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Atmospheric Sciences & Global Change
Research Highlights

November 2017

New approach to geoengineering simulations is significant step forward

New algorithm for modeling stratospheric sulfate aerosol injections featured in special issue of Journal of Geophysical Research

Volcanic eruption
Scientists from PNNL, the National Center for Atmospheric Research, and Cornell University studied one much-discussed geoengineering approach: mimicking volcanic eruptions by creating reflective particles in the upper atmosphere that cool the planet.

The Science

Geoengineering—large-scale interventions designed to modify the climate—could take many forms. A team of scientists from Pacific Northwest National Laboratory, the National Center for Atmospheric Research, and Cornell University developed a specialized algorithm for an Earth system model that varies the amount and location of one type of geoengineering—sulfur dioxide injections into the upper atmosphere—and found that the approach could potentially be used to limit Earth's warming.

The Impact

Previous studies looking at simulated effects of geoengineering on Earth's climate have raised concerns about the potential side effects. One of the common features of those simulations is uneven cooling of the globe. In this study, scientists found that a specific approach to geoengineering could avoid that uneven cooling, limiting warming in multiple areas simultaneously. They caution, however, that there are other potential side effects and more research is needed to determine if this approach would be practical, or even possible, in the real world. The possibility of a global geoengineering effort to combat warming also raises serious governance and ethical concerns.

Summary

The team studied one much-discussed geoengineering approach: mimicking volcanic eruptions by creating reflective particles in the upper atmosphere that cool the planet. The scientists used the Whole Atmosphere Community Climate Model (WACCM), a state-of-the-art extension of the Community Earth System Model. The team recently updated the model to include particle growth and stratospheric wind variability. They successfully tested the model to see how well it could simulate the massive 1991 eruption of Mount Pinatubo, including the amount and rate of aerosol formation, as well as how those aerosols were transported around the globe and how long they stayed in the atmosphere. Then the scientists explored effects like cooling and precipitation after injecting sulfur dioxide at seven different latitudes and two different altitudes.

A team of scientists, including PNNL climate scientist Ben Kravitz, created a single model simulation with specific objectives: to limit average global warming to 2020 levels through the end of the century and to minimize the difference in cooling between the equator and the poles, as well as between the northern and southern hemispheres. The model successfully kept surface temperatures near 2020 levels against a background of increasing greenhouse gas emissions, and did so more evenly than in previous studies.

Funding

The research was funded in part by the Defense Advanced Research Projects Agency and the National Science Foundation, NCAR's sponsor.

Publications

B. Kravitz, D. MacMartin, M.J. Mills, J.H. Richter, and S. Tilmes, Journal of Geophysical Research: Atmospheres:

Data access

All the data from the experiments are available on the Earth System Grid at https://www.earthsystemgrid.org/dataset/ucar.cgd.ccsm4.so2_geoeng.html or http://dx.doi.org/10.5065/D6X63KMM

and https://www.earthsystemgrid.org/dataset/ucar.cgd.ccsm4.so2_ctl_fb.html or http://dx.doi.org/10.5065/D6PC313T.

More information

For more information, see the NCAR news release at https://www2.ucar.edu/atmosnews/news/129835/new-approach-geoengineering-simulations-significant-step-forward.


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