The rapid increase in global warming is primarily attributed to a decrease in the Earth's albedo.
In 2023, several alarming records were set, including rising sea levels, melting glaciers, and heatwaves at sea. The global average temperature surged to nearly 1.5 degrees above preindustrial levels, marking yet another record. Pinpointing the exact causes of this sudden rise has been a challenge for scientists. While the accumulation of greenhouse gases, the influence of El Niño, and natural events like volcanic eruptions account for much of the warming, there remains a gap of about 0.2°C that hasn't been fully explained. A team of researchers suggests that one possible cause for this unexplained temperature rise is the decrease in the planet's reflectivity, as certain types of clouds have diminished.
In 2023, alarming new records were set, including rising sea levels, melting glaciers, and heatwaves at sea. The global average temperature also reached nearly 1.5 degrees above preindustrial levels, another record. Identifying the causes of this rapid temperature rise has posed a challenge for researchers. While human influences like the accumulation of greenhouse gases, El Niño events, and volcanic eruptions account for much of the warming, a gap of roughly 0.2°C remains unexplained. A team led by the Alfred Wegener Institute has suggested a possible explanation: the planet's reduced reflectivity, as certain types of clouds have diminished.
Dr. Helge Goessling, the study's lead author from the Alfred Wegener Institute, stated, "In addition to the effects of El Niño and long-term warming from human-caused greenhouse gases, other factors like increased solar activity, volcanic water vapor, or fewer aerosol particles in the atmosphere have been discussed. However, even when accounting for all of these, the 0.2°C of unexplained warming persists."
This "0.2-degree-Celsius 'explanation gap'" is a central issue in climate research. To investigate further, climate modellers from the AWI and the European Centre for Medium-Range Weather Forecasts (ECMWF) analyzed satellite data from NASA and ECMWF's own reanalysis data, which combines observational data with weather models. They found that 2023 stood out for having the lowest planetary albedo in the records, meaning that less incoming solar radiation was reflected back into space. This reduction in albedo could explain the missing 0.2°C of warming.
The decline in Earth's albedo is partly due to the loss of Arctic snow and sea ice, reducing the planet's ability to reflect sunlight. However, the study suggests that this factor only accounts for 15% of the drop in planetary albedo. The researchers found that a significant contributor to the reduced albedo was the decline in clouds at lower altitudes. Their calculations show that, without this reduced albedo since December 2020, 2023's global mean temperature would have been about 0.23°C lower.
