Today the Kyoto Protocol to the United Nations Framework Convention on Climate Change comes into effect. Thirty-five industrialized countries have vowed to cut their greenhouse gas emissions to 5.2 percent below their 1990 levels by 2012. This will allegedly prevent catastrophic global warming caused by man-made gas emissions--chiefly carbon dioxide, which is emitted when fossil fuels like coal, oil, and natural gas are burned.
Kyoto is a solution in search of a problem. What are the chances that catastrophic global warming will occur in this century? That depends on a number of factors, but most importantly on how sensitive global climate is to accumulating greenhouse gas concentrations in the atmosphere, and how much greenhouse gases will be emitted over the coming years. If the climate is not very sensitive, then more greenhouse gases can be safely emitted. If less greenhouse gases are emitted, then the chances of catastrophic warming are reduced.
The debate over the sensitivity of the global climate to excess greenhouse gases is still in full swing and is not likely to be resolved soon. So let's look at the other side of the equation—how much greenhouse gases are likely to be emitted over the next 100 years?
The United Nations Intergovernmental Panel on Climate Change (IPCC), the international body charged with evaluating global warming science and policy, offered a number of scenarios in its last comprehensive report. Those scenarios used various computer simulations of greenhouse gas emissions levels and climate sensitivities to project a range of possible increases in global average temperatures from 1.5 to 5.8 degrees Celsius by 2100. (The 5.8-degree change would be about the same change as the increase that ended the last ice age 18,000 years ago.)
However, the alarming 5.8 degree Celsius forecast resulted from a combination of very sensitive computer climate models with economic projections that assumed such unlikely developments as essentially no improvements in energy production technologies over the next century and a world population of 15 billion people emitting four times the current per capita levels of carbon dioxide.
These projections are way out of line with actual trends. First, carbon dioxide emissions per capita have been essentially flat over the past two decades rather than rising. And world population will not rise to 15 billion. Nature published a study in July 2001 which estimated that world population would be 8.4 billion in 2100. The United Nations low variant trend projects a world population peaking in 2040 at 7.5 billion and then declining.
The notion that energy technologies will not improve over the next century is similarly absurdly untenable. In fact, carbon intensity per unit of energy produced has declined by a third over the past century. The world has been moving progressively away from high carbon/low hydrogen fuels like wood and coal to lower carbon/high hydrogen fuels like oil and natural gas. Jesse Ausubel, director of the Program for the Human Environment at Rockefeller University, puts it this way: "Think of hydrogen and carbon competing for market niche as did horses and automobiles, or audio cassettes and compact discs, except the H[ydrogen]/C[arbon] competition extends over 300 years. In 1800 carbon had 90 percent of the market. In 1935 the elements tied. With business continuing dynamic as usual, hydrogen will garner 90 percent of the market around 2100."
What drives decarbonization? As people use more energy in their daily lives, they turn to more powerful sources that take up less space. Instead of firewood, they use natural gas for heating and cooking. Instead of hay-fueled horses, they use automobiles. Instead of candles and whale oil lamps, they use fluorescent bulbs. Regarding the latter Ausubel notes that "a middle-class urban American household in 1800 would have spent perhaps 4 percent of its income on illumination: candles, lamps, oil, and matches. A middle-class urban American household today spends less than 1 percent of its income on illumination, and consumes more than 100 times as much artificial illumination as did its predecessor of two centuries ago. Happily, lamps do not occupy 100 times the space they occupied 200 years ago."
Ausubel concludes: "In contrast to what many believe, the stable dynamics of the energy system permit reliable forecasts. Decarbonization essentially defines the future of energy supply."
Of course, a lot of work, technological progress, and investment still must take place to keep the decarbonization trend rolling. But just as no one in 1900 could have foreseen the technological developments in energy production and use that fuel our modern world, neither can anyone, including the IPCC, reliably predict what fuel mix people in 2100 will be using. Nevertheless, Ausubel gamely outlines a plausible decarbonized future in which energy is produced in Zero Emission Power Plants by burning natural gas and burying the excess carbon dioxide. Furthermore, he envisages hydrogen and electricity produced by nuclear reactors and distributed through continental supergrids consisting of pipelines transporting liquid hydrogen that cools superconducting electric power lines.
The IPCC's vision of no technological progress, accelerating population growth, and higher per capita carbon dioxide emissions is the most implausible assumption imaginable for the 21st century. Without those far-fetched conjectures, there's no real possibility of catastrophic global warming. Thus, there is no need for the expensive and intrusive Kyoto Protocol to limit global energy production and carbon emissions. As the technological and population trends I've discussed become more obvious, the nations that have just put Kyoto into force will drop out. As for the previous couple of centuries of decarbonization, Ausubel points out that "neither Thomas Jefferson nor Queen Victoria decreed it." The 21st century will need no such decrees either. 
Ronald Bailey is Reason's science correspondent. His new book, Liberation Biology: A Moral and Scientific Defense of the Biotech Revolution will be published in early 2005.
