Japan's continued commitment to nuclear energy will be important in reducing its carbon dioxide emissions and also in improving nuclear safety on a global scale, the head of MIT's Department of Nuclear Science and Engineering said Saturday.

"Japan is still the third-largest economy in the world and is a major emitter, and of course a larger emitter (of carbon) today than it was four years ago," professor Richard Lester told reporters in Tokyo.

Although the population is decreasing and the nation is trying to increase the use of renewable energies like solar and wind, "there is, in my judgment, almost no likelihood that Japan will be able to achieve the kinds of reductions in carbon emissions that the world will look to," said Lester, who was in Japan to visit the Kashiwazaki-Kariwa nuclear plant in Niigata Prefecture.