this massive scale of fossil fuel dependence pollutes the Earth

Every year, the world uses 35 billion barrels of oil.This massive scale of fossil fuel dependence pollutes the Earth and it won't last forever.Scientists estimate that we've consumed about 40% of the world's oil.According to present estimates,at this rate, we'll run out of oil and gas in 50 years or so,and in about a century for coal.On the flip side, we have abundant sun, water, and wind.These are renewable energy sources,meaning that we won't use them up over time.