The global energy scene is in a state of flux. Large-scale shifts include: the rapid deployment and steep declines in the costs of major renewable energy technologies; the growing importance of electricity in energy use across the globe; profound changes in China's economy and energy policy, moving consumption away from coal; and the continued surge in shale gas and tight oil production in the United States. These changes provide the backdrop for the World Energy Outlook-2017, which includes a full update of energy demand and supply projections to 2040 based on different scenarios. The projections are accompanied by detailed analyses of their impact on energy industries and investment, as well as implications for energy security and the environment. The report this year includes a focus on China, which examines how China's choices could reshape the global outlook for all fuels and technologies. A second focus, on natural gas, explores how the rise of shale gas and LNG are changing the global gas market as well as the opportunities and risks for gas in the transition to a cleaner energy system. Finally, the WEO-2017 introduces a major new scenario - the Sustainable Development Scenario - that outlines an integrated approach to achieving internationally agreed objectives on climate change, air quality and universal access to modern energy.