For many of us in Southern California, the marine layer is a lifesaver. Those low decks of clouds — you might know them as June Gloom or May Gray — roll in off cool, ocean waters, shading coastal regions and cooling beaches and West Side cities even as the Inland Empire scorches. Now, we may be losing them. A new study by a Caltech climate scientist and two colleagues suggests those familiar low decks of stratus clouds could eventually become a casualty of the increasing CO2 emissions that are warming the planet.