The Earth is reflecting less and less sunlight into space, especially in the Northern Hemisphere. The decline over the last 20 years is clearly measurable, as current NASA data shows.
A research team led by Dr. Norman G. Loeb from NASA’s Langley Research Center investigated how much radiant energy the Earth reflects back into space. To do this, they analyzed satellite data from the last 24 years, including values for solar radiation, albedo, and radiation balance.
The result? Since 2001, both Northern and Southern Hemispheres have become darker and now reflect less sunlight.
Radiation absorption has increased by a total of 0.83 watts per square meter per decade. The Northern Hemisphere is particularly affected, absorbing an additional 0.34 watts per square meter. Although some of this excess is offset by air and ocean currents, a net increase of 0.21 watts per square meter per decade remains.
Earlier studies suggested that such currents largely equalize the imbalance between north and south, but current measurements now indicate that this balance is being increasingly disturbed.
Several factors for reduced reflection
- Shrinking ice: In the Arctic, areas of snow and ice are receding and darker surfaces are absorbing more energy.
- Aerosols and clouds: Air pollution has decreased in Europe, China, and the US. Fewer suspended particles means less cloud formation and therefore less reflected radiation.
- Southern Hemisphere effects: Bushfires and the volcanic eruption of Hunga Tonga have released extra aerosols, which have increased reflection in the short term, but not enough long-term.
Consequences for global climates
The shift in reflection shows that equalization mechanisms—such as clouds and ocean currents—are no longer fully effective. This means that the Earth, especially the Northern Hemisphere, is storing more energy over the long term. For regions such as Europe and North America, this could mean additional warming.
The study emphasizes how important it is to include these changes in climate models. Whether the global system can rebalance itself in the long term or whether the symmetry break will persist remains to be seen, but it’s a crucial question for the future of global climates.
This article originally appeared on our sister publication PC-WELT and was translated and localized from German.
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