The ever-flickering light

To date, ecologists involved in global change have focused on the consequences of changes in air temperature. Concurrently, the amount of sunlight reaching the surface of the Earth has been declining, resulting in so-called ‘global dimming’. Now, Wild et al. and Pinker et al. have reported a reversal in this trend in some regions that has occurred over the past 15 years or so. These new findings, combined with earlier work, show that the transparency of the atmosphere can vary substantially over periods of at least 20–50 years. Thus, the ecological consequences of sustained trends in the occurrence of sunlight at the surface of the Earth need a more careful assessment than was previously thought.