We provide a fast and efficient method for calculating global annual mean carbon dioxide emissions from the combustion of fossil fuels by combining data from an established data set with BP annual statistics. Using this method it is possible to retrieve an updated estimate of global CO2 emissions six months after the actual emissions occurred. Using this data set we find that atmospheric carbon dioxide emissions have increased by over 40% from 1990 to 2008 with an annual average increase of 3.7% over the five-year period 2003–2007. In 2008 the growth rate in the fossil fuel carbon dioxide emissions was smaller than in the preceding five years, but it was still over 2%. Global mean carbon dioxide emissions in 2008 were 8.8 GtC yr−1. For the latter part of the last century emissions of carbon dioxide have been greater from oil than from coal. However during the last few years this situation has changed. The recent strong increase in fossil fuel CO2 emissions is mainly driven by an increase in emissions from coal, whereas emissions from oil and gas to a large degree follow the trend from the 1990s.

We examine ship‐based observations of atmospheric O2 and CO2 in the southern Pacific Ocean made during two voyages: in February 2003 and in April 2004. We found, for the Austral late summer to autumn, evidence of a maximum in Atmospheric Potential Oxygen (APO) (an atmospheric tracer that is conservative with respect to terrestrial biological activity, APO ≈ O2 + CO2) centered around 50°S owing to biologically driven O2 outgassing (associated with strong productivity in the Sub‐Tropical Convergence Zone) and evidence in the February voyage of a decreasing APO trend from 57°S south toward the Antarctic coast. The observed APO variability appears to be primarily determined by the interplay between atmospheric transport and the spatial distribution of O2 air‐sea flux resulting from regional differences in biological production. Comparisons of these observations with APO derived from coupling the TM3 atmospheric transport model with flux estimates from (1) the PISCES‐T ocean biogeochemistry model, and (2) O2 and CO2 climatologies, show that both PISCES‐T and the climatology reproduce the observed gradient and curvature of APO but underestimate the magnitude of the observed APO maximum in the mid southern latitudes. Although the temporal limitation of our data does not permit us to calculate the annual mean APO gradient, the results support previous model predictions of a decreasing APO trend from the mid to high southern latitudes.

The possible use of 14CO measurements to constrain hydroxyl radical (OH) concentrations in the atmosphere is investigated. 14CO is mainly produced in the upper atmosphere from cosmic radiation. Measurements of 14CO at the surface show lower concentrations compared to the upper atmospheric source region, which is the result of oxidation by OH. In this paper, the sensitivity of 14CO mixing ratio surface measurements to the 3-D OH distribution is assessed with the TM5 model. Simulated 14CO mixing ratios agree within a few molecules 14CO cm−3 (STP) with existing measurements at five locations worldwide. The simulated cosmogenic 14CO distribution appears mainly sensitive to the assumed upper atmospheric 14C source function, and to a lesser extend to model resolution. As a next step, the sensitivity of 14CO measurements to OH is calculated with the adjoint TM5 model. The results indicate that 14CO measurements taken in the tropics are sensitive to OH in a spatially confined region that varies strongly over time due to meteorological variability. Given measurements with an accuracy of 0.5 molecules 14CO cm−3 STP, a good characterization of the cosmogenic 14CO fraction, and assuming perfect transport modeling, a single 14CO measurement may constrain OH to 0.2–0.3×106 molecules OH cm−3 on time scales of 6 months and spatial scales of 70×70 degrees (latitude×longitude) between the surface and 500 hPa. The sensitivity of 14CO measurements to high latitude OH is about a factor of five higher. This is in contrast with methyl chloroform (MCF) measurements, which show the highest sensitivity to tropical OH, mainly due to the temperature dependent rate constant of the MCF–OH reaction. A logical next step will be the analysis of existing 14CO measurements in an inverse modeling framework. This paper presents the required mathematical framework for such an analysis.

