The response of atmospheric CO sub 2 to changes in land use Page: 12 of 54
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annual loss of carbon from the vegetation and soils of all ecosystem types and geographic
regions plus the annual loss from the decay pools for harvested material is an estimate
of annual global carbon release to the atmosphere from changes in land use, The models
assume that there is no net exchange of carbon between the atmosphere and ecosystems
not disturbed by land use change.
History A (Figure 3) is the population-based estimate of Houghton et al. [1983]. We
estimated carbon release before 1825 by linear extrapolation from the 1825 value to zero
release before 1770. We assumed constant release at the 1980 value for the period 1980-
1987.
Histories B and C (Figure 3) are more recent estimates [Houghton, 1989] that incor-
porate revised estimates of land-use change, carbon stocks in tropical ecosystems, and the
reduction in soil carbon following forest clearing [Houghton et al., 1985, 1987]. History B
is a high estimate based on medium-to-high estimates of tropical biomass; history C is the
corresponding low estimate based on low estimates of tropical biomass, We estimated pre-
1860 carbon release by linear extrapolation to zero release before 1770, and we assumed
constant release at the respective 1985 values for 1986 and 1987.
A fraction of the carbon added to the atmosphere from the anthropogenic sources
penetrates the ocean surface as CO2 and is distributed throughout the ocean according
to the dynamics of each model. The mass of carbon remnaining in the atmosphere is
converted to CO2 concentration based on the molecular weights of carbon and air and
the dry air, mass of the atmosphere. The simulated history of change in atmospheric CO2
concentration is then compared with the observed history specified by CO2 measurements
from the Siple Station, Antarctica, ice core [Nefiel et al., 1985; Friedli et al,, 1986 and the
monitoring station at Mauna Loa Observatory, Hawaii, (Kecling, 1986]. (The Mauna Loa
measurements approximate muean global concentrations within 0,2-0.3 pL L' [Ganu.ron
et al., 1986].)
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King, A. W.; Emanuel, W. R. & Post, W. M. The response of atmospheric CO sub 2 to changes in land use, article, January 1, 1990; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc1187253/m1/12/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.