[1] This paper documents a global Bayesian variational inversion of CO 2 surface fluxes during the period . Weekly fluxes are estimated on a 3.75°× 2.5°(longitudelatitude) grid throughout the 21 years. The assimilated observations include 128 station records from three large data sets of surface CO 2 mixing ratio measurements. A Monte Carlo approach rigorously quantifies the theoretical uncertainty of the inverted fluxes at various space and time scales, which is particularly important for proper interpretation of the inverted fluxes. Fluxes are evaluated indirectly against two independent CO 2 vertical profile data sets constructed from aircraft measurements in the boundary layer and in the free troposphere. The skill of the inversion is evaluated by the improvement brought over a simple benchmark flux estimation based on the observed atmospheric growth rate. Our error analysis indicates that the carbon budget from the inversion should be more accurate than the a priori carbon budget by 20% to 60% for terrestrial fluxes aggregated at the scale of subcontinental regions in the Northern Hemisphere and over a year, but the inversion cannot clearly distinguish between the regional carbon budgets within a continent. On the basis of the independent observations, the inversion is seen to improve the fluxes compared to the benchmark: the atmospheric simulation of CO 2 with the Bayesian inversion method is better by about 1 ppm than the benchmark in the free troposphere, despite possible systematic transport errors. The inversion achieves this improvement by changing the regional fluxes over land at the seasonal and at the interannual time scales. Citation: Chevallier, F., et al. (2010), CO 2 surface fluxes at grid point scale estimated from a global 21 year reanalysis of atmospheric measurements,

We present an estimate of net ecosystem exchange (NEE) of CO₂ in Europe for the years 2001 through 2007. It is derived with a data assimilation that uses a large set of atmospheric CO₂ mole fraction observations (<70 000) to guide relatively simple descriptions of terrestrial and oceanic net exchange, while fossil fuel and fire emissions are prescribed. Weekly terrestrial sources and sinks are optimized (i.e., a flux inversion) for a set of 18 large ecosystems across Europe in which prescribed climate, weather, and surface characteristics introduce finer scale gradients. We find that the terrestrial biosphere in Europe absorbed a net average of 2212165 TgC yr22121 over the period considered. This uptake is predominantly in non-EU countries, and is found in the northern coniferous (221294 TgC/yr) and mixed forests (221230 TgC yr22121) as well as the forest/field complexes of eastern Europe (221285 TgC yr22121). An optimistic uncertainty estimate derived using three biosphere models suggests the uptake to be in a range of 2212122 to 2212258 TgC yr22121, while a more conservative estimate derived from the a-posteriori covariance estimates is 2212165±437 TgC yr22121. Note however that uncertainties are hard to estimate given the nature of the system and are likely to be significantly larger than this. Interannual variability in NEE includes a reduction in uptake due to the 2003 drought followed by three years of more than average uptake. The largest anomaly of NEE occurred in 2005 concurrent with increased seasonal cycles of observed CO₂. We speculate these changes to result from the strong negative phase of the North Atlantic Oscillation in 2005 that lead to favorable summer growth conditions, and altered horizontal and vertical mixing in the atmosphere. All our results are available through http://www.carbontracker.e

Evidence indicates that the densely cultivated region of northeastern China acts as a source for the wind-borne agent of Kawasaki disease (KD). KD is an acute, coronary artery vasculitis of young children, and still a medical mystery after more than 40 y. We used residence times from simulations with the flexible particle dispersion model to pinpoint the source region for KD. Simulations were generated from locations spanning Japan from days with either high or low KD incidence. The postepidemic interval and the extreme epidemics (1979, 1982, and 1986) pointed to the same source region. Results suggest a very short incubation period (<24 h) from exposure, thus making an infectious agent unlikely. Sampling campaigns over Japan during the KD season detected major differences in the microbiota of the tropospheric aerosols compared with ground aerosols, with the unexpected finding of the Candida species as the dominant fungus from aloft samples (54% of all fungal strains). These results, consistent with the Candida animal model for KD, provide support for the concept and feasibility of a windborne pathogen. A fungal toxin could be pursued as a possible etiologic agent of KD, consistent with an agricultural source, a short incubation time and synchronized outbreaks. Our study suggests that the causative agent of KD is a preformed toxin or environmental agent rather than an organism requiring replication. We propose a new paradigm whereby an idiosyncratic immune response, influenced by host genetics triggered by an environmental exposure carried on winds, results in the clinical syndrome known as acute KD.northeastern China source | agriculture | heart disease | FLEXPART | cereal croplands

Most lakes and reservoirs have surface CO 2 concentrations that are supersaturated relative to the atmosphere 1 . The resulting CO 2 emissions from lakes represent a substantial contribution to the continental carbon balance 2-4 . Thus, the drivers of CO 2 supersaturation in lakes need to be understood to constrain the sensitivity of the land carbon cycle to external perturbations 4-6 . Carbon dioxide supersaturation has generally been attributed to the accumulation of inorganic carbon in lakes where respiration exceeds photosynthesis 7,8 , but this interpretation has faced challenges 9-11 . Here we report analyses of water chemistry data from a survey of Spanish reservoirs that represent a range of lithologies, using simple metabolic models. We find that, above an alkalinity threshold of 1 mequiv. l −1 , CO 2 supersaturation in lakes is directly related to carbonate weathering in the watershed. We then evaluate the global distribution of alkalinity in lakes and find that 57% of the surface area occupied by lakes and reservoirs-particularly in tropical and temperate latitudes-has alkalinity exceeding 1 mequiv. l −1 . We conclude that lake inputs of dissolved inorganic carbon from carbonate weathering should be considered for the CO 2 supersaturation of lakes at both regional and global scales.There are two main mechanisms leading to CO 2 supersaturation in lakes and reservoirs: in situ net ecosystem production (NEP) imbalanced towards net heterotrophy 7 (that is, respiration exceeding photosynthesis); and inputs of groundwater or surface water with high dissolved inorganic carbon (DIC) content coming from both weathering of minerals and soil respiration in the watershed 10-14 . Among these, NEP is usually considered to be the main factor driving CO 2 supersaturation in lakes 7,8 . However, most studies relating CO 2 supersaturation to NEP have focused on relatively dilute, low-alkalinity lakes, despite the fact that CO 2 concentration in water is strongly modulated by the carbonate equilibrium (that is, the chemical reactions relating the different forms of DIC). Therefore, we lack conclusive evidence of the impact of NEP on CO 2 supersaturation in a range of systems showing contrasting DIC content.To test how DIC content can drive CO 2 supersaturation and modulate the relationship between NEP and CO 2 concentration, we use data from a nationwide study 15 including 202 measurements of dissolved oxygen (DO), DIC, alkalinity and CO 2 concentration in the surface layer of a set of Spanish reservoirs covering a wide range of DIC content and trophic states (Supplementary Table 1 and Data). We use the observed DO disequilibrium relative to the atmosphere as a surrogate for surface lake NEP, and investigate its impact on observed DIC and CO 2 concentrations considering three metabolic models. The models combine assumptions concerning the DIC loading from the watershed and the effect of lake NEP (Fig. 1a). All three models assume that the DIC generated during weathering of minerals in the watershed (DIC W ) dominates DIC...