Super El Niño Threatens to Push Global Temperatures Past Critical 1.5°C Threshold

Yagua Indigenous people carrying water and goods due to the low level of the Amazon River in Colombia, in October 2024. | Luis Acosta/AFP via Getty Images

This story was originally published by Inside Climate News and is reproduced here as part of the Climate Desk collaboration.

The Pacific Ocean is a giant climate cauldron, with a powerful heat engine that influences storms, fisheries, and rainfall patterns worldwide. Scientists are closely monitoring the tropical Pacific for signs of a strong El Niño—the warm phase of an ocean-atmosphere cycle that can intensify and alter these global impacts.

In a world already warmed by greenhouse gases, a strong El Niño over the next 12 to 18 months could push the planet’s average annual temperature permanently past the 1.5 degrees Celsius warming threshold, a critical limit recognized in scientific and political agreements as a turning point for potentially irreversible climate impacts.

Recent research also indicates that strong El Niño events can trigger “climate regime shifts”—abrupt, long-lasting changes in heat, rainfall, and drought patterns.

How El Niño Releases Ocean Heat

El Niño acts as one of Earth’s largest natural release valves for ocean heat. The process begins with shifts in ocean currents and winds over the Pacific. These changes push massive stores of tropical ocean heat eastward from the Western Pacific Warm Pool—a region between Australia and Indonesia—toward Japan. This area holds the warmest ocean waters on the planet, covering a region four times the size of the continental United States.

When this ocean heat spreads across the equatorial Pacific, it releases into the atmosphere in pulses. These pulses disrupt weather patterns, redirect high-altitude winds, raise global temperatures, bleach coral reefs, and disrupt fisheries and marine ecosystems. On land, the effects include intensified rainstorms and flooding in some regions, while others face extreme heat, drought, and wildfires.

Historical Impact of El Niño on Global Temperatures

In 2015, heat from the tropical Pacific helped push the global annual average temperature irreversibly past 1 degree Celsius above pre-industrial levels. By 2024, Earth experienced the hottest year on record, further amplified by another El Niño event.

Climate scientist James Hansen told Inside Climate News that even a moderately strong El Niño in the next 12 to 18 months could drive the average global temperature to about 1.7 degrees Celsius above pre-industrial levels. Hansen expressed doubt that the world will cool back below the 1.5°C mark after the El Niño subsides.

Passing this threshold is not an abrupt “climate cliff,” but it marks the point where critical systems—such as forests, water cycles, rainfall patterns, and temperature stability—begin to destabilize. These systems have sustained human societies and ecosystems for millennia.

Consequences of Crossing the 1.5°C Threshold

Even below the 1.5°C threshold, some regions already face erratic water supplies. In California, reservoirs sometimes fail to fill in dry years and overflow during extreme rainfall events. Coral reefs from Australia to the Caribbean have experienced severe bleaching, signaling stressed marine ecosystems.