Mr. Yukio Hatoyama, head of the Democratic Party of Japan and the prime minister-in-waiting, has announced that Japan will seek a 25 percent cut in greenhouse gas emissions from 1990 levels by 2020. This is an ambitious target that could put Japan on the path to a low-carbon society. It could also give impetus to international efforts to work out a new framework for reducing emissions in and after 2013. The current Kyoto Protocol expires in 2012.

In June, Prime Minister Taro Aso proposed reducing greenhouse gas emissions by 15 percent from 2005 levels by 2020 (8 percent reduction from 1990s levels). This represents net reductions in emissions in Japan. Mr. Hatoyama's target is believed to include reductions that developing countries have achieved as a result of Japan's financial and technological assistance and gas absorption by forests.

Japan's emissions increased 9 percent in fiscal 2007 from fiscal 1990 levels. Under the Kyoto Protocol Japan must, between fiscal 2008 and fiscal 2012, reduce emissions by 6 percent from 1990 levels. It is almost a foregone conclusion that some industries in Japan will put up strong resistance to Mr. Hatoyama's severe target. The DPJ leader took a top-down approach, apparently to force a transformation of industrial structure conducive to large emissions cuts.

The DPJ needs to show as soon as possible a detailed and concrete road map for reducing greenhouse gas emissions. It also may have to reconsider its plan to make expressways toll-free, a move that environmental groups fear will lead to increased use of expressways and, therefore, more carbon dioxide emissions.

Japan's greenhouse gas emissions account for about 4 percent of the global total (compared to about 40 percent by the United States and China combined). Mr. Hatoyama said Japan's lone efforts cannot stop global warming and made it clear that his promise won't become effective unless other major emitter countries agree to emission-reduction efforts. To facilitate negotiations, Japan should present effective proposals to enable developing countries to combat global warming.