Japan may find itself the odd man out as Prime Minister Shinzo Abe presents his government's blueprint for combating climate change this weekend at the summit of the world's leading industrialised democracies. The host for the Group of Seven meeting, German Chancellor Angela Merkel, has indicated she supports a pledge of eventual zero carbon emissions. Japan favours coal, gas and nuclear power over green energy despite rapid growth in investment in renewables since all its nuclear reactors were taken offline after the 2011 disaster in Fukushima. Curbing global warming will be among many items on the agenda when G7 leaders meet today and tomorrow at Schloss Elmau, 100km south of Munich. Japan is the world's No 3 economy and its fifth-largest emitter of greenhouse gases that contribute to global warming. Abe plans to explain to fellow leaders its target of a 26 per cent reduction from 2013 levels of carbon emissions by 2030. That compares with an intended 26 to 28 per cent cut by 2025 from 2005 levels for the United States, and the European Union's target of a 40 per cent reduction from 1990 levels, or 35 per cent from 2005. Japanese officials defend their plan as comparable to or even exceeding the goals set by other major economies. "Some committee members said it was too ambitious and they said it could not be done, but it was decided to set this target," said Masakazu Toyoda, a government adviser and chairman of the Institute of Energy Economics, Japan. Solar and wind power generation are too unstable and costly to provide more than marginal power generation capacity, especially given the need to extend power grids from major cities like Tokyo to more remote areas considered most suitable for wind power, he said. As for zero emissions, the world's carbon dioxide pollution level hit a record 396 parts per million in 2014, way above the 350 level of heat-trapping gases in the atmosphere seen by some scientists and environmental groups as a safe level. In Toyoda's view, limiting emissions to 450 parts per million by 2050 would be "very difficult". "With additional effort to introduce advanced technology, the realistic target should be 550," he said in a briefing on Thursday. Japan's long-term energy plan is evolving and actual trends will depend on various factors, including nuclear plant restarts, the pace of decline in the population, changes in technology and expanded use of solar panels and other renewable energy by households and businesses. The country faces unique challenges as an island nation with scant conventional resources. Unlike European countries, it cannot use regional electricity grids. Abe's government is seeking restarts of reactors that meet upgraded safety standards, and in the meantime fossil fuels remain the preferred option for bridging energy supply gaps. Japan could do far better, given the trend towards wider, ad hoc adoption of renewable energy in the private sector, said Tomas Kaberger, chairman of the Japan Renewable Energy Foundation and a former head of Sweden's energy agency. "It's just a matter of very costly delays to an industrial development that will be inevitable for global competition reasons. Japan cannot be the last fossil country in the world," he said.