For decades, global warming due to greenhouse gas emissions has been a well-established fact. However, the series of record-breaking global temperatures observed in 2023 and 2024 exceeds usual projections. Scientists are now facing the enigma of this exceptional overheating.
The phenomenon can be partially attributed to natural climate variability. Experts explain that the previous years were marked by three successive La Niña events, a climatic oscillation that temporarily masks warming by intensifying heat absorption in the oceans. In 2023, the shift to El Niño, known for its opposite effect, released this energy, pushing global temperatures to levels unseen in 100,000 years, according to paleoclimatologists.
Multiple Hypotheses
Several hypotheses are emerging to explain this extraordinary situation. First, the reduction in low-altitude clouds, linked to changes in atmospheric composition, could have allowed greater heat absorption by the Earth’s surface. This hypothesis is supported by a recent study analyzing the impacts of cleaner maritime fuels mandated since 2020, which reduced sulfur emissions responsible for partial cooling.
Furthermore, natural carbon sinks such as oceans and forests are showing signs of weakening. A preliminary study last summer revealed an unprecedented decline in these carbon dioxide (CO2) absorption mechanisms. For instance, the Arctic tundra is now emitting more CO2 than it stores, a concerning phenomenon confirmed by data from the NOAA (National Oceanic and Atmospheric Administration).
Climate Resilience in Question
For some experts, these developments could indicate a weakening of climate resilience. Johan Rockström of the Potsdam Institute for Climate Impact Research recently highlighted that the accelerated warming of oceans is a phenomenon scientists cannot yet fully explain. He warns that this could be an early sign of global destabilization.
During the American Geophysical Union conference, researchers like Gavin Schmidt, Director of NASA’s Goddard Institute, acknowledged that the functioning of the climate system might be changing. If temperatures remain high beyond 2025, a reassessment of current climate models will be necessary.
An Uncertain Future
Climatologists caution that runaway climate change, though difficult to detect, cannot be ruled out. Sonia Seneviratne, an expert from ETH Zurich, calls for further research to understand the impact of multiple factors such as solar activity, volcanic eruptions, and the role of anthropogenic emissions.
As the planet enters an unprecedented climate phase, the need for data and concrete action to limit greenhouse gas emissions becomes more urgent than ever.
