In accordance with the GCOS Implementation Plan 2016, GCOS aims to identify a core set of climate change indicators to be used as a basis for reporting climate change to the public. The need to inform the public on the range of climate impacts beyond temperature is clear. A small and limited set of global indicators should demonstrate the range and speed of climate change.
Many different bodies are already presenting different sets of climate indicators. The aim is not to replace these sets of indicators but to identify a core set of 5 to 10 indicators that can be used to report on the general state of the climate to a broad audience. In general, there are two types of indicators: those describing the physical state of the climate system and its historical development (lagging indicators), and those looking at future impact, risk and adaptation (leading indicators). Here, indicators of the former type are identified; further work will be needed to consider the latter.
The latest GCOS Implementation Plan was presented to UNFCCC in November 2016 at Conference of the Parties in Marrakech, Morocco. UNFCCC encouraged all parties of international organizations to implement this plan, which includes developing these two types of climate indicators.
Two meetings held by GCOS in Geneva have agreed that climate indicators should meet the following criteria:
- Relevance: each one should be a clear and understandable indicator of global climate change, which has broad impact for a range of audiences. Some indicators will also have national and regional values
- Representativeness: indicators as a package should provide a representative picture of changes to the earth system related to climate change
- Traceability: indicators should be calculated using an internationally agreed and published method
- Timeliness: indicators should be calculated regularly (at least annually) with a short lag between the end of the period and publishing the data
- Limited number: to allow clear and concise communication, the number of indicators should be limited to less than 10