[Data processing and QA/QC of atmosphere CO2 and CH4 concentrations by a method of GC-FID in-situ measurement at Waliguan station].

To strengthen scientific management and sharing of greenhouse gas data obtained from atmospheric background stations in China, it is important to ensure the standardization of observations and establish the data treatment and quality control procedure so as to maintain consistency in atmospheric carbon dioxide (CO2) and methane (CH4) measurements from different background stations. An automated gas chromatographic system (Hewlett Packard 5890GC employing flame ionization detection) for in situ measurements of atmospheric CO2 and CH4 has been developed since 1994 at the China Global Atmosphere Watch Baseline Observatory at Mt. Waliguan, in Qinhai. In this study, processing and quality control flow of CO2 and CH4 data acquired by HP ChemStation are discussed in detail, including raw data acquisition, data merge, time series inspection, operator flag, principal investigator flag, and the comparison of the GC measurement with the flask method. Atmosphere CO2 and CH4 mixing ratios were separated as background and non-background data using a robust local regression method, approximately 72% and 44% observed values had been filtered as background data for CO2 and CH4, respectively. Comparison of the CO1 and CH, in situ data to the flask sampling data were in good agreement, the relative deviations are within +/- 0.5% for CO2 and for CH4. The data has been assimilated into global database (Globalview-CO2, Globalview-CH4), submitted to the World Data Centre for Greenhouse Gases (WDCGG), and applied to World Meteorological Organization (WMO) Greenhouse Gas Bulletin and assessment reports of the United Nations Intergovernmental Panel on Climate Change (IPCC).

An atmospheric perspective on North American carbon dioxide exchange: CarbonTracker.

We present an estimate of net CO(2) exchange between the terrestrial biosphere and the atmosphere across North America for every week in the period 2000 through 2005. This estimate is derived from a set of 28,000 CO(2) mole fraction observations in the global atmosphere that are fed into a state-of-the-art data assimilation system for CO(2) called CarbonTracker. By design, the surface fluxes produced in CarbonTracker are consistent with the recent history of CO(2) in the atmosphere and provide constraints on the net carbon flux independent from national inventories derived from accounting efforts. We find the North American terrestrial biosphere to have absorbed -0.65 PgC/yr (1 petagram = 10(15) g; negative signs are used for carbon sinks) averaged over the period studied, partly offsetting the estimated 1.85 PgC/yr release by fossil fuel burning and cement manufacturing. Uncertainty on this estimate is derived from a set of sensitivity experiments and places the sink within a range of -0.4 to -1.0 PgC/yr. The estimated sink is located mainly in the deciduous forests along the East Coast (32%) and the boreal coniferous forests (22%). Terrestrial uptake fell to -0.32 PgC/yr during the large-scale drought of 2002, suggesting sensitivity of the contemporary carbon sinks to climate extremes. CarbonTracker results are in excellent agreement with a wide collection of carbon inventories that form the basis of the first North American State of the Carbon Cycle Report (SOCCR), to be released in 2007. All CarbonTracker results are freely available at http://carbontracker.noaa.gov.

Contributions to accelerating atmospheric CO2 growth from economic activity, carbon intensity, and efficiency of natural sinks.

The growth rate of atmospheric carbon dioxide (CO(2)), the largest human contributor to human-induced climate change, is increasing rapidly. Three processes contribute to this rapid increase. Two of these processes concern emissions. Recent growth of the world economy combined with an increase in its carbon intensity have led to rapid growth in fossil fuel CO(2) emissions since 2000: comparing the 1990s with 2000-2006, the emissions growth rate increased from 1.3% to 3.3% y(-1). The third process is indicated by increasing evidence (P = 0.89) for a long-term (50-year) increase in the airborne fraction (AF) of CO(2) emissions, implying a decline in the efficiency of CO(2) sinks on land and oceans in absorbing anthropogenic emissions. Since 2000, the contributions of these three factors to the increase in the atmospheric CO(2) growth rate have been approximately 65 +/- 16% from increasing global economic activity, 17 +/- 6% from the increasing carbon intensity of the global economy, and 18 +/- 15% from the increase in AF. An increasing AF is consistent with results of climate-carbon cycle models, but the magnitude of the observed signal appears larger than that estimated by models. All of these changes characterize a carbon cycle that is generating stronger-than-expected and sooner-than-expected climate forcing.

Saturation of the southern ocean CO2 sink due to recent climate change.

Based on observed atmospheric carbon dioxide (CO2) concentration and an inverse method, we estimate that the Southern Ocean sink of CO2 has weakened between 1981 and 2004 by 0.08 petagrams of carbon per year per decade relative to the trend expected from the large increase in atmospheric CO2. We attribute this weakening to the observed increase in Southern Ocean winds resulting from human activities, which is projected to continue in the future. Consequences include a reduction of the efficiency of the Southern Ocean sink of CO2 in the short term (about 25 years) and possibly a higher level of stabilization of atmospheric CO2 on a multicentury time scale.