Over the last decade, the Global Climate Observing System (GCOS), in support of the UNFCCC, have put together a set of requirements for satellite data to meet the needs of the climate change community. These are broken down into key physical, chemical or biological variables of the Earth system, or 'Essential Climate Variables' (ECVs) as they are known. The goal is to provide stable, long-term, satellite-based ECV data products for climate modellers and researchers. To respond to this need for climate-quality satellite data, the European Space Agency (ESA) has set up a new programme, the ESA Climate Change Initiative (CCI) which started in 2010.

Sea level was one of the ECVs selected from the beginning of the programme 8 years ago: it is a very sensitive index of climate change and variability which integrates the ocean warming, mountain glaciers and ice sheet melting. Understanding the sea level variability and changes implies an accurate monitoring of the sea level variable at climate scales, in addition to understanding the ocean variability and the exchanges between ocean, land, cryosphere and atmosphere.

One of the objectives of this paper is to present the main improvements performed during the different 2 first phases of the project. During Phase I of the Project (2010-2013), the best altimeter algorithms have been selected for the production of a first set of sea level maps. During phase II of the Project (2014-2016), the time series has benefited from yearly temporal extensions. A full reprocessing of the monthly sea level maps was carried out and is now available for users. This new product benefits from the development of improved radar altimeter standards which have contributed to increase the sea level ECV homogeneity and to reduce the altimetry errors, consolidated with a thorough error characterisation. In addition, the climate modelling group has contributed to the assessment of the products. Specific tasks were undertaken to validate the sea level in coastal areas and to improve its estimation in the Arctic region.

We also present the results obtained in the ongoing phase of the project started from January 2018 onwards. Following the main conclusions of the project, the altimeter errors have been better characterised and GMSL uncertainties estimated for several time spans during the altimetry era. The on-going work reveals that coastal areas display larger sea level trend uncertainties than open ocean using global sea level products (e.g., SL_cci ECVs). However, the development of dedicated algorithms has allowed the reduction of sea level errors. The production of coastal sea-level products based on the combination of XTRACK geophysical corrections and ALES retracking in selected areas of interests (Mediterranean Sea, Northern Europe, Western Africa) is on-going. Preliminary coastal sea level trends estimated in the western Africa region along Jason-2 tracks over 2008-2016 show that use of ALES retracking allows estimating sea level trends very close to the coast compared to XTRACK only or classical GDRs products. Ongoing work has for objective to estimate coastal sea level trends over a longer period (2002 to present) using both Jason-1 and Jason-2 data, and extend the analysis in the other two regions. A better understanding of sea-level processes linking the open ocean and coastal areas at climate scales is expected.

Information on biomass and its changes is of fundamental importance in quantifying both the natural and anthropogenic components of the terrestrial carbon cycle, and thus is a key factor in understanding climate change. The recognition of above-ground biomass (AGB) as an Essential Climate Variable within the Global Climate Observing System is primarily based on its role as a carbon source under Land Use Change and as a sink through vegetation growth, primarily in forests. However, information on biomass, its spatial distribution, and its changes, can constrain carbon cycle calculations in several other ways, including as an initial condition for carbon calculations (perhaps as a proxy for forest age), as a key variable in estimating carbon residence time, as a means of testing carbon models, and a means of inferring landscape carbon dynamics. For many developing countries, especially in the tropics, management of their forest resources is likely to form an important component of their Nationally Determined Contributions (NDCs). An essential element in this is to quantify how forest activities contribute to increasing or mitigating carbon emissions, which largely comes down to quantifying biomass changes, together with the associated changes in other carbon pools. Because many developing countries do not have an extensive National Forest Inventory, remote sensing observations can play an important part in providing this core information on positive and negative emissions associated with forest management. In response to this need, the CCI-Biomass project is concerned with providing global AGB maps and AGB change maps using an approach that maximizes the use of spaceborne C and L-band radar, optical and LiDAR data. Current methods of estimating AGB will be improved using biome-specific investigations that will take account of regional and local forest canopy structure and biophysical conditions. This development will be carried out in close partnership with the in situ biomass measurement community and will include extensive validation based on in situ and airborne lidar data. Though the products are principally aimed at the carbon cycle and Earth System Modelling communities, this presentation will discuss their considerable potential to provide support for the NDCs of individual countries.

