Earth Observatory Image of the Day: Thirteen Years of Greening from SeaWiFS

From 1998 to 2010, the Sea-viewing Wide Field-of-view-Sensor, or SeaWiFS, made a simple but elegant measurement: how “green” is the Earth. That is, how much chlorophyll—the pigment that helps turn sunlight into organic energy for plants—is present in the seas and on land. Those measurements offered a window into the planet’s ability to support life. The long, well-calibrated data record also gives scientists one of the best benchmarks to study the planet’s biological response to a changing environment.

The image above shows SeaWiFS data as a global average over the entire 13-year record. For the oceans, the colors represent the concentration of chlorophyll and indicate where phytoplankton most often bloomed since 1998. On the land, data are depicted as a Normalized Difference Vegetation Index (NDVI), which shows the density of green vegetation. An NDVI of zero means no green plants and a high value (0.8 or 0.9) is a thick canopy of green leaves.