Agriculture modeling is important to the carbon cycle

To understand Earth’s changing climate, scientists often turn to computer simulations based on science. Researchers strive to make Earth system models as accurate as possible. Factors such as wind currents, air quality, and weather patterns all play a role. But current modeling has often left out one important activity: farming.

Now, research from the Pacific Northwest National Laboratory (PNNL) is published in Journal of Geophysical Research: Biogeological Sciences It was found that representing the impact of agricultural crops more realistically in a land system model could increase model skill by 40 percent.

“The differences between the observations and the results of the previous model were very significant,” said Ben Bond Lamberti, an Earth scientist at PNNL. “Our new approach helps remove biases and errors from the model. This means it should be easier to see the footprint of climate change in carbon fluxes from these regions.”

It is well understood that agriculture plays an important role in the carbon cycle. Through photosynthesis, plants take in carbon dioxide from the air and use it to feed themselves and, ultimately, us. While all crops contribute to the carbon cycle, changing agricultural processes can greatly affect the amount of carbon uptake. In fact, one possible way to mitigate climate change involves using agriculture to capture more carbon dioxide.

“Agriculture affects both local and regional climate,” said Eva Sinha, a PNNL earth scientist and lead author of the study. “This makes it an important part of climate models. The better we can represent the realities of agriculture, from crop type to land management practices, the more accurate our climate projections will be.”

Modeling is important

Modeling is an essential tool for studying climate. Historical weather patterns help researchers look at past climate patterns, but understanding the future requires projecting different possible outcomes. Earth system models are the only way to display at high resolution different potential climate receivers around the world. The more closely they reflect real-world conditions, the better they can predict. The PNNL-led team presented crop rotation in the Earth component of the DOE Exascale Earth System model. Researchers are using this model to study global climate, including how it interacts with energy-related science.

Previously, the simulations treated all farmland the same way throughout the year. The new representation allowed the team to reflect different types of land uses, specifically the rotations of the corn and soybean crops often grown across the Midwestern United States. When the research team ran the model with crop rotations represented, the results of carbon exchange between crops and air were much closer to the observed values.

The observed values ​​play an important role in evaluating the results of the model. An accurate model should produce results that are relatively close to the observations, given the correct inputs. Since incorporating representations of different crops brought the model results significantly closer to the observed values, it is likely that the model will provide more accurate representations of the carbon cycle in the future.

“We thought a more accurate representation of the crops would improve the model,” Sinha said. “But we didn’t expect it to be much better.”

Crop management and carbon management

As researchers look to predict climate for the 21st century and beyond, their focus is on remaining uncertainty. Many of the ways in which human behavior affects climate are poorly understood and difficult to model. Agricultural management falls under both categories.

The increase in model resolution could have major implications for understanding how the terrestrial carbon cycle will change in different climate futures. Crops can act as a natural carbon sink. Understanding how different crops and agricultural practices affect the carbon cycle can help researchers better identify changes to the carbon cycle due to climate change and changes that may be from different agricultural practices.

The team plans to study how agricultural choices affect the amount of carbon in the atmosphere – past, present and future. “We want to understand what would happen if we made crops part of the solution,” said Bond-Lamberti. “Modeling can help us understand which choices will have the greatest impact.”