Climate change has already brought important modifications to many environmental systems, both natural and human. High resolution remotely sensed products are robust, offering decent environmental assessments, but constraints in computational requirements for the processing of such data sets may require highly efficient parallel processing algorithms, and it is difficult to provide results for extended areas. Moderate resolution remotely sensed products constitute a reasonable compromise suitable to cover extended areas at an acceptable resolution, therefore providing environmental assessments easily at the regional and continental scales. Remotely sensed low resolution environmental data are convenient when global scale analysis is the case. A crucial concern of all environmental scientists who use remotely sensed information is that those data sets cannot and should not completely substitute for Earth-based environmental monitoring. In situ monitoring will always be necessary to calibrate and validate remotely sensed products.