ECV Rationalization

The need to understand how climate is changing has never been greater, and we cannot understand what we do not observe.    

The GCOS Essential Climate Variables (ECVs) have facilitated the implementation of the observing system through a user-driven process, guiding investment decisions and mobilizing climate observing communities. The first set of ECVs were developed by GCOS in the late 1990’s and since then the list has grown to 55 current ECVs.  

Diagram showing achievements in climate data. Focus areas: simplification, fairness, transparency, consistency, and clarification of concepts in climate monitoring. Includes related icons and notes.
Achievements in ECV Rationalization: Simplified, fair, consistent, and transparent climate monitoring.

In 2024 GCOS started a process aimed at the rationalization of the ECV list. A Task Team was formed who worked in delivering a simpler, fairer, more consistent and more transparent set of ECVs. The main preliminary outputs of the rationalization process comprise: 

  1. the formalization of a governance process to adopt new ECVs
  2. a revised definitions for ECVs and ECV quantities
  3. a proposal for an updated set of ECVs (ECV rationalization list v1.0)

GCOS has undertaken a round of consultations to provide an opportunity to a selection of GCOS stakeholders including GCOS co-sponsors, space agencies, and ECV users to influence the process before delivering an updated ECV list.

The ECV rationalization list 2.0 will be open for public review in Q2 2025 and the final list will only come into force at the end of 2026, after adoption by GCOS Steering Committee.