title: Carbon residence time dominates uncertainty in terrestrial vegetation responses to future climate and atmospheric CO2.
abstract: Future climate change and increasing atmospheric CO2 are expected to cause major changes in vegetation structure and function over large fractions of the global land surface. Seven global vegetation models are used to analyze possible responses to future climate simulated by a range of general circulation models run under all four representative concentration pathway scenarios of changing concentrations of greenhouse gases. All 110 simulations predict an increase in global vegetation carbon to 2100, but with substantial variation between vegetation models. For example, at 4 °C of global land surface warming (510-758 ppm of CO2), vegetation carbon increases by 52-477 Pg C (224 Pg C mean), mainly due to CO2 fertilization of photosynthesis. Simulations agree on large regional increases across much of the boreal forest, western Amazonia, central Africa, western China, and southeast Asia, with reductions across southwestern North America, central South America, southern Mediterranean areas, southwestern Africa, and southwestern Australia. Four vegetation models display discontinuities across 4 °C of warming, indicating global thresholds in the balance of positive and negative influences on productivity and biomass. In contrast to previous global vegetation model studies, we emphasize the importance of uncertainties in projected changes in carbon residence times. We find, when all seven models are considered for one representative concentration pathway × general circulation model combination, such uncertainties explain 30% more variation in modeled vegetation carbon change than responses of net primary productivity alone, increasing to 151% for non-HYBRID4 models. A change in research priorities away from production and toward structural dynamics and demographic processes is recommended.
authors.affiliation: Department of Geography, University of Cambridge, Cambridge CB2 3EN, United Kingdom.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Friend
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lucht
authors.forename: Tim T
authors.initials: TT
authors.lastname: Rademacher
authors.forename: Rozenn
authors.initials: R
authors.lastname: Keribin
authors.forename: Richard
authors.initials: R
authors.lastname: Betts
authors.forename: Patricia
authors.initials: P
authors.lastname: Cadule
authors.forename: Philippe
authors.initials: P
authors.lastname: Ciais
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Clark
authors.forename: Rutger
authors.initials: R
authors.lastname: Dankers
authors.forename: Pete D
authors.initials: PD
authors.lastname: Falloon
authors.forename: Akihiko
authors.initials: A
authors.lastname: Ito
authors.forename: Ron
authors.initials: R
authors.lastname: Kahana
authors.forename: Axel
authors.initials: A
authors.lastname: Kleidon
authors.forename: Mark R
authors.initials: MR
authors.lastname: Lomas
authors.forename: Kazuya
authors.initials: K
authors.lastname: Nishina
authors.forename: Sebastian
authors.initials: S
authors.lastname: Ostberg
authors.forename: Ryan
authors.initials: R
authors.lastname: Pavlick
authors.forename: Philippe
authors.initials: P
authors.lastname: Peylin
authors.forename: Sibyll
authors.initials: S
authors.lastname: Schaphoff
authors.forename: Nicolas
authors.initials: N
authors.lastname: Vuichard
authors.forename: Lila
authors.initials: L
authors.lastname: Warszawski
authors.forename: Andy
authors.initials: A
authors.lastname: Wiltshire
authors.forename: F Ian
authors.initials: FI
authors.lastname: Woodward
mesh_terms: D001272:Atmosphere / Q000737:chemistry*; D002244:Carbon / Q000493:pharmacokinetics*; D057486:Carbon Cycle / Q000502:physiology*; D002245:Carbon Dioxide / Q000032:analysis*; D057231:Climate Change; D003198:Computer Simulation; D005544:Forecasting; D008962:Models, Theoretical; D010944:Plants / Q000378:metabolism*; D013997:Time Factors; D035501:Uncertainty
chemical_list: D002245:Carbon Dioxide; D002244:Carbon
keywords: DGVM; GVM; ISI-MIP; NPP; turnover