Figure 5.6

Figure caption

Figure 5.6 | Time series of CO₂ concentrations and related measurements in ambient air. (a) Concentration time series and MLO-SPO difference, (b) growth rates, (c) ¹⁴C and¹³C isotopes, and (d) O₂/N₂ ratio. The data for Mauna Loa Observatory (MLO) and South Pole Observatory (SPO) are taken from the Scripps Institution of Oceanography (SIO)/University of California, San Diego (Keeling et al., 2001). The global mean CO₂ are taken from National Oceanic and Atmospheric Administration (NOAA) cooperative network (as in Chapter 2), and Greenhouse Gases Observing Satellite (GOSAT) monthly mean XCO₂ (mixing ratio) time series are taken from National Institute for Environmental Studies (Yoshida et al., 2013). CO₂ growth rates are calculated as the time derivative of deseasonalized time series (Nakazawa et al., 1997). The D(O₂/N2) are expressed in per meg units (= (FF/M) × 10⁶, where FF = moles of O₂ consumed by fossil-fuel burning, M = 3.706 × 10¹⁹, total number of O₂ molecules in the atmosphere (Keeling and Manning, 2014). The¹⁴CO₂ time series at Barring Head, Wellington, New Zealand (BHD) is taken from GNS Science and NIWA (Turnbull et al., 2017). The multivariate ENSO index (MEI) is shown as the shaded background in panel (b); (warmer shade indicates El Niño). Further details on data sources and processing are available in the chapter data table (Table 5.SM.6).