Study Finds Earth Reflecting Less Sunlight as Northern Hemisphere Darkens Faster

Study Finds Earth Reflecting Less Sunlight as Northern Hemisphere Darkens Faster
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The Earth is reflecting less sunlight back into space than in previous decades, a trend scientists say is accelerating climate change and altering the planet’s energy balance, according to The Nation. A new analysis led by Norman Loeb at NASA’s Langley Research Center examined 24 years of CERES satellite observations and found that from 2001 to 2024 the planet dimmed more than at any other point in the satellite record.

The decline in reflectivity—known as albedo—is uneven, with the Northern Hemisphere darkening far more rapidly than the Southern Hemisphere. Researchers identified an energy shift of about 0.34 watts per square metre per decade. Although small in absolute terms, long-term changes at this scale can influence sea-ice cycles, snow cover, wind systems, cloud behaviour and ocean currents.

Scientists attribute much of the dimming to the loss of bright, reflective surfaces. Arctic summer sea ice and spring snow cover in the Northern Hemisphere have both fallen sharply, replaced by darker land and ocean surfaces that absorb greater amounts of solar energy. The decline in low-lying clouds has further reduced reflectivity, widening the hemispheric imbalance.

Atmospheric factors are also reshaping the Earth’s albedo. While water vapour and cloud formations play important roles, aerosols—tiny particles that scatter sunlight—are particularly influential. Improved air-quality regulations across northern industrial regions have reduced aerosol levels, allowing more sunlight to be absorbed. Meanwhile, the Southern Hemisphere continues to experience periodic boosts in natural aerosols from wildfires and volcanic activity.

Researchers say the widening reflectivity gap is pushing the Earth’s energy system out of equilibrium, with the north now absorbing more heat than it emits. They note that climate models may need updating to reflect this growing hemispheric divergence and to better predict future environmental impacts.