If climate goals are set, how will they be met?

NUSA DUA, Indonesia —Here's a recipe to head off the worst effects of global warming:

1. Start with 30 new nuclear power plants around the world.

2. Add 17,0000 wind turbines, 400 biomass power plants, two hydroelectric dams the size of China's Three Gorges Dam, and 42 coal or natural-gas power plants equipped with still-experimental systems to sequester their carbon-dioxide emissions underground.

3. Build everything in 2013. Repeat every year until 2030.

It's an intentionally implausible plan presented this week by the International Energy Agency to make a point: For all the talk about emissions reductions, the actual work is way beyond what the world can achieve.

As delegates from 190 countries gather here on the island of Bali to negotiate a "road map" for the successor to the 1997 Kyoto Protocol on global warming, some experts are questioning whether the meeting has lost touch with the reality of fighting climate change.

So far, the thousands of delegates have consumed themselves in a debate over setting caps on emissions of greenhouse gases that are the primary culprit in climate change.

The United States and China — the world's two biggest carbon polluters, each accounting for about 20 percent of worldwide emissions — have opposed hard caps.

While the debate continues, the most fundamental question of what it will take to achieve meaningful reductions largely has been forgotten.

The U.N. Intergovernmental Panel on Climate Change stated in its landmark reports in 2007 that annual worldwide emissions must be cut at least in half by 2050 to avoid the most serious consequences of global warming, such as severe sea-level rise and prolonged droughts.

The recipe from the IEA, a Paris-based energy-research group, is one way to get there while still meeting the world's increasing demand for power. But no one is banking on its implementation soon.

"When the governments or the people in the negotiations decide on such a target reduction as 50 percent by 2050, they have to realize the implications," said Nobuo Tanaka, head of the IEA and a top energy authority.

The talks in Bali are built around the idea that reductions would be driven by an international trading system for greenhouse gas emissions. The system would essentially be a stronger version of Kyoto, which expires at the end of 2012.

Countries would be assigned caps on their total emissions. If a country polluted below its quota, it could sell its surplus allowances on the market. If it exceeded its cap, it would have to purchase allowances. Over time, as caps were lowered and the price of allowances rose, it would become cheaper to invest in carbon-cutting technology and clean-energy alternatives than to keep polluting the air.

But some economists said that the trading scheme is too weak to generate the massive investments needed to divert the world from fossil fuels. To begin with, there is no easy way to enforce such agreements.

"Nobody is going to invade France, Russia or the United States, or break off diplomatic relations or boycott a country," said Thomas Schelling, a University of Maryland economist who studies environmental policy.

Japan, Canada and most of Western Europe are not on pace to meet their relatively modest targets established by Kyoto.

"I can't imagine anything effective coming out of Bali," Schelling said. "Frankly, they just don't know what else to do."

Schelling said that countries must begin to focus on ways to encourage the development of new cleaner-energy technologies. He and 36 other experts, including three Nobel Prize winners, recently called upon the U.S. government to increase spending on clean-energy development from $3 billion to at least $30 billion a year in an effort they likened to the Manhattan Project and the Apollo space program.

"We went into World War II with biplanes and came out with jet fighter planes," said Ken Caldeira, a climate scientist at Stanford University and co-author of the petition. "If we took this problem seriously, a decade from now there would be no need to make cars that emit [carbon dioxide] into the atmosphere."

James Connaughton, chairman of the White House Council on Environmental Quality, countered that private investment now funds a sizable chunk of research in the U.S. He also pointed to recent government investments in wind power, as well as billions of dollars the government has spent over many years trying to develop nuclear fusion.

Tanaka said the IEA did not consider the possibility of clean fusion energy because the technology seemed unlikely in the next 30 years.