Not Sky-High

Some argue that this can be achieved only with fundamental breakthroughs in technology. But our analysis estimates that 70 percent of the technologies needed are either available today or are likely to be commercially viable in the coming decade. Renewable technologies, such as solar, wind and geothermal, already account for 12 percent of Germany's power today and have the potential for dramatic expansion. For example, we estimate that the renewables share of U.S. power could almost triple from 8 percent today to 23 percent by 2030 at a reasonable cost.

But even with rapid renewables growth, other low-carbon sources will be needed. Nuclear is controversial, but it will be a part of the low-carbon strategy for some countries. Another controversial technology is carbon capture and storage (CCS), sometimes called "clean coal." Using CCS, carbon emissions from power and industrial plants are captured and stored deep underground, often in disused oil and natural-gas fields. The technology has been used by the oil and gas industry for many years, but never at the enormous scales required by the power sector. Significant investment is required to pilot such CCS programs at a commercial scale.

In the transport sector there is a race between technologies. Auto engineers believe they can modify conventional engine designs to double or even triple fuel efficiency with a minimal impact on performance. Likewise, new generations of hybrids are in the works; there is much effort going into better battery designs for electric vehicles; and the next generation of biofuels promises more performance for less money, and with minimal impact on land usage and food prices. Finally, city planners continue to find ways to better leverage public transport and design smart cities that reduce commuting distances.

Still, we will need more. Even though 70 percent of the technologies required are available or on the horizon, that still leaves 30 percent to come from new technologies we don't have today. Entrepreneurs, venture capitalists and company labs around the world are working on a plethora of innovations. But at $10 billion per year, these investments are still tiny compared with the $369 billion the world will spend this year exploring for new sources of oil.

Efforts to increase carbon productivity must go even beyond new technologies. Preserving and expanding the world's tropical forests could make a significant dent in carbon emissions. When trees in these forests are cut down, their absorptive capacity is lost and net emissions go up. Deforestation is often driven by the economic needs of very poor people and thus is a complex issue. But recognizing the value of the world's forests and paying to keep trees standing may be significantly cheaper than other ways of reducing emissions.

Finally, businesses and consumers will need to team up to change long-ingrained behaviors. For example, Wal-Mart made a commitment through the Clinton Global Initiative to sell only concentrated laundry detergents, which it estimates will save 1.5 billion liters of water, 43,000 metric tons of plastic and 57,000 metric tons of cardboard, not to mention the energy and carbon emissions to manufacture and transport this unnecessary material. Independent studies show that concentrated detergents have 20 percent lower carbon emissions through their life cycle than traditional products.