Japan's promise to cut greenhouse gases by 26 percent by 2030 as part of a global deal to fight climate change has drawn quick criticism from environmental groups that say the effort is both statistically unsound and too timid.

Prime Minister Shinzo Abe's government said the reductions will be made from a 2013 baseline. That year, Japan recorded its second-highest emissions level ever as it burned heaps of fossil fuels to replace all nuclear power lost in the wake of the Fukushima core meltdowns triggered by the Great East Japan Earthquake.

Using 2013 as a benchmark, Japan's effort would appear more ambitious than European Union proposals. But using 1990 or 2005 as a base year would leave Japan trailing the pack of richer industrial nations working to rein in the pollution blamed for global warming.