Climate scientists have long considered methane to be among the major greenhouse gases that humanity has to reduce its emissions. But surprisingly, the results of a new scientific study show that this gas also has an air-cooling effect, and that its contribution to warming may be lower than expected.
The study, carried out by researchers from the University of California Riverside, recently published in the journal Nature Geoscience, found that methane in the atmosphere also reduces rainfall as it absorbs sunlight reaching Earth.
Methane and other warming gases play the role of a cover that prevents heat from leaving the atmosphere (Shutterstock)
Methane heats and cools the atmosphere at the same time
Climate scientists agree on the important role methane plays in the planet's climate change. The gas, whose concentration in the atmosphere has increased almost 2.5 times since the beginning of the industrial era, is responsible for 30 percent of global warming, according to a report by the United Nations Environment Programme.
Methane emitted into the atmosphere acts as a cover that prevents the heat released from Earth into space from exiting the atmosphere. When Earth absorbs sunlight and later re-releases it in long waves into space, methane and other warming gases circulating in the atmosphere prevent these waves from exiting the atmosphere, warming it up.
Some previous scientific studies have estimated that methane, because of its chemical composition, has a short-term warming potential of about 80 times more than carbon dioxide.
But the new study found unexpected results for the true role of methane in the atmosphere. In addition to absorbing long-wave energy, methane also turns out to absorb energy from the sun, known as shortwave energy, according to a statement published by the University of California Riverside on its website.
This absorption, in addition to reducing the amount of solar radiation reaching the Earth's surface, stimulates the formation of clouds that cool the atmosphere, canceling out up to 30% of the heat it generates through the greenhouse effect.
Shortwave methane absorption, stimulates the formation of cooling clouds but reduces precipitation (Getty Images)
Reduces rainfall as well
In contrast, the researchers also found that methane reduces rainfall levels expected under current global warming models by about 60 percent, as methane provides additional energy into the atmosphere, which it obtained from the condensation of evaporated water in the atmosphere.
It is known that the amounts of long-wave radiation emitted by Earth and shortwave radiation from the sun escaping the atmosphere in space are usually greater than those absorbed within it. To maintain thermal balance, the atmosphere compensates for lost energy by refueling heat caused by water vapor condensation processes that lead to precipitation, snow or hail. With methane, heat from water condensation is no longer needed.
In addition, the results of the study showed, according to the statement, that the decrease in the amount of solar radiation that reaches the surface of the Earth by absorbing methane for short waves, reduces the amount of water evaporated. Since the amounts of water evaporated and condensed are equal, low evaporation in turn leads to less rainfall.
According to researchers who hope the study's findings will be taken into account to develop climate change simulation models, this new discovery will help understand more details about how methane and possibly other greenhouse gases affect the climate system.