According to climate scientists’ analysis of data from the ERA5 dataset, January 2025 becomes the warmest on record, with a temperature anomaly of 1.75°C higher than the pre-industrial (1850–1900) average. The exceptionally high temperatures observed worldwide, which affected both the northern and southern hemispheres, clearly indicated this record-breaking abnormality.

According to statistics collated and posted on social media by weather historian M. Herrera, on January 31, temperature records were broken in places like Madagascar in the southern hemisphere and Jamaica in the northern hemisphere. The European Centre for Medium-Range Weather Forecasts (ECMWF), which also runs the Copernicus Climate Change Service (C3S) for the European Commission, provides the ERA5 dataset.

Even though La Niña conditions usually result in lower global temperatures, January 2025 was the first January to be noticeably warmer than the El Niño or neutral years surrounding it. This January broke the previous record set in 2024, according to climate scientist Zeke Hausfather of the non-profit Berkeley Earth, who described the change as unexpected, given the current La Niña phase.

Role of ENSO and Persistent Warming Trends

El Niño episodes, or times when sea surface temperatures in the equatorial Pacific were getting close to El Niño conditions, were associated with the previous record for January temperatures in 2024, 2020, and 2016. Global warming is typically exacerbated by El Niño, the warm phase of the El Niño-Southern Oscillation (ENSO). The World Meteorological Organization (WMO) declared the most recent El Niño in July 2023, which lasted until June 2024. In 2024, the annual temperature anomaly was 1.55°C higher than pre-industrial values, making it the warmest year on record.

The National Oceanic and Atmospheric Administration (NOAA) declared La Niña conditions in December 2024, and they are predicted to last until between February and April 2025. In contrast to the previous three-year La Niña from 2020 to 2023, which witnessed extreme heat waves despite the phenomenon’s typical cooling effect, NOAA has warned that this La Niña period is likely to be brief.

The WMO warned in December 2024 that natural climate cycles like ENSO may be superseded by greenhouse gas emissions from fossil fuels, which are still the primary cause of global warming. Although the record January temperatures indicate otherwise, climate experts had predicted that 2025 would be colder.

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Implications for Global Climate Patterns

According to Hausfather’s explanation on his website, The Climate Brink, 2023 and 2024 were both extraordinarily warm years, with global temperatures hovering around the crucial 1.5°C threshold compared to pre-industrial levels. Although a relatively strong El Niño that peaked in November 2023 contributed to 2024’s high temperatures, he pointed out that 2025 was supposed to be colder.

Global temperatures have often been lower during La Niña years than during nearby El Niño or neutral years. This trend was broken as January 2025 becomes the warmest on record, with global temperatures surpassing or approaching the upper bounds of other post-El Niño occurrences. According to Hausfather, this surprising record may hint that 2025 will be warmer than anticipated.

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