This Handbook aims to demonstrate that without the capabilities offered by satellite EO, there would be insufficient information for climate change studies and insufficient evidence with which to inform our decision- making on policies aimed at mitigation and adaptation to climate change. Nor would we be able to check the effectiveness of our mitigation strategies in terms of the trends of key ECVs. Earth-based measurement systems alone cannot provide the synoptic global picture that is required.
The work of GCOS, with its sponsors and partners in support of the UNFCCC, has established a clear community consensus on the observations that are required to deliver 50 ECVs needed to detect, monitor, predict, adapt to and mitigate climate change in the Earth system. CEOS and GCOS together have identified 28 of the ECVs that are largely dependent on satellite observations and have specified a number of actions required to ensure the necessary continuity or technical characteristics required for climate studies.
The vision of a global observing system for climate will only be realised through a well planned and sustained international coordination effort, involving a number of challenges.
Effective Institutional Arrangements
Effective institutional arrangements have been proven to be fundamental to the progress achieved to date in establishing consensus on climate information requirements and coordination in the provision of observations to address them. The cooperation between CEOS and GCOS in support of the information requirements of the UNFCCC and its Parties is fundamental to the future success of the Convention and demonstrates the importance of strong partnerships between observation planners and global environmental governance frameworks like the UNFCCC.
CEOS is recognised as the primary international forum for coordination of the EO programmes of space agencies worldwide. Recognising also the importance of long-term space-based observing systems provided by operational satellites that are primarily used for weather observations, CEOS undertakes its climate-related coordination in association with CGMS.
The broad range of scientific challenges and priorities demanded of space-based observations can only be fulfilled through international cooperation. The Architecture for Climate Monitoring from Space coordinated by the CEOS-CGMS Working Group on Climate is an appropriate framework for such international cooperation. There is a need for an integrated observational approach that is
strategically designed to be cost effective and sustained over decades, yet remains targeted on key challenges and promotes the fusion of theory, models and observations. Where relevant, this approach should also address the linkage to societal benefits, as this can facilitate greater support and funding for such observation systems.
The importance of these institutional arrangements in support of the UNFCCC must be recognised and suitable political support and resources provided for their continued success. Planning and implementation of satellite observations can take years from inception and efficient processes need to be in place, linking the policy needs of UNFCCC and its parties with the observing requirements defined by GCOS and the planning processes of the space agencies.
Ensuring Continuity of Future Observations
A fundamental commitment by governments investing in space-based EO is needed to ensure continuation of the required observations at an acceptable level of accuracy and coverage.
CEOS will aim to ensure continuity, consistency and inter- comparability of the priority measurements throughout the coming decades, consistent with the requirements of climate studies for trend monitoring and change detection.
The Climate Monitoring from Space Architecture provides a vehicle for comprehensive review of the state of progress towards the full range of ECVs and to establish actions necessary to address shortcomings. Funding and execution of the individual satellite programmes remains the responsibility of individual governments and their space agencies and CEOS will continue to be dependent on their funding and capacity to deliver the EO satellite programmes.
Adopting and Reporting ‘Climate Indicators’
Part II of this Handbook contains a substantial article on the need to adopt and popularise the use of a number of climate indicators that can become the recognised lexicon and reference for discussions by both policymakers and the public regarding the symptoms of climate change.
It is widely recognised in the scientific community that the use of global surface temperature as the focus for political messaging is a gross over-simplification and obfuscates significant underlying issues regarding the distribution of energy within the climate system.
The proposed climate indicators would be reliable, simple, have a long-term history, reflect a range of possible symptoms of climate change, integrate as far as possible many wider effects of change, be easily interpreted and conversely difficult to misinterpret. They need not be the same for policy makers and the public, but they must be accessible to both. Candidates include: surface temperature; sea level; atmospheric carbon dioxide; energy content of the climate system; total solar irradiance; measures of extreme climate event occurrence and intensity; and arctic sea ice extent and volume.
Such a dashboard of climate indicators, mostly derived from satellite data, might be included by GCOS in future updates to its Implementation Plan as a way to communicate better and more simply the changes in the Earth system linked to changing climate. Many of the likely measurements are provided by satellite observations and CEOS is ready to ensure that the necessary coordination is put in place to guarantee the observations needed in support of regular and routine updates to the vital signs and their reporting to society. This process must also reflect the political efforts in relation to achievement of the Sustainable Development Goals (SDGs) and support the societal linkages between disaster risk reduction, sustainable development and climate change.
Ensuring Accuracy of Climate Observations
Measuring long-term global climate change from space is a daunting task. The climate signals we are trying to detect are extremely small: temperature trends of only a few tenths of a degree Celsius per decade, ozone changes as little as 1% per decade and variations in the Sun’s output as tiny as 0.1% per decade or less.
Accuracy is an important attribute of a climate observing system and helps to advance the understanding of physical processes in the Earth’s climate system. CEOS space agencies foresee a series of highly accurate climate- reference instruments in order to measure with high spectral resolution the energy reflected and emitted by the Earth. These instruments would provide reliable long- term records of climate forcings, response and feedbacks to monitor climate change. Their records would also serve as the validation data needed to test and evaluate climate model predictions. The benchmark instruments would also constitute a reference standard, or calibration observatory, in space that can be applied to other environmental satellite sensors that are not as well calibrated, eg the sensors on operational weather satellites. Such calibrations can be performed by comparing coincident observations of the benchmark instruments with the other sensors.