Monday , January 17 2022

Climate change makes the Earth darker, which in turn heats the climate



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According to new research, in an unexpected turn of events, it seems that climate change is making the Earth a little fainter.

Image credits Arek Socha.

One of the properties that define planets throughout space is their “albedo.” Many different elements take into account this property which, in its simplest definition, is the measure of the amount of incoming light reflected by a planetary body. Therefore, the albedo of a planet can have a significant effect on the environmental conditions of its surface.

But the opposite also happens and the climatic conditions of the surface can influence the global albedo of a planet. New research explains that climate change is already affecting the Earth’s albedo, causing a significant drop in our planet’s ability to reflect light in the last 20 years or so.

No recoil

“Albedo’s fall came as a surprise to us when we looked at the last three years of data after 17 years of almost flat albedo,” said Philip Goode, a New Jersey Institute of Technology researcher and author main of the new study.

The authors worked with earth-breaking data recorded by the Big Bear Solar Observatory in Southern California from 1998 to 2017. They also used earth-reading satellite readings during the same period. of time. The brightness of the earth is the light reflected from the Earth into space, and it is what makes the Moon so bright in the night sky.

However, according to the team, the Earth recedes by about half a watt less per square meter of its surface than 20 years ago. In perspective, the typical light bulb uses about 60 watts. A single LED uses about 0.015 watts. The authors explain that it is equivalent to a 0.5% decrease in the reflectance of the Earth.

The two main components that decide the amount of sunlight that reaches the Earth are the brightness that the Sun shines and the reflection that our planet has. But the team reports that the albedo drop they have observed does not correlate with any periodic change in the Sun’s brightness, meaning the drop was caused entirely by changes in the Earth’s reflectance.

This drop is fed mainly by the warming of the ocean waters. The authors point to a reduction in low, bright reflective clouds in the eastern Pacific Ocean over the past two decades, as evidenced by measurements taken as part of NASA’s clouds and the Earth’s radiant energy system project ( CERES). Sea surface temperature increases have been recorded in this area following the reversal of the Pacific Decade Oscillation (PDO).

A weaker Earth means that the planet absorbs much more of the solar energy entering the Earth’s climate systems. Here it is likely to contribute to global warming. The authors estimate that this additional sunlight is of the same magnitude as the sum of anthropogenic forced climate over the past two decades.

“It’s actually very troubling,” said Edward Schwieterman, a planetary scientist at the University of California at Riverside who did not participate in the new study. For some time, many scientists had hoped that a warmer Earth could produce more clouds and higher albedo, which would then help moderate warming and balance the climate system, he said. “But that proves the opposite is true.”

The paper “Earth’s Albedo 1998-2017 as Measured From Earthshine” has been published in the journal Geophysical research letters.

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