SPIE Proceedings [SPIE Third International Asia-Pacific Environmental Remote Sensing Remote Sensing of the Atmosphere, Ocean, Environment, and Space - Hangzhou, China (Wednesday 23 October 2002)] Ecosystems Dynamics, Ecosystem-Society Interactions, and Remote Sensing Applications for Semi-Arid and Arid Land - Response of the grassland in Hulun Buir Steppe of northeast China to global warming based on NOAA/AVHRR NDVI