El Niño effect: September 2026 was world's second-hottest as global ocean temperatures set new record

September 2026 delivered another stark warning about the pace of global warming. The month ranked as the second-hottest September in recorded history, while global ocean surface temperatures climbed to an unprecedented high for any month, extending a record-breaking streak to four consecutive months.

The latest assessment from the US National Oceanic and Atmospheric Administration's National Centers for Environmental Information (NOAA NCEI), published on October 9, also highlighted below-average sea ice at both poles and unusually intense hurricane activity in the eastern North Pacific.

Persistent El Niño conditions added to the warmth across the tropical Pacific, contributing to elevated global ocean temperatures. The findings point to a climate system under sustained pressure, with 2026 on course to rank among the five warmest years ever recorded.

What are the key findings

1. Second-hottest September on record: Global surface temperatures were 1.33°C above the 20th-century average. September 2023 remains the warmest, with September 2026 trailing by just 0.07°C. It was also the 51st consecutive September with temperatures above the historical average.

2. Global oceans set another record: Ocean surface temperatures averaged 1.10°C above the historical average, setting a record for any month. This was the fourth consecutive month in which the global ocean temperature anomaly reached a new high.

3. Sea ice shrank at both poles: Global sea ice covered 8.54 million square miles, around 800,000 square miles below the 1991-2020 average. Antarctic sea ice recorded its third-smallest September extent in 48 years, while Arctic sea ice ranked 13th-lowest.

4. Pacific hurricane activity surged: Nineteen tropical storms formed worldwide during September. The eastern North Pacific recorded eight tropical storms, seven hurricanes and five major hurricanes. The latter two figures were September records for the basin.

Why are ocean temperatures particularly concerning?  

The oceans absorb most of the excess heat trapped by greenhouse gases, making sea surface temperatures an important indicator of the changing climate. Warmer oceans can also supply additional heat and moisture to developing storms, potentially increasing rainfall and intensification risks.

NOAA's September figures show that ocean warming was not confined to one region. Record-high temperatures extended across the central and eastern tropical Pacific, as well as parts of the Atlantic, Indian and Southern oceans.

However, a record ocean temperature does not automatically mean every region will experience stronger storms or more rainfall. Local impacts depend on atmospheric conditions, ocean circulation and other climate factors.

How is El Niño contributing to the warming?

El Niño is a natural climate phenomenon in which sea surface temperatures in the central and eastern equatorial Pacific become unusually warm. It influences atmospheric circulation and can alter rainfall, temperatures and storm patterns across the world.

NOAA attributed much of the exceptional warmth across the tropical Pacific to persistent El Niño conditions.

The latest US Climate Prediction Center assessment, issued on October 8, said El Niño was continuing to strengthen, with a strong-to-very-strong event likely to persist through January-March 2027.

The phenomenon can amplify global average temperatures, although it is distinct from the long-term warming driven primarily by human-caused greenhouse gas emissions. Its regional consequences vary: some areas may face drought, while others experience heavier rainfall or flooding.

NOAA considers it very likely that 2026 will rank among the five warmest years on record, with the highest probabilities favouring second place.

The outlook is significant because the year-to-date ranking already places 2026 close to the top of the historical record. The final position will depend on temperatures during the remaining months.

What does this mean for India?  

The report recorded one tropical storm in the North Indian Ocean during September, which brought heavy rainfall and flooding to central-eastern India.

For India, the wider concern is how a strengthening El Niño interacts with the monsoon system and regional ocean temperatures. El Niño is often associated with a greater risk of below-normal monsoon rainfall over India, but the relationship is not deterministic: some El Niño years still experience normal or above-normal rainfall.

The implications extend beyond rainfall totals. Temperature extremes, water availability, agricultural output and electricity demand can all be affected by the interaction of global warming with natural climate variability. The September report alone, however, does not establish a forecast for India's next monsoon season.