A US study shows that increasing concentrations of carbon dioxide (CO 2 ) in the atmosphere result in improved photosynthesis, helping trees grow faster. Scientists at the University of Georgia, USA, have evaluated the response of loblolly pines to increasing concentrations of CO 2 and measured the photosynthesis, respiration and growth under different experimental conditions. They wanted to find out if these bene ficial effects might be modified by other factors such as increasing air temperatures. The benefits outweigh the potential harm that may result from rising global temperatures.