New research shows that although methane traps large amounts of heat in the Earth’s atmosphere, it also creates cooling clouds that offset 30% of the heat.
Greenhouse gases like methane create a kind of blanket in the atmosphere which traps heat from the Earth’s surface, called longwave energy, preventing it from radiating out into space. This heats the planet.
In addition to absorbing longwave radiation, it turns out that methane also absorbs incoming radiation from the sun, known as shortwave radiation. “This should warm the planet,” said Robert Allen, who led the research project. “But counterintuitively, the shortwave absorption encourages changes in clouds that have a slight cooling effect.”
Both types of radiation-longwave (from Earth) and shortwave (from sun)-escape from the atmosphere more than they are absorbed into it. The atmosphere needs compensation for the escaped energy, which it gets from heat created as water vapor condenses into rain or snow.
“Essentially, precipitation acts as a heat source, making sure the atmosphere maintains a balance of energy,” said study co-author Ryan Kramer.
By holding on to energy from the sun, methane is introducing heat the atmosphere no longer needs from precipitation.
In addition, methane shortwave absorption decreases the amount of solar radiation reaching the Earth’s surface. This then reduces the amount of water that evaporates. In general, precipitation and evaporation are equal, so a decrease in evaporation leads to a decrease in precipitation.
www.scitechdaily.com/climate-science-shock-methanes-unexpected-cooling-impact-unveiled