Five of the top 10 underwriters of approximately $7 billion in green bonds come from Sweden and Japan, with Skandinaviska Enskilda Banken (SEB) and Daiwa Securities Group Inc. underwriting the most of such investments since their inception in 2007.

Bloomberg reported that London-based HSBC Bank and New York’s JPMorgan Chase took third and fourth place on the list, compiled by Bloomberg New Energy Finance and released Monday. Factors driving the ranking include government incentives for investment for environmental projects in Scandinavia and Japan making such bonds attractive, while the credit crunch in the U.S. and Europe tend to discourage those regions’ banks’ willingness to take on such projects.

Green bonds often come from leading development banks and fund projects for clean air, water and energy to help fight climate change and the people who are affected by it. The World Bank has issued $3.3 billion of them; next is the European Investment Bank with $1.8 billion in issues. The two banks were the developers of such bonds. Third in issuance is the Asian Development Bank, which has produced $897 million in green bonds.

According to California State Treasurer Bill Lockyer, who bought $400 million of World Bank green bonds in December, a deal managed by SEB, investors like such bonds because their yields are approximately double those of U.S. Treasury notes, while they carry the same top-notch credit rating. In the report, he was quoted saying, “It’s very safe. It accelerates the conversion to a noncarbon economy and it makes money.”

James Cameron, executive vice chairman of the U.K. investment manager Climate Change Capital, was quoted saying, “Scandinavian countries have always been very tuned into environmental themes. There’s something about the culture that recognizes the value of conservation in economic terms.”

Chris Jones, global head of medium-term notes and local currency syndicate at HSBC Holdings, said in the report that Japan “historically has been more culturally aware about socially responsible investment products.”

Stockholm-based SEB underwrote $1.9 billion of bonds, and Tokyo-based Daiwa about $1.2 billion, according to New Energy Finance. Swedbank was sixth with $327.5 million, and Mizuho International and Nomura International, both part of Tokyo-based institutions, ranked seventh and eighth respectively.

Swedish and Japanese banks together accounted for $4.03 billion of green bond offerings. That is nearly double the $2.6 billion underwritten by British and American banks and TD Securities, a unit of Toronto-Dominion Bank.