El Niño Phenomenon records historic warming in the Pacific Ocean in October 2026

Scientists have identified a method capable of determining the reliability of El Niño and La Niña forecasts with a horizon of up to one year. This new discovery has the potential to improve warnings about extreme weather events, granting more time for communities and authorities to prepare against droughts, floods, and other environmental consequences.

The study, published in the scientific journal Science Advances this Friday (23), analyzed a set of over 7,500 historical forecasts generated by climate models from nine countries. The researchers concluded that the conditions observed in the Pacific Ocean at the time a forecast begins significantly affect its accuracy in subsequent months.

The most relevant finding demonstrated that forecasts initiated under La Niña conditions maintained a good level of performance, even when attempting to anticipate the behavior of the climate system for an entire year. In contrast, those forecasts that began under neutral conditions proved considerably less reliable.

El Niño and La Niña represent opposite phases of the phenomenon known as the El Niño-Southern Oscillation (ENSO), a natural climate pattern linked to variations in the sea surface temperatures of the tropical Pacific. These changes impact atmospheric circulation, potentially altering rainfall and temperature patterns in various parts of the globe.

Although these events generally peak around December and can be predicted with certainty about six months in advance, projecting them over longer periods remains a scientific challenge.

The research indicates that monitoring the initial state of the ocean helps distinguish between forecasts with a higher chance of being correct and those that require greater caution. According to Mandy Freund, a co-author of the study and a researcher at the University of Melbourne (Australia), the stable performance of forecasts initiated during La Niña suggests that these circumstances make the tropical Pacific system more predictable over the following year.

The ability to anticipate these phenomena with greater certainty can assist governments, emergency services, and populations in planning preventive actions, organizing resources, and mitigating risks. However, scientists emphasize that there are still steps to complete before this discovery can be directly implemented in daily forecasts, although the study already offers a path to refine alert systems and increase preparation time for seasonal climate changes.

Images captured by NASA reveal that certain areas of the Pacific Ocean transitioned from greenish hues to a deeper blue between 2025 and 2026. This transformation is directly linked to El Niño, a climatic event characterized by the warming of ocean waters, which, according to specialists, is causing a decrease in phytoplankton populations, microscopic organisms vital to marine ecosystems.

The variation was detected by the Ocean Color Instrument, installed on the PACE satellite, which monitors changes in visible light to analyze the distribution of these microorganisms. This current episode may be the most intense El Niño ever documented, presenting tropical Pacific temperatures approximately 4°C above the normal value, as detailed in an article published on the IFLScience website.

Phytoplankton encompasses thousands of species of microscopic beings that perform photosynthesis and produce various pigments, being responsible for part of the chromatic variations of the oceans. Typically, in the equatorial area of the Pacific, green species rich in chlorophyll predominate.

These organisms depend on colder waters with a higher nutrient content. During the El Niño period, the increase in sea surface temperature restricts the ascent of deep waters that bring these nutrients, which harms phytoplankton development.

The data provided by the PACE satellite allows for the observation of this modification: bluer tones generally signal a lower concentration of phytoplankton, while greenish or yellowish areas indicate higher concentrations.

For much of 2025, a band of greenish water extended across the Pacific, covering from Latin America to Southeast Asia. In 2026, under the influence of El Niño, this band lost intensity, notably in the central and western parts of the ocean.

The reduction of these organisms can impact multiple levels of the marine food web. Organisms such as krill, zooplankton, and filter-feeding mollusks feed on phytoplankton and subsequently serve as food for larger species. With the scarcity of organisms at the base of this chain, the food supply decreases for other species, generating consequences that can propagate throughout the entire oceanic system.

Water warming also affects fishing activity. According to the article, vessels operating off the coast of Latin America's Pacific have been returning with incomplete nets, while commercially traded fish, such as tuna and anchovies, migrate to colder waters. This scenario has contributed to the increase in prices of these fishery products.

The effects of this phenomenon transcend the marine environment. Although it begins with water warming in the central and eastern regions of the Pacific, El Niño causes alterations in climate and weather patterns in various parts of the globe.

Matthew Kehrli, chief research scientist for the PACE satellite team at NASA's Goddard Space Flight Center, stated in a release that tracking the results of the data in real time is very satisfying for researchers.

Josh Willis, a scientist from the NASA Jet Propulsion Laboratory's sea level missions project in California, also highlighted the scope of the phenomenon. He stated that El Niño affects practically everyone in some way whenever it occurs.

The text points out that tropical Pacific temperatures are about 4°C above average. A previous episode of similar intensity occurred between 1997 and 1998, when El Niño was associated with 23 thousand deaths and a global economic loss of US$ 5.7 trillion.