Surprise effect: Methane cools even as it heats up

Most climate models do not yet take into account a new discovery by the University of California, Riverside: methane traps a large amount of heat in the Earth's atmosphere, but also creates cooling clouds that offset 30 % of heat. Greenhouse gases such as methane create a kind of blanket in the atmosphere that captures heat from the Earth's surface, the so-called long-wave energy, and prevents its radiation into space. This makes the planet warmer. “A blanket doesn't generate heat unless it's electric. You feel warm because the blanket inhibits your body's ability to release heat into the air. This is the same concept,” explained Robert Allen, UCR assistant professor of earth sciences. It turned out that, in addition to absorbing long-wave energy, methane also absorbs energy coming from the Sun, the so-called shortwave energy. "That should warm the planet," said Allen, who led the research project. "However, shortwave absorption counterintuitively promotes changes in clouds that have a slight cooling effect." This effect is detailed in the journal Nature Geoscience, along with a second finding that the research team did not fully expect. Although methane generally increases precipitation, accounting for shortwave energy absorption suppresses this increase by 60 %.