Earth has a mysterious triple symmetry that may influence its climate

• 01A line of symmetry runs along the 27° east and 153° west meridians, dividing Earth into two halves with nearly equal reflectivity
• 02Jianhao Zhang at the National Oceanic and Atmospheric Administration and colleagues identified this east-west symmetry in satellite observations spanning 25 years
• 03The two hemispheres separated by this line are nearly equal in three respects: albedo in clear skies, cloud reflectivity, and the fraction covered by ice-free oceans
• 04Year-to-year shifts in the exact line of symmetry are strongly related to the phase of the El Niño-Southern Oscillation (ENSO), according to the research team
• 05Zhang stated that the east-west symmetry may be connected to ENSO as 'a large-scale adjustment mechanism that helps keep the long-term east-west symmetry centred near 27° east'
• 06The north-south symmetry appears to be weakening due to climate change effects on sea ice and clouds, while the east-west symmetry is currently stable, according to Øivind Hodnebrog
• 07Zhang noted that if mechanisms maintain the east-west symmetry, attempts to increase albedo in one hemisphere through geoengineering might be negated by global-scale feedback loops

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Researchers at the National Oceanic and Atmospheric Administration discovered a previously unknown line of symmetry along the 27° east and 153° west meridians that divides Earth into two halves with nearly equal reflectivity of light, persistence over 25 years of satellite data, and balanced distribution of land, oceans, and clouds. The exact position of this line shifts slightly year to year in correlation with El Niño-Southern Oscillation cycles, suggesting it may be maintained by a global climate mechanism rather than being coincidental. The discovery has implications for geoengineering proposals, as it indicates potential global feedback loops that could counteract efforts to artificially increase planetary reflectivity.