American cities are significantly undercounting their greenhouse gas emissions because of flawed data, study says

American cities are significantly undercounting their greenhouse gas emissions because of flawed data, study says

US cities are significantly undercounting their greenhouse gas emissions, according to a new study published this week in Nature Communications.

The researchers compared self-reported emissions data from 48 US cities to independent estimates based on federal data about factories, power plants, and roads, among other sources. They found cities are under-reporting by nearly 20%. When adjusted to include all US cities, that figure exceeds the total emissions of the state of California by almost 24%.

Mitigating the emissions of greenhouse gases, which include carbon dioxide and methane gas, is an essential step in addressing climate change. But, the researchers say, there is currently no universal way that cities measure emissions, and inconsistent and inaccurate data make mitigation much more difficult.

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"We haven't had a systematic regulatory approach to controlling greenhouse gas emissions in the US," Kevin Gurney, the paper's lead author and a Northern Arizona University professor, told The New York Times.

Instead, cities all use different methods for reporting their emissions, and many are leaving out specific fuels or sources, resulting in the inconsistent data.

On average, the