Scientists Sound Alarm on Climate

Early in his career, a scientist named Mario J. Molina was pulled into seemingly obscure research about strange chemicals being spewed into the atmosphere. Within a year, he had helped discover a global environmental emergency, work that would ultimately win aNobel Prize.

Now, at 70, Dr. Molina is trying to awaken the public to an even bigger risk. He spearheaded a committee of the American Association for the Advancement of Science, the world’s largest general scientific society, which released a stark report Tuesday on global warming.