Dr. Gurney said the mistakes seemed to be simple miscalculations. “I don’t think there is an attempt to systematically or deliberately underestimate emissions,” he said. While some cities have correctly estimated their emissions, he noted, “whether that’s right for the right reasons or the wrong reasons, it’s hard to figure out.”
Dr. Gurney’s work is funded by the National Institute of Standards and Technology, and one of the authors, Kimberly Mueller, is a scientist there. James R. Whetstone, an official in the institute’s greenhouse gas measurement program, called the new paper “an important step forward” in correctly measuring greenhouse gases from cities. “What will serve the country best is if we have a consistent way of determining emissions going from the city level to the national level,” he said.
The National Institute of Standards and Technology, he noted, focuses much of its efforts on atmospheric monitoring, and so Dr. Help Gurney “measure the same thing in different ways”, gaining confidence in the results.
Previous studies by researchers at the University of Michigan, Harvard and the federal government have found that emissions of methane, another powerful greenhouse gas, are also underestimated by many cities. Dr. Gurney said that “both gases really should be part of this systematic approach.”
The cities’ efforts so far, said Dr. Gurney, was a commendable venture, but “they haven’t had many tools to do it.” What’s more, he said, “Cities are struggling to pick up the waste and fill pits, let alone keep detailed records of their emissions.”
Reducing emissions in a city, he says, requires an in-depth understanding of where the biggest problems are, including specific highways and industries congestion, so that authorities can take targeted action that delivers the greatest benefit at the lowest cost. Building high-occupancy lanes or fast bus lanes on any highway can be a waste; it would be better, he said, to know which road projects could do the most good.