The need for greenhouse gases (GHG) observations in the GMES program
There has been remarkable progress over the past decade in the development of in-situ GHG measurement techniques, modeling approaches and the creation of a global terrestrial and atmospheric GHG Observing System (GEO Carbon Strategy, 2010). Local ecosystem flux measurements recorded continuously by flux towers (Valentini et al., 2000), combined with concentration measurements made at atmospheric stations are now used to derive estimates of GHG fluxes over large regions of the globe (Janssens et al. 2003, Beer et al. 2010, Xiao et al. 2008, 2011, Chevallier et al. 2010). Global mapping of greenhouse gas fluxes delivers a major improvement in understanding how the biogeochemical cycles of greenhouse gases regulate the climate of the Earth. Importantly, this provides the scientific basis for the crucial development of emission reduction policies.
The GMES Atmosphere Core Service (Implementation Group) has identified as its two priorities the consolidation of in-situ GHG atmospheric monitoring through the Atmospheric component of the ICOS infrastructure in Europe and the harmonization of multiple-source datasets (GACS, 2009; GISC, 2011). In-situ GHG data are identified as critical information to "enable monitoring of long term trends" and to "ensure validation of global satellite retrievals".
The working paper on the GMES Global Land Monitoring Core Services (Dolman et al., 2010) identified among key Thematic Services "land data assimilation systems for the carbon and water cycles", and recognized the necessity to validate global data assimilation products using in situ networks such as FLUXNET, CARBOEUROPE, now integrated at the European level into the Ecosystem component of the ICOS Infrastructure (www.icos-infrastructure.eu).
The strategic goal of ICOS-INWIRE is to enable and extend the provision of GHG data from relevant monitoring networks as identified in the GISC (2011) report to the GMES Atmosphere and Land Core Services. This includes enabling harmonized in-situ GHG measurements from multiple networks, including from stations in poorly covered regions, and from ground-based remote sensing stations of the Total Column Carbon Observing Network (TCCON). The concept is to enhance the capabilities of the ICOS Research Infrastructure jointly with the TCCON network, by developing new software and database tools, and autonomous GHG stations with intelligent sensor systems capable to collect and transmit continuous data from challenging environments to identified users, i.e. operational centers and data assimilation systems (e.g. ECMWF). The convergence between in-situ and space GHG observations will be achieved in ICOS-INWIRE through 1) combining ground-based remote sensing (TCCON) and surface in-situ measurements (ICOS) to validate satellite retrievals and 2) providing these data to the ECMWF assimilation system, that merges the in situ, total column and satellite data-streams.