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| Titel |
Scenario and modelling uncertainty in global mean temperature change derived from emission-driven global climate models |
| VerfasserIn |
B. B. B. Booth, D. Bernie, D. McNeall, E. Hawkins, J. Caesar, C. Boulton, P. Friedlingstein, D. M. H. Sexton |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
2190-4979
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| Digitales Dokument |
URL |
| Erschienen |
In: Earth System Dynamics ; 4, no. 1 ; Nr. 4, no. 1 (2013-04-08), S.95-108 |
| Datensatznummer |
250017773
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| Publikation (Nr.) |
 copernicus.org/esd-4-95-2013.pdf |
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| Zusammenfassung |
| We compare future changes in global mean temperature in response to different
future scenarios which, for the first time, arise from emission-driven rather
than concentration-driven perturbed parameter ensemble of a global climate
model (GCM). These new GCM simulations sample uncertainties in atmospheric feedbacks, land carbon cycle,
ocean physics and aerosol sulphur cycle processes. We find broader ranges of
projected temperature responses arising when considering emission rather than
concentration-driven simulations (with 10–90th percentile ranges of 1.7 K
for the aggressive mitigation scenario, up to 3.9 K for the high-end,
business as usual scenario). A small minority of simulations resulting from
combinations of strong atmospheric feedbacks and carbon cycle responses show
temperature increases in excess of 9 K (RCP8.5) and even under aggressive
mitigation (RCP2.6) temperatures in excess of 4 K. While the simulations
point to much larger temperature ranges for emission-driven experiments, they
do not change existing expectations (based on previous concentration-driven
experiments) on the timescales over which different sources of uncertainty
are important. The new simulations sample a range of future atmospheric
concentrations for each emission scenario. Both in the case of SRES A1B and
the Representative Concentration Pathways (RCPs), the concentration scenarios
used to drive GCM ensembles, lies towards the lower end of our simulated
distribution. This design decision (a legacy of previous assessments) is
likely to lead concentration-driven experiments to under-sample strong
feedback responses in future projections. Our ensemble of emission-driven
simulations span the global temperature response of the CMIP5 emission-driven
simulations, except at the low end. Combinations of low climate sensitivity
and low carbon cycle feedbacks lead to a number of CMIP5 responses to lie
below our ensemble range. The ensemble simulates a number of high-end
responses which lie above the CMIP5 carbon cycle range. These high-end
simulations can be linked to sampling a number of stronger carbon cycle
feedbacks and to sampling climate sensitivities above 4.5 K. This latter
aspect highlights the priority in identifying real-world climate-sensitivity
constraints which, if achieved, would lead to reductions on the upper bound
of projected global mean temperature change. The ensembles of simulations
presented here provides a framework to explore relationships between
present-day observables and future changes, while the large spread of
future-projected changes highlights the ongoing need for such work. |
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