Improving representation of Human-Earth system interactions

Abstract

Climate changes have important implications for regional and global energy systems, land use, agriculture, water, human health, and settlement. These systems, in turn, have important implications for climate change. Many of the existing climate change projections use emissions scenarios developed by assuming that feedbacks from a changing climate will not influence emissions. Thus, these scenarios potentially miss important feedbacks between human and Earth systems. To assess these feedbacks and to better understand how climate change and human systems interact, we have developed a new scientific tool, the integrated Earth System Model (iESM). The iESM couples an Integrated Assessment Model (IAM) and an Earth System Model (ESM) in a common modeling infrastructure. Three experiments were designed to introduce the development steps: 1) Experiment 0: Coupling land use and land cover information from GCAM to CESM, 2) Experiment 1: Additional coupling of climate change effects on ecosystem productivity from 
CESM to GCAM, producing a two-way coupling (or feedback loop), 3) Experiment 2: Additional coupling of energy and industrial CO2 emissions from GCAM to 
CESM, completing a second feedback loop. Each development step was designed to answer different science question. Our results show that terrestrial systems interact strongly with human systems, and the nature of those interactions can have a significant impact on climate change on decadal scales. This two-way coupled Earth system model evolves differently from others that ignore feedbacks from the climate to human system. Thus, it can be used to generate more consistent projections of future climate change. For the next step, we will implement the representations of Human-Earth interactions into the ACME model.