Our understanding of the Earth’s climate is rooted in observations of the atmosphere, oceans, and land surface, including the hydrological and carbon cycles and the cryosphere. Using weather observations that are made regularly over a period of time, we can quantify long-term average conditions and gain insight into an area’s climate. Climatologists use climate normals—30-year historical averages of variables like temperature and precipitation—as benchmarks to put, for example, the magnitude of a current heatwave or rainstorm into historical context. In areas where direct observations are sparse, observations are combined with models through reanalysis to arrive at numerical descriptions of recent climate. Reanalysis data are used for monitoring climate change, as well as for research, education and commercial applications.
The WMO Catalogue for Climate Data is a trustworthy source for climate data. The datasets have been assessed through an internationally agreed maturity evaluation process. An initial set of 18 global climate datasets has been so far submitted by the international domain Subject Matter Experts (SMEs) and assessed. The content of the catalogue is expected to expand quickly in the future with including other global data sets as well as regional and national climate datasets.
State of the Climate Indicators
The State of the Climate Indicators are a set of seven parameters that describe the changing climate without reducing climate change to only temperature. They comprise key information for the most relevant domains of climate change: temperature and energy, atmospheric composition, ocean and water as well as the cryosphere.
Data repositories and archives play a critical role as the source for the observational data used in the study of weather and climate. After over two centuries of recording observations on physical media – and the last 20 years on digital media – these records are at risk.
Centennial Observing Stations
Long-term meteorological observations are part of the irreplaceable cultural and scientific heritage of mankind that serve the needs of current and future generations for long-term high quality climate records. They are unique sources of past information about atmospheric parameters, thus are references for climate variability and change assessments. To highlight this importance, WMO has a mechanism to recognize centennial observing stations.