NASA observes signs of El Niño in the Pacific

What Satellites Observe

NASA describes satellite signals of El Niño. To interpret its intensity and development, we need to distinguish ocean observations, climate indices, and forecasts: they are not interchangeable measurements.

El Niño is a natural climate pattern that occurs approximately every two to seven years and is characterized by warmer-than-normal water temperatures in parts of the equatorial Pacific. According to NASA, it can weaken or reverse the trade winds, redistribute ocean heat, and alter rainfall.

Observations indicate that warm-water Kelvin waves had reached the eastern Pacific by early April and that surface temperatures were beginning to rise. NASA reports local variations in sea level: in some areas, the water was up to 1 to 1.3 feet above normal; around Indonesia and northern Australia, levels were lower than usual.

The Ocean Color Instrument aboard the PACE satellite recorded bluer hues in equatorial zones that are usually greener. NASA associates this change with lower phytoplankton abundance: weakened trade winds reduce the upwelling of nutrient-rich deep water. The decrease may affect the marine food web.

A Coupled System, Not Just Warm Water

The National Weather Service educational material on ENSO describes the relationship between the equatorial ocean and atmospheric circulation. Under typical conditions, the trade winds push surface water westward. Changes in these winds alter the distribution of warm water and the upwelling of cooler water in the east.

This mechanism helps explain why temperature, sea level, and biological conditions can vary together. It does not mean that each indicator measures the same variable. A surface-height anomaly is a difference in level relative to a reference; it should not be read as temperature or confused with the global average rise in sea level.

What the October Bulletin’s Probability Means

The CPC Diagnostic Discussion published on October 8, 2026 distinguishes between periods and thresholds. It gives an 83 % probability that the three-month RONI value will reach at least +2,5 °C in October–December; for September–November it gives 54 % and for November–January 70 %. These are forecasts for different time windows, not parts of a total that can be added together.

The 83 % does not certify a record that has already been measured or describe the probability of an identical impact in every country. The bulletin also discusses the likely persistence of strong or very strong conditions: this wording has a different scope from the three-month threshold. When communicating a probability, we need to retain the variable, threshold, issue date, and forecast period.

Ocean Color and Biological Evidence

NASA’s report adds PACE observations: a change in hues is interpreted in relation to phytoplankton. This is a valuable observation because it connects physical and biological conditions. However, a color variation is not, on its own, a count of all species or a quantitative forecast of fishery catches.

The explanation of upwelling provides a plausible mechanism for this relationship, while specific effects on a food web require further observations. We do not present an abundance curve invented from the colors in an illustration. The table preserves the distinctions between signals, interpretation, and an open question.

How to Track Developments Without Losing Context

Successive bulletins may change as new observations arrive and models are updated. A dated news story does not replace consulting the current diagnostic. The term anomaly also requires identifying the product’s reference; two maps with different scales cannot be compared solely by which one has the more intense red.

To assess a local risk, it is useful to consult regional forecasts and their probabilities. ENSO status provides climate context, but it does not by itself determine a city’s weather or the outcome of a harvest. This additional information clarifies the cited forecast and preserves cautions about causality and geographic scope.