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| Titel |
Multiple greenhouse gas feedbacks from the land biosphere under future climate change scenarios |
| VerfasserIn |
Benjamin Stocker, Raphael Roth, Fortunat Joos, Renato Spahni, Marco Steinacher, Soenke Zaehle, Lex Bouwman, Xu-Ri Xu-Ri, Colin Prentice |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250074099
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| Zusammenfassung |
| Atmospheric concentrations of the three important greenhouse gases (GHG) CO2, CH4, and
N2O are mediated by processes in the terrestrial biosphere. The sensitivity of terrestrial GHG
emissions to climate and CO2 contributed to the sharp rise in atmospheric GHG
concentrations since preindustrial times and leads to multiple feedbacks between the
terrestrial biosphere and the climate system. The strength of these feedbacks is determined by
(i) the sensitivity of terrestrial GHG emissions to climate and CO2 and (ii) the greenhouse
warming potential of the respective gas. Here, we quantify feedbacks from CO2, CH4, N2O,
and land surface albedo in a consistent and comprehensive framework based on a
large set of simulations conducted with an Earth System Model of Intermediate
Complexity.
The modeled sensitivities of CH4 and N2O emissions are tested, demonstrating that
independent data for non-land (anthropogenic, oceanic, etc.) GHG emissions, combined with
simulated emissions from natural and agricultural land reproduces historical atmospheric
budgets within their uncertainties.
21st-century scenarios for climate, land use change and reactive nitrogen inputs (Nr) are
applied to investigate future GHG emissions. Results suggest that in a business-as-usual
scenario, terrestrial N2O emissions increase from 9.0 by today to 9.8-11.1 (RCP 2.6)
and 14.2-17.0 TgN2O-N/yr by 2100 (RCP 8.5). Without anthropogenic Nr inputs,
the amplification is reduced by 24-32%. Soil CH4 emissions increase from 221 at
present to 228-245 in RCP 2.6 and to 303-343 TgCH4/yr in RCP 8.5, and the land
becomes a net source of C by 2100 AD. Feedbacks from land imply an additional
warming of 1.3-1.5°C by 2300 in RCP 8.5, 0.4-0.5°C of which are due to N2O and
CH4.
The combined effect of multiple GHGs and albedo represents an increasingly positive
total feedback to anthropogenic climate change with positive individual feedbacks from CH4,
N2O, and albedo outweighing the diminishing negative feedback from CO2 fertilisation of
terrestrial C storage.
This positive feedback from terrestrial biogeochemistry amplifies the traditionally defined
physical equilibrium climate sensitivity by 23-28%,
Strong mitigation, reducing Nr inputs and preserving natural vegetation limits
the amplification of terrestrial GHG emissions and prevents the land biosphere
from acting as an increasingly strong amplifier of anthropogenic climate change. |
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