How much money should be pumped into the "clean energy" bubble?

1. From this article:

UNITED NATIONS (Reuters) - U.S. institutional investors pledged at a U.N. summit on Thursday to invest $10 billion over two years in technologies that aim to reduce greenhouse gas emissions and to pressure companies to disclose their risks associated with climate change.
...
John Sweeney, the president of the AFL-CIO, a federation of unions, told the summit that some of the $5 trillion of union workers' retirement funds should be invested in ways that help fight climate change. "These deferred wages of working people are the capital that can fuel the energy economy of the future," he said.

Some analysts have said green technologies like solar power, ethanol and biodiesel are forming an investment bubble that could soon pop.

2. From that article on Gore and subprime carbon:

A report by the McKinsey Global Institute released at the U.N. conference said major investments over the next decade in boosting the output from various types of energy that consumers use could earn investors double-digit rates of return.

3. Given that billions of dollars in private money are pouring into these "clean" technologies, do we really need to inject a lot of public money too?

From Hillary Clinton's website:

A $50 billion Strategic Energy Fund, paid for in part by oil companies, to fund investments in alternative energy. The SEF will finance one-third of the $150 billon ten-year investment in a new energy future contained in this plan;

4. A related post is here, entitled "Clean energy will make Gore rich".