NEW YORK, March 22 (Reuters) - The United States is developing a system to track atmospheric levels of carbon dioxide, the main greenhouse gas, which could help scientists project future climate change, a government researcher said.

The CarbonTracker monitors carbon dioxide levels throughout North America to create an Internet-based map. Carbon-emitting areas, such as cities and industry centers, show up in red and carbon sinks, such as forests, are represented in blue.

Pieter Tans, head of the National Oceanic and Atmospheric Administration's greenhouse gas cycles group, which created the system, said it could help researchers verify their climate models. It could also facilitate any future trade in carbon credits by monitoring whether industries are actually cutting emissions, he said.

The tracker will soon use more data from sources, including monitors in airplanes and countries beyond North America, to broaden the map.

"We hope this will evolve into a much denser network, so we can say meaningful things about whether states or large metropolitan areas are successful in limiting net emissions of CO2," Tans said in a telephone interview.

The United States, the world's top emitter of carbon dioxide, does not regulate greenhouse gases.

But banks, as well as carbon trading firms that took shape when the European Union started trading carbon credits in 2005, are gearing up for potential U.S. trade. They take heart in the growing political pressure in the country to tackle climate change by putting mandatory limits on the gas.

Canada's federal environment office, Environment Canada, provided a quarter of the data for the project, Tans said.

Tans said the project was working with researchers from China and India to try to expand the project to those countries, which are growing carbon emitters.

AlertNet news is provided by