Researchers have identified a second line of symmetry dividing Earth into halves with equal reflectivity along the 27° east and 153° west meridians. The finding, based on 25 years of satellite data, reveals unexpected balance in clear-sky albedo, cloud reflectivity and ice-free ocean coverage. It may connect to the El Niño-Southern Oscillation and affect future geoengineering plans.
A team led by Jianhao Zhang at the National Oceanic and Atmospheric Administration uncovered the east-west division after analysing satellite records. The symmetry has held steady across the full observation period despite year-to-year shifts tied to ENSO phases. Zhang noted that the triple balance in land-ocean distribution, clear-sky reflection and cloudy-sky reflection makes the pattern unlikely to be random. Øivind Hodnebrog of the Centre for International Climate Research agreed the feature appears robust and potentially linked to major climate variability. Martin Jucker at the University of New South Wales cautioned it could still prove coincidental given global atmospheric circulation. Zhang added that stronger understanding of cloud and circulation responses is needed before assessing geoengineering impacts. Unlike north-south albedo symmetry, which shows signs of weakening, the east-west line remains stable in current models.