A new integrated climate model incorporates large-scale human impact data. Image credit: ORNL.Supercomputer Titan was used to create a new integrated computational climate model designed to reduce uncertainties in future climate predictions. The integrated Earth System Model (iESM) explores interactions among human systems, the physical climate system and biological components of the Earth system.

"The model we developed and applied couples biospheric feedbacks from oceans, atmosphere and land with human activities, such as fossil fuel emissions, agriculture and land use,” said Peter Thornton, deputy director of the Climate Change Science Institute at Oak Ridge National Laboratory in Tennessee. Titan, a 27-petaflop Cray XK7, is also located at the facility.

Previously, researchers were unable to directly couple an Earth system model with feedback from large-scale human activity, such as how energy production and consumption affects the planet.

Thornton's team was awarded 85 million compute hours to improve the Accelerated Climate Modeling for Energy (ACME) effort, sponsored by the U.S. Department of Energy’s Earth System Modeling program. ACME collaborators are currently focused on developing an advanced climate model capable of simulating 80 years of historic and future climate variability and change, within three weeks of computing effort.

Ongoing tuning and optimizing has brought the team closer to reaching that goal. The team can now run about three or four simulated years per day, about twice the output of earlier code versions. Thornton notes that the target is the ability to simulate five years per day.

For iESM to take the next step, a more consistent land surface representation between coupled models will be necessary. The team also aims to include dimensions such as water management and storage, agricultural productivity and commodity pricing structures. "These improvements are vital since there is concern that fresh water resources might be the pinch point that gets felt first," Thornton said.

The ACME program has achieved a number of milestones over its three years of existence. "What's unique about ACME is that it's pushing the system to a higher resolution than has been attempted before," Thornton said. "It's also pushing toward a more comprehensive simulation capability by including human dimensions and other advances, yielding the most detailed Earth system models to date."

Results from the ACME model will contribute to the Coupled Model Intercomparison Project (CMIP), part of the World Climate Research Programme based in Geneva. The CMIP provides foundational material for climate change assessment reports.