Tiny particles resulting from fuel burning appear to be interfering with the formation of rain, snow and ice on one of China's mountains. As aerosols increase in the atmosphere, fewer droplets collide with one another to form raindrops. Atmospheric scientists studied records from the past 50 years at a meteorological observatory that sits at the peak of sacred Mount Hua. They not only found that visibility from the two-kilometer-high summit has, on average, declined from roughly 30 to 10 kilometers, but they also showed that rainfall has dropped by as much as 17 percent compared with the precipitation in neighboring areas. The findings explain the widely observed trend—from Canada to South Africa to Israel—of a decrease in highland precipitation compared with that in adjacent lowlands. Pollution is not just obscuring the view; it is also choking the mountain streams. The researchers report their work in the March 9 Science.