A new research project has started in 2003 to develop Continuous CO₂ Measurement Equipment (CME) and Automatic Air Sampling Equipment (ASE) for commercial airlines. CMEs are planning to be installed on five aircrafts and fly to South East Asia, East Asia, Europe, North America, Pacific and Australia. Routine air sampling by ASE will be done twice a month between Japan and Australia. After issuing the certification, first observation flight by Boeing 747-400 will be conducted in October, 2005. Preliminary observation by small research aircraft indicates that CME produces reasonable results.

There is growing evidence that the rate of anthropogenic CO₂ uptake in the ocean is changing over time. Several programs are poised to assess current and future ocean CO₂ uptake rates, but there are issues with how to extrapolate these measurements to decadal-scale changes over entire ocean basins. One possibility is to exploit the growing network of ARGO floats that are collecting profiles throughout the global oceans. We explore the viability of this approach and make recommendations for how the ARGO network might be made more useful for biogeochemical applications.

We present an analysis of terrestrial net CO₂ fluxes from North America for the period 2000-2004. These fluxes consist of hourly maps at ~70km×100km resolution that are consistent with observed atmospheric CO₂ mixing ratios, as well as with varying climatic conditions across different ecosystems as observed from space. The flux maps are created in a newly developed ensemble data assimilation system that consists of the atmospheric Transport Model v5 (TM5), the Vegetation Photosynthesis Respiration Model (VPRM), and an efficient Bayesian least-squares algorithm to optimize the fluxes from different biomes in VPRM against CO₂ mixing ratios from the NOAA-CMDL observing network. The stochastic nature of the ensemble data assimilation system allows us to consistently include uncertainty on net CO₂ fluxes from the neighboring oceans and more distant continents in the flux estimates for North America.

Atmospheric CO₂ concentrations have been obtained from the Atmospheric Infrared Sounder (AIRS) radiance data within the European Centre for Medium-Range Weather Forecasts (ECMWF) data assimilation system. In a first explorative configuration, a subset of channels from the AIRS instrument has been assimilated providing estimates of tropospheric column-averaged CO₂ mixing ratios representative of a layer between the tropopause and about 700 hPa at observation locations only. Results show considerable geographical and temporal variability with values ranging between 370 and 382 ppmv. The 5-day mean estimated random error is about 1%, which is confirmed by comparisons with flask observations on board flights of Japanese airliners in the west-Pacific region. This study demonstrates the feasibility of global CO₂ estimation using high spectral resolution infrared satellite data in a numerical weather prediction data assimilation system. Currently, the system is being improved to treat CO₂ as a full three-dimensional atmospheric variable included in the forecast model. This allows more flexibility in the constraints on the CO₂ estimation as well as the possibility of assimilating other data sources (e.g., near-infrared satellite data and flasks). The CO₂ fields provided by the data assimilation system have great potential to assist the surface flask network in constraining current top-down carbon flux estimates.

Measurements of atmospheric CO₂ began in 1957-1958 at a wide range of locations, including at fixed stations, on ice floes, on oceanic expeditions, and on aircraft flights, with logistical and financial support provided by the International Geophysical Year (IGY) program. Although the measurement effort was reduced in scope immediately following the IGY, today, measurements are made at more than 100 locations.  Over this same time interval, emissions of CO₂ from fossil fuel combustion increased from 2.3 thousand million metric tons per year (GtC/yr) in 1958 to 7.1 GtC/yr in 2003 [Marland et al., 2005, and personal communication].  More than 90% of this CO₂ was released into the northern hemisphere where it lingered before mixing fully world-wide.  The atmospheric CO₂ concentration, in response, rose faster in the northern hemisphere than in the southern, the interhemispheric difference increasing from near zero during the IGY to about 3 parts per million (ppm) in 2003. For all northern hemisphere stations where our program has measured CO₂, the gradient changes relative to the South Pole are generally proportional to the rate of fossil fuel CO₂ emissions, disregarding seasonal and short term interannual variability in the CO₂ data.  Here, we use this fact to diagnose how the carbon cycle has evolved over the past half century.

A discrepancy exists between current estimates of the Southern Ocean air-sea flux of CO₂.  The most recent estimate using a combination of direct and climatologically-derived pCO₂ measurements [Takahashi et al., 2002] (herein referred to as T02) suggests a Southern Ocean CO₂ sink that is nearly two times greater that that suggested from general circulation models, atmospheric inverse models [Gurney et al., 2002] and oceanic inverse models [Gloor et al., 2003]. Here we employ an independent method to estimate the Southern ocean air-sea flux of CO₂.  Our method exploits all available surface measurements for Dissolved Inorganic Carbon (DIC) and total alkalinity (ALK) from 1986 to 1996. We show that surface age-normalized DIC can be predicted to within ~8mmol/kg and ~10mmol/kg for ALK using standard hydrographic properties, independent of season.  The predictive equations are used in conjunction with World Ocean Atlas (2001) climatologies to estimate an annual cycle of DIC and ALK, while the pCO₂ distribution is calculated using standard carbonate chemistry.  For consistency we use the same gas transfer relationship and wind product from Takahashi et al, [2002] however, we include the effects of sea-ice. We estimate a Southern Ocean CO₂ sink (>40°S) of -0.19±0.26 Pg C for 1995. Our estimates are smaller than those estimated by Takahashi et al, [2002], but consistent with atmospheric / oceanic inverse methods, general circulation models and provides further evidence that the Southern Ocean CO₂ sink in relation to its oceanic surface area, is moderate on a global scale.

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.

We estimated the production of bomb radiocarbon using available information on atmospheric nuclear bomb tests, the simple (radio-)carbon cycle model GRACE (Global RadioCarbon Exploration Model) and atmospheric observations as constraints. Subsequent forward simulations of the bomb radiocarbon inventory in the different carbon reservoirs turned out to be in very good agreement with recent observation-based estimates, therewith for the very first time allowing to close the global bomb radiocarbon budget. Besides confirming original stratospheric bomb ¹⁴C data published in the reports of the Health and Safety Laboratories [Telegadas, 1971, and references therein], our results confirm recent observation-based ocean bomb radiocarbon inventory estimates for the time of GEOSECS (1970s) and WOCE (1990s) from Peacock [2004] and Key et al. [2004], but refute the GEOSECS ocean inventory estimates from Broecker et al. [1985, 1995].