Harmonization of global land use change and management for the period 850–2100 (LUH2) for CMIP6

TLDR

Human land use has altered Earth's surface properties, and future expansion is expected to intensify, prompting CMIP6 ESMs to assess combined effects of land use and emissions on the carbon–climate system. The study documents the land use patterns employed in CMIP6 ESM simulations by presenting LUH2, which links updated historical reconstructions with eight future projections. LUH2 generates annual fractional land use, transitions, management, and secondary land data at 0.25° resolution from 850–2100 by integrating HYDE historical data, IAM scenarios, Landsat observations, and updated algorithms, while aligning historical and future periods. The new LUH2 products contain more than 50 times the information content of CMIP5 datasets and enable improved estimates of land use impacts on the global carbon–climate system. Abstract.

Abstract

Abstract. Human land use activities have resulted in large changes to the biogeochemical and biophysical properties of the Earth's surface, with consequences for climate and other ecosystem services. In the future, land use activities are likely to expand and/or intensify further to meet growing demands for food, fiber, and energy. As part of the World Climate Research Program Coupled Model Intercomparison Project (CMIP6), the international community has developed the next generation of advanced Earth system models (ESMs) to estimate the combined effects of human activities (e.g., land use and fossil fuel emissions) on the carbon–climate system. A new set of historical data based on the History of the Global Environment database (HYDE), and multiple alternative scenarios of the future (2015–2100) from Integrated Assessment Model (IAM) teams, is required as input for these models. With most ESM simulations for CMIP6 now completed, it is important to document the land use patterns used by those simulations. Here we present results from the Land-Use Harmonization 2 (LUH2) project, which smoothly connects updated historical reconstructions of land use with eight new future projections in the format required for ESMs. The harmonization strategy estimates the fractional land use patterns, underlying land use transitions, key agricultural management information, and resulting secondary lands annually, while minimizing the differences between the end of the historical reconstruction and IAM initial conditions and preserving changes depicted by the IAMs in the future. The new approach builds on a similar effort from CMIP5 and is now provided at higher resolution (0.25∘×0.25∘) over a longer time domain (850–2100, with extensions to 2300) with more detail (including multiple crop and pasture types and associated management practices) using more input datasets (including Landsat remote sensing data) and updated algorithms (wood harvest and shifting cultivation); it is assessed via a new diagnostic package. The new LUH2 products contain > 50 times the information content of the datasets used in CMIP5 and are designed to enable new and improved estimates of the combined effects of land use on the global carbon–climate system.