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Researchers map CO2 emissions for entire Los Angeles Megacity to help improve environmental policymaking

A team from Northern Arizona University, Arizona State University, the University of Michigan, the National Institute of Standards and Technology (NIST) and NASA’s Jet Propulsion Laboratory have developed a high-resolution, bottom-up emissions map that includes every building and road in the Los Angeles megacity basin for a total of 176 million tons of CO2 per year.

The results are published in Earth Systems Science Data. The Los Angeles megacity—the third-largest metropolitan area in the world—occupies 4,850 square miles and houses more than 18.5 million people.

Professor Kevin Gurney of Northern Arizona University, who specializes in atmospheric science, ecology and public policy, has spent several years developing a standardized system as part of the Hestia Project that quantifies and visualizes greenhouse gases emitted in urban regions down to each street and building, identifying problem areas and showing where public policy is—or is not—making a difference. His goal is to provide cities with a means to strategically address problem areas instead of taking a sweeping and costly approach.

We’re providing city stakeholders with a scalpel instead of a hammer. For example, about 60 percent of roadway emissions come from 10 percent of the roads. With Hestia, I can tell them which roads those are, and they can develop specific policy to address just those roads. The same is true for buildings. We can identify the ones with the highest emissions and track how well efforts to reduce those emissions are working. Policymakers can see progress.

—Professor Gurney

Mapping Los Angeles was the latest effort in a long-term project that involves collaborators at NASA, the National Oceanic and Atmospheric Administration (NOAA), NIST, the University of Colorado, Pennsylvania State University, the Scripps Institution of Oceanography at the University of California, San Diego, the University of Utah, GNS Science in New Zealand and Purdue University. Other cities Gurney has mapped to this degree are Indianapolis, Salt Lake City and Baltimore. However, Gurney expects the Los Angeles mapping to have the most significant implications, especially considering the sheer size and scope of the area.

It’s the first megacity for which we’ve quantified emissions down to the scale of every building and roadway. Nothing has been left out of an area that includes 80 cities and five counties. California has an aggressive policy when it comes to carbon dioxide emissions, and people want to know what the best policy options are and whether those policies are working. We can provide the information to local governments and they can take immediate action. And if we can do this for the entire Los Angeles Megacity, we can do it anywhere in the United States.

—Professor Gurney

One of the strengths of the approach is the incorporation of atmospheric monitoring of CO2 from ground-based and satellite instruments.

By synthesizing the detail of building and road-scale emissions with the independence and accuracy of atmospheric monitoring, we have the best possible estimate of emissions with the most policy-relevant detail.

—Professor Gurney

Animated graphics help people visualize their city and their personal emissions to illustrate how their actions are affecting the environment in which they live. Gurney hopes that will inspire people to become more engaged in policy development.

Data from the LA Basin mapping project are available on the NIST website.


  • Gurney, K. R., Patarasuk, R., Liang, J., Song, Y., O’Keeffe, D., Rao, P., Whetstone, J. R., Duren, R. M., Eldering, A., and Miller, C. (2019) “The Hestia fossil fuel CO2 emissions data product for the Los Angeles megacity (Hestia-LA),” Earth Syst. Sci. Data, 11, 1309–1335 doi: 10.5194/essd-11-1309-2019


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