Greenhouse Gases related to the Carbon Cycle (CM-GHG)

Principal Participants: Strong, Walker, Nassar, Polavarapu, Worthy; Stakeholders: Griffith, Toon, Wennberg; Canadian Gov't Departments: Environment Canada (EC), Canadian Space Agency (CSA); International Orgs: TCCON, JAXA, NASA, ESA; HQP: 25% RA + 2 graduate students.

Rationale Increases in the concentrations of the greenhouse gases CO2 and CH4 are well documented (Forster et al., 2007). As permafrost thaws, there also is concern that large-scale emissions of CH4 and/or CO2 will occur, creating a positive feedback loop on global warming (Tarnocai, 2009). The Group on Earth Observations (GEO) Carbon Strategy (Ciais et al., 2010) notes that “Understanding the global carbon cycle, and predicting its evolution under future climate scenarios is one of the biggest challenges facing science today.” with uncertainties due to lack of sufficient knowledge about carbon sinks, feedbacks between climate change and carbon reservoirs, and anthropogenic emissions from fossil fuel burning and land use change. Better understanding of these issues is essential for well-informed policies regarding greenhouse gas emissions. The issues are more acute at high latitudes where measurements are scarce and the magnitude and distribution of carbon sinks and sources are poorly known.

Japan’s GOSAT mission and NASA’s planned OCO-2 mission are both targeting global column CO2 (as well as CH4 for GOSAT). The Total Carbon Column Observing Network (TCCON), established in 2004, is proving vital to ensuring the precision and accuracy of satellite observations from GOSAT and future missions, since it is the only accepted method of directly linking the satellite column observations to in situ greenhouse gas (GHG) data and WMO standards. It consists of a global network (currently 20 sites) of rigorously calibrated Bruker 125HR Fourier transform infrared (FTIR) spectrometers. Using in situ profiles of CO2 and CH4, the absolute calibration of TCCON is tied to the surface networks (Wunch et al., 2010), while the column measurements can be directly compared to satellite data. In June 2010, PEARL was confirmed as a new TCCON station, the northernmost in the network and the only one in Canada. Since then, PEARL data have been used in validation of the v2.8 Atmospheric CO2 Observations from Space GOSAT retrievals (Wunch et al., 2011), the first estimate of the global distribution of CO2 surface fluxes using data from 14 TCCON stations (Chevallier et al., 2011), and evaluation of greenhouse gas distributions in a chemistry-transport model based on an atmospheric general circulation model (Saito et al., 2012).