ice albedo and its partition, sea ice age, and sea ice drift). This will permit a more complete
monitoring of the sea ice environment and its interactions in the global climate system. Al
seven variables are essential, feasible, and cost effective and thus fully qualify as GCOS ECVs.
Furthermore, these seven ECVs much better reflect the many advances allowed by Earth ob-
servation satellites in the last decade. To organize the variables as ECVs (not ECV products) is key
to avoid exacerbating the challenges with today’s model, noting that the majority of GCOS ECVs
have one or two ECV products today. The seven new ECVs will close critical coverage gaps in eX-
isting variables such as temperature, albedo, and snow. It will finally reconcile the treatment of
sea ice variables with what is the practice in other domains of GCOS, e.g., the ocean surface ECVs.
Once the seven sea ice variables become ECVs, implementation and funding agencies will
take on the challenge for renewed research and development efforts to further improve the
algorithms and prepare more mature CDRs. A focus at first, the mature and sustained CDRs
will later open many opportunities for cross-ECV activities (including with other spheres of
the climate system) and ingestion into the future coupled climate reanalyses in support to
WMO’s Earth system approach strategy.
An upcoming opportunity for GCOS to revise its list of ECVs is the preparation of the next
implementation plan (IP-2022). The sea ice community will look forward to assisting in that
regard.
Acknowledgments. We are thankful to the WMO GCW Project Office (Rodica Nitu and Nora Krebs) for
facilitating the consultations, fostering engagements, and supporting the development ofthis paper. We
are thankful to the GCOS/GOOS/WCRP co-sponsored Ocean Observations Physics and Climate Panel
(Belen Martin Miguez) for providing insights into the ECV/EOV framework. The views expressed in
‘his article are those of the authors based on their own scientific expertise and experience and do not
aecessarily reflect the position of their institution of affiliation. PH’s contribution was funded under
he Australian Government’s Antarctic Science Collaboration Initiative program, and contributes to
Project 6 of the Australian Antarctic Program Partnership (ASCI000002). PH acknowledges support
‘hrough the Australian Antarctic Science Projects 4496 and 4506, and the International Space Science
Institute (Bern, Switzerland) project #405.
Data availability statement. No data were used or produced for this paper.
Appendix A: Terminology
We recall here the terminology adopted by GCOS and that we use in this contribution. To help
avoid confusion we also discuss the GCOS terminology and compare it to that used otherwise
in the climate community.
Definitions. The definitions below are from GCOS (2016, appendix B) (the wording was
shortened and adapted).
An Essential Climate Variable (ECV) is a physical, chemical, or biological variable or
group of linked variables that critically contributes to the characterization of the Earth’s
zlimate.
The term ECV product denotes parameters that need to be measured for each ECV. For in-
stance, the ECV cloud property includes at least five different geophysical variables where
aach of them constitutes an ECV product. An ECV holds at least one ECV product.
A Climate Data Record (CDR) is a time series of measurements of sufficient length,
consistency and continuity to determine climate variability and change.
A Fundamental Climate Data Record (FCDR) is a CDR which consists of calibrated and
qualitv-controlled sensor data. A CDR is often based on an FCDR.
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