COPENHAGEN—Revolutionizing the energy industry to achieve a target concentration of greenhouse gases in the atmosphere of no more than 450 parts per million (ppm) would require building 17 nuclear power plants a year between now and 2030; 17,000 wind turbines a year; or two hydropower dams on the scale of Three Gorges Dam in China, according to the International Energy Agency. Such an effort would require an investment of $10.5 trillion during the next 20 years but would ultimately yield savings of $8.6 trillion, the IEA estimated.

At present, concentrations of greenhouse gases in the atmosphere have reached 387 ppm and are rising fast, with some two ppm added per annum. In order to slow and ultimately halt such increases—while also accommodating economic growth, particularly in the developing world—non–carbon-emitting power sources, such as wind and nuclear, will need to be added in ever-increasing numbers. Presently, announced commitments for CO2-emission cuts from the various nations of the globe, particularly those form the developed countries grouped in the Organization for Economic Co-operation and Development (OECD) are more likely to deliver greenhouse gas concentrations of 550 ppm, says IEA executive director, Nobuo Tanaka. "This is about a 3-degree [Celsius] average temperature rise by the end of the century."

"The majority of [greenhouse gas emission] reductions should happen in non-OECD countries; the opportunity is there, but it doesn't say who pays for that," Tanaka said here Monday at a press conference. To achieve 450 ppm "in 2030, we need 13.8 [billion metric tons] of reductions." Large reductions are needed in OECD nations, too, but more cost-effective reductions can be made in non-OECD countries.

But global energy use is set to fall in 2009 for the first time since 1981 as a result of the global economic crisis, reducing the need for emission reductions by a full two billion metric tons, according to the IEA. "This is a window of opportunity if [the Copenhagen conference] sets out ambitious targets and achieves it," Tanaka says.

Without new policies, the IEA predicts energy use will begin to grow again within a few years, increasing by 40 percent by 2030 (paired with a 40 percent increase in carbon dioxide emissions). The bulk of that increase (77 percent) will still come from fossil fuels as well being driven primarily (93 percent) by growth in developing countries, such as China and India.

To achieve 450 ppm, the concentration of greenhouse gases in the atmosphere associated with a 2-degree Celsius rise in global average temperatures (a target advocated by the European Union), the "aggregate of fossil-fuel demand will peak out in 2020," Tanaka says. "Coal should decline or peak out much earlier," including the shutting down of some coal-fired power plants before the end of their useful lifetimes.

Yet, even in that scenario, oil and natural gas use would continue to rise, with increased production largely coming from OPEC countries, in the IEA's opinion. "As a whole, still in 2030 [under the 450-ppm scenario] dependency on fossil fuels is about 67 percent," Tanaka says. "Currently it's about 82 percent."

This would still require a major investment in new electricity generation from renewable resources, particularly wind power because it is a well-established and relatively cheap technology. "For every $100 that goes into electricity, $72 must go into renewables, in which wind plays the most important role, " IEA Chief Economist Fatih Birol says.

Of course, such an investment in wind also means a major investment in improving the grid in countries and regions such as the U.S. and E.U. in order to cope with electricity generation that fluctuates, such as with wind power. Turbine manufacturers, such as Vestas of Denmark, General Electric of the U.S., and Suzlon of India have had maintenance issues with gearboxes and other mechanical parts. And it would be challenging to produce the amount of wind turbines required. "The industry is not ready today," says Tanti Tulsi, Suzlon CEO, although he also notes that part of that is difficulties in securing permits as well as a lack of grid investment and available funds. "The industry can deliver but the whole system has to work together."

Already, however, wind is the largest share of new installed electricity generation capacity in the U.S. and E.U., according to the Global Wind Energy Council. "We are installing a wind turbine every three hours, 24/7," adds Michael Zarin, Vestas director of government relations. "There's nothing alternative about wind energy anymore."

"Ten to 15 years ago, if you said in 2008 that there'd be more new investment in renewables than in fossil fuels or nuclear, they'd laugh at you," says Nick Nuttall, a spokesman for the United Nations Environment Programme. "But that is indeed what happened in that year."

A single nuclear power plant takes at least 10 years to build in the U.S., says Paul Genoa, director of policy development for the Nuclear Energy Institute. But there are currently 53 new nuclear reactors under construction or planned around the globe for 2020, capable of producing 42 gigawatts of electricity. "We need 96 gigawatts of new nuclear, or 69 plants, to meet [U.S. CO2-reduction legislation] commitments based on [Energy Information Administration] analysis," Genoa says. That goal would make of U.S. electricity generation 33 percent nuclear.

Energy efficiency could deliver a full half of the needed reductions but "even the best countries are not capturing more than 60 percent of our energy-efficiency recommendations," IEA's Tanaka says. "We are likely to miss one fifth of the mitigation potential."

With some signs of progress, such as the global boom in renewable energy, the real issue becomes speed. "A renewable energy revolution is underway," says Steve Sawyer, secretary general of the Global Wind Energy Council, "the only question is whether we can make it happen in time."

Moving slowly will only add to the eventual cost. "If we don't start now, the delay adds about $500 billion per year. This is the cost of inaction," Tanaka says. "There are many co-benefits: cost savings, energy security, lower pollution. A technology revolution is necessary."