Warming oceans reduce the brightness of Earth, according to a new study.
The study, which was published in Geophysical Research Letters, measured the light reflected from Earth to the Moon, which is known as Earthshine, and satellite measurements and discovered that Earth's reflectance, or albedo, has dropped in the last two decades.
The findings show that in the last 20 years, the light reflected by Earth has dropped by half a watt. Most of this drop occurred in the last three years of the data.
"The albedo drop was such a surprise to us when we analyzed the last three years of data after 17 years of nearly fatal albedo," said Philip Goode, a researcher at New Jersey Institute of Technology and lead author of the study.
There are two factors that affect the brightness of the sunlight from Earth: the sun's brightness and the reflectivity of Earth. When trying to discover what was causing the dimming of Earth, the researchers found no correlation between the brightness of the sun and the dimming, so they concluded that the cause of the dimming must come from Earth.
An examination of satellite measurements from NASA's Clouds and the Earth's Radiant Energy System (CERES) project showed that there has been a reduction in bright reflective clouds over the Pacific Ocean.
This same area in the Pacific Ocean is where sea temperatures have increased significantly.
"It's actually quite concerning," said Edward Schwieterman, a planetary scientist external to study.
Schwieterman explained that scientists hoped that a warmer Earth would increase clouds and albedo rates, thus helping moderate the temperatures of Earth and moderating the climate system, but that the study "shows the opposite is true."