Ikea, the Swedish retailing behemoth, is installing "Solar Shops" in its U.K. superstores to sell solar panels. It's a defiant move given that the British government has slashed subsidies for homeowners who sell surplus electricity to the national grid. This suggests that the market is picking up where government aid left off; perhaps Britain will achieve its target of generating 15 percent of its energy from renewable sources by 2020 after all.

Harnessing the sun to meet our energy needs, from portable chargers reviving our mobile phones to sun farms spreading across acres of desert, remains key for reducing carbon emissions. But there's a much simpler way to help save the planet, in the form of the humble light bulb.

Science is transforming our ability to light buildings and streets more efficiently. An old-style fluorescent light tube, for example, consumes about 58 watts of power. A year ago, LED bulbs typically needed between 25 and 27 watts. Today, that's down to 22 watts, and will continue to decline. "The technology improves every year," says Toby Costin, the founder of a London-based company called Social Power Partnerships.