Global change in terrestrial net primary productivity (NPP), 1982-1999. NPP was calculated using mean fraction of absorbed photosynthetically active radiation and leaf area index derived from two different Advanced Very High- Resolution Radiometer (AVHRR) data sets. Areas of increase in NPP are colored green and areas of decrease in brown. Credit: R. Nemani, NASA Ames Research Center [first presented in Science, 300, 1560-1563 (6 June 2003)].