Abstract: Measurements of midday vertical atmospheric CO2 distributions reveal annual-mean vertical CO2 gradients that are inconsistent with atmospheric models that estimate a large transfer of terrestrial carbon from tropical to northern latitudes. The three models that most closely reproduce the observed annual-mean vertical CO2 gradients estimate weaker northern uptake of -1.5 petagrams of carbon per year (Pg C year-1) and weaker tropical emission of +0.1 Pg C year-1 compared with previous consensus estimates of -2.4 and +1.8 Pg C year-1, respectively. This suggests that northern terrestrial uptake of industrial CO2 emissions plays a smaller role than previously thought and that, after subtracting land-use emissions, tropical ecosystems may currently be strong sinks for CO2.

Abstract: The last two abrupt warmings at the onset of our present warm interglacial period, interrupted by the Younger Dryas cooling event, were investigated at high temporal resolution from the North Greenland Ice Core Project ice core. The deuterium excess, a proxy of Greenland precipitation moisture source, switched mode within 1 to 3 years over these transitions and initiated a more gradual change (over 50 years) of the Greenland air temperature, as recorded by stable water isotopes. The onsets of both abrupt Greenland warmings were slightly preceded by decreasing Greenland dust deposition, reflecting the wetting of Asian deserts. A northern shift of the Intertropical Convergence Zone could be the trigger of these abrupt shifts of Northern Hemisphere atmospheric circulation, resulting in changes of 2 to 4 kelvin in Greenland moisture source temperature from one year to the next.

Abstract: In most linear imaging problems, where the model to be sought is expanded in a set of basis functions, it is common practice to truncate the set at a certain (arbitrary) level. The solution then depends on the chosen parameterization, and neglected basis functions may leak into the solution to produce artifacts in the retrieved model. An unbiased estimate of the coefficients of the true model may be obtained in the chosen finite basis set ; here, a method to suppress leakage is illustrated on an example of global seismic tomography.

Abstract: We present a 650-year Antarctic ice core record of concentration and isotopic ratios ((13)C and (18)O) of atmospheric carbon monoxide. Concentrations decreased by ~25% (14 ppbv) from mid-1300s to the 1600s, then recovered completely by the late 1800s. (13)C and (18)O decreased by about 2 and 4 respectively from mid-1300s to the 1600s, then increase by about 2.5 and 4 by the late 1800s. These observations and isotope mass balance model results imply that large variations in the degree of biomass burning in the Southern Hemisphere occurred during the last 650 years, with a decrease by about 50% in the 1600s, an increase of about 100% by the late 1800s, and another decrease by about 70% from the late 1800s to present day.

Abstract: Westerly winds in the Southern Ocean have increased in intensity and moved poleward. Using long-term demographic and foraging records, we show that foraging range in wandering albatrosses has shifted poleward in conjunction with these changes in wind pattern, while their rates of travel and flight speeds have increased. Consequently, the duration of foraging trips has decreased, breeding success has improved, and birds have increased in mass by more than 1 kilogram. These positive consequences of climate change may be temporary if patterns of wind in the southern westerlies follow predicted climate change scenarios. This study stresses the importance of foraging performance as the key link between environmental changes and population processes.