Maybe it’s a favorite sweater or the device you’re using—something you’ve recently worn, held, or eaten very likely passed through the Panama Canal. The roughly 82-kilometer-long channel connecting the Pacific Ocean and the Caribbean Sea (and, ultimately, the Atlantic Ocean) has been an important artery of global shipping since it opened in 1914. This year, the canal’s relevance has been thrust into the political spotlight as President Donald Trump and Secretary of State Marco Rubio have expressed a desire for the United States to reclaim ownership of it.
In recent years the operation of the Panama Canal has been increasingly affected by changes in rainfall, and some data suggest that more shifts are on the way. Delays and reductions in traffic caused by these events portend a more volatile future for the shipping route should climate change alter periodic weather patterns.
The Panama Canal is built around a system of locks. Ships, ranging from privately owned yachts to gigantic Neopanamax vessels capable of transporting more than 13,000 standard cargo containers, traverse three locks to gain roughly 25 meters in elevation and three locks to drop back down on the other side. That process, which takes 8–10 hours, confers enormous savings in both time and fuel: Ships traveling from the Pacific Ocean to the Atlantic Ocean or vice versa would otherwise take a route around the southern tip of South America.
“Five percent of shipping globally traverses the Panama Canal.”
“Five percent of shipping globally traverses the Panama Canal,” said Mark Russo, the chief science officer at Everstream Analytics, a supply chain risk analytics company in Elmhurst, Ill. “It’s a critical artery for global trade.”
Precipitation is key to ensuring that Gatun Lake, the artificial lake that makes up a major part of the canal, remains full enough for Neopanamax ships to safely navigate without running aground. The lake loses water not only to evaporation and deliberate pumping—it supplies some of the region’s drinking water—but also to the very operation of the canal: Each day, about 7 billion liters of water are extracted to supply the locks.
Panama fortunately tends to receive a lot of rainfall: on average, more than 2,000 millimeters each year. “Panama is an incredibly wet country,” said Steven Paton, the director of the Physical Monitoring Program at the Smithsonian Tropical Research Institute in Panama City. But the past 3 decades have included three relatively dry years in the canal’s watershed. In water years 1998, 2016, and 2024 rainfall dipped below 1,750 millimeters. (Water years span the 12-month period between 1 October and 30 September.)
Water-scarce years tend to occur about once every 2 decades, said Patton, and the relatively tight clustering of dry years is unprecedented in the watershed’s 144-year precipitation record, he added. “We’ve never seen that before.”
Years of Scarcity
Because of low water levels in Gatun Lake during those years, the Panama Canal Authority significantly reduced the number of ships passing through the canal. A total of 11,240 vessels traversed the canal in 2024, compared with 14,080 in 2023. The Panama Canal Authority also limited ships’ maximum draft. Reducing a vessel’s draft—that is, the depth at which it sits in the water—means removing cargo, Russo said. Such rearranging takes time and results in longer queues at the locks. “That ultimately slows down the vessels moving through,” he said.
Researchers have been keen to understand whether such collisions between supply chain logistics and the weather at the Panama Canal will become more commonplace in the future. Shipping companies reserve a spot in line at the canal more than a year in advance, so such a forward-looking perspective is important, Russo said. “If you’re planning on your shipments through the Panama Canal, you can get out of in front of those risks a year in advance.”
Not surprisingly, all three of the recent water-scarce years in the Panama Canal watershed corresponded to El Niño years, during which warmer-than-average ocean water in the equatorial Pacific unleashes a slew of atmospheric trickle-down effects that culminate in less rain falling in Central America. Such teleconnections between oceanic and atmospheric processes are nothing new, said Michael McPhaden, a physical oceanographer at NOAA’s Pacific Marine Environmental Laboratory in Seattle. “This has been going on for millions of years.”
As of now, there’s not convincing evidence that climate change is altering the frequency of the cycle between El Niño years and their converse, known as La Niña years. That cycle, lasting anywhere from 2 to 7 years, is known as the El Niño–Southern Oscillation (ENSO). Recent research showed that the 2024 precipitation observed in Panama was consistent with the ENSO cycle and could not be conclusively attributed to the effects of climate change.
The Big Get Bigger
What is changing as the planet warms is the intensity of big storms. “The strong events are getting stronger,” said McPhaden. Over the recent instrumental record, there’s been about a 10% increase in storm intensity, and modeling suggests another 10% increase may occur over the next century, he said. “We’ll see more frequent strong events in the future potentially.”
“We know that forest cover is critical.”
Though having more rain in the Panama Canal watershed might seem like a boon to ship traffic, there is such a thing as too much precipitation. In 2010, record-setting rainfall temporarily caused a complete shutdown of the Panama Canal. The problem was the rapidly rising water level in Gatun Lake, which threatened to overtop an earthen dam between the lake and the Chagres River. “You never ever want to overtop an earthen dam because it begins to erode exponentially fast,” said Patton. Crews worked around the clock to siphon water, but the lake still crept to within 1 meter of the top of the dam.
Efforts are underway to better understand the hydrology of the Panama Canal watershed. Such work could help canal managers steel the shipping route against future weather-driven events like those of 1998, 2010, 2016, and 2024. An example is the Agua Salud Project, run by the Smithsonian Tropical Research Institute, which studies forest cover in the region. Forests act like sponges, absorbing rainfall and releasing it in a controlled manner. That’s key to ensuring reasonably constant water levels in Gatun Lake, said Patton. “We know that forest cover is critical.”
Though the trials of the dry past year are still fresh in many people’s minds, there’s also a sense of optimism right now that 2025 will be a good year for ship traffic through the Panama Canal—current water levels in Gatun Lake are the highest they’ve been in the past 5 years.
—Katherine Kornei (@KatherineKornei), Science Writer
13 February 2025: This article has been updated to correct a source’s name.