Only one thing is certain about the future of energy: with a growing world population and a growing economy, the demand for energy is bound to increase. This could pose a challenge to us for three reasons.
First, much of our energy comes from non-renewable sources. As of 2005, petroleum accounted for 37% of energy use, natural gas 23%, coal 26%, and radioactive elements (i.e., nuclear power) 6%. The remaining 8% of energy use represented renewable resources, such as hydroelectric, geothermal, solar, biofuels, or burning trees. In the long run, the supplies of the non-renewable fuels will dwindle. However, that will arguably take a very long time, because as a fuel becomes scarce, its price should rise, which would encourage the development of new technologies to identify new supplies. A reasonable example of this sort of argument has been made for uranium ( see the World Nuclear Association site for a detailed, almost belabored, discussion). So, while in principle we may never run out of energy, in practice, the increasing costs for non-renewable resources might limit our ability to use them.
Second, concern is growing that worldwide energy use is changing the climate, by increasing the concentration of greenhouse gases in the atmosphere. In 2005, about 86% of our energy came from petroleum, natural gas, or coal, which releases carbon dioxide into the atmosphere when it is burned. Although it is unclear how this will effect the climate in any given spot on earth, two general effects seem quite likely. First, global warming should cause sea levels to rise noticeably, both by melting polar ice in Antarctica and Greenland, and because warmer water simply takes up more volume. This could expose coastal populations to flooding, and potentially displacing millions of people from their homes. Second, a warming climate should change rainfall patterns in some areas, which could lead to droughts or floods that would displace yet more people. In addition, there are concerns that a warmer climate will be more hospitable to some insect borne diseases, such as malaria, and that warmer oceans could produce stronger hurricanes that would exacerbate the damage caused by rising sea levels.
To someone sitting in Michigan is sub-zero winter temperatures, global warming might seem like a trivial problem. However, if millions of people find their homes worthless, or even uninhabitable, their moving could lead to costly political and social upheavals. Therefore, scientists and governments are debating how to limit our output of greenhouse gases, such as carbon dioxide and methane, in order to reduce the eventual amount of global warming.
Finally, the reliance of any country on non-renewable sources of energy often poses political and security risks. For instance, finding oil in a country that doesn't have a strong industrial base tends to be a very bad thing for a country. In many cases, the revenue from the oil ends up in the hands of a small minority. Moreover, having natural resources like oil tends to be bad for the rest of a country's economy, because it drives up the value of the currency, thereby making other products from the country less competitive on the international market. As a result, countries with oil tend to be less-than-ideal partners on the international stage, which has led many in the U.S. to call for the development of more domestic sources of energy.
Unfortunately, dealing with the above issues has proved to be very, very difficult. The basic problem is that any solution will increase the cost of energy, which decreases the productivity of the economy. At the moment, there is little agreement about how the costs should be distributed. Political debates often turn into lightning storms, forming wherever the hot air of political buzzwords runs up against the cold wall of "not in my backyard." Somehow, despite the fact that energy is covered relentlessly in the media, there seems to be very little discussion about what the actual problems we're facing are.
These pages are our effort to make sense of the magnitude of the problem faced as we try to cope with growing demand for energy. Our approach is similar to that taken by David MacKay in his book, "Sustainable Energy --- without the hot air." His book focused on the potential for sustainable energy in the United Kingdom, and was detailed and thorough. For now, our approach will be a more cursory one, focusing on issues facing the United States. We want to provide order-of-magnitude estimates of what needs to be done to secure the energy future of the United States, and to develop a sustainable pattern that developing countries can emulate.
As a starting point, we have decided to look at how much energy is used by the largest economies.