Environmentalists hope President Barack Obama’s administration will allow the state of California to impose its own limits on greenhouse gas emissions for cars. The state’s top air quality regulator said he was optimistic about the Obama administration’s decision which might be taken by May.

In 2007, the Bush administration denied California’s request to implement its own greenhouse gas emissions limits. With the new administration stepping in, the Environmental Protection Agency chief, Mary Nichols, sent a letter to EPA Administrator Lisa Jackson in which he asked her to review California’s request.

If the new administration decides to allow California to impose its own greenhouse gas emissions limits, the move will most likely create a precedent which at least a dozen other U.S. states will use to impose stricter limits. Californian authorities want to reduce the emissions by 30 percent by 2016, which is the most ambitious effort to tackle the problem of the global warming.

If the Obama administration agrees with California’s request, as much as 17 states will most likely proceed to enforce greenhouse gas emissions limits. The limits will force car manufacturers to produce more fuel-efficient vehicles. Considering the fact that the 17 states account four approximately 50 percent of the U.S. auto market, the decision is a very difficult one.

After being denied in December 2007 the right to impose their own standards and regulations for carbon dioxide emissions from automobiles, the coalition of 17 states, side by side with cities and environmental groups, sued the Environmental Protection Agency (EPA) in an attempt to determine the agency to find out whether the greenhouse-gas emissions cause damage to the public health and if so, to regulate the emissions from new cars and trucks.

Back then, the EPA refused to set emission levels for green house gases arguing that the effects of the gases are still a “substantial scientific uncertainty” as well as the measures to counter these effects.

The EPA has concluded in December that the heat-entrapping gases are a menace to public health, but the process of issuing regulations stalled after the EPA sent the results to the White House.

Now, a year later, California wants to be allowed to impose not only greenhouse gas emissions limits, but also to require car producers to make cars using paints that reflect more heat, tires that roll smoother and improved air conditioning in order to increase efficiency.

If the presidential administration grants the 17 states the right to impose their own limits on heat-trapping gases, about a half of the U.S. population and more than 50% of the car market will require the auto producers to make vehicles that are 30 percent cleaner, said Nichols.