The discovery divides two hemispheres that reflect similar amounts of light and could be useful in testing climate models.
A team of researchers identified a hitherto unknown line of symmetry which divides Earth into eastern and western hemispheres, with both halves reflecting almost identical amounts of sunlight back into space.
The discovery could provide climate scientists with a powerful new tool to test climate models and understand the mechanisms that regulate the planet’s temperature.
The , published in the journal Nature, was led by Jianhao Zhang of the National Oceanic and Atmospheric Administration (NOAA). Using 25 years of satellite observations collected by NASA’s CERES mission between 2001 and 2025, researchers analyzed how much solar energy is reflected by different regions of the Earth.
Scientists have long known about a curious balance between the Northern and Southern hemispheres, which reflect approximately the same amount of sunlightdespite large differences in land area, cloud cover and human activity. Looking for other potential patterns, Zhang and his team discovered a new axis that extends along the meridians of 27° East and 153° West. This line runs through parts of Europe, Türkiye, Africa and Alaska, dividing the globe into two halves that exhibit remarkably similar levels of solar reflection.
Researchers discovered that the two hemispheres share several important characteristicsincluding almost equal proportions of ice-free oceans and land, comparable cloud cover and balanced levels of reflected solar radiation, says the .
The team describes the phenomenon as a “triple symmetryIt is unique because no other east-west divide produces the same balance, persistent because it remains stable over time, and structurally balanced because both halves contain similar distributions of land, ocean, and cloud systems.
Researchers believe the mechanism behind symmetry may be linked to the El Niño-Southern Oscillation (ENSO), one of the most influential factors in global climate patterns. Variations in ENSO appear to cause slight changes in the hemisphere that reflects the most sunlight from year to year, while large-scale atmospheric circulation helps maintain long-term balance.
In addition to its scientific novelty, the discovery may have practical applications. The newly identified symmetry offers a benchmark for testing climate models, helping researchers assess whether simulations accurately reproduce Earth’s radiation budget.
