The miracle of life on earth depends on a delicate balance. The sun’s rays penetrate the earth’s atmosphere and warm the planet. At the same time, some of this solar energy is reflected back into space to ensure that the planet doesn’t heat up too much.
But since humans have pumped greenhouse gases into the atmosphere, the earth’s energy balance has tilted. Greenhouse gases prevent additional energy from being reflected back into space, causing global temperatures to rise.
This energy imbalance is “the most fundamental metric that defines the status of global climate change,” scientists said in a 2016 Nature climate change Items. Everything else about global climate change – including the warming of the planet – is a symptom of the mismatch of energy in and energy out.
Now, say scientists, the imbalance is getting more and more one-sided. New research published this month in Geophysical research letters roughly doubled between 2005 and 2019.
The overall imbalance is still relatively small – a difference of about 0.3% in radiation versus radiation. But a little goes a long way. The global mean temperatures on earth have risen by almost 2 degrees Fahrenheit over the past 150 years.
The new measurements illustrate what is physically happening to the planet at the core level, said lead study author Norman Loeb, a NASA climate scientist.
“I think this is a much more basic measurement than surface temperature,” he said. “This is the entire planet that is being added to or removed from the entire planet.”
The team relied on two different sets of data, both of which independently reflect the Earth’s energy imbalance. They first looked at NASA’s satellite data, which was collected by instruments that measure the flux of radiation in and out of the Earth’s atmosphere.
Then they looked at measurements of ocean heat collected by the Argo Float Network, an international ocean observation system with drift sensors scattered around the world. The ocean absorbs about 90% of the planet’s excess energy, making ocean heat a key indicator of changes in energy balance.
Both sets of data independently showed that the Earth’s energy imbalance was increasing. The trends they generated were statistically indistinguishable from one another – almost identical.
The “incredible match” between the two records suggests that both are correct, noted Loeb.
The researchers also performed additional analysis to find out why the imbalance is rapidly worsening. Greenhouse gases in the atmosphere are clearly an important driver. But as the planet warmed, this triggered other feedback cycles that further exacerbated the imbalance.
Melting ice is one of these feedback loops.
Sea ice in the Arctic has declined dramatically in recent decades in response to rising temperatures. Sea ice is highly reflective and helps deflect sunlight away from the planet. When it disappeared, more solar radiation was able to penetrate the earth’s surface.
Cloud cover is another factor, albeit a much more complicated one.
Clouds can either capture solar energy or reflect it back into space, depending on the type of cloud, local climatic conditions, and other factors. The study suggests that changes in cloud cover overall increased the amount of solar radiation absorbed by the planet. But it is unclear how or why.
It’s possible that some of these cloud changes are related to shifts in a natural climate cycle, the researchers added. But some of them are also likely due to man-made climate change.
It is a reminder that not all climate change impacts are linear. The climate system is full of feedback loops that can accelerate the rate at which the planet is warming and changing.
If the earth’s energy imbalance worsens further, the researchers warned, they would expect “even more severe climate changes in the coming decades”.
Computer simulations and models can help scientists make such predictions about the future. The new measurements, in turn, can help scientists test the accuracy of their models and ensure that they reflect what is happening to the planet at the most basic levels.
“My hope is that this study will inspire people in the modeling community to … test the models in innovative ways that will allow us to say more about what will happen in the future,” said Loeb. “There is still a lot to do on the modeling side to decipher this a little further.”
Reprinted from E&E News with permission from POLITICO, LLC. Copyright 2021. E&E News provides important news for energy and environmental professionals.