The Paris Agreement recognises that the world is facing unavoidable climate change and engages all countries to tackle this global issue. In order to react in an appropriate way, it is of prime importance to monitor these changes. Monitoring mechanisms for greenhouse gas emissions have been built up under the enhanced transparency framework of the UNFCCC. The UNFCCC recognized at COP23 the importance of observation-based monitoring for deriving extra evidence on the current trends of global anthropogenic GHG emissions and as such for the global Stocktake planned for 2023.
The European Commission is investing in climate change monitoring with the Copernicus Climate Change Services of DG GROW, in climate change mitigation with a new EU strategy for GHG reductions, and in climate change adaptation evaluating measures enhancing climate resilience and ecosystem based adaptation. The EU efforts in monitoring, mitigating and adapting are illustrated with the following three examples.
Firstly, climate services can contribute to fostering sustainable use of land, ecosystems and water. Monitoring the current status and pressures on e.g. cropland, forests, rivers and coastal areas might help to understand the actions needed. Even though climate change is a global issue, local pressures are evolving which need local action but evaluated in a global framework for sustainable development. This EU effort focusses in particular on international cooperation and development in Africa.
The Joint Research Centre (JRC) of the European Commission has been involved since the nineties in the use of Earth Observation Technologies for sustainable development in Africa. Meanwhile an operational and distributable open-source data processing tool for Earth Observation products, the so-called ‘eStation’ has been installed in more than 130 African institutions in the framework of the programme supporting Monitoring Environment and Security in Africa, by implementing environmental monitoring services in the field of agriculture and food security, forest and rangeland monitor, water balance, fire monitoring and fisheries. The eStation is adapted for the treatment of the Sentinel-3 data, in addition to the Copernicus Global Land products, and is being delivered to African partners.
In addition JRC is supporting the implementation of climate services and related applications in a programme for the African, Caribbean and Pacific countries, supported under the European Development Fund. In this initiative, there is a fundamental role for Copernicus, in particular the Copernicus Climate Change (with the Climate Data Store) and Global Land Service and includes beside the technological transfer and support capacity building also management of geospatial information, cross-sector analysis, development of information systems and fostering of the science & policy interface.
Secondly, climate change and related environmental and socio economic disruptions have become one of the key risks to Europe's future prosperity and security, and it is far beyond the capacity of single country or actor to manage these risks meaningfully. At the same time Europe is well placed to exploit the opportunities within this challenge, and gain early mover advantages from the vital transition of the energy sector and the necessary changes in transportation, agriculture in particular, as part of a shift in the general approach to resource efficiency in all sectors of the economy. A coherent EU position across the different sectoral policies is aimed at by the new strategy for a GHG emission mitigation.
Upon invitation of the European Council of March 2018, the European Commission prepared a proposal for a strategy for long-term EU GHG emissions reduction, which should pave the way for a modern, technologically advanced and competitive economy. This should be based on a largely carbon-free energy system, which in turn would contribute to improving the quality of life, addressing the social challenges across Europe and minimising the negative impacts of climate change. The newly released "Special Report on Global Warming of 1.5ºC", prepared also with the participation of JRC scientists and approved by the Intergovernmental Panel on Climate Change (IPCC), illustrates exactly the urgency for taking action and the need to ramp up our ambitions. Especially for Europe, a high level of ambition aiming at a net zero greenhouse gas economy already by 2050 will give a strong signal to the global community regarding our commitment to the Paris Agreement, the objectives of the Sustainable Development Goals, and the fight against climate change in general.
Thirdly, sustainable development of our economies and societies needs to consider adaptation to climate change (for example, we need to understand where we can expect extended crop growing seasons or new agricultural regions to occur, which green and blue sectors of the economy have the greatest job creation, where construction of climate resistant infrastructure is required). Anticipating climate change impacts with adaptive strategies will be cheaper, more effective and more complete than reacting to change and responding to emergencies. The Common Agricultural Policy reform aims to protect farmers from climate change impacts while ensuring that the farming does not worsen the climate change problem.
Mainstreaming climate change adaptation affects not only agriculture but a wide range of sectorial policies, such as coastal areas, ocean governance, buildings, water management, energy, disaster risk reduction, health, agriculture, forestry, fisheries and aquaculture and transport. At EU and Member State level there is the EU adaptation strategy, that was adopted by the EU in 2013 and that aims at a more climate-resilient Europe by improved coordination and building capacity to respond to climate change. The strategy focuses on promoting action by member states, adaptation in key vulnerable sectors, and better informed decision-making.

Reliable and up-to-date information about anthropogenic Greenhouse Gas (GHG) emissions and their removal by natural sinks is crucial for societies and policy-makers to make informed decisions to tackle climate change. While political decisions and the global stocktaking process as defined by the Paris Agreement happens at the national / regional level, stabilizing the global Earth’s temperature at a certain level requires tracking the balance between GHG sources and sinks at global scale.

The “REgional Carbon Cycle Assessment and Processes” (RECCAP-1), promoted by the Global Carbon Project (GCP) and carried out by the international carbon cycle community in 2011-2014, delivered an unprecedented synthesis of the mean carbon balance and changes over the period 1990–2009 for all subcontinents and ocean basins. The global coverage provided, for the first time, opportunities to link regional budgets with the global carbon budget, and to investigate trends in global and regional fluxes.
The GCP now reports annually on the evolution of CO2 sources and sinks, their uncertainties and the resulting Global Carbon Budget [1], in phase with the United Nations Framework Convention on Climate Change annual Conference of the Parties (UNFCCC COP). Even though top-down (observation-based) and bottom-up (model-based) estimates of the ocean and biospheric sinks agree over long-time scales, important inconsistencies are found for particular years and at regional-level [1]. These inconsistencies limit our ability to constrain key processes/regions in the global C-cycle and to provide information at spatial and temporal scales relevant for global stocktaking and policy-making. Compared to the time of RECCAP-1, a much wider constellation of satellite-based surface monitoring products of climate and ecological variables is now available, many of them within the framework of ESA-CCI. At the same time, data-driven methods to estimate ocean and land CO2 fluxes that can make use of such data are now widely used.

