Albedo is the measure of the fraction of sunlight that is reflected by a surface or body, expressed as a ratio between 0 and 1, where 0 indicates total absorption of light and 1 signifies complete reflection. It plays a crucial role in determining climate and energy balance; for instance, Earth’s average albedo is about 0.3, meaning it reflects approximately 30% of incoming solar radiation, while surfaces like snow have a high albedo near 1, reflecting most sunlight, and darker surfaces like forests have lower albedo values due to higher absorption[1][2][3].

Record Global Warming in 2023 Linked to Declining Planetary Albedo

In 2023, the world witnessed a series of alarming climate records, including rising sea levels, melting glaciers, and unprecedented heatwaves at sea. The global mean temperature soared to nearly 1.5 degrees Celsius above preindustrial levels, marking another record-breaking year for climate change.

Researchers have struggled to pinpoint the exact causes of this sudden temperature rise. While factors such as anthropogenic greenhouse gas emissions, the El Niño weather phenomenon, and natural events like volcanic eruptions account for a significant portion of the warming, they still leave a gap of approximately 0.2 degrees Celsius unexplained. A team from the Alfred Wegener Institute has proposed a potential explanation: a decrease in certain types of clouds has made the planet less reflective.

“In addition to the influence of El Niño and the expected long-term warming from anthropogenic greenhouse gases, several other factors have already been discussed that could have contributed to the surprisingly high global mean temperatures since 2023,” says Dr. Helge Goessling, lead author of the study.

Dr. Goessling notes that increased solar activity, significant water vapor from volcanic eruptions, and fewer aerosol particles in the atmosphere could also play roles. However, even when these factors are considered, there remains an unexplained warming of about 0.2 degrees Celsius.

The research team utilized satellite data from NASA and reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) to analyze trends in planetary albedo—an important measure of how much solar radiation is reflected back into space. Their findings indicate that 2023 had the lowest planetary albedo recorded since at least 1940.

“What caught our eye was that, in both the NASA and ECMWF datasets, 2023 stood out as the year with the lowest planetary albedo,” states Dr. Thomas Rackow from ECMWF.

Decline in Low-Altitude Clouds

The decline in planetary albedo is attributed mainly to a reduction in low-altitude clouds, particularly in the northern mid-latitudes and tropics. This trend has been especially pronounced in the Atlantic Ocean region, where significant temperature records were observed in 2023.

The researchers’ analysis revealed that while Arctic snow and sea ice loss contributes to surface albedo decline, it only accounts for about 15% of the recent decrease in planetary albedo. The majority of this decline is linked to lower cloud cover at mid-latitudes.

“If there are fewer low clouds, we only lose the cooling effect,” explains Dr. Goessling.

Implications for Future Climate

The implications of these findings are significant. A reduction in low clouds not only diminishes cooling effects but may also accelerate global warming due to feedback mechanisms between rising temperatures and cloud formation.

Dr. Goessling warns that if this trend continues, we could see global temperatures exceeding 1.5 degrees Celsius sooner than anticipated. This would necessitate a reevaluation of carbon budgets associated with international climate agreements and highlight an urgent need for adaptive measures against future weather extremes.

Let’s get those low-altitude clouds going, people. Do your part.

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[1] https://en.wikipedia.org/wiki/Albedo
[2] https://www.vaia.com/en-us/explanations/physics/astrophysics/planetary-albedo/
[3] https://www.britannica.com/science/albedo
[4] https://cneos.jpl.nasa.gov/glossary/albedo.html
[5] https://de.wikipedia.org/wiki/Albedo
[6] https://www.climate-service-center.de/products_and_publications/publications/detail/062675/index.php.de
[7] https://www.studysmarter.de/schule/geographie/nachhaltigkeit/albedo/
[8] https://www.awi.de/en/about-us/organisation/profile.html (Alfred Wegener Institute; World Meteorological Organization )