Science

Scientists detect a subtle but alarming shift: Earth is getting darker — and it’s changing our climate

For more than twenty years, satellite measurements have shown that the Earth is reflecting less sunlight, affecting its climate balance.

David Cuéllar Greg Heilman

Update: Oct 31st, 2025 14:04 EDT

After more than twenty years of satellite observations, scientists have confirmed a surprising shift: Earth is reflecting less sunlight into space.This subtle dimming—recorded between January 2001 and December 2024 by NASA’s CERES (Clouds and the Earth’s Radiant Energy System) satellite—shows that both the Northern and Southern Hemispheres are absorbing sunlight more quickly than before.

What’s behind the planet’s “darkening”?

The phenomenon is linked to a drop in Earth’s albedo—a scientific term describing how much sunlight the planet reflects back into space. In simple terms, the lower the albedo, the darker Earth becomes.

Researchers say this isn’t just an interesting data point—it’s another warning sign about climate change. A darker planet absorbs more solar energy, which can amplify global warming and alter weather patterns.

How albedo works

Albedo depends on the reflectivity of clouds, ice, oceans, and land surfaces.Bright areas such as snowfields, polar ice caps, and deserts bounce a large portion of sunlight back into space. Darker surfaces like open ocean or bare rock, on the other hand, absorb more of it.

Today, Earth’s average albedo is 0.29—meaning the planet reflects about 29% of incoming sunlight. As glaciers melt and snow cover shrinks, darker surfaces are left exposed, reducing the planet’s ability to reflect solar radiation.

A surprising north–south balance

One intriguing finding is that both hemispheres have roughly the same average albedo, a phenomenon known as interhemispheric symmetry.That balance surprises many researchers: since the Southern Hemisphere is dominated by ocean, it should, in theory, be darker. Scientists believe that cloud cover helps offset this difference—though new research suggests that cloud behavior is far more complex than previously thought.

Where the biggest changes are happening

The team led by Norman Loeb at NASA’s Langley Research Center found that the drop in reflectivity isn’t uniform. The Northern Hemisphere, where much of the world’s landmass and human activity is concentrated, has seen the sharpest decline.

The role of aerosols and atmospheric particles

Tiny airborne particles—known as aerosols—also play a role. These include dust, soot, sea salt, and volcanic ash. Aerosols can promote cloud formation, which under certain conditions increases Earth’s reflectivity.

However, depending on their type and concentration, aerosols can also absorb sunlight or alter cloud properties in unpredictable ways. This makes them a key but complicated piece of the climate puzzle.