In a stunning investigation, NOVA reports on the discovery that the amount of sunlight reaching Earth is dropping--a big surprise given international concern over global warming. Less sunlight might hardly seem to matter when our planet is stewing in greenhouse gases, but the discovery of global dimming has led some scientists to claim that the earth’s climate is heating up much faster than most previous predictions.

Scientists have long known that increasing air pollution endangers our respiratory health. But they had not fully considered the impact of pollution on the amount of sunlight reaching Earth. Some scientists now believe that global dimming may disturb rainfall patterns and contribute to severe droughts and famines.

The good news is that, in some regions, pollution controls have slowed and possibly even halted global dimming during the last decade. The bad news--and the ironic twist in this story--is that without pollution, we will no longer have the cooling effects of global dimming. Instead, we may be confronted with the true power of global warming, which we may have seriously underestimated due to the dimming sun.