While many politicians have tagged the phrase "job growth" onto their arguments for climate change legislation, a recent report is bolstering the case with hard numbers on how lucrative such legislation might be for the economy.

The study, released by the Boulder, Colorado-based non-profit American Solar Energy Society and the Washington, D.C.-based Management Information Services, reports that by aggressively pursuing renewable energy and energy efficiency measures, such as deploying solar panels for buildings and reducing greenhouse gas emissions, more than 4.5 million jobs could be created in the U.S. by 2030. The report was based on the number of existing "green collar" jobs and the revenues they generated.

"This is something that the country wants to see happen," says Brad Collins, executive director of the ASES. "We can create a vibrant U.S. manufacturing installation industry, capable of competing with other countries."

The report highlights several renewable energy technologies, including biofuels and wind power, which will spur the most job opportunities. Collins says entrepreneurs could be at the forefront of the boom.

"They're going to look to energy efficiency, because it's been proven to be an area for rapid growth," he says.

Jennifer Layke, deputy director of the climate and energy program at the Washington, D.C.-based World Resources Institute, which focuses on international climate change policy, says the government's hesitance on investing in climate change could be derived from the many companies who fear they will lose business from a shift toward renewable energy technologies.

"The key question that we've been facing is, 'Do we see an increase in a green jobs scenario?" says Layke. "Many of the businesses that we work with have cited both negative and positive implications for their businesses."

However, Layke says, the difficulty some businesses may have transitioning to new types of technology doesn't negate the viability of renewable energy resources. 

"Coal mining and power plants are not nearly as job-intensive as building upgrades and weatherization," she says. "There are enough low-cost opportunities that we can change our economy without too high cost to consumers."