Estimation of changes in characteristics of the climate and carbon cycle in the 21st century accounting for the uncertainty of terrestrial biota parameter values |
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| Authors: | A V Eliseev |
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| Institution: | 1.A.M. Obukhov Institute of Atmospheric Physics,Russian Academy of Sciences,Moscow,Russia |
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| Abstract: | ensemble simulations with the A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS) climate
model (CM) for the 21st century are analyzed taking into account anthropogenic forcings in accordance with the Special Report
on Emission Scenarios (SRES) A2, A1B, and B1, whereas agricultural land areas were assumed to change in accordance with the
Land Use Harmonization project scenarios. Different realizations within these ensemble experiments were constructed by varying
two governing parameters of the terrestrial carbon cycle. The ensemble simulations were analyzed with the use of Bayesian
statistics, which makes it possible to suppress the influence of unrealistic members of these experiments on their results.
It is established that, for global values of the main characteristics of the terrestrial carbon cycle, the SRES scenarios
used do not differ statistically from each other, so within the framework of the model, the primary productivity of terrestrial
vegetation will increase in the 21st century from 74 ± 1 to 102 ± 13 PgC yr−1 and the carbon storage in terrestrial vegetation will increase from 511 ± 8 to 611 ± 8 PgC (here and below, we indicate the
mean ± standard deviations). The mutual compensation of changes in the soil carbon stock in different regions will make global
changes in the soil carbon storage in the 21st century statistically insignificant. The global CO2 uptake by terrestrial ecosystems will increase in the first half of the 21st century, whereupon it will decrease. The uncertainty
interval of this variable in the middle (end) of the 21st century will be from 1.3 to 3.4 PgC yr−1 (from 0.3 to 3.1 PgC yr−1). In most regions, an increase in the net productivity of terrestrial vegetation (especially outside the tropics), the accumulation
of carbon in this vegetation, and changes in the amount of soil carbon stock (with the total carbon accumulation in soils
of the tropics and subtropics and the regions of both accumulation and loss of soil carbon at higher latitudes) will be robust
within the ensemble in the 21st century, as will the CO2 uptake from the atmosphere only by terrestrial ecosystems located at extratropical latitudes of Eurasia, first and foremost
by the Siberian taiga. However, substantial differences in anthropogenic emissions between the SRES scenarios in the 21st
century lead to statistically significant differences between these scenarios in the carbon dioxide uptake by the ocean, the
carbon dioxide content in the atmosphere, and changes in the surface air temperature. In particular, according to the SRES
A2 (A1B, B1) scenario, in 2071–2100 the carbon flux from the atmosphere to the ocean will be 10.6 ± 0.6 PgC yr−1 (8.3 ± 0.5, 5.6 ± 0.3 PgC yr−1), and the carbon dioxide concentration in the atmosphere will reach 773 ± 28 ppmv (662 ± 24, 534 ± 16 ppmv) by 2100. The
annual mean warming in 2071–2100 relatively to 1961–1990 will be 3.19 ± 0.09 K (2.52 ± 0.08, 1.84 ± 0.06 K). |
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