US cities undercount their emissions by 18 percent: study

US cities undercount their emissions by 18 percent: study
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When U.S. cities self-report emissions, they reportedly miss nearly 20 percent of the greenhouse gases spewed into the air on average, according to a new study. 

In the study published Tuesday in the journal Nature Communications, researchers compared 48 cities’ self-reported emission inventories to their own projections. 

The researchers’ projections compile emissions from sources such as factories, power plants and roadways as well as census block groups using publicly available data. 

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They found that the results of cities' self-reported data varied widely when compared to their own data, with Torrance, Calif., undercounting by 145.5 percent, while Benicia, Calif., overcounted by 63.5 percent. 

Among the cities that had the biggest undercounts were Cleveland, which undercounted by 90 percent, Boulder, Colo., which undercounted by nearly 74 percent and Los Angeles which undercounted by 53 percent, according to the study.

They also determined that if they extrapolate their average finding of underreporting 18.3 percent to every U.S. city, the undercounted pollution would be 23.5 percent larger than the emissions from the entire state of California in 2015. 

Cities’ self-reported inventories are used to develop policies including setting climate goals. 

"The concern is that if we're undercounting emissions, then our strategies to reduce emissions are not going to be ambitious enough to reach our targets," said Geoffrey Roest, one of the study's authors. 

It also comes as the country prepares to set its own climate goals. President Biden recently signed an executive order to rejoin the Paris climate agreement, in which countries agreed to reduce their emissions in an attempt to prevent the world from warming by more than 2 degrees Celsius. 

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White House climate adviser Gina McCarthyGina McCarthyWhite House details environmental benefits plan for disadvantaged communities Tom Brady to Biden: '40 percent of the people still don't think we won' Clean electricity standard should be a no brainer amid extreme climate impacts MORE recently said that the administration would announce its greenhouse gas reduction target under the deal before an Earth Day climate summit.

Roest said that at the national level, the study shows a need for a consistent methodology to count emissions across the country. 

"Now that we're entering the Paris climate agreement, hopefully we'll have a little bit more top-down structure and support for cities that want to understand their own greenhouse gas emissions," he said.  

Updated at 5:46 p.m.