The World Meteorological Organization (WMO) is a specialized agency of the United Nations (UN), headquartered in Geneva, Switzerland, responsible for promoting international cooperation in atmospheric science, climatology, hydrology, and geophysics. It is an intergovernmental institution with a membership of 193 countries and territories. The WMO originated from the International Meteorological Organization (IMO), a non-governmental body founded in 1873 to facilitate the exchange of weather data and research. The WMO itself was formally established by the World Meteorological Convention of 1947, which entered into force on March 23, 1950, replacing the IMO and beginning operations as a UN specialized agency in 1951. This transition solved the problem of needing a formal intergovernmental framework to standardize observations and ensure the "free and unrestricted" exchange of meteorological and hydrological data across national borders.
The WMO's mechanism is governed by the World Meteorological Congress, which meets every four years to set policy, and it maintains Technical Regulations that include "Standard practices and procedures" (using "shall") and "Recommended practices and procedures" (using "should") to ensure global interoperability and standardization of data collection and exchange. Key programs include the World Weather Watch for global monitoring and the World Climate Programme for climate change monitoring. The WMO is a parent organization, along with the UN Environment Programme (UNEP), of the Intergovernmental Panel on Climate Change (IPCC), and it also connects to the Green Climate Fund (GCF), having been the first UN specialized agency to formalize its relationship with the GCF in 2016. A recent change involves the recommendation to update the 30-year baseline for calculating Climatological Standard Normals (CLINO) from 1981-2010 to 1991-2020 to better reflect the rapidly changing climate, while the fixed 1961-1990 period is still recommended for tracking global climate anomalies.