Climate Scientists Say Last Month Was a Once-in-a-Century Moment

Ocean temperatures across the globe hit their second-highest April reading ever recorded this year — and scientists say that milestone may be the opening act of something far more serious. Forecasters are now warning there’s a real chance we’re heading into one of the strongest El Niño events in a century, with new data pointing to a rapid shift in ocean conditions already underway.

The numbers alone are striking. The European Union’s Copernicus Climate Change Service found that sea surface temperatures across the extrapolar global ocean — all oceans outside the icy Arctic and Antarctic regions — averaged 21 degrees Celsius (69.8°F) in April 2025. That’s the second highest April average ever recorded, beaten only by April 2024, which came in at 21.04°C (69.87°F).

The difference between those two readings is razor-thin. But the direction of travel, and what it might signal for the months ahead, is what’s catching the attention of climate scientists and weather forecasters worldwide.

What El Niño Actually Is — and Why a “Super” One Is Different

El Niño is the warm phase of a natural, multi-year climate cycle that affects weather patterns across the entire planet. During an El Niño event, unusually warm water accumulates in the central and eastern tropical Pacific Ocean. That shift in ocean heat doesn’t stay local — it ripples outward, pushing global temperatures higher and increasing the likelihood of extreme weather events including droughts, floods, and wildfires.

A standard El Niño is disruptive enough on its own. A “super” El Niño — an unusually intense version of the same phenomenon — amplifies all of those effects. More heat, more volatility, more risk stacked on top of an already warming planet driven by human-caused climate change.

Earth’s last El Niño ran from June 2023 to April 2024, delivering a significant burst of additional warmth to global temperatures during that period. The world is barely out of that cycle, and forecasters are now watching signs that a new one could be forming.

The Data Behind the Warning

The Copernicus Climate Change Service — part of the European Union’s earth observation program — tracks sea surface temperatures as one of the key indicators of where the climate system is heading. Their April 2025 findings showed conditions consistent with a transition toward El Niño.

Forecasters have put the odds of a “super” El Niño emerging this year at roughly one in four. That may not sound overwhelming, but in climate terms, a 25% probability for an event of that magnitude warrants serious attention. These are the kinds of odds that drive emergency preparedness planning at national and international levels.

What makes the current situation particularly notable is the timing. April’s near-record ocean temperatures are arriving so close on the heels of the 2023–2024 El Niño — and on top of a long-term warming trend — that there’s very little baseline “cooling off” between cycles.

Why This Matters Beyond the Weather Forecast

El Niño events don’t just mean hotter summers for some regions. They reshape weather systems across continents. Parts of the world that rely on seasonal rainfall for agriculture can face devastating droughts. Other regions see flooding and landslides. The increased heat also creates ideal conditions for wildfires to ignite and spread rapidly.

When a super El Niño stacks on top of human-driven global warming — which has already pushed baseline temperatures higher than at any point in recorded history — the combined effect can push extreme weather events into territory we’ve rarely or never seen before. Scientists have consistently noted that El Niño acts as a multiplier: it takes whatever the background climate is doing and turns up the intensity.

The 2023–2024 El Niño contributed to a string of record-breaking temperature months globally. If a new and potentially stronger event takes hold in 2025, the years ahead could break records that themselves were only just set.

Who Feels It First — and Hardest

The effects of El Niño are not distributed equally. Tropical and subtropical regions tend to bear the sharpest immediate impacts, particularly in terms of rainfall disruption. Communities dependent on subsistence farming, regions already experiencing water stress, and areas prone to wildfire are among the most exposed.

But the reach extends much further. Disruptions to global agricultural output affect food prices everywhere. Extreme heat events linked to El Niño have repeatedly overwhelmed public health infrastructure in countries at every income level. Insurance costs, infrastructure planning, and disaster response budgets all feel the downstream effects.

For the average person, the practical reality is this: a super El Niño in 2025 would likely mean a higher chance of record-breaking heat, more intense storms in some regions, and greater wildfire risk — all arriving during a period when climate systems are already under unprecedented stress.

What to Watch for in the Months Ahead

The key window for El Niño development is typically the second half of the calendar year. Forecasters will be monitoring sea surface temperatures in the central and eastern Pacific closely through the coming months to determine whether the warming trend accelerates into a confirmed El Niño — and if so, how strong it becomes.

The Copernicus Climate Change Service and other major forecasting bodies will continue publishing updated assessments as new data arrives. The current picture — near-record April ocean temperatures and a 25% chance of a super El Niño — is a signal worth watching, not a certainty. But given what the last El Niño delivered to global temperatures, the world has every reason to pay close attention to what comes next.

Frequently Asked Questions

What is El Niño?
El Niño is the warm phase of a natural multi-year climate cycle that raises global temperatures and increases the likelihood of extreme weather events like droughts, floods, and wildfires.

What makes a “super” El Niño different from a regular one?
A super El Niño is an unusually strong version of the event, which amplifies its temperature and weather impacts significantly beyond what a standard El Niño produces.

How likely is a super El Niño in 2025?
Forecasters have estimated a roughly one in four chance — approximately 25% — that a super El Niño could emerge this year.

What did April 2025 ocean temperatures show?
The European Union’s Copernicus Climate Change Service found that extrapolar global ocean surface temperatures in April 2025 averaged 21°C (69.8°F), the second highest April reading ever recorded, just below April 2024’s all-time record of 21.04°C.

When did the last El Niño occur?
Earth’s most recent El Niño ran from June 2023 to April 2024, adding extra heat to already rising global temperatures during that period.

When will we know if a new El Niño is confirmed?
The clearest picture will emerge in the coming months, as forecasters track sea surface temperatures through the second half of 2025 — the typical development window for El Niño events.