The document discusses the importance of energy efficiency in reducing greenhouse gas emissions and overcoming barriers to achieving large-scale energy efficiency. It proposes that green banks can help by providing massive amounts of up-front capital needed to finance energy efficiency programs. Green banks would raise capital from various sources and leverage funds to support billions of dollars in loans and investments for clean energy and efficiency projects. This could help achieve substantial reductions in emissions by overcoming financial and other barriers that currently limit energy efficiency spending.