Long-Range Energy Developments revolution. Figure 1 shows the decline and rise of market shares of various In the middle of the last century wood types of primary energy in the United was the predominant source of energy, States. The data are plotted in such a meeting roughly 70 to 80 percent of the deway that a logistic curve becomes a mand. This meant large-scale gathering straight line. It should be noted that and led to a first energy crisis, which was there are remarkable regularities in

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... e Summary. Most studies of energy supply and demand ignore either global interdependence or the long time spans necessary to adjust to new energy sources. The International Institute for Applied Systems Analysis has therefore studied on a global scale, for seven major world regions, the balance between energy supply and demand for the next 50 years. Reported here are the results for two benchmark scenarios. In the "low" scenario world energy consumption increases from today's 8.2 terawatt-year per year to 22 terawatt-year per year in 2030; in the "high" scenario, consumption increases to 35 terawatt-year per year. The study showed that time will be the limiting constraint in adapting the energy supply infrastructure to changing resource availability; resources will be available until the second half of the next century, but a strong shift will be required to low-grade fossil fuels such as shale oil and tar sands. Each scenario studied indicated increased environmental problems associated with increased use of fossil fuels, and potential geopolitical problems associated with the world distribution of resources. overcome by a fundamental change in technology: Coal was used as a substitute for wood. The higher density of coal meant not only more energy but also easier storability and transportability, features