Here we present recent results of the ESA-CCI pilot project to support, in cooperation with the GCP, a second phase of RECCAP (RECCAP-2). We evaluate the agreement between terrestrial fluxes estimated by atmospheric inversions based on in-situ measurements and by dynamic global vegetation models (DGVMs) for a group of eighteen regions encompassing key biomes and countries / political regions. In order to explain discrepancies between top-down and bottom-up approaches, we investigate land-use change emissions as a possible source of uncertainty at a regional scale, by comparing land-use change emissions from DGVMs and bookkeeping models and land-use/land-cover change datasets. Furthermore, we investigate the sensitivity of regional terrestrial C fluxes to climate. Our study also highlights the potential of ESA-CCI products to advance understanding of key processes in the global carbon-cycle.


[1] Le Quéré et al. Global Carbon Budget 2017, Earth Syst. Sci. Data, 10, 405-448, https://doi.org/10.5194/essd-10-405-2018, 2018.

Spectrally-resolved water-leaving radiances and chlorophyll concentration are recognised as Essential Climate Variables (ECV) by the Global Climate Observing System which establishes accuracy, stability and resolution requirements for ECVs. Global time-series datasets of ECVs are key to studying phytoplankton dynamics at seasonal and inter-annual scales, leading to an understanding of the role of phytoplankton in marine biogeochemistry, the global carbon cycle and the response of marine ecosystems to climate variability, change and feedback processes. Generation of a long time-series of ocean-colour data is not a trivial task: there are a number of algorithms to choose from, for both the atmospheric correction and product retrieval; satellites have finite life spans, so data from individual sensors (including MERIS, Aqua-MODIS, SeaWiFS, VIIRS and OLCI) from late 1997 to 2019, with differing sensor characteristics, need to be merged without introducing artefacts.
ESA’s Climate Change Initiative (OC-CCI) is undertaking research to address the Ocean Colour ECV, with support and help from NOAA, NASA and the global climate research community, including marine ecosystem modellers and remote sensing scientists, who provide on-going feedback. Products are validated against fiducial reference measurements; uncertainty characteristics, quantified on a pixel-by-pixel basis, facilitate applications and interpretations consistent with the quality of the data.
Continuity in ECV production is vital to ensure continued use by the scientific community and the ocean-colour dataset are being sustained through the Climate Change Service, and also available through the Copernicus Marine Environment Monitoring Service as part of the long-term European Copernicus programme, while research and development will continue as part of the recently launched CCI program extension (‘CCI+’).
The latest release of the CCI (version 4) aims at greater consistency in processing by using a single atmospheric correction (HYGEOS Polymer) and source of ancillary data (ERA) for all input sensors, as well as extending the time-series to 21 years (1997-2018). Version 4 is also available at 1-km and is paving the way for introduction of Sentinel 3A,B OLCI data.
This presentation will describe characteristics of OC CCI v4, comparisons to previous CCI and other ocean colour records and evaluation against GCOS requirements and in situ observations.

OC CCI Team:

Groom1, S.; Sathyendranath1, S.; Jackson1, T.; Lavender2, S.; Brockmann3, C.; Brotas4, V.; Cipollini5, P.; Chuprin1, A.; Donlon5, C.; Franz10, B.; Krasemann6, H.; Mélin7, F.; Müller3, D.; Platt1, T.,; Santoleri11, R.; Steinmetz8, F.; Swinton2, J.; Valente4, A.; Wang9, M.; and the wider Ocean Colour Climate Initiative collaborators and contributors.
1 Plymouth Marine Laboratory, Prospect Place, Plymouth, PL1 3DH, UK
2 Telespazio VEGA UK Ltd., 350 Capability Green, Luton, Bedfordshire LU1 3LU, UK
3 Brockmann Consult, Max-Planck-Straße 2, D-21502 Geesthacht, Germany
4 Centro de Oceanografia, Faculdade de Ciencias, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
5 European Space Agency, ECSAT and ESTEC
6 Helmholtz-Zentrum Geesthacht, Zentrum für Material- und Küstenforschung GmbH, Max-Planck-Straße 1 I 21502 Geesthacht, Germany
7 Institute for Environment and Sustainability, Joint Research Centre, European Commission, 21027 Ispra, Italy
8 HYGEOS, 165 Avenue de Bretagne, 59000 Lille, France
9 NOAA STAR, Satellite Oceanography & Climatology Division, Marine Ecosystems & Climate Branch
10 NASA, Goddard Space Flight Center, Mail Code: 616.2, Greenbelt , MD 20771
11 CNR, Rome, Italy