Info

FIGURE 14.13 Concentrations of atmospheric C02 measured using gases trapped in ice cores from Byrd Station, Antarctica, from 5000 to 40,000 years before the present (bp) (adapted from Anklin et al, 1997).

four decades of atmospheric monitoring. The rate of increase at Mauna Loa was ~0.8 ppm per year during the 1960s, f .3 ppm per year in the 1970s, and f .5 ppm per year during the f980s (tPCC, 1996). However, the rate of increase slowed during the 1989-1993 period, with the value in 1992 of 0.6 ppm per year being the smallest rate of increase since continuous monitoring began (IPCC, 1996; Conway et al., 1994). The growth rate subsequently increased again to over 2 ppm per year in 1994 (IPCC, 1996). The reasons for the changes in the rate of growth are not clear, but probably not surprising given the complex cycling mechanisms for carbon (Fig. 14.11). For example, exchange between the atmosphere and the terrestrial biosphere and the oceans is believed to have substantial year-to-year variability, which can be affected by such events as the El Nino Southern Oscillation (ENSO). Possible reasons for the variability are discussed in detail in the IPCC document (1996).

Current data on atmospheric C02 concentrations and temporal trends as well as those of other trace gases are available from the U.S. Department of Energy's Carbon Dioxide information Analysis Center (CDIAC) (World Wide Web page is http://cdiac.esd.ornl.gov/cdiac). CDIAC also has available a number of additional data packages on global change issues such as trends in temperature and precipitation.

As discussed earlier, although C02 warms the troposphere, it cools the stratosphere since it efficiently radiates infrared out to space. This effect can contribute to changes in the temperature profile in the stratosphere and potentially have a signficant impact

FIGURE 14.13 Concentrations of atmospheric C02 measured using gases trapped in ice cores from Byrd Station, Antarctica, from 5000 to 40,000 years before the present (bp) (adapted from Anklin et al, 1997).

Was this article helpful?

0 0

Post a comment