#21 Land-use for ACME

Abstract

Human land-use activities have significantly altered biogeochemical and biogeophysical properties at local to planetary scales, and these alterations have influenced the environment including the Earth’s climate system. The global climate modeling community recognizes these effects, and the Coupled Model Intercomparison Project (CMIP6) recently made land-use a required forcing, and endorsed the Land Use Model Intercomparison Project (LUMIP) to organize the communities’ study of the effects of land-use on climate (both activities lead by Hurtt, and supported by separate DOE-SciDAC award). Yet the precise magnitude and character of land-use effects on climate remain uncertain, and this uncertainty in turn limits the accuracy of future projections. The overall goal of this contribution is to develop an expanded and fully consistent treatment of land-use of in ACME. Achieving such consistency will eliminate major sources of within model error/uncertainty, and will give ACME a unique capability among global models. There are two major Objectives. Objective 1 is to establish use of the new expanded land-use dataset in ACME. For CMIP6, the new required land-use forcing dataset is updated and contains ~50x the information used in CMIP5. This new information is at higher resolution over longer time domain, and includes additional new land-use transitions, crop types, crop rotations, and agriculture management information not previously available. Objective 2 is to develop and implement fully consistent (1 carbon cycle) historical land-use treatment for ACME. Global land-use history datasets are traditionally developed independently offline using best available historical information, and then used as input to global models. While useful, this separation leads to inconsistencies, as past land-use activities may be prescribed in areas inconsistent with modeled climate and vegetation. These inconsistencies in turn lead to model errors. To eliminate these errors, a fully consistent treatment of land-use in global models is needed and unique opportunity for ACME.  These objectives are ACME LG-144 and LG-145, respectively. Progress and results on these objectives will be presented.