Canadell,
J.G., Kirschbaum, M.U.F., Kurz, W.A., Sanz, M.-J., Schlamadinger, B.,
Abstract. The capacity to partition the
natural, indirect, and direct human-induced effects on terrestrial carbon (C)
sources and sinks is a fundamental prerequisite to be able to predict future
dynamics of the net terrestrial C sink and its contribution to atmospheric CO2
growth. It will take a number of years before we can fully attribute
quantitative estimates to the contribution of various C processes to the net C
balance. In a policy context, factoring out natural and indirect human-induced
effects on C sources and sinks from the direct human-induced influences is seen
as a requirement of a C accounting approach that establishes a clear and
unambiguous connection between human activities and the assignment of C credits
and debits.
We present options for factoring out
these various groups of influences, including the legacies from forest
management prior to the reference year (1990):
i)
selecting
longer accounting or measurement periods to reduce the effects of interannual
variability;
ii)
correction
of national inventory results for inter-annual variability;
iii)
use
of activity-based accounting and C response curves;
iv)
use
of baseline scenarios or benchmarks at the national level; and
v)
stratification
of the landscape into units with distinct average C stocks.
Other, more sophisticated modeling
approaches (e.g., demographic models in combination with forest inventories;
process-based models) are possible options for future C accounting systems but
their complexity and data requirements make their present adoption more
difficult in an inclusive international C accounting system.
Keywords: AFOLU; carbon cycle;
forests; Kyoto Protocol; LULUCF; Marrakech Accords; C sink processes; C source
processes.
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