The Conservation Bomb

There will be 10 billion people on Earth by 2100 -- and all of them can live comfortably if advances in energy-saving technology continue.

by Richard A. Muller

Technology for Presidents

from Technology Review Online

June 14, 2002

I have friends who otherwise like me but consider me morally depraved for thinking that the population bomb is not going to kill us all. It is an unpopular time to be an optimist. But a recent discovery in population dynamics, and a fascinating discovery I call "Rosenfeld's Law," may eventually drive the world toward a happier conclusion.

The prevailing pessimism dates back to 1798, when Thomas Rohr Malthus wrote his “Essay on the Principle of Population,' one of the most influential treatises ever published. “Population, when unchecked,' he said, “increases in a geometrical ratio, and subsistence for man in an arithmetical ratio." In other words, population grows exponentially, resources grow linearly. The dreadful conclusion was that disease and famine were not only inevitable, but that they served an essential function in reducing population. Some politicians argued it was immoral to intervene. This bleak outlook gave economics its famous nickname: "The Dismal Science.'

Some think that Malthus was overly optimistic. In one of the more unusual articles published in Science (Vol. 132, pp. 1291-1295, 1960), Heinz von Foerster and colleagues argued that population growth was a good match to the random two-body collision equation, in which the birth rate dn/dt is proportional to the square of the number of people, nxn. (The relation of this equation to the then raging sexual revolution was apparent to many readers.) Foerster's solution to the two-body equation is not exponential, but grows even more rapidly. It exhibits a singularity: the population was to hit infinity on November 13, 2026. Although the article covered serious material, a tongue-in-cheek aspect was evident from the fact that the date happens to fall on a Friday the 13th.

Whether or not population grows to infinity, many people believe that the population bomb is the inevitable and ultimate disaster, and that only population control can stop it. Malthus thought the catastrophe was imminent in 1798. The Earth has had several population doublings since then, but food production has kept pace. Present-day starvation and hunger come not from shortages but from inadequate distribution and inequities in buying power.

In 1968 Paul Ehrlich wrote The Population Bomb, a bestseller in which he predicted that mass starvation would devastate the world in the 1970s. Revolutions in agricultural production delayed the crisis, but Ehrlich is still convinced it is coming -- and soon. His forecasts have not changed: he has always predicted that the disaster will happen within the next ten years.

But even if we don't run out of food, could we run out of environment? According to this point of view, the Earth is finite, and accumulating pollution will eventually make life miserable. The source of pollution is people. Before you have children, file an environmental impact report. Read it, then think again.

Yet when I do the math, I cannot be pessimistic. I find hope in a discovery that I call Rosenfeld's Law. Arthur Rosenfeld is a former professor of physics at the University of California at Berkeley, founder of Berkeley's Center for Building Sciences, a former senior advisor to the Department of Energy on energy efficiency, and currently a California energy commissioner. He is one of the world's true experts on conservation, and in a recent study of the history of energy use, he made a rather remarkable discovery (footnote). From 1845 to the present, the amount of energy required to produce the same amount of gross national product has steadily decreased at the rate of about 1 percent per year. This is not quite as spectacular as Moore's Law of integrated circuits, but it has been tested over a longer period of time. One percent per year yields a factor of 2.7 when compounded over 100 years. It took 56 BTUs (59,000 joules) of energy consumption to produce one (1992) dollar of GNP in 1845. By 1998, the same dollar required only 12.5 BTUs (13,200 joules).

Past conservation growth wasn't completely constant. During the oil crisis of the 1970s, conservation improved at 4 percent per year. Rosenfeld believes that with a little government encouragement, we can sustain a 2 percent rate per year indefinitely. Energy companies that don't want the public to reduce consumption have tried to persuade us that this much conservation would mean discomfort. Rosenfeld did the opposite. “Conservation means not putting on a sweater,' he entitled one of his presentations. Turn up the thermostat, if you like it warm! But, at the same time, reduce your energy bills by putting better insulation into your walls. If you don't want to invest the money, let someone else pay for it. It won't be hard to find someone. The yield on conservation investment is 20 percent per year, tax free!

Past conservation efforts have been far more successful than many people appreciate. It was conservation that liberated us from the control of the oil cartel in the 1970s. The members of the Organization of Petroleum Exporting Countries were more addicted to U.S. dollars than we were to oil. A little bit of extra conservation on our part (3 percent per year during the crisis period) drove down their income and forced them to increase production.

The steady pace of conservation would do little good if population outraced it. But there is encouraging news about population growth. The United Nations now estimates that the population of the world will peak, sometime in this century, at about ten billion. That sounds bad -- it is much higher than the current level -- but it is a peak. After that, the population will decrease slowly. The predictions are now believed to be quite robust, as a paper in Nature last August documented (Vol. 412, pp 543-545, 2001). Malthus's population bomb is fizzling. The year 2026 will pass without a singularity.

What is happening? Where was Malthus wrong? At a United Nations conference last March, demographers discussed many possible explanations. The most appealing one was that the declining growth is a consequence of the expanding worldwide rights of women. Others attribute it to poverty reduction. Wealthy people have fewer children, for reasons we don't fully understand. Western TV is also cited: people see happy families with small numbers of children. I get the sense that scientists are groping, putting forth plausible explanations for an observed fact that they didn't predict. Fertility is declining far faster than expected in many regions, even in nations with no government family planning efforts (e.g., Brazil).

The happy news comes when we combine limited population with conservation growth. The conservation bomb wins. Rosenfeld points out that at 2 percent growth -- the 2 percent solution -- conservation outruns population by a large factor. Two percent compounded over 100 years reduces energy use by a factor of 7.2. By 2100, with a world population of 10 billion people, everyone can be living at the current European standard of living and yet expending half the energy we are using today.

The solution may lie in making the developing world wealthy. What a delightful vision! Economics -- the glorious science. Wealth reduces population growth; conservation wins; the environment is cleaner; the world is happier. If we allow conservation to putter along at 1 percent, on the other hand, then in 2100 we will be using 40 percent more energy than today. That may be acceptable, but there is a catch: if the United States' standard of living continues to increase, and the developing world wants to match that increase too, then the energy requirements may continue upward. The two percent solution is painless and preferable, but to achieve it probably requires conscious government-led efforts to develop cleaner, more energy-efficient technologies in areas like power generation, transportation, manufacturing and environmental control. Cancellation of research programs in these areas is self defeating. The solution to pollution is conservation.

*A.H.Rosenfeld, T. M. Kaarsberg, J. J. Romm, “Efficiency of Energy Use', in The Macmillan Encyclopedia of Energy, John Zumerchik, editor in chief, Macmillan Reference USA, 2001.