Investing in a clean energy economy. (Read Time: 100 minutes). Seriously addressing climate change requires reducing greenhouse gas emissions by at least 80 percent by 2050 in the U.S. and across all major economies. We find that this goal is technically and economically achievable using commercial or near-commercial technology. Most important, we find that meeting the goal does not require an energy miracle or unprecedented spending. The transition to a cleaner energy economy rests on three pillars: moving from fossil fuels to electricity wherever possible, generating electricity with low or zero carbon emissions, and using energy much more efficiently.