British Sky Broadcasting has become the first media company to become "carbon neutral" in one of the strongest signals yet that concerns over global warming are changing business.

The company has reduced its carbon dioxide emissions, arising mainly from its use of energy, through energy efficiency measures, buying its electricity from renewable sources, such as wind farms, and by helping to fund renewable energy projects. The latter means the company's remaining greenhouse gas emissions are balanced out by reductions in emissions in other parts of the world, making it "carbon neutral" overall.