Climate Change Is Making The Earth Reflect Less Light
New research suggests that as the climate on Earth changes, the planet is reflecting less light. The link between climate change and the brightness of the planet is clouds. Scientists have long struggled to create models showing how clouds respond to climate change. Researchers also want to know how changing clouds might shape the climate of the Earth in the future.
The new research suggests the Earth is reflecting less light as the climate changes. Study researchers think the reflectivity change has to do specifically with cloud dynamics over the Pacific Ocean. Researchers leveraged 20 years of observations of a phenomenon called "earthshine," which is light reflected from the Earth on the surface of the moon's dark side.
The observations also use data from another measurement of Earth's reflectivity, called albedo, and the sun's brightness. Different sections of the Earth reflect different amounts of light, with oceans reflecting relatively little light while the land reflects about twice as much light as the ocean. However, clouds are highly reflective. Researchers say that clouds reflect about half of the sunlight that hits them, with the major driver of that reflection being snow and ice.
Researchers combine data with observations from the NASA CERES project that has been in operation since 1997, utilizing instruments on NASA and NOAA satellites. The two data sets combined show that over 20 years, the amount of light Earth reflected dropped by 0.5 percent, equating to about half a watt less light per square meter. Most of the change came in the last three years of data in the earthshine data set.
According to researchers, during the time the data covers, the sun went through two periods of maximum activity and one period of lesser activity. The change in solar activity didn't meaningfully correlate with dips in the reflectance of Earth. That fact led project researchers to determine the change in reflected light is coming from a change on Earth, particularly a loss of bright low-altitude clouds over the eastern Pacific ocean. Temperature increases at the ocean surface have also been noted in that region correlating climate change with decreased reflectivity.