From wood to coal to oil and gas, the sources of energy on which civilization depends have always changed as technology advances. Now renewables are overtaking fossil fuels, with wind and solar energy becoming cheaper and more competitive. Bruce Usher, professor of professional practice at the Business School and co-director of the Tamer Center for Social Enterprise, explains the extraordinary growth in wind and solar energy; the trajectory of the transition from fossil fuels to renewables; and the implications for industries, countries, and the climate. He shows how governments and businesses with a farsighted approach will reap long-term benefits while others will trail behind amid the threat of catastrophic climate change.