The organizations responsible for the world’s three leading environmental assessment systems for buildings have agreed to establish consistent methods for measuring and reporting carbon dioxide (CO₂) emissions.

The U.K.-based Building Research Establishment (BRE) Trust, the U.S. Green Building Council (USGBC), and the Green Building Council of Australia, plan to "map and develop common metrics to measure emissions of CO₂ equivalents from new homes and buildings.” Along with the UK Green Building Council, the three groups, which administer the BREEAM, LEED, and Green Star rating systems respectively, signed a memorandum of understanding at the Ecobuild conference held in London earlier this month. “If we are to address the impacts of climate change and give a strong message to the industry, it is important that all the rating tools work together,” says Martin Townsend, director of BREEAM.

The goal of the efforts, according to the organizations, is to allow comparisons of buildings rated by different tools. The organizations have no plans to fold the various systems into one. “Each rating tool has grown in response to market needs in different countries, and it is healthy for them to be different in some respects,” says Townsend. Michelle Moore, UGBC senior vice president of policy and affairs, agrees: “We all just want to measure apples to apples,” she says.

For several years the USGBC has been working on a revamp of LEED to place more emphasis on reducing carbon emissions and mitigating global warming. Set to launch in late April, the new rating system, known as LEED 2009, could reflect further refinements that result from the London agreement within a year. “There’s an urgency relating to climate change and, if anything, greenhouse gas emissions are increasing more rapidly than we imagined,” says Moore.

In the U.S., buildings are the largest single source of heat-trapping greenhouse gases, contributing almost 40 percent of such emissions to the atmosphere, according to some estimates. “The economy is in the news right now because it’s the point of pain, but the clock is ticking on the environmental front,” says Moore, adding, “buildings are a big part of the problem and they can be a big part of the solution.”