(ORDO NEWS) — UC Riverside researchers found that methane not only traps heat in the atmosphere, it also creates cooling clouds that offset 30% of the heat.
Absorption of shortwave energy by methane, contrary to common sense, causes a cooling effect and suppresses the increase in precipitation by 60%.
This discovery highlights the need to account for all known effects of greenhouse gases in climate models.
Most climate models don’t yet account for a new UC Riverside discovery: Methane traps a lot of heat in Earth‘s atmosphere, but also creates cooling clouds that offset 30% of the heat.
Greenhouse gases, including methane, create a kind of blanket in the atmosphere, trapping heat from the Earth’s surface, called long-wave energy, and preventing it from radiating into space . This makes the planet hotter.
“A blanket doesn’t create heat unless it’s electric. You feel warm because the blanket interferes with your body’s ability to release heat into the air.
It’s the same concept,” explained associate professor of geosciences Robert Allen of the University of California.
In addition to absorbing longwave energy, it turns out that methane also absorbs incoming energy from the Sun, known as shortwave energy.
“This should warm the planet,” said Allen, who led the research project.
“But, contrary to common sense, shortwave absorption contributes to cloud changes that have little cooling effect.”
Although methane generally increases precipitation, accounting for shortwave energy absorption suppresses this increase by 60%.
Both types of energy (long-wave from the Earth and short-wave from the Sun) leave the atmosphere more than they are absorbed.
The atmosphere needs to compensate for the energy it releases from the heat created when water vapor condenses into rain, snow, sleet, or hail.
“Essentially, precipitation acts as a heat source, keeping the energy balance in the atmosphere,” said study co-author Ryan Kramer of NASA‘s Goddard Space Flight Center and the University of Maryland.
Methane changes this equation. By trapping energy from the sun, methane releases heat that the atmosphere no longer needs to get from precipitation.
In addition, shortwave absorption of methane reduces the amount of solar radiation reaching the Earth’s surface.
This, in turn, reduces the amount of evaporating water. As a rule, precipitation and evaporation are equal, so a decrease in evaporation leads to a decrease in precipitation.
The research team discovered the above results by creating detailed computer models that simulate both the long and short wavelength effects of methane.
In the future, they would like to conduct additional experiments to find out how different concentrations of methane will affect the climate.
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