U
- U ThantUN Secretary-General from 1961 to 1971
- U.S.–Canada Air Quality AgreementEnvironmental accord
- UK Student Climate NetworkEnglish and Welsh environmental organisation
- Ukraine and weapons of mass destructionUkraine, formerly a republic of the Soviet Union (USSR) from 1922 to 1991, once hosted Sov
- UmweltbundesamtGerman environmental agency
- UN MandateThe term UN mandate is typically used to refer to a long-term international mission which
- UN World Water Development ReportGlobal report
- Unconventional wind turbinesWind turbines of unconventional design
- Under2 CoalitionThe Under2 Coalition is a coalition of subnational governments that aims to achieve greenh
- UNECE Environmental Performance ReviewsThe UNECE Environmental Performance Review (EPR) (French: Examen des performances environn
- Unexploded ordnanceExplosives that have not fully detonated
- United Kingdom and weapons of mass destructionThe United Kingdom is one of the five official nuclear-weapon states under the Treaty on t
- United Kingdom National Renewable Energy Action PlanThe United Kingdom National Renewable Energy Action Plan was the National Renewable Energy
- United Nations Conference on Sustainable Development2012 international conference in Brazil
- United Nations Convention on the Law of the SeaInternational maritime law
- United Nations Convention to Combat DesertificationInternational treaty on environmental protection
- United Nations Environment OrganizationProposals for the creation of a United Nations Environmental Organization (UNEO) have come
- United Nations Environment ProgrammeUN environmental response agency
- United Nations General Assembly Resolution 31/721976 resolution approving the Environmental Modification Convention
- United Nations Global CompactNon-binding United Nations pact
- United Nations Regional Centre for Peace and Disarmament in AfricaUnited Nations regional office in Togo
- United Nations Regional Centre for Peace and Disarmament in Asia and the PacificUnited Nations regional office in Nepal
- United Nations Regional Centre for Peace, Disarmament and Development in Latin America and the CaribbeanUnited Nations regional office in Peru
- United Nations Scientific Committee on the Effects of Atomic RadiationOrganization of the United Nations
- United Nations Security Council Resolution 15402004 resolution on non-proliferation of WMDs
- United Nations Sustainable Development GroupConsortium of the Secretary-General of the UN
- United States and state terrorismTerrorism allegations against the U.S.
- United States and state-sponsored terrorismU.S. support given to terrorist and paramilitary organizations
- United States and weapons of mass destructionThe nuclear weapons of the United States comprise the second-largest arsenal in the world,
- United States biological weapons program1943–1973 military research program
- United States chemical weapons programThe United States chemical weapons program began in 1917 during World War I with the creat
- United States Fish and Wildlife ServiceUnited States federal government agency
- United States Fish and Wildlife Service list of endangered mammals and birdsEndangered species list
- United States Forest ServiceAgency of the U.S. Department of Agriculture
- United States National Library of MedicineWorld's largest medical library
- United States Naval AcademyService academy in Annapolis, Maryland, US
- United States Statutes at LargeOfficial record of Acts of Congress and concurrent resolutions
- UpcyclingRecycling waste into products of higher quality
- Upflow anaerobic sludge blanket digestionForm of anaerobic digester used for wastewater treatment
- Uranium in the environmentUranium in the environment is a global health concern, and comes from both natural and man
- Uranium mining and the Navajo peopleThe relationship between uranium mining and the Navajo people began in 1944 in northeaster
- Uranium mining debateRadiological impact of uranium mining
- Urban green spaceGreen area in an urban location
- Urban runoffSurface runoff of water caused by urbanization
- Urban terrorismTargeted use of terrorism in urban populations
- US–UK Mutual Defence AgreementNuclear weapons security pact
- USCGC JamesUSCGC James (WMSL-754) is the fifth Legend-class cutter of the United States Coast Guard.
- Uses of radioactivity in oil and gas wellsRadioactive sources are used for logging formation parameters. Radioactive tracers, along
- Utricularia vulgarisUtricularia vulgaris (greater bladderwort or common bladderwort) is an aquatic species of