disease, education, democracy, and population (Smalley, 2005). Energy is key because solving all these problems requires sustainable power on a global scale. Without it civilization collapses. Concentrated fossil fuels are a one-shot boon of nature. Coal being still relatively abundant, humankind might have deferred an energy revolution to another primary power source to the twenty-second century, or even later, were it not for global warming. Coal burned for electricity and even shortages caused by peak oil can be handled at higher cost by making synthetic fuels from coal. But potentially catastrophic global warming is the "canary in the mine." It trumps everything else; moving the climate/energy issue to the front of the list.

To generalize the Shellenberger-Nordhaus thesis, there is little evidence that politicians of any persuasion appreciate the magnitude of the problem, or can articulate a vision to address it. The most relevant questions are being asked by energy scientists and engineers: Are there technologies likely to lead to a low-carbon world in time and still allow global GDP to continue growing 2 to 3 percent per year ("Energy's Future," 2006)? What global energy systems should we be aiming at? Can we get

there in time? One leading economist put it this way: "The trouble with the global warming debate is that it has become a moral crusade when it's really an engineering problem. The inconvenient truth is that if we don't solve the engineering problem, we're helpless" (Samuelson, 2006).

The issue of "energy security” makes the need for an energy technology revolution a viable policy option even for "red" states and others indisposed see global warming for the threat it is. Two hundred years of innovation-the famous "Yankee ingenuity"-are behind America's ascent to world power (Evans, 2004). Applied science and entrepreneurship enabled by government research and development since World War II (Bush, 1945) are a historically appropriate response for the United States.

The need is clear. Figure 2, from Smil (1999), shows oil reserves around the world, with the lion's share in the Persian Gulf. But Saudi Arabia, Iran, and Iraq are powderkegs of post-9/11 Islamic fundamentalism. Some Al Qaeda ideologues have drawn up a plan aimed at establishing an Islamic caliphate throughout the Middle East, in which attacks against the petroleum industry are critical to the deterioration of American power through constant expansion of the circle of confrontation (Wright, 2006). And because oil is internationally traded, it is irrelevant whether oil imports by the United States originate under a particular Middle Eastern desert. The more oil money that flows to Saudi Arabia, Iran, etc., the more money that flows to Al Qaeda, Hezbollah, and other terrorist groups that we are ostensibly at war with. As Tom Friedman of the New York Times has repeatedly emphasized, our addiction to oil combined with lack of any serious policy to develop alternatives is why the United States is funding both sides of the "War on Terror."

We know that world hydrocarbon resources are limited. Virtually all major crude oil and natural gas reservoirs have been mapped by seismic probes. Every day, the world consumes about 80 million barrels of oil, a rate that has been increasing with economic growth but is ultimately constrained by geological abundance to peak in coming decades (Deffeyes, 2001). From a global warming perspective, the coming oil peak, accelerated by China and India with booming GDPs, is problem

atic because it is forcing a transition back to coal for primary energy and thus "recarbonizing" the energy supply since coal emits more CO2 per unit of energy than oil or natural gas. And, of course, oil prices are rapidly rising, headed for $100 per barrel or more. Figure 3 shows the current range of oil production rate projections. As with the climate change deniers, some "cornucopian" economists say the oil peak is overblown. But consider that oil companies are motivated to inflate, not deflate, their reserve estimates to raise their corporate valuations on Wall Street. Royal Dutch Shell, for example, was recently compelled by the US Security and Exchange Commission to revise its reserve estimate downward 20 percent, suggesting an oil peak sooner rather than later. In any case, most petroleum geologists agree the world will be "out of gas" by the end of the century.

I want to be clear that I am a technological optimist. I believe we can solve the climate/energy problem. But there is no silver bullet and it will not be easy. It will take the greatest engineering effort in history; bigger than the Manhattan project to build the bomb, bigger than the Fig. 4

Apollo program to land a man on the moon, bigger than the mobilization to fight World War II. Moreover, the effort has to be international in scope with sufficient inducements for developing giants China and India to sign on. This problem will not solve itself through the invisible hand of the market. Relevant costs and values are not being captured. We are moving rapidly in the wrong direction. Particularly serious is that we are investing in the wrong infrastructures for a sustainable energy world. Vision and imagination are critical. Sooner or later the world will realize this. The longer we wait, the harder the job will be.

Exponential growth cannot be sustained indefinitely on a finite planet. We could, and I believe should, try to maintain 2 to 3 percent per year world GDP growth to the end of the century (a likely minimum for developing nations to attain income equity) as CO2 emissions are held constant, decreased, and eventually phased out by mid-century. This would-based on our best current models-keep the atmospheric CO2 concentration below 500 parts per million (ppm) and global warming below 2 degrees Celsius. Higher than 2 degrees could trigger dangerous human interference with the climate system, according to criteria recently adopted by the European Union (Edmonds and Smith, 2006). Two degrees may not sound like much, but more could put us on a planet-changing trajectory with irreversible melting of the Greenland and Antarctic icecaps, which would inundate the world's coastal zones (Hansen, 2006; Gore, 2006). A big job, given that atmospheric CO2 has already risen to 380 ppm-100 ppm above the preindustrial level from fossil fuel burning and deforestation so far. To do it, some combination of emission-free primary power sources and primary power demandreduction equivalent to generating 100 to 300 percent of present power from some as yet unidentified set of power systems will be needed by mid-century (figure 4, based of Hoffert et al., 1998; 2002).

How hard is that? Consider that 2050 is nearer in the future than when Fermi's first nuclear reactor (then called an "atomic pile") went critical in December 1942 at the University of Chicago is in the past. We now produce about 5 percent of primary energy worldwide from nuclear power (this is virtually all for electricity; roughly 18 percent

of electricity generation is nuclear; the rest is from fossil fuels, mostly coal and hydroelectricity). If we need some new carbon-emission free "energy source X" 50 years hence, the implied growth of these new power sources is 20 to 60 times faster than nuclear power, the last revolutionary power source deployed on a large scale. Not impossible, but we do have to concentrate. Below are some ideas that could work if we get serious.

For starters, we could dramatically accelerate what some engineers believe is the most ready for prime time major emission-free energy source: coal with carbon capture and sequestration (CCS). Figure 5 depicts coal gasification plants making electricity and hydrogen with the CO2 pumped to reservoirs underground, the rationale being that we have large coal resources that can play a role in a transition to a sustainable energy system if we can get the energy out while putting CO2 (and other pollutants) away in reservoirs underground. One problem is that coal with CCS deployment is unlikely before pilot plants demonstrate that the combined technology works. Iindividual components like coal gasification, combined cycle power plants, and even CO2 sequestration