American cities including Atlanta, Miami and New Orleans that set goals to slash planet-warming greenhouse emissions are lacking the data to measure their progress, scientists said in a new report.

Some 40% of U.S. cities that committed to cutting emissions are unable to assess their programs because costly tallies of their emissions are inadequate, said the American Council for an Energy-Efficient Economy (ACEEE), a nonprofit organization. "City resources are always tight," said David Ribeiro, the report's lead author and a senior research manager at ACEEE.

The lack of data could also be due to emission-cutting goals having only recently been adopted, or to insufficient political will, Ribeiro said. Of the 75 cities surveyed, just over 20% had pledged to cut emissions and were able to measure advances with recently produced evidence. Cities account for two-thirds of the world's energy demand and 70% of energy-related emissions, the report said, citing cited International Energy Agency data.

Plans to cut emissions have grown increasingly ambitious in the United States since President Donald Trump vowed in 2017 to leave the landmark Paris climate accord, said Katie Walsh of CDP, formerly known as the Carbon Disclosure Project, a non-profit that supports collection of environmental data. The report said Los Angeles pledged to reduce its greenhouse gases by 100 percent by 2050, thus virtually eliminating them, compared to 2016, with municipal data projecting it would meet that goal.

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But in another 21 cities, authorities had not collected enough emission data to track their progress, it said on Wednesday. With about 870,000 residents, Indianapolis, Indiana, was among the largest cities lacking data to assess its progress toward becoming carbon neutral – producing no more climate-changing emissions than can be offset by other means – by 2050.

Other large cities hampered by insufficient data include Nashville, Tennessee, Detroit, Michigan, and Louisville, Kentucky, the report said. Lucy Hutyra, a Boston University associate professor of earth and environment, said pledging to reduce greenhouse gasses was a good "aspirational first step." But, she added, "Without a clear plan for monitoring the efficacy of emissions reduction policies, it is all aspiration." (VOA)