For decades, Earth's Northern and Southern Hemispheres maintained a surprising balance—despite stark contrasts in land, pollution, and city density, both sides reflected nearly equal amounts of sunlight into space.
But that planetary symmetry is now breaking.
A new NASA-led study analyzing 24 years of satellite data has revealed that the Northern Hemisphere is absorbing significantly more solar energy than the Southern Hemisphere—about 0.34 watt per square meter per decade. While that may sound minor, it represents an immense and growing energy imbalance that could reshape global climate patterns by influencing rainfall, wind, and ocean currents.
The causes of this tipping point are both natural and human-made. Melting snow and ice are exposing darker surfaces that absorb more sunlight. Efforts to reduce air pollution have also lowered the amount of light-reflecting aerosols, especially in heavily industrialized northern regions. Meanwhile, a warming north holds more water vapor, which traps additional heat. What’s troubling scientists is that cloud cover—once a key equalizer in balancing hemispheric sunlight—hasn’t adjusted to offset these changes. The result: a slow, planetary tilt toward imbalance, the consequences of which remain uncertain.
Source: "Emerging hemispheric asymmetry of Earth’s radiation." Proceedings of the National Academy of Sciences of the United States of America, 29 September 2025.