The Greenhouse Effect is a natural phenomenon that warms up the earth. It works on the same principles as the ordinary garden glasshouse, which allows the light to get in, but does not allow the heat to get out. The earth is surrounded by a shield of atmospheric gases primarily nitrogen (78 %), and oxygen (21%). The remainder of the air composition is made up of what are called as “trace gases,” which include carbon dioxide (CO₂), methane (CH₄) etc. The earth maintains its temperature through insulation with a 'thermal blanket' of greenhouse gases which allow penetration of the sun's rays but prevent some heat radiating back into space. Light from the sun penetrates the atmosphere and reaches the earth surface, warming it up.

Atmospheric observations obtained during intensive field experiments are used to characterize regional sources and test data assimilation techniques. In this study, the STEM-2K1 (Sulfur Transport Eulerian Model, version 2K1) and its adjoint model are applied to the analysis of observations from aircraft platforms made during the summer 2004 ICARTT (International Consortium for Atmospheric Research on Transport) experiment. Observed ratios between CO₂ and tracers and model derived airmass markers are used to identify emission signatures, indicating the influence of different sources. Model derived influence functions along with assimilated transport model results of anthropogenic tracers are used to characterize the anthropogenic CO₂ emissions in the Midwest during the summer 2004 period. This analysis gives an initial look at the Midwest domain which is the focus of the expansion of NOAA Climate Monitoring and Diagnostic Laboratory’s tall tower observation network and the upcoming Mid-Continent NACP Intensive Campaign.

Results of airborne CO₂ and CO observations from the NSF/NCAR C-130 platform during the Gulf of Tehuantepec Experiment (GOTEX 2004) and the Airborne component of the Carbon in the Mountains Experiment (ACME 2004) will be presented. A modified commercial vacuum ultraviolet fluorescence instrument monitored CO mixing ratios. CO measurements were used to help identify air masses recently influenced by combustion emissions. CO₂ mixing ratios were measured using a pressure- and temperature-controlled LI-COR 6252 analyzer.  Control of time response allowed operation of the CO₂ instrument in two modes for application to either low altitude eddy covariance or higher altitude mixing ratio measurements. Performance will be assessed, including accuracy estimates derived from intercomparison activities.

We present a synthesis Bayesian inverse method to optimize one year of daily fluxes at model resolution (50x50 km over Europe) by inversion of continuous CO₂ measurements, daily averaged over Europe (10 sites). Based on a synthetic data analysis, we studied the impact of three different spatial and temporal correlations on flux errors. We found that the present network is too sparse to efficiently constrain European fluxes at model resolution even with the assumption of perfect transport. However, the agreement between the optimized fluxes and the true fluxes is improved when aggregated in space and time, mainly for 8-10 days fluxes over Western Europe. This region is indeed surrounded by our network. The spatial correlation scheme used was found to have a negligible impact on this agreement. Adding a white noise on pseudo-data to simulate transport model errors largely degrades the agreement. Using real data, European flux variations becomes unreasonably large due to the inability of our transport model to properly represent the CO₂ concentrations at continental sites.

The synoptic scale atmosphere-biosphere interaction can cause anomalies of ~10 ppm with length scale of ~1000 km in the monthly averaged surface CO₂ concentration. These anomalies may contribute to the errors and uncertainties of CO₂ inversion estimates.

Biomass burning is an important source of atmospheric CO₂, aerosols and chemically important gases. It is as important to global chemistry as industrial activities in the developed world [Crutzen and Andreae, 1990]. Biomass burning is a key component of the global carbon budget, currently releasing 2.6 GtC from fires in the tropical and subtropical ecosystems (van der Werf et al. [2003], to be compared to the 5.6 GtC released from fossil fuels) to the atmosphere each year, most of it being emitted in the form of carbon dioxide, although there is important spread amongst various estimates. Biomass burning contributes up to 40% of gross atmospheric CO₂ (IPCC, 2001), 38% of tropospheric O₃, and 10 % of CH₄.

In order to further our understanding of the biophysical and biogeochemical mechanisms that control the fate of fossil fuel carbon emissions, we are simulating an hourly global atmospheric carbon dioxide concentration field ([CO₂]) for the year 2000 with realistic diurnal, synoptic and seasonal variability, including quantified errors.  In addition, we are simulating carbonyl sulfide (COS) for a continental mixed temperate forest to test a hypothesis that errors in seasonal simulations of CO₂ result from incorrect specification of springtime onset of photosynthesis rather than incorrect timing of ecosystem respiration.

Satellite measurements of total column CO₂ can be used in inverse models to help isolate sources and sinks; however, using satellite concentrations in inversions may introduce spatial, temporal, and clear-sky errors. Using a coupled ecosystem-atmosphere model, we found that using satellite measurements to represent temporal averages will introduce large errors into the inversion and that inverse models must sample the concentrations at the same time as they are measured.  Spatial and local clear-sky errors are much smaller than the instrumental errors, although they increase with domain heterogeneity. Inverse models can minimize sampling errors by using homogenous regions and sampling the CO₂ concentrations at the same time as the satellite.

For the purpose of exploiting upcoming measurements of atmospheric CO₂ vertical profiles by aircrafts and continuous CO₂ data recorded along tall towers as part of the North American Carbon Plan (NACP), a direct carbon budgeting approach is being developed.