This article appeared on Page A1 of the Sunday New York Times.
ven as the world's expanding
population and economy increase atmospheric concentrations of carbon
dioxide that scientists say are warming the earth, the global energy system is moving steadily away from
the carbon-rich fuels whose combustion produces the gas.
Experts say atmospheric levels of carbon dioxide may be double that of the pre-industrial era by the end of the next century. But they also say the levels would be much higher except for a trend toward lower-carbon fuels that has been going on for more than 100 years, but has been largely unnoticed except by a small band of energy specialists.
The question now, they say, is whether the trend can be accelerated enough to stave off or lessen what many scientists believe is a potentially disruptive global warming.
For nearly a century and a half, fuels with high amounts of carbon have progressively been replaced by those containing less. First wood, which is high in carbon, was eclipsed in the late 19th century by coal, which contains less.
Then oil, with a lower carbon content still, dethroned King Coal in the 1960's.
Now analysts say that natural gas, lighter still in carbon, may be entering its heyday, and that the day of hydrogen -- providing a fuel with no carbon at all, by definition -- may at last be about to dawn.
As a result, the experts estimate, the world's economy today burns less than two-thirds as much carbon per unit of energy produced as it did in 1860. In the United States, they estimate, the trend toward lower-carbon fuels combined with greater energy efficiency has, since 1950, reduced by about half the amount of carbon spewed out for each unit of economic production.
But because economic growth and population growth have been so rapid over the decades, overall atmospheric concentrations of carbon dioxide have steadily risen, to the point that the concentrations may well have doubled by the year 2100.
Mainstream scientists say that this much carbon dioxide could warm the earth, on average, by 3 to 5 degrees Fahrenheit. By comparison, that is about half as much as it has warmed since the depths of the last ice age 18,000 to 20,000 years ago.
A change of this magnitude would likely have widespread consequences for the world's climate, weather and human life.
Now, as representatives of 150 governments meet in Bonn in the latest round of global talks on measures to further reduce carbon-dioxide emissions, analysts both in and out of industry say that the next quarter-century is shaping up as a period of technological and economic ferment offering a chance to accelerate the trend toward a low-carbon economy and, eventually, a no-carbon one.
In Bonn, the delegates are trying to work out the details of an agreement forged two years ago in Kyoto, Japan, that could speed up the trend. Their work is not expected to be finished for at least a year, and the Kyoto agreement still must be ratified by a sufficient number of countries after that.
However that may turn out, "the decarbonization of the energy system is the single most important fact to emerge from the last 20 years of analysis" of the system, said Dr. Jesse H. Ausubel, an expert on energy and climate at Rockefeller University in New York City. Dr. Ausubel predicts that this evolution will produce a carbon-free energy system by the end of the 21st century.
Among some recent signs of the trend are these:
Toyota has introduced a similar "hybrid" automobile in Japan, and these cars are "literally kick-the-tires examples of the decarbonized economy," said Hal Harvey, president of the Energy Foundation, a partnership of foundations that promotes energy efficiency and renewable energy.
Other auto makers are also planning hybrids, which are being viewed as a transition, ultimately, to vehicles powered by hydrogen fuel cells that emit no carbon.
In its planning, the General Motors Corporation has "embraced fuel cells as the technology of choice," but with hybrids coming first, said John Williams, the leader of the company's internal team on global climate issues.
And while auto companies are looking down that track, some of the world's biggest energy companies are looking to provide the appropriate fuels.
Hydrogen, in particular, has attracted fresh interest.
Until recently, "the hydrogen option was seen as rather distant," said Ged R. Davis, an executive of Shell International in London who analyzes such questions for Royal Dutch/Shell, one of the world's largest energy companies. "Now it is looking closer, perhaps over the next decade or two," Davis added. "Most of the energy and car companies are looking at this rather seriously." Shell itself has established a hydrogen subsidiary.
In the nearer term, hydrogen would be used in fuel cells for cars, trucks and industrial plants, just as it already provides power for orbiting spacecraft. But ultimately, hydrogen could also provide a general carbon-free fuel.
