Atmospheric CO2 and 13CO2 Exchange with the Terrestrial Biosphere and Oceans from 1978 to 2000: Observations and Carbon Cycle Implications

Abstract

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Earth’s Climate System

“…3.1.1.0.median_netcdf.zip Figure 1.7 shows CO 2 (Keeling et al 1976), the O 2 /N 2 ratio (Keeling et al 1996), and δ 13 C of CO 2 (Keeling et al 2005) from Mauna Loa Observatory (MLO) as well as CO 2 from the South Pole (SPO) (Tans et al 1990). For CO 2 , the solid black line shows monthly mean data from NOAA ESRL, based on the same file given in Methods for Fig.…”

“…15 Atomic mass is the sum of the number of protons and neutrons. (Keeling et al 1976) and the South Pole (Tans et al 1990); (b) ratio of atmospheric O 2 to N 2 measured at the Mauna Loa Observatory in units of per meg, where 1 per meg = 0.00001 % (Keeling et al 1996); (c) abundance of 13 C in atmospheric CO 2 at Mauna Loa relative to a standard in units of per mil, where 1 per mil = 0.1 % (Keeling et al 2005). See Methods for further information (i.e., uncharged).…”

“…Most importantly, biological properties of a compound are mass dependent: our bodies prefer 12 C over the other two heavier forms of carbon that are digested, because lighter molecules diffuse more readily through our capillaries. The term isotopic composition, as used here, refers to the relative abundance of 13 C in a sample of atmospheric CO 2 compared to the sum of 12 C, 13 C, and 14 C in the same sample, and is expressed using the notation δ 13 C. Figure 1.7c shows a time series of δ 13 C recorded at MLO (Keeling et al 2005). The downward decline of δ 13 C means atmospheric CO 2 is getting isotopically lighter over time.…”

The use of δ13C values of leporid teeth as indicators of past vegetation

“…Though plants with the same photosynthetic pathway will have different isotopic composition due to species differences (Cerling and Harris, 1999), the δ 13 C value of CO 2 (Keeling et al, 2005), changes in irradiance (Ehleringer et al, 1986;Zimmerman and Ehleringer, 1990), water stress (Ehleringer, 1993), and even the structure of the surrounding vegetation (Medina et al, 1986), they provide reasonable estimates which, when applied to our estimates of C 3 /C 4 percentages from modern vegetation data, allow us to create a general estimate of the seasonal cycle in plant δ 13 C on the Edwards Plateau.…”

Climate Change, Society Issues and Sustainable Agriculture

“…Combining his calculations with existing work suggesting that the burning of fossil fuels could significantly alter the concentration of carbon dioxide in the atmosphere (Högbom, 1894), Arrhenius later became the first person to predict the possibility of man-made global warming (Arrhenius, 1908, Weart, 2008. Now, the recent record of atmospheric CO 2 levels at the Mauna Loa Observatory in Hawaii, known as the "Keeling curve", clearly shows a steady increase from 1958 ( Figure 1, Keeling et al, 2001, 2005, Scripps, 2008. Moreover, the comparison of modern CO 2 levels with ancient ones shows clearly that atmospheric CO 2 has now reached an unprecedented high level during the last 400,000 years, reaching 383 ppm in 2007 ( Figure 2).…”