A Bayesian ensemble data assimilation to constrain model parameters and land-use carbon emissions

• Main Authors: S. Lienert, F. Joos
• Format: Article
• Language: English
• Published: Copernicus Publications 2018-05-01
• Series: Biogeosciences
• Online Access: https://www.biogeosciences.net/15/2909/2018/bg-15-2909-2018.pdf

A dynamic global vegetation model (DGVM) is applied in a probabilistic framework and benchmarking system to constrain uncertain model parameters by observations and to quantify carbon emissions from land-use and land-cover change (LULCC). Processes featured in DGVMs include parameters which are prone to substantial uncertainty. To cope with these uncertainties Latin hypercube sampling (LHS) is used to create a 1000-member perturbed parameter ensemble, which is then evaluated with a diverse set of global and spatiotemporally resolved observational constraints. We discuss the performance of the constrained ensemble and use it to formulate a new best-guess version of the model (LPX-Bern v1.4). The observationally constrained ensemble is used to investigate historical emissions due to LULCC (<i>E</i>_LUC) and their sensitivity to model parametrization. We find a global <i>E</i>_LUC estimate of 158 (108, 211) PgC (median and 90 % confidence interval) between 1800 and 2016. We compare <i>E</i>_LUC to other estimates both globally and regionally. Spatial patterns are investigated and estimates of <i>E</i>_LUC of the 10 countries with the largest contribution to the flux over the historical period are reported. We consider model versions with and without additional land-use processes (shifting cultivation and wood harvest) and find that the difference in global <i>E</i>_LUC is on the same order of magnitude as parameter-induced uncertainty and in some cases could potentially even be offset with appropriate parameter choice.