Gail Tverberg over at the blog "Our Finite World" has a post titled World Energy Consumption Since 1820, and the lead graphic is astonishing:
"Peak oil" was a dumb shit theory that became really popular for a time during the last decade. It actually referred to the peak production point of oil, after which production would decline. People assumed that this meant that we were running out of oil. What it actually meant is that oil would become too difficult to locate and extract economically, and prices would become too high, leading to declining demand. It's actually a sound theory. What I should say is that people who believe the popular notion of peak oil are dumb shits. But somehow, pointing out the dumb-shittery of individuals is considered rude.
However, there is a peak oil that is bound to occur no matter how much oil reserves we have left. Look back at that chart above. Our population is continuing to grow. In fact, the population will continue to grow, reaching a peak of about 14 billion people sometimes in the next century, roughly double today's population. Meanwhile, the amount of energy production people consume doubles every 40 years. Basically, we will need sixteen times as much energy production capacity in 2100 to sustain our population as we have now. Oil, coal and natural gas cannot provide this because they lack energy density - no matter how much we're able to pull out of the ground at any price, the burden of storing and distributing it will make it cost prohibitive to support global energy consumption.
The answer, of course, is that we need energy sources that are dense. All the global production of fossil fuels in one year would be comparable to the energy stored in the water that flows through the hoover damn in one day if the hydrogen were used in nuclear fusion reactions. What we truly need is hydrogen power - the most abundant element in the universe has reliably powered life on this planet for 4.5 billion years. (The sun.)