Methane is arguably the most dynamic greenhouse gas in the atmosphere. With human population increase and industrialization, pCH4 is now about 250% higher than it was in the early 1800s, and it has shown a significantly larger percentages increase than that of carbon dioxide, the gas which is most often the focus of greenhouse gas mitigation and adaptation strategies. Surprisingly, in the past decade, pCH4 has stabilized at a global average of ∼1750 ppb. Human impacts on methane are also important. The methane emissions from rice cultivation, cattle farming, and biomass burning clearly impact the atmospheric methane budget today and may have been important long before the industrial era. The baseline against which early human impacts on methane so far, have been measured is pCH4 levels in the past obtained from air trapped in ice cores. The goal in this chapter is to use measurements of the stable carbon isotopes of methane (δ13CH4) to help in source partitioning and thereby enhance the understanding of the LPIH methane budget. Carbon isotopes of methane are useful because the sources can be loosely binned into categories with distinct δ13CH4 values. Due to the small amount of air trapped in ice core bubbles and typical sample size requirements for δ13CH4 analyses, such measurements from ice cores have been scarce to date. This chapter reviews 2000-year records of pCH4 and δ13CH4 at high temporal resolution and precision from the Law Dome ice cores in Antarctica. This record reveals that contrary to expectations, δ13CH4, unlike pCH4, was not slowly varying in the pre-industrial period, and that its value was significantly different from that expected from previous estimates. These isotope analyses not only reveal the presence of a heavier human hand on the methane cycle than previously thought but also that methane history has been linked significantly to human history over the last two millennia.

A method for achieving continuous high precision measurements of atmospheric O-2 is presented based on a commercially available fuel-cell instrument, (Sable Systems, Oxzilla FC-II) with a precision of 7 per meg (approximately equivalent to 1.2 ppm) for a 6-min measurement. The Oxzilla was deployed on two voyages in the Western Pacific sector of the Southern Ocean, in February 2003 and in April 2004, making these the second set of continuous O-2 measurements ever made from a ship. The results show significant temporal variation in O-2, in the order of +/- 10 per meg over 6-hourly time intervals, and substantial spatial variation. Data from both voyages show an O-2 maximum centred on 50 degrees S, which is most likely to be the result of biologically driven O-2 outgassing in the region of subtropical convergence around New Zealand, and a decreasing O-2 trend towards Antarctica. O-2 from the ship-based measurements is elevated compared with measurements from the Scripps Institution of Oceanography flask-sampling network, and the O-2 maximum is also not captured in the network observations. This preliminary study shows that ship-based continuous measurements are a valuable addition to current fixed site sampling programmes for the understanding of ocean-atmosphere O-2 exchange processes.

Contributing Authors: G. Bodeker (New Zealand), O. Boucher (UK, France), W.D. Collins (USA), T.J. Conway (USA), E. Dlugokencky (USA), J.W. Elkins (USA), D. Etheridge (Australia), P. Foukal (USA), P. Fraser (Australia), M. Geller (USA), F. Joos (Switzerland), C.D. Keeling (USA), R. Keeling (USA), S. Kinne (Germany), K. Lassey (New Zealand), U. Lohmann (Switzerland), A.C. Manning (UK, New Zealand), S. Montzka (USA), D. Oram (UK), K. O’Shaughnessy (New Zealand), S. Piper (USA), G.-K. Plattner (Switzerland), M. Ponater (Germany), N. Ramankutty (USA, India), G. Reid (USA), D. Rind (USA), K. Rosenlof (USA), R. Sausen (Germany), D. Schwarzkopf (USA), S.K. Solanki (Germany, Switzerland), G. Stenchikov (USA), N. Stuber (UK, Germany), T. Takemura (Japan), C. Textor (France, Germany), R. Wang (USA), R. Weiss (USA), T. Whorf (USA)

The hydroxyl radical is the predominant atmospheric oxidant1, responsible for removing a wide range of trace gases, including greenhouse gases, from the atmosphere. Determination of trends and variability in hydroxyl radical concentrations2,3 is critical to understanding whether the ‘cleansing’ properties of the atmosphere are changing. The variability in hydroxyl radical concentrations on annual to monthly timescales, however, is difficult to quantify. Here we show records of carbon monoxide containing radiocarbon (14CO), which is oxidized by hydroxyl radicals4,5, from clean-air sites at Baring Head, New Zealand, and Scott Base, Antarctica, spanning 13 years. Using a model study, we correct for known variations in production of 14CO (refs 6, 7), allowing us to exploit this species as a diagnostic for short term changes in hydroxyl radical concentrations. We find no significant long-term trend in hydroxyl radical concentrations but provide evidence for recurring short-term variations of around ten per cent persisting for a few months. We also find decreases in hydroxyl radical concentrations of up to 20 per cent, apparently triggered by the eruption of Mt Pinatubo in 1991 and by the occurrence of extensive fires in Indonesia in 1997.