The government of Germany, one of the world’s largest economies, has set an ambitious goal for reducing greenhouse gas emissions: as of 2020, it wants to cut them by up to 40 percent of their level in 1990, the base year under the Kyoto Protocol.¹ Our study² of the technological opportunities to abate the country’s carbon emissions suggests that achieving a 30 percent target, while challenging, would neither curb economic growth nor require lifestyle changes or lower levels of comfort. But hitting targets higher than that could be very costly and politically contentious.

To many people inside and outside Germany, a 40 percent target may appear to be less of a stretch than it actually is. After all, the country has already reduced its emissions by 17 percent from the 1990 level, almost entirely by restructuring and modernizing the high-emission power and industrial sectors of the former East Germany. Emissions typically rise along with economic growth, and although the economy is growing, they are rising slowly overall because consumers and businesses are adopting energy-saving measures across the economy. But the country aims to reduce its emissions significantly while also phasing out its nuclear power—a zero-emission technology that generates...