The Hydrogen Solution

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Science  13 Aug 2004:
Vol. 305, Issue 5686, pp. 917
DOI: 10.1126/science.305.5686.917

If ever a phrase tripped lightly over the tongue, “the hydrogen economy” does. It appeals to the futurist in all of us, and it sounds so simple: We currently have a carbon economy that produces carbon dioxide (CO2), the most prominent of the greenhouse gases that are warming up the world. Fortunately, however, we will eventually be able to power our cars and industries with climate-neutral hydrogen, which produces only water. Well, can we? This issue of Science exposes some of the problems, and they're serious. To convert the U.S. economy in this way will require a lot of hydrogen: about 150 million tons of it in each year. That hydrogen will have to be made by extracting it from water or biomass, and that takes energy. So, at least at first, we will have to burn fossil fuels to make the hydrogen, which means that we will have to sequester the CO2 that results lest it go into the atmosphere. That kind of dilemma is confronted in virtually all of the proposed routes for hydrogen production: We find a way of supplying the energy to create the stuff, but then we have to develop other new technologies to deal with the consequences of supplying that energy. In short, as the Viewpoint by Turner in this issue (p. 972) makes clear, getting there will be a monumental challenge.

In a recent article (Science, 30 July, p. 616), Secretary of Energy Spencer Abraham calls attention to the Bush administration's commitment to the hydrogen solution. The Hydrogen Fuel Initiative and FreedomCAR Partnership, announced in the 2003 State of the Union message, aims “to develop hydrogen fuel cell-powered vehicles.” The United States also led the formation of the International Partnership for the Hydrogen Economy, a project in which Iceland, blessed with geothermal sources and an inventive spirit, appears to be ahead of everyone else (see p. 966). These and other initiatives are politically useful because they serve to focus public attention on the long-range goal. They rely on the premise that when the research on these new technologies is finished, we will have a better fix on the global warming problem; in the meantime, we'll put in place strictly voluntary measures to reduce CO2 emissions. That's the case being made by the Bush administration.


The trouble with the plan to focus on research and the future, of course, is that the exploding trajectory of greenhouse gas emissions won't take time off while we are all waiting for the hydrogen economy. The world is now adding 6.5 billion metric tons of carbon to the atmosphere in the form of CO2 annually. Some nations are cutting back on their share, but the United States, which is responsible for about a quarter of the world's total, is sticking firmly to business as usual. In each year, some of the added CO2 will be fixed (taken up by plants in the process of photosynthesis and thus converted to biomass) or absorbed by the oceans. But because the amount added exceeds the amount removed, the concentration of atmospheric CO2 continues to increase annually, and the added carbon remains in the atmosphere for many decades.

In fact, even if the United States and all other nations reduced the growth rate of annual emissions to zero, the concentration of greenhouse gases would continue to rise for the rest of the century, and average global temperature would increase in response. How hot it will get depends on various feedback factors: clouds, changes in Earth's reflectivity, and others. It is clear, however, that steady and significant increases in average global temperature are certain to occur, along with increases in the frequency of extreme weather events, including, as shown in the paper by Meehl and Tebaldi in this issue (p. 994), droughts and heat waves.

Another kind of feedback factor, of course, would be a mix of social and economic changes that might actually reduce current emissions, but current U.S. policy offers few incentives for that. Instead, it is concentrating on research programs designed to bring us a hydrogen economy that will not be carbon-free and will not be with us any time soon. Meanwhile, our attention is deflected from the hard, even painful measures that would be needed to slow our business-as-usual carbon trajectory. Postponing action on emissions reduction is like refusing medication for a developing infection: It guarantees that greater costs will have to be paid later.

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