Friday, June 03, 2011

Variable Land Carbon Sink

b, CO2 emissions from fossil fuel combustion and cement production, and from LUC. c, Land CO2 sink (negative values correspond to land uptake). d, Ocean CO2 sink (negative values correspond to ocean uptake).
Le Quéré C, Raupach MR, Canadell JG, Marland G, others. Trends in the sources and sinks of carbon dioxide. Nature Geoscience. 2009;2(12):831–836.

"An increasing total airborne fraction implies that total sinks are increasing more slowly than total emissions, so that sinks are not keeping pace with emissions.

The CO2 growth rate also varies strongly at interannual (1 to 10 y) time scales, through mainly biophysical mechanisms. Fluctuations in CO2 growth rate correlate with the El-Nino-Southern-Oscillation (ENSO) climate mode (Keeling and Revelle, 1985; Keeling et al., 1995; Jones and Cox, 2005), because the terrestrial carbon balance in tropical regions is tilted from uptake to release of CO2 during dry, warm El-Ni ˜ no events (Zeng et al., 2005; Knorr et al., 2005).

Volcanic events are also significant: the CO2 growth rate decreased for several years after the eruption of Mt. Pinatubo in June 1991 (Jones et al., 2001), probably because of increased net carbon uptake by terrestrial ecosystems due to higher diffuse solar radiation (Gu et al., 2003) and cooler temperatures (Jones and Cox, 2001) caused by volcanic aerosols."
1. Raupach MR, Canadell JG, Le Quéré C. Anthropogenic and biophysical contributions to increasing atmospheric CO2 growth rate and airborne fraction. Biogeosciences. 2008;5(6):1601–1613.

Carbon Tracker

Fig. 1. A demonstration of how carbon flux indices [GSNF, growing season net flux; DSNF, dormant season net flux; AMP, amplitude (|DSNF – GSNF|); NCF, net carbon flux (GSNF + DSNF)] are calculated. Any month for which the net carbon flux is negative is included in the GSNF (open vertical bars). Any month for which the net carbon flux is positive is included in the DSNF (filled vertical bars). Mean 2000–2008 fluxes shown for boreal North America (a) southern Africa (b) and tropical Asia (c).
GURNEY KR, ECKELS WJ. Regional trends in terrestrial carbon exchange and their seasonal signatures. Tellus B.

Fig. 2. Comparison of decadal mean net carbon flux for individual land regions. Black cross symbols (X) denote the mean of 13 TransCom 3 models, open circle symbols (O) denote mean of the three S07 TransCom 3 models, individual model estimates within the S07 average are denoted by a filled square, circle and triangle. Vertical error bars represent the total 1σ flux uncertainty (quadrature sum of model spread and the root mean square of individual model posterior uncertainty) associated with the mean of the 13 TransCom 3 models. (c) 2000–2008 mean net carbon flux.