The world energy system will not change overnight, of course, if it changes at all. And new products must ultimately stand the test of the marketplace. But some analysts say that the next two decades or so will be a time of unusual pressure for change, both for environmental and economic reasons, in which companies will be driven to compete for survival and dominance in some sort of emerging new energy system.
Whether companies are seriously pursuing new options or merely preserving them for the future, experts say there seems little doubt that the long-term trend toward decarbonization is real, and that it will most likely continue even in the absence of any shift to hydrogen or renewable energy sources like wind and solar power.
"The future decarbonization rate is likely to be at least as high as the historical one" of about three-tenths of a percent a year, said Dr. Nebojsa Nakicenovic, an expert on energy and the environment with the International Institute for Applied Systems Analysis, a research group in Laxenburg, Austria. The institute was one of the first groups to study the question.
Oil accounts for the biggest share of global energy consumption today, followed by coal and, closely, by natural gas. In most of the world except the United States and China, said Dr. Ausubel of Rockefeller University, coal is either defunct or on the way out, and natural gas will increasingly displace it.
According to several recent analyses, Dr. Nakicenovic said, recoverable natural gas now appears far more abundant than had been previously thought. The burning of gas produces, on average, only about a third of the carbon dioxide per unit of energy of coal, and about two-thirds that of oil.
Gas not only can fuel fixed facilities like industrial plants and furnaces, it can also be processed to produce hydrogen for use in carbon-free fuel cells to power automobiles and generate electricity. In those cells, there is no combustion; instead, hydrogen reacts chemically with oxygen to produce electricity. But when hydrogen is extracted from gas, the residual carbon must somehow be disposed of, possibly by pumping it back into depleted oil and gas wells.
Dr. Ausubel predicts that natural gas will become the dominant fuel of the next 40 to 50 years. If so, that alone would be enough to continue the long-term decarbonization trend.
China, which some experts think will emerge as the biggest carbon-dioxide emitter of the 21st century, has greatly reduced its energy consumption per unit of economic output, has closed several coal mines, is seeking to modernize industrial and power plants and is moving toward natural gas, many analysts say.
Not least, they say, the Chinese are worried about the health effects of coal's air pollution. Nevertheless, the Energy Information Administration reported last week, China's coal demand is expected to double by 2020.
So while the trend toward a carbon-free economy may continue, Dr. Ausubel says, it might not move rapidly enough to assuage the fears of those who are most concerned about global warming. He says that if the trend continues to evolve more or less naturally, with business as usual, it will take another century or so to decarbonize the energy system fully.
By then, he predicts, atmospheric concentrations of carbon dioxide will be around 500 parts per million, nearly double what they were before the industrial revolution. Mainstream scientists say that would be enough to change the earth's climate substantially, make droughts, heat waves and floods worse and raise the sea level to heights that would threaten many low-lying coastal areas and islands.
Some analysts say that 500 parts per million is a best-case estimate, and that business-as-usual could cause a tripling of pre-industrial carbon-dioxide levels.
Other experts think that concentrations could be held substantially below 500 parts per million if the trend toward decarbonization were to accelerate. Harvey of the Energy Foundation says "prospects are excellent" for an acceleration.
And Davis, the Shell executive, says his company's analyses suggest that if the proper incentives were in place, new energy technologies could be adopted broadly enough to bring about a peak in oil use and carbon-dioxide emissions by about 2020.
After that, there would be a decline.
One sort of incentive might lie in the Kyoto agreement, which calls for a group of 39 industrialized countries to reduce their carbon dioxide emissions by an average of 5 percent below 1990 levels over the period 2008 to 2012.
One mechanism for doing this is a system whereby a country that exceeds its reductions target can earn money by selling that extra reduction to another country that is having trouble meeting its target. A similar system, involving company-to-company trading, has been proposed for the United States.
While negotiators struggle over the terms of such arrangements and politicians wrangle over putting the Kyoto accord into effect, many energy analysts seem to agree on one thing: The ultimate goal ought to be a carbon-free economy based largely on hydrogen. Dr. Ausubel, for one, predicts that such an economy will materialize.
Many would agree with Williams of General Motors: "I think I'm on pretty solid ground in saying the long-term vision is hydrogen. But there's a lot of work between here and there."
Copyright 1999 The New York Times Company