Earth’s energy imbalance removes almost all doubts about man-made climate change

For decades, Earth’s energy system has been out of whack.

The stability of Earth’s climate depends on a delicate balance between the amount of energy the planet absorbs from the sun and the amount of energy the Earth sends back into space. But that balance has been upset in recent years – and the imbalance is growing, according to an article published Wednesday in the Nature Communications journal.

Changes in Earth’s energy system have major ramifications for the planet’s future climate and humanity’s understanding of climate change. The Princeton University researchers behind the article found that there is less than a 1% chance that the changes occurred naturally.

The findings undermine a key argument used by people who don’t believe human activity is responsible for most of climate change to explain global warming trends, offering little doubt that the planet’s energy imbalance can be explained. by the natural variations of the Earth.

The research also offers important information on how greenhouse gas emissions and other human-made consequences of climate change disrupt the planet’s balance and lead to global warming, the rise in the level of sea ​​and extreme weather events.

“With more and more changes on the planet, we have created this imbalance where we have excess energy in the system,” said Shiv Priyam Raghuraman, graduate student of atmospheric and oceanic sciences at Princeton and senior author of the ‘study. “This surplus manifests itself in different symptoms.”

Carbon dioxide emissions, methane and other greenhouse gases from human activities trap heat in the atmosphere, meaning the planet absorbs infrared radiation that would normally be released into space. Melting sea ice, changing cloud cover, and differences in the concentration of tiny particles in the air called aerosols – all of which are affected by climate change – also mean that the Earth reflects less solar radiation back into the cosmos.

“There is not this balance between the energy coming from the sun and the energy coming out of it,” Raghuraman said. “The question is: are these natural planetary variations, or is it us?

The researchers used satellite observations from 2001 to 2020 to determine that the Earth’s energy imbalance is increasing. They then used a series of climate models to simulate the effects on Earth’s energy system if human-caused climate change were removed from the equation.

Scientists found that natural fluctuations alone could not explain the trend observed over the 20-year period.

“It was almost impossible – a probability less than 1% – that such a large increase in imbalance was due to the Earth’s own oscillations and variations,” Raghuraman said.

The study focused on cause and effect, but Raghuraman said the findings have critical societal and political implications.

The oceans store around 90 percent of the planet’s excess heat, which causes seas to rise and can trigger the formation of hurricanes and other extreme weather events. The remaining heat is absorbed by the atmosphere and the earth, raising global surface temperatures and contributing to the melting of snow and ice.

If Earth’s energy imbalance continues to grow, the consequences that are already being felt today are likely to be exacerbated, said Norman Loeb, a physicist at NASA’s Langley Research Center in Hampton, Va., Who was not involved. in the study.

“We’re going to see the temperatures go up, the sea levels go up, more snow and ice melt,” Loeb said. “Everything you see in the news – Forest fires, droughts – these only get worse if you add more heat. “

Loeb led a joint study by NASA and the National Oceanic and Atmospheric Administration which found that Earth’s energy imbalance had roughly doubled from 2005 to 2019. The article was published last month in the Journal Geophysical Research Letters.

Loeb said the Princeton study confirms what was described in his own research, which used 14 years of observations from satellite sensors and a set of instruments in the ocean. He added that human activities, or what is known as anthropogenic forcing, undeniably has an effect, but that some natural variation is probably also at play. For example, some planetary oscillations can operate on cycles that last. decades, which can make it difficult to identify climate change fingerprints.

“The anthropogenic forcing is there, that’s for sure,” he said, “but the ocean is a key climate player and it operates at much slower timescales. Ideally, you really want to be able to have it. this type of measure over 50 years or more. “


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