If you haven't heard the term green job uttered hundreds of times of late from politicians, industry leaders, union leaders and environmentalists then you must have been hiding under a rock for the past year. No other term apart from global credit crunch seems to have had as much media coverage but what is all the fuss about?

In the US, President Obama has promised to spend $150 billion over 10 years creating 5 million new green energy jobs and he is not the only one to see the push to a low carbon economy as the answer.

Here in the United Kingdom and across Europe political leaders have been promoting the creation of renewable energy jobs as a very necessary step in the drive to reduce carbon emissions, and as one of the key levers in combating the current global financial crisis. In the UK, Prime Minister Gordon Brown has promised that this month's Budget will be a "job creator, a quality of life improver, and an environment-enhancing measure" outlining a "green" path to economic revival. Brown has previously said 400,000 new green jobs could be created over the next eight years if the UK transitions to a low carbon economy. But what is green collar? What makes it different from blue or white collar? Why does it matter? And why does the issue appear so controversial?

Some more skeptical have argued that the term green collar jobs is little more than "green washing" and a term used by politicians for political ends; they argue that actually green collar jobs are no different or perhaps less efficient than the blue collar jobs they are replacing. This is an argument that is sure to rage on for some time.

For all the talk of green jobs, there is probably equal confusion about what actually qualifies as a green job.

If an employee is working for a car manufacturer on a sports car: blue collar. If the same worker at the same company is working on a hybrid does is that a green collar job?

Phil Angelides, Chair of the Apollo Alliance (a coalition of environmental groups, labour unions and politicians promoting the low carbon economy) states that to be green a job "has to pay decent wages and benefits that can support a family. It has to be part of a real career path, with upward mobility. And it needs to reduce waste and pollution and benefit the environment."

His colleague and Chief Executive of the Apollo Alliance Lucy Blake adds "A green collar job is in essence a blue-collar job that has been upgraded to address the environmental challenges of our country."

Van Jones, social activist and advisor to President Obama says a green job is "a family-supporting, career-track job that directly contributes to preserving or enhancing environmental quality." Jones's site Green For All adds "most green collar jobs are middle-skill jobs requiring more education than high school, but less than a four-year degree -- and are well within reach for lower-skilled and low-income workers as long as they have access to effective training programs and appropriate supports".

So in the end does the definition really matter? Perhaps, but certainly not quite as much as the key issues of unemployment, economic recovery, climate change, energy security and peak oil, which the push for a low carbon economy seeks to tackle.

Environmental groups such as the Sierra Club state that green jobs are a victory for the environment and for workers. The founder of RenewableEnergyJobs.com, the global green job site, Sam Newell agrees. "To me it's quite simple, green jobs are good for the employee and good for the environment and that can't be bad." He argues "comparing the efficiency of green jobs with. those in other sectors of manufacturing or perhaps old energy doesn't quite add up. You are comparing apples and oranges; they are not like for like. It's pointless to compare them using one measure such as energy output per employee. You need to take a range of important factors such as carbon production and environmental impact into consideration which none of these arguments appears to do."

Green jobs are already a growing part of the global economy. As demand has risen for clean energy and environmentally responsible manufacturing, green workers are producing everything from solar panels to electric cars to organic clothing and food.

With the serious issues of climate change and the development of affordable, secure and sustainable energy sources for all it looks like the green job is here to stay regardless which definition you subscribe to.