World energy resources

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 10²¹joules.

The 2C target in global warming means only a quarter of existing, exploitable fossil fuel reserves are burnable.

Fossil fuel

Remaining reserves of fossil fuel are estimated as:

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.

World energy consumption

World total final consumption of 104,426 TWh (or 8,979 Mtoe) by fuels in 2012 (IEA, 2014)

World energy consumption refers to the total energy used by all of human civilization. Typically measured per year, it involves all energy harnessed from every energy source applied towards humanity's endeavors across every single industrial and technological sector, across every country. Being the power source metric of civilization, World Energy Consumption has deep implications for humanity's social-economic-political sphere.

Institutions such as the International Energy Agency (IEA), the U.S. Energy Information Administration (EIA), and the European Environment Agency record and publish energy data periodically. Improved data and understanding of World Energy Consumption may reveal systemic trends and patterns, which could help frame current energy issues and encourage movement towards collectively useful solutions.

The IEA estimated that in 2012 the world energy consumption was 13,371 Mtoe , or 5.6 × 10²⁰joules. From 2000–2012 coal was the source of energy with the largest growth. The use of oil and natural gas also had considerable growth, followed by hydro power and renewable energy. Renewable energy grew at a rate faster than any other time in history during this period, which can possibly be explained by an increase in international investment in renewable energy. The demand for nuclear energy decreased, possibly due to the accidents at Chernobyl and Three Mile Island.

Energy

In physics, energy is a property of objects which can be transferred to other objects or converted into different forms, but cannot be created or destroyed. The "ability of a system to perform work" is a common description, but it is difficult to give one single comprehensive definition of energy because of its many forms. For instance, in SI units, energy is measured in joules, and one joule is defined "mechanically", being the energy transferred to an object by the mechanical work of moving it a distance of 1 metre against a force of 1 newton. However, there are many other definitions of energy, depending on the context, such as thermal energy, radiant energy, electromagnetic, nuclear, etc., where definitions are derived that are the most convenient.

Common energy forms include the kinetic energy of a moving object, the potential energy stored by an object's position in a force field (gravitational, electric or magnetic), the elastic energy stored by stretching solid objects, the chemical energy released when a fuel burns, the radiant energy carried by light, and the thermal energy due to an object's temperature. All of the many forms of energy are convertible to other kinds of energy, and obey the law of conservation of energy which says that energy can be neither created nor be destroyed; however, it can change from one form to another.