Global warming continues every year - the changes in climate are already strongly felt by most of the world's inhabitants. Both last year and this year have repeatedly set temperature records, and in both years the average temperature was about 1.5°C above pre-industrial levels. Accumulated greenhouse gases in the atmosphere and some natural phenomena such as El Niño (a sudden abnormal change in the temperature of water in the Pacific Ocean off South America) and volcanic eruptions are partly to blame. But none of these fully explain such extraordinary heat.

Now a team of scientists from the Alfred Wegener Institute (Germany) believe the cause is a dramatic reduction in the number of low clouds. This in turn has reduced the Earth's albedo - a measure of how much sunlight is reflected back into space from our planet. To find an answer to the tantalizing question, the research team spent a long time analyzing satellite data as well as the European Center for Medium-Range Weather Forecasts' reanalysis data, in which a particular set of observations fit a complex model of atmospheric phenomena.

The analysis was truly extended, with some information going back to 1940, allowing for a detailed study of changes in the global energy balance and cloud cover at different altitudes. The observation found that 2023 stands out as the year with the lowest planetary albedo. Scientists emphasize that the planet's ability to reflect the sun's rays back into space has been declining since the 1970s. For the most part, this is due to the active melting of snow and ice in the Arctic, which also reflect light. And since 2016, the problem has worsened even more: the area of sea ice in Antarctica has significantly decreased. Now the decrease in planetary albedo has also been affected by a decrease in the amount of low clouds in the northern mid-latitudes and the tropics.

The study authors have three explanations for why low clouds are disappearing. First, it may be due to a global decrease in the concentration of anthropogenic aerosols in the atmosphere, which contribute to cloud formation and persistence. Second, natural climate fluctuations and their impact on the world's oceans may play a role. Third, global warming itself may reduce the amount of low clouds.

In the future, scientists plan to determine more precisely the reason for the decrease in the number of clouds, because if the decrease in the Earth's albedo is really caused by climate change, then in the future, as climate models show, we should expect new temperature records.