(CNN) – The new discovery that seems a little out of this world is a new reality for researchers who have been studying the universe for the past two decades.
The researchers found that the Earth is not as bright as it used to be, and that it has been darkening at a noticeable rate in recent years.
Using a telescope not much different than one you might have at home, researchers at Big Bear Solar Observatory have taken measurements every night for the past 20 years to study the solar cycle and cloud cover.
They did this by measuring the “ashy light,” which is produced when the “dark side of the moon picks up the Earth’s reflected brightness and returns that light,” According to NASA. The amount of terrestrial brightness varies from night to night and from season to season.
Ash light or an earth glow is a phenomenon that occurs when sunlight is reflected from the Earth on the dark side of the moon. The Moon then reflects a small portion of this light back to Earth. An observer on Earth sees this as a dimly lit view of the dark side of the moon. The best time to see this in the northern hemisphere is near the new moon during the northern spring months.
Philip Judd, a researcher at the New Jersey Institute of Technology and lead author of New study.
After 20 years of measuring “ghost light,” they discovered it was fading.
“It’s actually sunlight reflected off the Earth, and that’s what fades out,” Judd said.
In fact, Earth now reflects about half a watt of light per square meter than it did 20 years ago, which equates to a 0.5% reduction in Earth’s reflectance. The Earth reflects about 30% of the sunlight that illuminates it.
“In a lot of these things you can put logic aside and there can be a lot of surprises,” Good said. “This is one of those surprises.”
For the first 17 years, the data looked fairly similar, so much so that the researchers almost discontinued the rest of the study.
“We weren’t very excited about doing the data for the last three years because it looked like it hadn’t changed in 17 years, but we finally decided to do it because we promised ourselves 20 years of data, so we did it,” Judd said.
In a surprising turn of events, the last three years of his study showed that the light from the ash had greatly diminished. So much so that they thought their statements were wrong.
This graph shows the Earth’s mean annual brightness or matte black light from 1998 to 2017. The blue line shows the annual albedo of CERES, another annual measure of Earth’s reflectance, from 2001 to 2019. The black lines and dashed blue lines are illustrating the most It is appropriate that the Earth’s reflectance has decreased in the past 20 years. Credit: Goode et al. (2021), Geophysical Research Letters
“When we looked at the data for the past three years, it looked different,” Judd said. “Reflection decreased significantly. So we thought we had done something wrong. So we redo that a few times and it turned out to be correct.”
They realized that the data did not correlate with variation in the sun’s brightness due to its solar cycles, which means that the cause must be something else.
What they notice is a decrease in cloud cover. Sunlight bounces off the cloud tops and is reflected back into space. As cloud cover decreases, more sunlight enters.
“The Earth receives more heat because of less reflected light, so more sunlight enters the visible spectrum,” explains Good.
The largest decrease in cloud cover occurred on the western coasts of North and South America, the same region where sea surface temperatures have risen due to a reversal of a climatic condition called Pacific Decadal Oscillation (PDO).
This graph shows the warm (red) and cold (blue) phases of the Pacific Decadal Oscillation (PDO). Earth is currently in a cold phase of PDO.
PDO is a term used to refer to long-term temperature fluctuations in the Pacific Ocean. The warming and cooling of the oceans at different locations has a direct impact on the path of the jet stream. This shift in the jet stream has a direct impact on long-term climatic and weather conditions, especially on the western coasts of North and South America.
“Off the west coast of the American continent, the lower clouds were consumed and more sunlight entered, so we recorded a decrease in Earth’s reflectance,” Good said.
Goode has stopped claiming that it has a direct effect on accelerating global warming. “Sure, the Earth receives an extra half watt per square meter, but it’s going to be a guess as to what the Earth decides to do with that energy.”
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