It is estimated that the world's cities spew some 70 percent of global greenhouse gases, but often, they don't know where those gases are coming from.

To address that knowledge gap, a sustainability group and a coalition of the world's largest cities are banding together to come up with a universal protocol for measuring and reporting heat-trapping gases.

The aim is to ensure that local lawmakers know where to look when trying to curb warming temperatures and provide mayors across the globe with a standard template to compare information with each other.

With that knowledge, they could be more likely to gain funding for clean-energy projects from the World Bank, which is corresponding on the project, said Jennifer Ewing Thiel, director of tools and technical innovation at ICLEI USA. Last week World Bank President Robert Zoellick said his institution supported development of a new standard.

ICLEI will be joining with the C40 Cities Climate Leadership Project, which represents the largest cities in the world and just sponsored a climate change conference in São Paulo, to complete the protocol. ICLEI represents more than 1,000 local governments in 70 countries.

"Cities of all sizes play an important role in combating the impact of climate change. Establishing a single global standard for reporting greenhouse gas emissions will empower local governments to accelerate their actions and access funding for mitigation and adaptation projects," said New York City Mayor Michael Bloomberg, chairman of C40.

Totting up apples and oranges
There are existing protocols for city measurement of greenhouse gases. ICLEI has an existing standard, for example, as does the World Bank.

The problem is that the existing blueprints often measure different things and need to be merged together, explained Ewing Thiel. As an example, she said one might not cover city airports, while the other one does.

The result has been a hodgepodge of numbers from place to place, with cities sometimes establishing their own methodologies to wade through the confusion.

A report released during the C40 event in São Paulo cited some of the difficulties.

Half of the cities surveyed in a recent survey include building, transportation and street lighting in their inventories, while the others do not, for example. Some cities estimate total city emissions, while others focus on their 10 "primary sources." Some focus on annual emissions, while some focus on year ranges.

The new protocol would provide a list of what emitting facilities should be covered, along with formulas of how things should be measured and compiled, said Ewing Thiel. The protocol would cover citywide emissions, and should be ready for international climate talks in November in Durban, South Africa, she said.

Lots of spreadsheets, but gaps in the data Many of the input numbers would come from entities already gathering greenhouse gas data, such as utilities assessing greenhouse gas releases from landfills. A single standard should streamline some of the paperwork for government officials, said Ewing Thiel.

"There's a lot of city staff swimming in hundreds of spreadsheets," she said. It also should help lawmakers direct their efforts. It's hard to put policies in place for buildings, if you don't know the degree to which they contribute to city emissions, she said.

The idea of a new standard is a step in the right direction but has limits, said Mike Blackhurst, who recently accepted an assistant professor position at the University of Texas, Austin, in civil, environmental and architectural engineering. He co-authored a study ready for publication in a peer-reviewed journal about the ability of cities to develop greenhouse gas inventories.

He said part of the obstacle is that there is difficulty assessing what are termed "Scope 3" emissions from cities, or greenhouse gas output that is not directly in their city borders. A city buying hundreds of computers, for example, can't fully assess emissions associated with those computers in the production process, which might have taken place around the world.

City transportation, which is a huge source of emissions, is also hard to measure, he said. Short of estimating the miles traveled by all vehicles within municipal boundaries, there are gaps in the data, he said. More sampling of transportation patterns would help with lack of knowledge in that sector, he said.

"We're a little premature in thinking we can come up with a good standard now," he said.

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC., 202-628-6500