Climate change is dimming Earth's brightness

The warming of the ocean waters has caused a drop in the brightness of the Earth, as revealed by measurements of the light of the planet that illuminates the surface of the Moon and from satellites. According to a study in AGU Geophysical Research Letters , the decrease in the level of light began twenty years ago.

The warming of the water in the ocean is one of the factors that has caused this decrease in the terrestrial brightness. The explanation is that there are fewer bright clouds that are reflecting the sunlight back into space.

Why is the Earth darkening

Decades of terrestrial light measurements and satellite measurements were used for the study . The net sunlight reaching the planet is affected by the brightness of the Sun and the reflectivity of the planet.

The study shows that there are no periodic changes in the sun's brightness so it is actually something caused by the Earth. The fact that the Earth is dark implies that there is extra solar energy that is in the atmosphere and the oceans, which contributes to global warming.

"The albedo drop came as a surprise to us when we looked at the last three years of data after 17 years of near-flat albedo," said Philip Goode, a researcher at the New Jersey Institute of Technology and lead author of the new study, referring to the Earth light data from 1998 to 2017 collected by the Big Bear Solar Observatory in Southern California. When the latest data were added to the previous years, the dimming trend became clear.

Climate change Earth's brightness

Two things affect the net sunlight reaching Earth: the brightness of the Sun and the reflectivity of the planet. The changes in the Earth's albedo observed by the researchers did not correlate with periodic changes in the Sun's brightness, meaning that lhe changes in Earth's reflectivity are caused by something on Earth.

Specifically, there has been a reduction in bright, reflective low clouds over the eastern Pacific Ocean in more recent years, based on satellite measurements made as part of the Clouds and the Earth's Radiant Energy System (CERES) project.

That is the same area, off the western coasts of North and South America, where se have recorded increases in sea surface temperatures due to the reversal of a climatic condition called the Pacific Decadal Oscillation, with probable connections to global climate change.

The dimming of the Earth can also be seen in terms of how much more solar energy is being captured by the Earth's climate system. Once this important additional solar energy is in the Earth's atmosphere and oceans, May contribute to global warming, since the additional sunlight is of the same magnitude as the total anthropogenic climate forced during the last two decades.

"It's actually quite concerning," said Edward Schwieterman, a planetary scientist at the University of California at Riverside who was not involved in the new study. For some time, many scientists had hoped that a warmer Earth could generate more clouds and a higher albedo, which would later help moderate warming and balance the climate system, he said. "But this shows that the opposite is true."

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