Cities are known to be true sources of pollutants, and their residents contribute the most to global warming. However, environmental-oriented policies seem to have had a positive outcome in the West Coast’s metropolitan areas, where according to the latest statistics, carbon emissions have reached the lowest levels in the country in 2005.

In a top 100 U.S. metropolitan areas, more than half of them responsible for producing 56 percent of the carbon dioxide emissions nationwide, the East Coast ones were found to have the highest emission levels, compared to the West Coast.

The study, released by the Brookings Institution, took into consideration carbon emissions produced by fossil-fuels used in transportation (by cars and trucks) and in homes (heating systems, cooking etc.), covering almost two-thirds of the U.S. population.

The disparities between the two coasts have a logical explanation: while the West Coast is greatly advantaged by the weather, by strict environmental policies, as well as population density, the East Coast relies more on the traditional sources of energy, which produce higher levels of carbon dioxide.

By comparison, the West Coast cities have already begun to develop and implement projects based on alternative sources of energy, while the mild weather requires less usage of the heating or cooling systems.

California is well known for its tough environmental policies, as well as for the efforts to rely more on renewable resources, such as solar energy, bio-fuels and hydro-electricity. Studies have shown that bio-fuels might soon become, as Henry Ford anticipated, the fuel of the future.

Pacific Gas & Electric has already started off a series of green projects, such as the production of natural gas from cow manure. PG&E also invested in solar thermal energy, and the first power plants to produce it are expected to become functional by 2011.

According to the mandatory state regulations in California, by 2010 at least 20 percent of the electricity produced in the state should come from renewable resources. These regulations became a necessity as the state began to face excessive greenhouse problems.

On average, every resident in a metropolitan area produces 2.47 tons of carbon dioxide per year, less than a U.S. resident produces on average (2.87 tons). However, in some metropolitan areas, such as Lexington, Ky., the average per capita carbon production was of 3.81 tons, compared to Honolulu, where it reached 1.5 tons.

The causes for such differences could lie in the climate conditions, as well as the types of fuels used, the development of rail transportation and the costs of energy (which are higher on the West Coast, compared to the East Coast).

As carbon dioxide concentrations increased at an alarming rate, environmental agencies began pleading for the regulation of emission standards from automobiles, power plants and other types of pollutants, and some states, such as California, have even been granted the right to establish their own admissible levels of carbon emissions.

The solution to all of our problems lies in our hands, researchers say, adding that we should rely less on fossil-fuels, start investing more in renewable energy sources, and establish the adequate emission standards.