Harmonization of Global Land-Use Scenarios for the Period 1500-2100 for IPCC 5th Assessment

The 5th IPCC assessment will employ new integrated climate and carbon cycle models (CMs) that, for the first time, will use gridded scenarios of future land-use activities. In preparation for this assessment, the international modeling community is developing four Representative Concentration Path (RCP) scenarios developed by four Integrated Assessment Modeling teams (IAMs). The RCP scenarios include land-use changes and will be used as input to CMs. However, the diversity of approaches and requirements among IAMs and CMs for tracking land-use change, along with the dependence of model projections on land-use history, presents a challenge for effectively passing data between these communities and for smoothly transitioning from the historical estimates to future projections. Our goal is to bridge the two communities by developing a harmonized set of land-use scenarios that smoothly connects historical reconstructions of land- use with future projections, in the format required by CMs. We compute consistent global gridded maps of land-use activities and recovering lands as well as the underlying land-use transitions including the effects of wood harvest and shifting cultivation. We build upon the method of Hurtt et al. 2006 and use gridded historical maps of crop and pasture data from HYDE 3.0 1500-2000 (Klein Goldewijk, in prep), historical national wood harvest and shifting cultivation estimates from Hurtt et al. 2006, future agricultural and wood harvest data from IAMs (AIM, IMAGE, MESSAGE, and MiniCAM) 2000-2100, and future climate and CO2 data from IAMs. The resulting half degree gridded maps of subgrid-scale land-use and underlying transitions smoothly progress from past to future in a format that can be used as input into CMs. This harmonized set of products will provide the first consistent set of land-use change and emission scenarios in a consistent format for a large community of CMs to enable studies of the effects of gridded land-use changes on the global carbon-climate system.