Earth’s Falling Reflectivity Means the Planet Is Getting Darker—And Hotter– www.scientificamerican.com

By Ryan Green edited by Andrea Gawrylewski

The view of Earth from space is famously familiar—bright blue ocean, swirling gyres of white clouds, touches of terrestrial green. The luminosity of this image is the result of the sun’s rays shining on the planet, where they’re either reflected or absorbed by materials on Earth’s surface and in our atmosphere. But a new study that examined Earth’s overall brightness reveals that something eerie is happening to that familiar picture.

Scientists measure the planet’s brightness by factoring in how much light reaches earth and how much is reflected back out to space (as measured by orbiting satellites). This reflectivity is known as albedo, and Earth’s overall albedo has been decreasing for decades. But according to a new study published recently in Proceedings of the National Academy of Sciences USA, that change isn’t uniform: the Northern Hemisphere is getting even darker than its southern counterpart. This loss of brightness could result in increased warming in the Northern Hemisphere, throwing Earth’s weather systems out of balance.