The 2023–24 El Niño was not the strongest in NOAA’s modern record. Yet the year it ended was hotter than the years following every stronger event.
01 — The pulse
A strong Pacific warming met an already warm planet.
El Niño shifts heat from the tropical Pacific into the atmosphere and usually nudges global temperature upward after a short lag. NASA says the strong 2023 event helped push 2024 above the previous global record—but the event itself was only part of the heat.
The ONI peak and global anomaly use different reference periods and measure different things; they should not be added or directly compared.
02 — The staircase
El Niño makes peaks. The whole temperature line is climbing.
El Niño-influenced years often rise above their neighbours, but later “ordinary” years now sit above earlier El Niño peaks. The natural cycle shapes the bumps; it does not explain the long upward slope.
Annual global surface temperature anomaly relative to 1951–1980. Dots mark the ending calendar year of NOAA warm episodes, a consistent comparison convention rather than a claim that El Niño caused the full annual anomaly.
03 — The mismatch
A stronger El Niño does not guarantee a hotter world.
Event strength helps explain year-to-year variation, but it cannot erase the baseline. The 1997–98 event peaked 0.4°C higher in the Niño 3.4 region than 2023–24; its ending year was 0.67°C cooler globally on NASA’s unchanged scale.
Each dot is one NOAA warm episode meeting the historical five-season ONI threshold. Vertical position is NASA’s anomaly in the episode’s ending year. Labelled events are the four highest ONI peaks since 1950.
04 — What to remember
The Pacific supplies the pulse. Greenhouse gases raise the platform.
The four strongest events make the separation visible: El Niño can put a warm year over the top, while the long-term accumulation of heat makes each new event start from a different climate.
El Niño changes which year is hottest. Long-term warming changes what “hottest” means.