Abstract
Observations show an increasing amplitude in the seasonal cycle of CO2 (ASC) north of 45°N of 56 ± 9.8% over the last 50 years and an increase in vegetation greenness of 7.5–15% in high northern latitudes since the 1980s. However, the causes of these changes remain uncertain. Historical simulations from terrestrial biosphere models in the Multiscale Synthesis and Terrestrial Model Intercomparison Project are compared to the ASC and greenness observations, using the TM3 atmospheric transport model to translate surface fluxes into CO2 concentrations. We find that the modeled change in ASC is too small but the mean greening trend is generally captured. Modeled increases in greenness are primarily driven by warming, whereas ASC changes are primarily driven by increasing CO2. We suggest that increases in ecosystem-scale light use efficiency (LUE) have contributed to the observed ASC increase but are underestimated by current models. We highlight potential mechanisms that could increase modeled LUE.
| Original language | English |
|---|---|
| Pages (from-to) | 11,339-11,349 |
| Journal | Geophysical Research Letters |
| Volume | 43 |
| Issue number | 21 |
| DOIs | |
| State | Published - Nov 16 2016 |
Funding
This work was supported by the Grantham Institute: Climate Change and the Environment–Science and Solutions for a Changing Planet DTP, grant NE/L002515/1 and is a contribution to the AXA Chair Programme in Biosphere and Climate Impacts. All data used for this analysis are publicly available with full sources detailed in the supporting information. We thank Peter Rayner and an anonymous reviewer for their helpful comments on the manuscript. Funding for the Multiscale synthesis and Terrestrial Model Intercomparison Project (MsTMIP; http://nacp.ornl.gov/MsTMIP.shtm) activity was provided through NASA ROSES grant NNX10AG01A. Data management support for preparing, documenting, and distributing model driver and output data was performed by the Modeling and Synthesis Thematic Data Center at Oak Ridge National Laboratory (ORNL; http://nacp.ornl.gov), with funding through NASA ROSES grant NNH10AN681. Finalized MsTMIP data products are archived at the ORNL DAAC (http://daac.ornl.gov). Biome-BGC code was provided by the Numerical Terradynamic Simulation Group at University of Montana. The computational facilities were provided by NASA Earth Exchange at NASA Ames Research Center. CLM4 and GTEC simulations were supported in part by the U.S. Department of Energy (DOE), Office of Science, Biological and Environmental Research. Oak Ridge National Laboratory is managed by UTBATTELLE for DOE under contract DE-AC05-00OR22725. CLM4-VIC research is supported in part by the U.S. Department of Energy (DOE), Office of Science, Biological and Environmental Research. PNNL is operated for the U.S. DOE by BATTELLE Memorial Institute under contract DE-AC06-76RLO1830. DLEM developed in International Center for Climate and Global Change Research, Auburn University has been supported by NASA Interdisciplinary Science Program (IDS), NASA Land Cover/Land Use Change Program (LULUC),NASA Terrestrial Ecology Program, NASA Atmospheric Composition Modeling and Analysis Program (ACMAP), NSF Dynamics of Coupled Natural-Human System Program (CNH), Decadal and Regional Climate Prediction using Earth System Models (EaSM), DOE National Institute for Climate Change Research, USDA AFRI Program, and EPA STAR program. LPJwsl work was conducted at LSCE, France, using a modified version of LPJ version 3.1 model, originally made available by the Potsdam Institute for Climate Impact Research. ORCHIDEE is a global land surface model developed at the IPSL institute in France. The simulations were performed with the support of the GhG Europe FP7 grant with computing facilities provided by “LSCE” or “TGCC.” SiB3 research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. TEM6 research is supported in part by the U.S. Department of Energy (DOE), Office of Science, Biological and Environmental Research. Oak Ridge National Laboratory is managed by UT-BATTELLE for DOE under contract DE-AC05-00OR22725. VISIT was developed at the National Institute of Environmental Studies, Japan. This work was mostly conducted during a visiting stay at Oak Ridge National Laboratory. This study was supported by KAKENHI Grand No. 26281014 by the Japan Society of Promotion of Science.
Keywords
- NPP
- carbon cycle
- greening
- light use efficiency
- terrestrial biosphere model