Overview
- A peer-reviewed PNAS paper using 24 years of CERES satellite observations reports a global darkening with the Northern Hemisphere dimming faster than the Southern Hemisphere.
- The hemispheric divergence in absorbed energy is small but measurable, increasing by roughly 0.34 watts per square meter per decade.
- Authors link the shift to aerosol–radiation interactions, loss of surface albedo from rapid Arctic sea-ice decline, and water vapor and cloud changes that reduce reflectivity.
- Ocean and atmospheric circulation have not erased the recent North–South imbalance, and the study suggests clouds may have limited capacity to compensate.
- Observations show the Northern Hemisphere warming relative to the south and wetter conditions in the Northern Hemisphere tropics, prompting calls for longer monitoring and model updates, with some scientists discussing geoengineering ideas.