In a Live Science story, Andera Thompson reports on “An extensive and previously unknown “twilight zone” of particles in the atmosphere could complicate scientists’ efforts to determine how much the Earth’s climate will warm in the future.”

The area around clouds has given us trouble,” said study team member Lorraine Remer of NASA’s Goddard Space Flight Center in Greenbelt, Md. “The instruments detected something there, but it didn’t match our understanding of what a cloud or an aerosol looked like. What we think we’re seeing is a transitional zone where clouds are beginning to form or are dying away, and where humidity causes dry particles to absorb water and get bigger.” Scientists have been aware of an indistinct “halo” surrounding individual clouds, but the newly detected zone is much more extensive, taking up as much as 60 percent of the atmosphere previously labeled as cloud-free.

The blue light from the atmosphere in the original image is first subtracted. The twilight zone is revealed after the darker parts of the image are enhanced. Credit: Koren et al., Geophysical Research Letters

“The effects of this zone are not included in most computer models that estimate the impact of aerosols on climate,” said lead author Ilan Koren of the Weizmann Institute of Science, in Israel. “This could be one of the reasons why current measurements of this effect don’t match our model estimates.”

The study was published in the April 18 issue of the journal Geophysical Research Letters.