Here is a video about global NDVI change from 1981-2006.
The video starts from July, 1981.
Each frame represents half a month, using data from GIMMS.
You can watch it with browser supports html5.
ps: NDVI is short for Normalized Difference Vegetation Index,
a simple graphical indicator that can be used to assess whether the target being observed contains live green vegetation or not(from Wikipedia)