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Mona Pereth
Veteran
Veteran

Joined: 11 Sep 2018
Gender: Female
Posts: 7,810
Location: New York City (Queens)

03 Oct 2021, 9:50 am

According to The Weather Channel India, via Twitter:

Quote:
Climate Change is making the Earth lose its shine
According to the study, the Earth's reflectance has decreased as a result of warming ocean waters. Our home planet now reflects almost half a watt less light per square metre than it did 20 years ago.

This means the Earth is somehow absorbing more energy from the Sun, causing a rise in global average temperature.

According to the news story itself:

Quote:
Digging deeper, the scientists studied satellite observations taken as part of NASA's Clouds and the Earth's Radiant Energy System (CERES) programme. The findings revealed a decline in the bright, reflective low-lying clouds over the eastern Pacific Ocean in recent years.

That is the same area—off the west coasts of North and South America—where increases in sea surface temperatures have been documented. The rise in temperatures directly affects the reversal of a climatic condition known as the Pacific Decadal Oscillation, with possible links to the climate crisis.

I do have a question, though, about how they detected a reduction in the Earth's overall reflectivity (before attributing it to a specific location on Earth):

Quote:
While gazing at the crescent moon immediately after sunset or before sunrise, you may notice that aside from the dazzling crescent, the rest of the moon appears as a dark but faintly glowy disc. The light that bounces off the Earth gives the unlit part of a crescent moon a pale glow, which is referred to as earthshine.

...

Researchers investigated the Earth's ‘albedo’ by studying earthshine at the Big Bear Solar Observatory in California between 1998 and 2017—that’s over 1,500 nights of data. They could determine how much light is reflected by the planet thanks to this analysis.

"The albedo drop was such a surprise to us when we analysed the last three years of data after 17 years of nearly flat albedo," said Philip Goode, a researcher at New Jersey Institute of Technology and the lead author of the study.

The researchers then deduced that there were two plausible explanations for this phenomenon: either the Sun's brightness had changed (reducing the light reaching the Earth and thereby leaving little light for the Earth to reflect) or the Earth's reflectivity itself had decreased.

However, they soon realised that the fluctuations in the albedo had nothing to do with the periodic shifts in the Sun's brightness. This left the Earth's reflectivity—meaning something had gone wrong down here.

The article doesn't mention this, but presumably they also ruled out (or compensated for) changes in the air quality near the Big Bear Solar Observatory, such that less of the "earthshine" may have been visible to them there?


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