Study says that El Niño, and not climate change, was the main cause of the low rainfall that hit the Panama Canal

WASHINGTON (AP) — The weather phenomenon known as El Niño — not climate change — was largely responsible for the low rainfall that disrupted shipping in the Panama Canal last year, scientists said Wednesday.

A team of international scientists found that El Niño – a natural warming of the central Pacific that alters climate around the world – doubled the likelihood of the low precipitation that Panama received during last year’s rainy season. This drought has reduced water levels in the reservoir that supplies freshwater to the Panama Canal and supplies drinking water to more than half of the Central American country.

Human-caused climate change was not the main factor in the Central American country’s unusually dry monsoon season, the World Weather Attribution group concluded, after comparing precipitation levels with climate models for a simulated world with no current warming.

The study has not yet been published in a peer-reviewed scientific journal, but it follows scientifically accepted techniques, and previous studies have often been published months later.

“Natural variability plays a critical role in driving many extremes,” said Kim Cobb, a climate scientist at Brown University who was not involved in the study. “This is an important reminder that climate change is not always the answer.”

Panama experienced one of the driest years on record last year, receiving below-average rainfall during seven of the eight months of the rainy season from May to December.

As a result, since last June, the Panama Canal Authority restricted the number and size of ships passing through the Panama Canal due to low water levels in Lake Gatun, the channel’s main hydrological reserve. Global shipping is still being disrupted.

To test whether climate change played a role, the team of scientists analyzed meteorological data against computer simulations accurate enough to capture precipitation in the region. Such models simulate a world without the current 1.2 degrees Celsius (2.2 degrees Fahrenheit) of warming since pre-industrial times, and assess the likelihood of a lack of rain in an unwarming world loaded with fossil fuels.

Climate models did not show a trend similar to the drought Panama suffered last year. In fact, many models show a wetter trend in the region due to climate change caused by carbon dioxide and methane emissions produced by burning coal, oil and natural gas.

However, the analysis showed that El Nino reduced 2023 rainfall by around 8%, and that it is unlikely that Panama would have experienced such a dry rainy season without the influence of the meteorological phenomenon. Researchers said increased demand for water in the region has worsened shortages.

The group used more than 140 years of precipitation records collected at 65 weather stations – a “statistician’s dream,” said Clair Barnes, a researcher at Imperial College London and one of the study’s authors.

“So we are very confident that El Niño is driving the low precipitation,” said climate scientist Friederike Otto, also from Imperial College, who coordinates the attribution study team.

The World Weather Attribution group was launched in 2015, largely out of frustration that it had taken so long to determine whether climate change was behind an extreme weather event. Studies like theirs, within the scope of attribution science, use real-world meteorological observations and computer models to determine the probability of a given event before and after climate change, and whether global warming has affected its intensity.

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