TOKYO — At 12:30 p.m. on a recent Wednesday, the Ministry of the Environment offices here were almost completely in darkness, lit only by the silver-blue glow of computer screens.

All of the government ministry offices are supposed to go dark for an hour in the middle of each day to save energy and reduce greenhouse gas emissions. Satoru Morishita, deputy director general of global environment affairs at the ministry, said the policy is a daily reminder of the stakes of climate change.

“We’re trying to change behaviors in addition to changing attitudes on climate change, and from that, to change the whole society,” Mr. Morishita said in an interview.

But the Japanese people, particularly young people, do not seem to be heeding Mr. Morishita’s wishes. A recent government survey showed that nearly 75 percent of Japanese people ages 18 to 29 expressed interest in climate change, an impressive figure by international standards. But it is a noticeable drop from the close to 90 percent interest stated by the same age group just a few years ago.