A Simple Object-Oriented and Open Source Model for Scientific and Policy Analyses of the Global Carbon Cycle–Hector

Abstract:

Simple climate models play an integral role in policy and scientific communities. They are used in climate mitigation scenarios within integrated assessment models, complex climate model emulation, and uncertainty analyses. Here we describe, Hector an open source, object-oriented, simple global climate carbon-cycle model. This model runs essentially instantaneously while still representing the most critical global scale earth system processes, e.g., carbon fluxes between the ocean and atmosphere, and respiration and primary production on land. Hector has three main carbon pools: an atmosphere, land, and ocean. The terrestrial carbon cycle is represented by a simple design with respiration and primary production, accommodating arbitrary geographic divisions into, e.g., ecological biomes or political units. The ocean carbon cycle actively solves the inorganic carbon system in the surface ocean, directly calculating air-sea fluxes of carbon and ocean pH. Hector reproduces the large-scale global trends found in historical data of atmospheric [CO₂] and surface temperature and simulates all four Representative Concentration Pathways. Hector’s results compare well with current observations of critical climate variables, MAGICC (a well-known simple climate model), as well as, model output from the Coupled Model Intercomparison Project version 5. Hector has the ability to be a key analytical tool used across many scientific and policy communities due to its modern software architecture, open source, and object-oriented structure. In particular, Hector can be used to emulate larger complex models to help fill gaps in scenario coverage for future scenario processes.