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Publication Date
1 September 2020

New Methods to Simulate CO2 Uptake in Various Earth Ecosystems

Researchers introduced a simulated carbon cycle to the Energy Exascale Earth System Model.
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The addition of carbon cycle modeling to the Energy Exascale Earth System Model broadens its utility and enables the study of how changes in carbon storage can impact climate.

The Energy Exascale Earth System Model (E3SM) is a state-of-the-art Earth system model that simulates how Earth’s climate responds to various influences, including atmospheric concentrations of carbon dioxide gas (CO2). However, accurately predicting the amount of CO2 in the atmosphere requires simulating how much CO2 is removed from the atmosphere by forests, other land ecosystems, and the ocean. A group of researchers used E3SM to simulate how land and ocean ecosystems take up carbon dioxide gas from the atmosphere and how various factors, including temperature and precipitation patterns, nutrient availability, and land cover, affect this uptake. This massive effort required scientists from five national laboratories and two universities to overcome the numerous challenges involved in developing and testing new features of the model, carrying out the simulations on major supercomputer platforms, and evaluating the model’s prediction through comparisons with a large suite of observations.


Including climate-ecosystem interactions in E3SM enables researchers to study past and future changes in carbon dioxide storage in natural ecosystems. For example, the model allows for analysis of the occurrence and impact of wildfires and droughts—recent causes of major property damage across Australia and the western United States. Ongoing work to extend the model to include representations of energy systems will enable scientists to use E3SM to answer questions like: “How does climate impact energy use and the availability of energy resources such as wind, hydroelectric, and solar power?”


Changes in climate and rising CO2 concentrations can alter the amount of carbon taken up by Earth’s ecosystems. For example, warming temperatures that increase plant growth and higher CO2 concentrations “fertilize” plants can enhance CO2 uptake from the atmosphere. However, droughts reduce plant growth, and wildfires damage forests, resulting in diminished CO2 uptake or releasing stored CO2 into the atmosphere.

By simulating these effects, the enhanced E3SM enables researchers to understand and quantify potential changes in CO2 based on future conditions. The simulations begin in 1850, before the industrial revolution, and simulate the Earth system’s responses to human activities, including industrial emissions, deforestation, and agricultural expansion. The team focused on modeling atmospheric CO2 removal by plants through photosynthesis and then determining if it remained stored in plants, soils, and wood products, or was released back to the atmosphere through microbial decomposition with climate warming and land use and land cover changes. Using satellite observations and other datasets, the team showed that the model better simulated land ecosystem behavior than older, similar models. Researchers submitted a subset of the simulations to an international model comparison effort to help the scientific community assess how much is known, and what still remains to be learned, about the simulation of ecosystem-climate interactions.

Point of Contact
L. Ruby Leung
Pacific Northwest National Laboratory (PNNL)
Funding Program Area(s)