’s Physical Monitoring Program in Panama. He and the other scientists who conducted the new analysis wanted to know: Was this just bad luck? Or was it related to global warming and therefore a harbinger of things to come?
To answer the question, the researchers looked both at weather records in Panama and at computer models that simulate the global climate under different conditions.
The scientists found that scant rain, not high temperatures that cause more water to evaporate, was the main reason for low water in the canal’s reservoirs. The weather records suggest that wet-season rainfall in Panama has decreased modestly in recent decades. But the models don’t indicate that human-induced climate change is the driver.
“We’re not sure what is causing that slight drying trend, or whether it’s an anomaly, or some other factor that we haven’t taken into account,” said Clair Barnes, a climate researcher at Imperial College London who worked on the analysis. “Future trends in a warming climate are also uncertain.”
El Niño, by contrast, is much more clearly linked with below-average rainfall in the area, the scientists found. In any given El Niño year, there’s a 5 percent chance that rainfall there will be as low as it was in 2023, they estimated.
At the moment, El Niño conditions are weakening, according to the National Oceanic and Atmospheric Administration. La Niña, the opposite phase of the cycle, is expected to appear this summer.
The scientists who analyzed the Panama Canal drought are affiliated with World Weather Attribution, a research initiative that examines extreme weather events soon after they occur. Their findings about the drought haven’t yet been peer reviewed.