New technologies will be required if the world economy is to grow without accelerating climate change.

Since the industrial revolution, economic growth has gone hand in hand with the consumption of fossil fuels and the release of ever greater amounts of carbon dioxide into the atmosphere - leading many scientists and politicians to call now for a new, technological revolution. Here we survey options for power-generation and transport, and also engineering solutions to reflect sunlight or remove CO2 from the atmosphere.

Fuel	About	Pros	Cons	Viability
Clean coal	Range of technologies to pre-treat coal to reduce emissions, burn it more efficiently, or capture and store carbon emissions.	Most abundant and widely distributed fossil fuel. Preserves existing industry and makes use of existing infrastructure.	Uses more coal per kWh than normal coal power. Produces some pollutants, such as heavy metals. Coal is a finite resource.	Small-scale trials under way. Huge investment(c $3trn) needed by 2050. Estimated cost: 5-13 cents/kWh (double normal coal).
Geothermal	Uses naturally hot rocks, or temperature differences, beneath Earth's surface to heat water directly or drive turbines.	Constant renewable energy source in some locations. Highly efficient for heating living spaces. Long hardware lifetime.	Underground heat only available in some locations. Energy can "dry up" for years. Can in some locations release toxic gases.	Currently less than 1% of global capacity. US and Australia investing in new technologies. Estimated cost: 5-11 cents/kWh.
Nuclear	Harnesses energy from the controlled splitting of atoms, releasing heat that is harvested to drive turbines.	Significant historical experience and technology developed. Can provide heat and electricity. Plentiful fuel supplies.	Perceived as risky. Strong opposition from green campaigners. Creates radioactive waste. Fuel can be weapons security risk.	Set for a comeback after years in shadow. New reactors behind schedule. Disputed cost. One estimate: 4-8 cents/kWh.
Marine	Exploits energy of shifting tides, underwater currents, or shoreline and offshore waves.	Large and infinitely renewable resource. Tidal energy very regular. Can be exploited on small or large scale.	No consensus on best means to capture energy. Large projects may disrupt natural water flow, tides and ecosystems.	Little expected before 2030. Technology uncertain, so wide cost range: 15-30 cents/KWh (double or triple coal).
Wind	Using the wind, on land or at sea, to drive turbines.	Significant experience and mature industry and infrastructure. Infinitely renewable resource. Can be deployed in range of project sizes.	Intermittent resource. Not efficient for all locations. Windfarms interrupt radar signals, can be noisy and regarded by some as unsightly.	Currently about 1% of global supply. Onshore cheaper than offshore. High energy storage costs are handicap. Quite low cost: 7-14 cents/kWh.
Solar	Gathers energy from sunlight, using light to generate electricity directly (photovoltaic) or to heat liquids to drive a turbine.	Infinitely renewable and most abundant zero-carbon resource. Silent and no effects on local environment.	Like wind and marine, intermittent. Current photovoltaic designs complex; if widely used, chemicals could become scarce.	US investing heavily, EU planning plant in Africa. Cost still high (13-35 cents/kWh) but expected to fall. Price of solar panels falling.
Hydroelectric	Generates electricity by damming water and constraining flow through turbines. Most widely deployed renewable strategy.	Well-established as a large-scale energy source. Can also be used for energy storage if run in reverse.	Dams disrupt ecosystems and are a public health risk if they burst. Can trap decaying matter that creates pollution.	One of the cheapest forms of electricity. Development focusing on small hydro-electric power. Estimated cost: 2-6 cents/kWh.

Published: November 2009