Earth, our «pale blue spot» in the universe as astronomer Carl Sagan called it, is becoming less and less pale. A recent study published in the journal AGU - Geophysical Research Letters, shows that the warming of ocean waters has caused a decrease in the brightness of our planet.
The researchers used decades of measurements of Earth's brightness - calculated based on the reflected glow from the Earth that illuminates the dark side of the Moon - and satellite measurements to find a significant drop in Earth's reflectance over the past two decades.
The Earth now reflects about half a watt less light per square metre than it did 20 years ago. This equates to a reduction of 0.5% in the Earth's reflectivity, scientists say. A significant drop, as the Earth reflects about 30% of the light coming from the Sun.
Most of the change comes in the last three years of the Earth glow data set, which the researchers analysed up to 2017. The CERES data continues through 2019 and shows an even steeper drop at the end of it. And during this period, the researchers found that the sun's brightness - which went through two periods of peak activity and a quiet period during the study - was not significantly linked to the dip in glare.
So a change in the amount of light the Earth reflects must come from a change in the Earth itself, the scientists thought. Specifically, CERES data noted a loss of bright low-altitude clouds over the eastern Pacific Ocean, on the western coast of the Americas, where scientists also recorded sharp increases in ocean surface temperatures.
The entire study was published in the journal Geophysical Research Letters.
