Our living planet is unique among all we have been able to explore in the universe so far. From our axial tilt that prevents too many extreme temperatures, to our golden cap zone, life on earth depends on many finely balanced, intertwined cycles that come together to produce the exact circumstances we need to thrive.
One of these cycles is the earth’s delicate energy system – input and output of the energy received from the sun.
This cycle dictates all planetary climate systems. On Mars, the seasonal change in energy balance – around 15.3 percent between Mars’ seasons, compared to 0.4 percent on Earth – is thought to cause the planet’s infamous epic dust storms.
For at least a while, before the 1750s, this fluctuating energy cycle on earth was relatively balanced. But we have now created an imbalance that has recently doubled in just 15 years.
“Net energy balance is calculated by looking at how much heat is absorbed from the sun and how much is able to radiate into space,” explains atmospheric scientist Kevin Trenberth of the National Center for Atmospheric Research.
“It is not yet possible to measure the imbalance directly, the only practical way to estimate it is through an overview of the changes in energy.”
Trenberth and the Atmospheric Physicist of the Chinese Academy of Sciences Lijing Cheng reviewed data from all components of the climate system: land, ice, ocean and atmosphere between 2000 and 2019, to make an overview of these changes.
The Earth’s atmosphere reflects almost a quarter of the energy that hits it, unlike the Moon which takes the full effect of the sun’s energy, leading to surface temperatures of around 100 ° C (212 ° F). Most of this energy is then absorbed by the moon and radiated back into space as thermal infrared radiation, better known as heat.
Again, it is the atmosphere that changes this process here on earth. Some molecules in our atmosphere capture heat before reaching space and holding it. Unfortunately for us, these are the greenhouse gases, which have now effectively enclosed the planet in a too warm blanket at the top of the atmosphere.
The extra trapped energy not only changes the place it ends up, but also affects the surroundings on the way to the final destination, the researchers explain in their paper.
“It is important to understand net energy gains, and how much and how much heat is redistributed in the earth’s system,” they write. “How much heat can be moved to where it can be purified from the earth via radiation to limit heating?”
While everyone has largely focused on raising the temperature, there is only one product of this extra energy. Only 4 percent of it goes to raising the temperature on land and another 3 percent goes to melting ice, Trenberth and Cheng calculated.
Nearly 93 percent are absorbed by the ocean, they found, and we are already witnessing the unpleasant consequences.
Even if less than 1 percent of the excess energy swirls around our atmosphere, it is enough to directly increase the severity and frequency of extreme weather events, from droughts to floods.
However, the increased atmospheric turbulence can also be useful.
“These weather events move energy around and help the climate system get rid of energy by radiating it into space,” the scientists explain.
Clouds and ice also help to reflect solar radiation before the long-wave heat that the gases capture. But both reflective clouds and ice are reduced by disturbances in this energy cycle.
There is still too much information missing for a comprehensive soil system model that accurately predicts specific outcomes in the short term, Trenberth and Cheng say. However, by incorporating their earth energy balance that takes into account each earth system component, this can be improved.
“Modeling the Earth’s energy balance is challenging, and its relevant observations and syntheses need improvement,” Cheng concludes.
“Understanding how all forms of energy are distributed across the globe and being sequestered or radiated back into space will give us a better understanding of our future.”
This research was published in Environmental research climate.