ERA5 data reveals a 1.75°C temperature anomaly, with new heat records set in both hemispheres despite ongoing La Niña conditions

January 2025 is expected to have been the warmest January on record, with global temperatures averaging 1.75°C above pre-industrial levels (1850-1900), according to analysis of the ERA5 dataset by climate scientists. The anomaly is particularly striking given the ongoing La Niña phenomenon, which typically leads to cooler-than-normal temperatures around the globe.

The warm temperatures in January were felt worldwide, spanning both the northern hemisphere’s winter and the southern hemisphere’s summer. Notably, records were broken in Jamaica and Madagascar on 31 January underscoring the unusual heat.

La Niña conditions are typically associated with cooler global temperatures, but the recent warmth has defied expectations. This follows a year in which 2024 became the warmest year on record, with temperatures 1.55°C above pre-industrial averages, as declared by the World Meteorological Organization (WMO).

The unusual warmth in January suggests that fossil fuel-driven greenhouse gas emissions continue to have a dominant effect on global temperatures, even as natural climatic cycles like La Niña temporarily cool certain regions.

Despite La Niña’s expected cooling impact for early 2025, the unprecedented warmth in January challenges predictions and indicates that the planet’s warming trend remains unrelenting. The National Oceanic and Atmospheric Administration (NOAA) expects this La Niña to be short-lived, unlike the extended 2020-2023 phase, but climate scientists are now questioning the ability of natural climate cycles to counteract the impacts of rising greenhouse gas emissions.