Why has the earth been “shining” in recent years?

Over the years, the Earth has been losing its brightness.

In other words, our planet reflects less light from the sun into space – according to a new study Geophysical Research Letters, From the American Geophysical Union (AGU), in September.

The authors of the research, from the United States and Spain, came to this conclusion after analyzing the dataThe amount of light reflected by the Earth on the Moon, With satellites and the Big Bear Solar Laboratory in California for the past 20 years.

Scientists still hope to point out the reasons for the decrease in the brightness of the Earth, but they already have some hypotheses.

Here we tell you what they are and what effects this phenomenon will have on the planet.

What is “albedo”

As is already known about light in general, light surfaces reflect it and dark ones absorb it.

The same thing happens with the light of the sun and the earth.

The dark parts of the planet absorb light and heat from our star; Light parts such as the ice surfaces of poles and clouds reflect them back into space.

The amount of sunlight that the Earth reflects back into space is known “Albedo” And, on average, it treats about 30% of the sunlight received.

NASA’s Earth Laboratory explains on its website that “snow cover, cloud cover, air pollution or changes in the landscape (such as forests or agricultural lands, for example) have subtle effects on the global albedo.”

In the last two decades, This reflex or albedo is reduced.

“The Earth now emits less than half a watt of light per square meter than it did 20 years ago, which is about 0.5% less than the Earth’s reflection,” says AGU.

This reduction of reflex Mainly focused on the last three years.

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Philip Goode, a researcher and lead author at the New Jersey Institute of Technology in the United States, says: “The fall of the albedo came as a surprise to us when we analyzed data from the last three years after a flat albedo 17 years later.

But what is the reason for this reduction?

Possible causes

The authors of the study did not detect changes in the brightness of the sun over the past three years, so the Earth’s reflection is not least related to the star, but to the planet’s causes.

Enrique Palle, one of the authors of the study and a researcher at the Institute de Astrophysica de Canarias (IAC), attributed the discovery to “significant” variations in the size of clouds in some parts of the Pacific Ocean. ) And from the Department of Astronomy at the University of La Laguna in Spain to BBC Mundo.

There are now low clouds – so bright white surfaces that reflect light – in the eastern Pacific, On the west coast of North and South America, according to data from NASA’s Cloud and Earth Radiant Energy System (CERES).

The reduction in clouds is due to an increase in sea temperature, “with potential links to global climate change,” the AGU said in a statement in September.

But Palle told the BBC Mundo that he did not know “if climate change is too easy (increase in sea temperature) the climate system is too complex” because they have only measured albedo in the last 20 years. “Natural processes have long cycles.”

“In other words, I think it may be due to climate change, but I think it’s too early to set aside. There may be natural cycles of clouds changing the albedo,” Palle said.

“There are episodes of rise and fall (temperature) in the course of global warming, so maybe we see a chapter on something,” the researcher added.

Cloud expert John Nielsen-Common, a professor in the Department of Atmospheric Sciences at A&M University in Texas, told the BBC Mundo that “clouds are closely linked to global warming and wind patterns in the atmosphere.”

“(But) the 20-year record of the Earth’s brightness is not really enough to separate these two effects,” said Nielsen-Common, who was not involved in the study.

To determine exactly what the variability of the albedo is, “we need to measure how this factor is changing over the coming years, and we need to measure the long haul to see if we can actually relate to it. For climate change Or just make sure it’s not a natural variant, “Palle said.

Effects

As they explore the reasons for the Earth’s decrease in brightness, scientists will find that the sun’s light and heat, which cease to reflect on Earth’s space, depend on the planet, the oceans, and the atmosphere. It can affect the temperature.

“If the amount of light reflected by the Earth changes over days or decades, it will have an impact on climate change because it will release more or less energy from the sun,” Palle told BBC Mundo.

“The obvious thing is that albedo has always been considered a standard thing in climate studies, but it is not and we have to measure it consistently. This will greatly affect our ability to predict climate change 20, 30 or 50 years later, “the scientist added.

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