Scientists are trying to find more environmentally-friendly ways to generate electricity and a change in public opinion is pressuring governments to find better energy solutions for the planet. However, most of the electricity generated globally is still produced by fossil fuels.
This is partly due to the fact that fossil fuels can generate a lot of power, compared to other energy sources, such as wind power or tidal power.
Other factors that could influence the decisions of governments to develop 'cleaner' energy are political and economic pressures. For example, countries like Saudi Arabia, whose economy is heavily based in extracting and exporting oil, have a strong interest in fossil fuels being used as a continuing energy source.
Other examples include growing economies, such as China. A large amount of energy is needed to support China's growing industry and to ensure that it keeps growing, which will allow them to compete with more developed countries.
However, with the cost of establishing renewable systems and recent discoveries of cheap gas resources, it is likely that more electricity will be generated using gas and less with renewables than the diagram suggests.