Recent global temperature surge intensified by record-low planetary albedo

In 2023, the global mean temperature soared to almost 1.5°C above the preindustrial level, surpassing the previous record by about 0.17°C. Previous best-guess estimates of known drivers, including anthropogenic warming and the El Niño onset, fall short by about 0.2°C in explaining the temperature rise. This gap persisted in 2024, during which the stronger El Niño contribution resulted in an even higher global annual-mean temperature, exceeding the symbolic 1.5°C threshold. Using satellite and reanalysis data, we identified a record-low planetary albedo as the primary factor bridging this gap. The decline is apparently caused largely by a reduced low-cloud cover in the northern mid-latitudes and tropics, in continuation of a multiannual trend. Further exploring the low-cloud trend and understanding how much of it is due to internal variability, reduced aerosol concentrations, or a possibly emerging low-cloud feedback will be crucial for assessing the present and expected future warming.