Euan Nisbet, a University of London earth sciences professor who has traveled the world testing the air for greenhouse-gas pollution, makes his way to a rocky outcropping on the eastern coast of Hong Kong Island on a sunny November afternoon. He takes out a battery-operated pump connected to a thin tube and a plastic bag to capture traces of the wind.
“This is a good day for collecting samples,” says Nisbet, 61, looking out to sea. “There’s a good, strong breeze blowing in from the mainland. It’s the breath of China.”