The mixing ratios of atmospheric CO₂ were observed at the summit of Mt. Fuji by using a system for continuous measurements during September 2002-February 2003 and May 2003-May 2004. The observed CO₂ variations at Mt. Fuji showed a seasonal cycle of the background level with a maximum around April and a minimum around August. A lot of episodic events with a large enhancement of CO₂ were found, and the episodic enhancements of CO₂ at Mt. Fuji were well associated with increased CO peaks observed at the same time. The enhancement ratios of CO to CO₂ mixing ratios (ΔCO/ΔCO₂) mainly showed lower values of less than 0.03 due to urban/industrial sources, while relatively higher ΔCO/ΔCO₂ ratios up to 0.08 were also found for the episodic events due to the biomass burning emissions. Three-dimensional transport model simulations of CO suggested that the major contributions for the increased events at Mt. Fuji were from China (~50%) and the other major regions were Southeast Asia and South Asia (~10%).

Future climate warming is expected to enhance plant growth in temperate ecosystems and to increase carbon sequestration. But although severe regional heatwaves may become more frequent in a changing climate, and their impact on terrestrial carbon cycling is unclear. Europe experienced a particularly extreme climate anomaly during 2003, with July temperatures up to 6°C above long-term means, and annual precipitation deficits up to 300 mmy^-1, that is 50% below the average. We used the 2003 heatwave as a ‘laboratory assistant’ to estimate the impact on terrestrial carbon cycling.

In a Carbon Cycle Data Assimilation System (CCDAS) one infers the values of the parameters controlling the function of a process model using various observations. One can then calculate quantities of interest from the optimized parameters and the model. One can also calculate the uncertainties on the parameters and propagate these to uncertainties of the calculated quantities. In Rayner et al. [2005] we assimilated atmospheric observations over two decades, into a terrestrial model and calculated fluxes over this period. Here we extend this work by calculating the response of the calibrated terrestrial biosphere to a GCM simulation of future climate. Using this combination we are able to comment on the fate of terrestrial carbon pools and fluxes under climate change, calculate the uncertainties of the response, and determine which parameters in the model are responsible for this uncertainty. We include an extra parameter that scales the climate change signal from the GCM projection. We thus extend the sensitivity and uncertainty analysis to include the climate sensitivity.

Ice cores are unique archives of past climatic and atmospheric conditions through the isotopic composition of the ice and the analysis of the air bubbles trapped. In 1999 Petit et al published the reconstruction of the Antarctic climate and atmospheric composition over the last 420 000 years from the Vostok ice core. This record covered the last four glacial inter glacial cycles back to the end of the marine interstadial 11 (MIS 11). It has revealed the close relationship between the atmospheric part of the carbon cycle and the climate. With CO₂ concentration oscillating between 180 and 280 ppmv during the last 4 climatic cycles. In a similar way the methane concentration followed closely temperature on glacial interglacial time scales, with millennial-scale structures during glacial times which appear out of phased with Antarctic temperature but, at least for the last glaciation, in phase with the Greenland rapid climatic oscillations, as revealed by the GISP and GRIP ice cores.

Measurements of the isotopic composition of carbon dioxide were performed on EPICA Dome C ice on 76 different depth levels covering the last 40’000 years. The time resolution is in the order of 500 years for the last 18’000 years. For each depth level at least two determinations were obtained. The d¹³C signals show different trends during the last 18000 years that are anti-parallel to the CO₂ concentration evolution as measured on the same ice core. However millennial scale deviations from these trends are observed for at least three time periods. The robustness and significance of these deviations are investigated by Monte Carlo simulations performed with different subsets of the measurements. The decreases of carbon isotopes could be connected with observed step-like increases of the CO₂ concentration. Furthermore, a similar evolution as for stable carbon isotopes is visible for detrended radiocarbon. We will discuss potential mechanisms responsible for the trends as well as for the millennial scale deviations in carbon-13, including changes in the thermohaline circulation as well as potential influences of a changing ¹⁷O-¹⁸O relationship.

The Amazon region represents a large stock of biomass as well as a potentially important sink for additional atmospheric CO₂. Climate change, land-use changes and their interaction present a risk to this role in the global carbon cycle. Both positive and negative feedbacks exist in the system that can lead to resilience but also to accelerated break-down of the carbon stocks and sinks. A set of linked projects will investigate elements of these processes in the coming years.

In this study we evaluate the individual and combined impacts of CO₂, climate and Ozone on future terrestrial carbon storage using the computationally efficient GCM analogue model coupled to the MOSES/TRIFFID land surface carbon cycle model. Ozone is modelled to have a significant detrimental effect on future plant productivity and hence terrestrial carbon storage, opposing the enhanced production and terrestrial carbon storage associated with elevated atmospheric CO₂ concentrations.

The Southern Annular Mode (SAM) is the leading mode of intraseasonal to interannual variability over the entire Southern Hemisphere, yet the impact of the SAM on the Southern Ocean carbon cycle is largely unknown. We investigate the impact of the SAM on surface wind, sea surface temperature (SST), chlorophyll concentration, and sea ice concentration on the basis of 8-day averaged satellite observations.  We find that Southern Ocean circulation and biogeochemistry react quite sensitively to this mode of variability, potentially resulting in air-sea CO₂ flux anomalies. Since variations in atmospheric CO₂ congruent with the SAM are small, we hypothesize that the SAM produces anomalous air-sea fluxes of both natural and anthropogenic CO₂, which act to compensate each other. 

Despite their relative small extension, wetlands are important as sources or sinks of C. But, due to their intermediate position between land and permanent water, they have been modified in the name of “health” or “productivity.” Such changes have altered substantially their ability to store/produce C greenhouse gasses but the main point is to establish until which point this changes are “structural” (implying the intrinsic environmental mechanisms), and therefore unrecoverable, or “casual” (implying not the environment processes but its “external”–not directly implied in the C storage/emission- components), and consequently recoverable. Temperate wetlands are strongly dependant on water availability due to their position but, on the other hand, use to be occupied by resistant species able to survive hard conditions. The example shown below presents a case of intense human activity on a Mediterranean wetland that has caused very intense changes in the flooded area but not so evident and perdurable in the main ecological relations implied in the C cycle.