HR: 17:30h
AN: GC54C-01    [Abstracts]
TI: A Millennium of Anthropogenic Land Cover Change and its Effects on Climate
AU: * Pongratz, J
EM: julia.pongratz@zmaw.de
AF: Max Planck Institute for Meteorology, Bundesstr. 55, Hamburg, 20146, Germany
AU: * Pongratz, J
EM: julia.pongratz@zmaw.de
AF: International Max Planck Research School on Earth System Modelling, Bundesstr. 55, Hamburg, 20146, Germany
AU: Reick, C
EM: christian.reick@zmaw.de
AF: Max Planck Institute for Meteorology, Bundesstr. 55, Hamburg, 20146, Germany
AU: Raddatz, T
EM: thomas.raddatz@zmaw.de
AF: Max Planck Institute for Meteorology, Bundesstr. 55, Hamburg, 20146, Germany
AU: Claussen, M
EM: martin.claussen@zmaw.de
AF: Max Planck Institute for Meteorology, Bundesstr. 55, Hamburg, 20146, Germany
AU: Claussen, M
EM: martin.claussen@zmaw.de
AF: Meteorological Institute, University of Hamburg, Bundesstr. 55, Hamburg, 20146, Germany
AB: Anthropogenic climate change is generally thought to have begun with the industrial revolution, when humans started to considerably alter the composition of the atmosphere by emissions from fossil fuels. Human impact on the environment, however, started much earlier: Thousands of years ago, land was already transformed for use in agriculture and livestock farming. It is recognized that anthropogenic land cover change at today's scale has a significant impact on local to global climate. Yet, the effects of pre-industrial land use are not well understood. A main obstacle is the lack of quantitative data on historic land use activity prior to AD~1700 and a detailed analysis of its effects on the surface energy balance and the carbon cycle. This contribution presents advancements in both aspects. First, we present a simple method that consistently estimates the extent of crop and pasture areas for AD~800 to 1700 on a geographically explicit scale based on population data. Published land use data are used from AD~1700 until present. Uncertainties associated with data and method, including the effects of agrotechnical development, are assessed, and data sets of highest and lowest possible land use dynamics are provided. This land use reconstruction can be used to assess the human impact on the environment in pre-industrial times at high spatial and temporal resolution. It will be made freely available to the scientific community. The millennial land use reconstruction is then used in a complex climate model to quantify changes in radiative forcing. Results show that the energy balance was significantly influenced by human activity already in AD~800. Regional monthly means of radiative forcing reach up to 2.5~W/m². Our results are in line with previous studies covering the recent centuries. The impact of pre-industrial land use change on the carbon balance is estimated using two independent approaches: a process-based soil and vegetation model, and a book-keeping model. Both methods show similar results with substantial carbon emissions in pre-industrial times. High regional dynamics are observed as a result of political and social changes.
DE: 0428 Carbon cycling (4806)
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
DE: 1632 Land cover change
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting