Offshore wind could become a cornerstone of the world's power supply as steep cost reductions and improved technology unleash the potential of the green energy source, the International Energy Agency said Friday.

Renewables replacing fossil fuel is crucial to meet a globally-agreed goal of limiting temperature rise to below 2 degrees Celsius this century, and the expansion of offshore wind could avoid 5-7 billion tons of carbon dioxide emissions from the power sector globally, according to the IEA.

Power generated from wind turbines at sea only accounts for 0.3 percent of global electricity generation today, the IEA said in what it called "the most comprehensive" study of offshore wind to date.