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The need to reduce greenhouse gas emissions is usually referred to as ‘decarbonisation’. Jonathan Porritt, the chairman of the UK Sustainable Development Commission, thinks that it is better to call it “re-solarisation”, because this is positive and solar power has immense potential. Solar photovoltaic (PV) cells generate electricity, and solar thermal heats water. Concentrated solar power (CSP), which uses mirrors to reflect sunlight to boil water and so generate electricity, has even greater potential – covering a very small percentage of the Sahara could generate enough electricity for the whole of the global economy.

There is significant progress being made on harnessing this potential in some key economies. For example, China has a target of 3Gw from solar by 2020, but Zhang Xiaoqiang, vice-chairman of China’s national development and reform commission, told The Guardian this week that China would meet and then surpass its 2020 targets for solar power (and also for wind), and is now contemplating more than tripling the targets. China generates only 120 megawatts from solar at present. Therefore, if the goal is tripled and met this would be a 75-fold expansion in just over a decade (see China launches green power revoloution to catch up on west).

In May, President Obama announced that his administration would spend around $400 million from the recent $787 billion economic stimulus package to expand the use of solar and geothermal energy throughout the USA. The US solar energy industry grew about 9% in 2008, but the recession cut demand for some solar installations. There are also CSP plants in California and Nevada.

Some European countries have also made progress. Germany has significantly expanded PV through its Feed-in Tariff. (In the past the price individuals received for the electricity produced, which was effectively paid for by all electricity consumers, was very high. It is now lower.) Southern European countries obviously have better solar potential than northern ones. The Spanish government has a target to install 3Gw of solar by 2012 and is also a major manufacturer of solar panels (though most are exported to Germany). A number of southern European member states of the EU, led by Italy, are actively exploring means to harness CSP in North Africa. This has exciting potential, though the Mediterranean grid would not be cheap to construct.

In Porritt’s view, re-solarisation does not mean just harnessing solar power. Wind, wave and tides are also caused by the sun, and can be used to power the world. Again, China, America and Europe are promising rapid progress. The current Chinese wind target is for 30Gw by 2020. However, Zhang told The Guardian that the new goal could be as much as 100Gw by 2020.