essential climate variable

The Global Climate Observing System (GCOS) is co-sponsored by the World Meteorological Organization (WMO), the Intergovernmental Oceanographic Commission of the United Nations Educational, Scientific and Cultural Organization (IOC-UNESCO), the United Nations Environment Programme (UN Environment), and the International Science Council (ISC). It regularly assesses the states of global climate observations of the atmosphere, land and ocean and produces guidance for its improvement. An expert panel lead by GCOS, provides definitions of Essential Climate Variables (ECVs) required to observe Earth’s changing climate in a systematic way.
GCOS works towards a world where climate observations are accurate and sustained, and access to climate data is free and open.

Essential climate variables (ECVs)
An Essential Climate Variable (ECV) is a physical, chemical or biological variable or a group of linked variables that critically contributes to the characterization of Earth’s climate.
ECV datasets provide the empirical evidence needed to document, understand and predict the evolution of climate, to guide mitigation and adaptation measures, to assess risks and enable attribution of climate events to underlying causes, and to underpin climate services. They are required to support the work of the UNFCCC and the IPCC.
ECVs are identified based on the following criteria:
• Relevance: The variable is critical for characterizing the climate system and its changes.
• Feasibility: Observing or deriving the variable on a global scale is technically feasible using proven, scientifically understood methods.
• Cost effectiveness: Generating and archiving data on the variable is affordable, mainly relying on coordinated observing systems using proven technology, taking advantage where possible of historical datasets.

“Glaciers” are an ECV of the terrestrial domain. Their changes provide independent and reliable evidence of climate change. Past, current and future glacier changes impact global sea level, the regional water cycle, and may increase local hazard risks. For this ECV, the following products are monitored:

last change 10/12/2025