NASA compares today’s El Niño with a powerful one from 1997

The story

NASA is comparing this year’s El Niño with a powerful one from 1997. Satellite maps show a similar pattern across the Pacific Ocean: the sea surface is higher than usual in parts of the central and eastern Pacific. Those measurements help scientists follow a climate event that can affect weather far beyond the ocean.

El Niño is part of a natural climate pattern that happens roughly every two to seven years. During it, water near the equator in the Pacific becomes warmer than usual. The equator is the imaginary line around Earth’s middle. Changes in this huge area of ocean can influence the air above it and weather elsewhere.

Usually, winds called trade winds push warm surface water toward the western Pacific. This helps keep the ocean warmer and its surface higher there than in the east. During El Niño, those winds weaken. Warm water can spread eastward, changing the usual arrangement of warm and cooler water across the ocean.

The ocean and atmosphere also affect each other. As warmer water moves east, it can help weaken the winds further. That allows more warm water to move. Scientists call this a feedback loop: one change helps produce another change, which then strengthens the first. Following both wind and water helps explain how the event grows.

Satellites give researchers a way to compare enormous areas of ocean. NASA’s maps use measurements of sea surface height. They show where the surface is above or below its usual level, rather than simply showing ordinary waves. Putting maps from different years beside one another makes large patterns easier to notice and compare.

The 1997–98 El Niño was one of the strongest in the satellite record. Another very strong event happened in 2015–16. Past events disrupted weather in different places, including bringing heavy rain to some regions and drought to others. Drought means an area goes through a long period without enough rain.

However, similar ocean maps do not mean every place will experience the same weather as before. Each El Niño develops differently. The location of the warmest water matters, and so does the atmosphere’s response. A comparison with 1997 is useful evidence, but it cannot tell a family exactly what the weather will be outside their home.

Scientists therefore keep collecting measurements instead of relying on a single picture. They compare new observations with older events and watch how conditions change. The important message is that Earth’s oceans and atmosphere are connected. Studying that connection helps people understand changing weather patterns while remembering that predictions always have limits.