Leveraging the need for indicators: An Outline Report (D3.4)

Global climate indicators are used to describe and monitor the state of the climate. Five of the seven ‘state-of-the-climate’ indicators used by the World Meteorological Organisation relate to the ocean, highlighting the ocean's significant impact on the climate, including ocean surface temperature, sea level, ocean heat content, sea ice extent, and ocean acidification. The ObsSea4Clim project focuses on physical ocean indicators, which are crucial for understanding the climate. 

Ocean indicators are necessary because they translate complex ocean data into simple, practical measures of the ocean's state and climate, which, when combined with science-based knowledge, can inform policymakers and other stakeholders and ultimately support decision-making for a sustainable future, benefiting both society and the economy.

Six science-based quality criteria have been identified for ocean indicators: verified, significant, scalable, justified, measurable, and accessible. Indicators should be rigorously assessed against these criteria to determine whether they are scientifically mature and ready for implementation. This will help ensure the scientific robustness.

One of the challenges in ObsSea4Clim is to define the proposed ocean indicators for the Essential Ocean Variables (EOVs) such as sea surface temperature (SST), subsurface temperature, sea surface height, and sea ice and to regionalise the indicators. Regionalised ocean indicators help understand which regions exhibit unique oceanic and climatic patterns, the factors driving these patterns, and how they relate to global trends.

For each proposed ocean indicator, the regions were identified, including both the global perspective, where relevant, and then progressively smaller regions and seas. Thematic regions are also included for some indicators. Legislative exclusive economic zones (EEZ) will be analysed in specific case studies. For each ocean indicator, the proposed measures and associated data have been identified and will now be analysed on a regionalised basis and tested for scientific robustness by the relevant lead institution in each case.

Extreme ocean indicators have also been identified. An extreme ocean event occurs when a physical or biogeochemical variable crosses a threshold that has a tangible impact on a physical process, ecosystem health, or the economy. Three target extremes have been identified: extreme temperature (or marine heatwaves - MHWs), extreme sea ice and extreme sea level.

A key conclusion of the discussions has been to promote testing several definitions for each extreme indicator rather than attempting to find a single universal indicator. Accordingly, the ongoing work within the project will establish a framework for defining extreme indicators, in which key parameters and characteristics can be selected on a case-by-case basis.