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The world's energy resources can be divided into fossil fuel, nuclear fuel and renewable resources. The estimates for the amount of energy in these resources is given in zettajoules (ZJ), which is 1021 joules. The 2C target in global warming means only a quarter of existing, exploitable fossil fuel reserves are burnable.〔http://www.theguardian.com/environment/2015/jan/29/shell-urges-shareholders-to-accept-climate-change-resolution Shell urges shareholders to accept climate resolution] Guardian 29 January 2015 〕 ==Fossil fuel== (詳細は Proven energy reserves, BP Statistical Review of World Energy 2010 )〕 These are the proven energy reserves; real reserves may be up to a factor 4 larger. Significant uncertainty exists for these numbers. Estimating the remaining fossil fuels on the planet depends on a detailed understanding of the Earth's crust. While modern drilling technology makes it possible to drill wells in up to 3 km of water to verify the exact composition of the geology, one half of the ocean is deeper than 3 km, leaving about a third of the planet beyond the reach of detailed analysis. In addition to uncertainty in real reserves, there is significant uncertainty in technological and economical factors that impact what percentage of reserves can be recovered gainfully. In general the easiest to reach deposits are the first extracted. Factors affecting the cost of exploiting the remaining reserves include the accessibility of fossil deposits, the level of sulfur and other pollutants in the oil and the coal, transportation costs, and societal instability in producing regions. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「World energy resources」の詳細全文を読む スポンサード リンク
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