This presentation describes in-situ atmospheric CO₂ measurements at Waliguan Observatory (WLG, 36°17'N, 100°54'E, 3816m asl) since 1994, together with 5-day isobaric back trajectory analysis.  We also use the Hybrid Single-Particle Lagrangian Integrated Trajectory (Hysplit-4) transport/diffusion model to simulate the CO₂ variation at WLG in January 1999 and compared with observations. A case study for polluted air mass transport event with a short-term elevated CO₂ has been conducted to further investigate the impact of source, sink and long-range transport of atmospheric CO₂.

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.

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].

Four CARIOCA Lagrangian buoys drifted in the North-East Atlantic Ocean between 38° and 45°N between February and August 2001. Daily cycles of pCO₂, SST and DIC are observed even in winter. Biological rates of carbon consumption, gross and net primary production,are determined in situ from the amplitude of the diel cycles and the time evolution of surface dissolved inorganic carbon. Over the 6 months period, February-August, the ocean in the studied area is a sink for atmospheric CO_2.The mean absorbed flux is equal to 3.8 mmoles/ m²/ day.

The results of atmospheric CO₂, CH₄ and CO measurements are presented. The measurements were made in air samples collected at heights of 4, 25, 100, 200 and 300 m above ground, and in the atmospheric column in Obninsk, Russia (55.11 N, 36.57  E, 183 m asl).

We carried out airborne campaigns over Europe in order to analyze atmospheric CO₂ variability at the regional scale. Data reveal a higher standard variation in the planetary boundary layer (PBL) against a lower one in the free troposphere (FT), where the air is more well mixed. Ground data generally agree well with airborne measurements when done in the FT, but not in the PBL where they are exposed to local disturbances. Ground stations located in the FT are shown to be representative of a regional scale while PBL observatories provide only locally representative measurements.

We present a new version of the global atmospheric tracer transport model driven by analyzed meteorology with diurnally varying mixing in the boundary layer capable of running globally at resolutions up to quarter degree longitude-latitude or higher. The impact of the higher resolution model can be visible in resolving city plumes, airmass boundaries, diurnal cycle, fronts and synoptic scale events often observed in continuous CO₂ monitoring site data.

In the CHIOTTO project (http://www.chiotto.org) as part of the CarboEurope cluster of projects (http://www.carboeurope.org) a network of 8 tall tower stations has been set up in Europe. Most towers are equipped for continuous high precision measurements of ambient CO₂, CH₄, CO and SF₆. Some stations are also equipped for continuous measurement of ²²²Rn and flask sampling. First measurement results are presented and evaluated using forward and inverse model calculations.

Systematic observations of the atmospheric CO₂ concentration, and carbon and oxygen isotope ratios of CO₂ (d¹³C and d¹⁸O) have been maintained at Japanese Arctic Observatory in Ny Ålesund (79°N, 12°E) and Antarctic station, Syowa (69°S, 40°E). The interannual variations of the CO₂ concentration and d¹³C in association with the occurrence of ENSO event were clearly observed at the both sites. The d¹⁸O values observed at Syowa Station showed significant increasing trend after 1999.

To examine concentration variations of atmospheric CO₂ in the sub-tropical region of East Asia, systematic air sampling with subsequent laboratory analysis has been made in the southernmost part of Japan since June 1993. A time series of measured CO₂ concentrations was analyzed for long-term trend, seasonal cycle and interannual variability, and the temporal CO₂ variations deduced were interpreted in terms of atmospheric transport and CO₂ flux regions.