by Nature Geoscience, Mar 12, 2025
A record-breaking start to 2025 extends the recent period of exceptional warmth and raises questions over the rate of ongoing climate change.
This January saw global mean surface temperature reach 1.75 °C above the preindustrial climate1. The unprecedented heat continues a period of warmth beginning in 2023 that has seen records repeatedly broken. The surge in temperature back in 2023 was in part expected due to the combination of human driven climate change and the onset of El Niño — which is characterized by higher global temperatures. However, the magnitude of the jump was surprising2 and many climate scientists expected temperatures to fall somewhat as El Niño came to an end in the second half of 2024. The continued record temperatures are puzzling and raise questions as to whether it is natural variability or an acceleration in anthropogenic warming. Quantifying the causes and impacts of the recent warmth could reveal important insights into our future.
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A third, potentially more concerning explanation for the drop in cloud cover is an emerging low-cloud feedback, whereby low cloud cover decreases with rising temperature, which further intensifies warming5. How clouds respond to warming remains one of the biggest uncertainties in understanding the climate response to carbon dioxide emissions. A strong low-cloud feedback could lead to more future warming than currently anticipated.
Pinning down the contributing factors to the recent exceptional warmth could prove invaluable for constraining our future trajectory. In particular, we need to clarify what has driven the observed changes in cloud cover. As records continue to fall, now more than ever, it is essential we understand the complex interplay between greenhouse gas driven warming and short-term climate variability.