Major companies could reduce their carbon emissions by as much as 50 percent and significantly increase energy efficiency by shifting to cloud computing, according to a new report. In an analysis of UK, French, and U.S. firms that have used cloud computing for at least two years, the Carbon Disclosure Project calculated that by 2020 U.S. companies with annual revenues of more than $1 billion can save $12.3 billion in energy costs and achieve carbon reductions equivalent to 200 million barrels of oil a year if they shift to shared data networks. The report said that large UK companies could achieve annual energy savings of £ 1.2 billion if they move to cloud computing. Cloud computing — in which data can be stored, managed, and processed on external servers as needed — allows companies to buy less hardware and also improves efficiency and flexibility. According to the report — which was conducted by the independent firm Verdantix and sponsored by AT&T — large companies plan to accelerate their adoption of cloud computing from 10 percent to 69 percent of their IT spending by 2020.