In 2004, the worldwide energy consumption of the human race was on average 15 terawatts (TW; 1 TW = 1 x 1012 W) with 86.5% from burning fossil fuels. This is equivalent to 471,000 PJ (1 PJ = 1 x 1015 J) per year. There is at least 10% uncertainty in these figures due to national variations in tracking consumption, and due to variations in energy content between particular barrels of oil or tons of coal.
The remaining worldwide energy resources are large, with the remaining fossil fuels totaling an estimated 0.4 YJ (1 YJ = 1024 J) and the available nuclear fuel such as uranium exceeding 2.5 YJ (1 YJ = 1024 J). Mostly thanks to the Sun, the world also has a renewable usable energy flux that exceeds 120 PW (8,000 times 2004 total energy usage), or 3.8 YJ/yr, dwarfing all non-renewable resources.
Despite the abundance of fossil fuels there are a number of pressures that may move the world’s energy consumption to alternative energy sources. These include political considerations over energy security and potential pressure from energy superpowers, environmental concerns related to global warming and sustainability, and economic pressure resulting from energy price rises, carbon emissions trading and green taxation.
This move is already starting to happen in some countries, notably as a result of the Kyoto Protocol, and further steps in this direction are proposed. For example, the European Commission has proposed that the energy policy of the European Union should set a binding target of increasing the maximum level of renewable energy in the EU’s overall mix from less than 7% today to 20% by 2020.