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  • × Max Planck Institute for Meteorology, Hamburg, Germany
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来源:Atmospheric Measurement Techniques

作者:Albert Ansmann;Holger Linné;Ina Mattis;等

使用许可:署名(BY)

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来源:Biogeosciences

作者:V. Gayler;T. Raddatz;V. Brovkin;等

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The factor separation of Stein and Alpert (1993) is applied to simulationswith the MPI Earth system model to determine the factors which cause thedifferences between vegetation patterns in glacial and pre-industrialclimate. The factors firstly include differences in the climate, caused by astrong increase in ice masses and the radiative effect of lower greenhousegas concentrations; secondly, differences in the ecophysiological effect oflower glacial atmospheric CO2 concentrations; and thirdly, the synergybetween the pure climate effect and the pure effect of changingphysiologically available CO2. It is has been shown that the synergy canbe interpreted as a measure of the sensitivity of ecophysiological CO2effect to climate. The pure climate effect mainly leads to a contraction or ashift in vegetation patterns when comparing simulated glacial andpre-industrial vegetation patterns. Raingreen shrubs benefit from the colderand drier climate. The pure ecophysiological effect of CO2 appears to bestronger than the pure climate effect for many plant functional types – inline with previous simulations. The pure ecophysiological effect of lowerCO2 mainly yields a reduction in fractional coverage, a thinning ofvegetation and a strong reduction in net primary production. The synergyappears to be as strong as each of the pure contributions locally, but weakon global average for most plant functional types. For tropical evergreentrees, however, the synergy is strong on global average. It diminishes thedifference between glacial and pre-industrial coverage of tropical evergreentrees, due to the pure climate effect and the pure ecophysiological CO2effect, by approximately 50 per cent.

    来源:Biogeosciences

    作者:J. O. Kaplan;Z. C. Yu;T. Kleinen;等

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    Global wetlands are believed to be climate sensitive, and are thelargest natural emitters of methane (CH4). Increased wetlandCH4 emissions could act as a positive feedback to futurewarming.The Wetland and Wetland CH4 Inter-comparison ofModels Project (WETCHIMP) investigated our present ability tosimulate large-scale wetland characteristics and correspondingCH4 emissions. To ensure inter-comparability, we useda common experimental protocol driving all models with the sameclimate and carbon dioxide (CO2) forcing datasets. TheWETCHIMP experiments were conducted for model equilibrium states aswell as transient simulations covering the last century. Sensitivityexperiments investigated model response to changes in selectedforcing inputs (precipitation, temperature, and atmosphericCO2 concentration). Ten models participated, covering thespectrum from simple to relatively complex, including modelstailored either for regional or global simulations. The models alsovaried in methods to calculate wetland size and location, with somemodels simulating wetland area prognostically, while other modelsrelied on remotely sensed inundation datasets, or an approachintermediate between the two.Four major conclusions emerged from the project. First, the suite ofmodels demonstrate extensive disagreement in their simulations ofwetland areal extent and CH4 emissions, in both space andtime. Simple metrics of wetland area, such as the latitudinalgradient, show large variability, principally between models thatuse inundation dataset information and those that independentlydetermine wetland area. Agreement between the models improves forzonally summed CH4 emissions, but large variation betweenthe models remains. For annual global CH4 emissions, themodels vary by ±40% of the all-model mean(190 Tg CH4 yr−1). Second, all models showa strong positive response to increased atmospheric CO2concentrations (857 ppm) in both CH4 emissions andwetland area. In response to increasing global temperatures(+3.4 °C globally spatially uniform), on average, the modelsdecreased wetland area and CH4 fluxes, primarily in thetropics, but the magnitude and sign of the response varied greatly.Models were least sensitive to increased global precipitation(+3.9 % globally spatially uniform) with a consistent smallpositive response in CH4 fluxes and wetland area. Resultsfrom the 20th century transient simulation show that interactionsbetween climate forcings could have strong non-lineareffects. Third, we presently do not have sufficient wetland methaneobservation datasets adequate to evaluate model fluxes ata spatial scale comparable to model grid cells (commonly0.5°). This limitation severely restricts our ability tomodel global wetland CH4 emissions with confidence. Oursimulated wetland extents are also difficult to evaluate due toextensive disagreements between wetland mapping and remotely sensedinundation datasets. Fourth, the large range in predictedCH4 emission rates leads to the conclusion that there isboth substantial parameter and structural uncertainty in large-scaleCH4 emission models, even after uncertainties in wetlandareas are accounted for.

      来源:Biogeosciences

      作者:V. Gayler;T. Raddatz;V. Brovkin;等

      使用许可:署名(BY)

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      来源:Biogeosciences

      作者:V. Gayler;T. Raddatz;V. Brovkin;等

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      The factor separation of Stein and Alpert (1993) is applied to simulationswith the MPI Earth system model to determine the factors which cause thedifferences between vegetation patterns in glacial and pre-industrialclimate. The factors firstly include differences in the climate, caused by astrong increase in ice masses and the radiative effect of lower greenhousegas concentrations; secondly, differences in the ecophysiological effect oflower glacial atmospheric CO2 concentrations; and thirdly, the synergybetween the pure climate effect and the pure effect of changingphysiologically available CO2. It is has been shown that the synergy canbe interpreted as a measure of the sensitivity of ecophysiological CO2effect to climate. The pure climate effect mainly leads to a contraction or ashift in vegetation patterns when comparing simulated glacial andpre-industrial vegetation patterns. Raingreen shrubs benefit from the colderand drier climate. The pure ecophysiological effect of CO2 appears to bestronger than the pure climate effect for many plant functional types – inline with previous simulations. The pure ecophysiological effect of lowerCO2 mainly yields a reduction in fractional coverage, a thinning ofvegetation and a strong reduction in net primary production. The synergyappears to be as strong as each of the pure contributions locally, but weakon global average for most plant functional types. For tropical evergreentrees, however, the synergy is strong on global average. It diminishes thedifference between glacial and pre-industrial coverage of tropical evergreentrees, due to the pure climate effect and the pure ecophysiological CO2effect, by approximately 50 per cent.

        来源:Biogeosciences

        作者:J. Winderlich;T. Kleinen;V. Brovkin;等

        使用许可:署名(BY)

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