“As we all know, a global low-carbon economy in 2050 is going to have to meet the energy needs of 9 or 10 billion people using technologies that will have to be more advanced than the technologies that are in place today,” he said. “Buildings, agriculture, machines must be dramatically more energy-efficient.”
“Cars, trucks and planes are going to have to run on electricity, biofuels or hydrogen,” Holdren said. "Electricity generation is going to need to come primarily from renewables and nuclear energy.