The Earth's Atmosphere 
The Earth Observatory
Earth's Weather 
European Space Agency, Envisat
The Global Atmosphere Watch Programme 
Global Hydrology and Climate Centre 
Gaia – the living planet - The Debate over the Gaia Hypothesis 
Hydrology and Water Resources Programme
Hydrology Web
The Nine Planets
Nutrient Overload: Unbalancing the Global Nitrogen Cycle
On-Line National Curriculum Science Syllabus Certificate Course  The Earth And Beyond
The Phosphorus Cycle 
Resource and Materials Use 
Surface Meteorology and Solar Energy Data Set
The Woods Hole Research Center: Global Carbon Cycle