January 2025 has shattered temperature records, marking the hottest start to a year ever recorded 1.7°C above pre-industrial levels. Many climate watchers expected a cooling effect due to the natural La Niña phenomenon, but global warming appears to be overpowering it. Scientists now warn that human-driven ocean warming is beginning to overwhelm natural climate patterns, making temporary cooling phases like La Niña less effective.
La Niña is part of the El Niño Southern Oscillation (ENSO), a climate pattern that influences global temperatures by shifting ocean heat between basins. While El Niño causes warming, La Niña typically brings cooler global temperatures by shifting heat away from the eastern Pacific. Historically, La Niña has helped suppress temperature spikes, but this year, even as the Pacific transitioned into La Niña conditions, global temperatures continued to climb.
One major reason for this unexpected warmth is that each La Niña cycle is unique. After a rare three-year La Niña that lasted from 2020 to early 2023, a moderate El Niño took hold, raising global temperatures. But when La Niña returned in late 2024, it was weaker than usual, and its cooling effect was minimal. Scientists believe this is because human-caused ocean warming has accelerated, making even traditionally cooler periods warmer than before.
Adding to the problem is the continued rise in greenhouse gas levels. Normally, La Niña years promote carbon absorption by land ecosystems, but in 2024 and early 2025, atmospheric carbon levels remained high. This suggests that the ability of ecosystems to absorb carbon may be weakening. Another factor is the reduction of industrial air pollution. While cleaner air is beneficial for health, it has also reduced atmospheric particles that once reflected sunlight, allowing more solar energy to heat the planet.
This January’s record-breaking temperatures highlight a troubling trend: natural climate variability is losing its ability to temporarily slow down global warming. Large parts of Europe, Canada, Siberia, South America, Africa, Australia, and even Antarctica recorded temperatures significantly above normal. With ocean temperatures remaining high, scientists warn that extreme weather events including heatwaves, droughts, and storms could become even more severe.
While a single warm month doesn’t define long-term climate trends, this record-breaking January reinforces the urgency of reducing greenhouse gas emissions. Without immediate and substantial cuts, natural climate cycles like La Niña will no longer be able to mask the growing impact of human-driven global warming.