Upon learning about Japan’s emissions reduction commitment, Yvo de Boer, general secretary of the UN Convention on Climate Change, said: “For the first time in two and a half years [since taking the job], I don’t know what to say.”

Environmental groups condemned the target as sophistry for using 2005 as its baseline year, rather than 1990, as does the 12-year-old Kyoto Protocol, to which Japan is a signatory.