The debate over the impact of "green" jobs on the economy continues.

The latest salvo came Monday from a group of university researchers seeking to shoot down studies showing that spending billions of dollars on stimulus for renewable energy, energy efficiency and "smart grid" will help employ millions of people.

Not so fast, the researchers said – many of those jobs will simply be shifted from existing "fossil fuel-based sectors," and others shouldn't be classified as "green" at all. Instead of spending government money on backing those industries, the authors of the "Seven Myths about Green Jobs" report want the free market to guide where job growth happens.

The report questioned the methodology of reports from groups like the Center for American Progress. The Center for American Progress recently claimed that $100 billion in green stimulus would create 2 million jobs in the next two years, four times the number of jobs that would be created by spending the same amount on the oil industry and 300,000 more than would be created by giving the money to boost consumer spending.

Other reports singled out for criticism in Monday's report included those from the American Solar Energy Society, the U.S. Conference of Mayors, and the United Nations Environmental Program. All of these sunny forecasts are hampered by lack of clarity over the definition of "green jobs," as well as unclear methodology in comparing potential jobs impacts of stimulus spending on other sectors, the report claimed.

Given the momentum behind the green jobs push, it's not clear whether criticisms like this will create much of a roadblock.

Renewable energy and energy efficiency remain some of the least gloomy industries in an otherwise bleak economic landscape. And President Barack Obama and the mostly Democratic members of Congress backing the $787 billion stimulus bill he signed into law last month have made creating jobs in new "green" industries a central part of their sales pitch (see Obama Signs Stimulus Package).

The package has billions of dollars in grants, loan guarantees, tax breaks and other funding that renewable energy, energy efficiency and "smart grid" industry groups have said will be critical to continued growth and the job creation to come with it (see Smart Grid Backers Push Investment for Job Growth).

President Obama's decision last week to hire activist and green jobs evangelist Van Jones as his special advisor on green jobs may indicate that policies Jones has advocated in his best-selling book The Green Collar Economy – such as focusing job programs on training poor people and cleaning up environmental contamination in poor communities – will likely play a role in the administration's policies.

Then there are on-the-ground examples of how "green" businesses are creating jobs that would have otherwise been lost.

Take Serious Materials, the green building materials startup that announced Monday it was reopening a formerly shuttered window factory in Pennsylvania to manufacture its energy efficient windows.

The plant closing left 150 unemployed, but Serious intends to hire 100 people to staff its operation there, one of two closed window plants it intends to reopen this year (see Serious Materials Shopping for Acquisitions in Bankruptcy Court).

Beyond economic impacts, investment in green technologies can help reduce America's dependence on imported oil and cut back on greenhouse-gas emissions from fossil fuel-fired power plants and transportation to mitigate the effects of global warming, environmental backers say.

The authors of Monday's report made it clear they didn't intend to attack the energy policies behind green stimulus plans, only to question the methodology behind their job growth claims.

Green jobs claims have also come under scrutiny from the left. Last month saw a report commissioned by labor unions, the Sierra Club and Change to Win claiming that many "green" employers provided unsafe working environments at low wages (see Who's Offering Good Green Jobs?). 

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