Space-based remote sensing observations of the atmosphere-ocean-land system have evolved substantially since the first weather satellite systems were launched almost 50 years ago. Earth observation satellites have proved their
capabilities to accurately monitor multiple aspects of the total Earth System on a global basis, unlike ground-based systems that are limited to land areas and cover only about 30% of the planet’s surface.
Currently, satellite systems monitor the evolution and impact of the El Niño, weather phenomena, natural droughts, vegetation cycles, the ozone hole, solar fluctuations, changes in snow cover, sea ice and ice sheets, ocean surface temperatures and biological activity, coastal zones and algal blooms, deforestation, forest fires, urban development, volcanic activity, tectonic plate motions, and more.
These various observations are used extensively in real-time decision making and in the strategic planning and management of industrial, economic, and natural resources. The proliferation of Earth observation satellites reflects their unique abilities and benefits, such as:
— wide area observation capability;
— non-intrusive observations allowing collection of data to take place without compromising national sovereignty;
— uniformity that enables the same sensor to be used at many different places in the world;
— rapid measurement capability, allowing sensors to be targeted at any point on Earth, including remote and inhospitable areas;
— continuity, with single sensors or series of sensors providing long time series of data suitable for climate studies.
Just one significant example – highlighted by the IPCC 4AR – is the global coverage of satellite ocean altimetry, provided over the last 15 years by the Topex/Poseidon and Jason satellites. These data have provided unambiguous evidence of non-uniform sea level rise in open oceans and have proven to be the most accurate and objective way to detect this rise in sea level.
The GCOS Implementation Plan notes that satellites provide a vital means of obtaining observations of the climate system from a global perspective, and that “a detailed global climate record for the future will not be possible without a major, sustained, satellite component”.
Although almost all Earth observing satellite systems were not specifically designed for climate monitoring, space agency efforts have initiated a remarkably comprehensive climate data record that is forming the basis for a better understanding of the Earth’s climate system. Much has been accomplished, but more remains to be done. Significant gaps remain in measurement capabilities and their continuity.
Noting GCOS advice on the significance of the satellite contribution to climate data records, the UNFCCC invited countries that support space agencies which operate Earth observing satellite programmes to provide a response to the needs expressed in the GCOS Implementation Plan
These countries agreed that the Committee on Earth Observation Satellites (CEOS), as the primary international forum for coordination of space-based Earth observations, was the appropriate international body to respond. CEOS
prepared and delivered to the UNFCCC an assessment of the adequacy of past, present, and future satellite measurements in support of GCOS. CEOS noted that responding to these needs represents a unique opportunity for space
agencies to review the way in which multi-agency cooperation on climate-related observations is prioritised, agreed, funded, implemented, and monitored. The UNFCCC has welcomed the CEOS initial report, commended space agencies for actions taken thus far, and requested CEOS to report on progress at future meetings.
Space agencies provide the basic satellite observations – Fundamental Climate Data Records (FCDRs) – needed to monitor global climate change. In turn, the end-user products for the Essential Climate Variables (ECVs) are
generated by a range of interested communities through a variety of approaches that link satellite observation data with in situ data and other information through assimilation into models and other products.
The various ECVs and the status of satellite data provision in support of them are identified at the Satellite Data Stewardship website of the U.S. National Climatic Data Center (NCDC) (www.ncdc.noaa.gov/sds). The site also identifies the linkage between individual ECVs and key IPCC questions and societal benefits.