Climate change 9 Coins, banknotes, medals, seals (numismatics) 3 Earth sciences 3 Environmental economics 3 Environmental policy & protocols 3 Management of specific areas 3 Meteorology & climatology 3 Agricultural science 2 Ecological science, the Biosphere 2 Energy technology & engineering 2 Engineering: general 2 Environmental management 2 History of engineering & technology 2 Physical geography & topography 2 Society & social sciences 2 Soil science, sedimentology 2 Sustainability 2 Analytical chemistry 1 Applied ecology 1 Human geography 1 Hydrology & the hydrosphere 1 International relations 1 Mensuration & systems of measurement 1 Physics 1 Political economy 1 Pollution & threats to the environment 1 Public administration 1 Regional & area planning 1 Service industries 1 Social issues & processes 1