Energy consumption may to continue to increase worldwide, with a heavy continued reliance on fossil fuels to meet the growing need.

Over the past 15 years, a period generally considered to have exhibited robust global economic growth, the consumption of energy worldwide has increased at about 1.5% per year. Forecasts for the next 20 years suggest energy consumption will grow by 2% per year, far outstripping recent growth. At this rate, the world would double its current consumption of energy in only 36 years. An increased push for greater energy efficiency in the developed world is expected to help curb growth, but the rapid industrialisation of billions of people in Asia, where energy use is less efficient, will probably continue to drive the search for more energy.

Recent price spikes in oil and natural gas suggest that the supply of these two largest energy sources is coming under strain. The expected accelerated growth of energy consumption will further tax supplies. However, the composition of energy sources will probably not vary much in the near to medium term. All current sources of energy will probably continue to be important, with a gradual shift to alternative sources in the industrialised world offset by the rapid energy consumption growth served by fossil fuels in the emerging world.

Oil has plenty of supplies to power our transportation needs for the next century, despite doomsday forecasts, but it is a finite resource and one day will need to be replaced. Coal still has plentiful reserves throughout the world, and the emergence of clean coal technologies is expected to drive a small revival of this once "dirty" fossil fuel. Natural gas is the current energy source of choice for growth, thanks to its relatively clean combustion and largely untapped supplies, but challenges remain in efficiently transporting it to market.

Despite current plentiful reserves of the three primary fossil fuels, infrastructure limitations and the desire for cleaner energy will likely make the use of alternative supplies paramount to meet the rising growth in demand. To put the demand for cleaner energy in perspective, it is estimated that by 2050 the world will need 30 TW yr (TeraWatt years) worth of carbon-free energy production to support a stable atmospheric carbon dioxide level of 400 ppm. For comparison, the world currently consumes about 12 TW yr of energy, and carbon dioxide levels are at 275 ppm. These estimated values are controversial, but even if significantly off, they still paint a picture of a dramatic need for not only more but also cleaner energy supplies.

Wind energy is currently the fastest growing energy source in the world thanks to advances in technology, but limitations on suitable sites will keep wind a modest if significant source of power. Biofuels catch a lot of interesting press, but the sheer size and scale of resources needed to generate large amounts of energy this way will probably keep it a fringe producer at best. Only nuclear and solar power have the potential to dramatically alter the energy supply landscape, as both could potentially produce enormous amounts of energy. The policy dilemma of nuclear power, abundant energy with no air pollution versus radioactive waste disposal, large upfront costs, and catastrophic accident potential, is one for legislators to debate. Expect some countries to eventually follow France's lead and "go nuclear" while the majority look elsewhere. Solar energy is currently cost prohibitive, but if technological improvements and rising prices for other energy sources allow it to become cost competitive, the whole energy landscape could change. Hydrogen and cold fusion are wildcards: are unlikely to materialise but they could have a profound impact if they did."

This will be enabled by:

"Rapid economic growth in the emerging world (especially Asia)
Higher prices for oil, leading to greater investment in oil extraction techniques and allowing supply to eventually rise to meet increased demand"

Early indicators include:

Price spikes in oil and natural gas
Increasing demand in the industrialised world for cleaner energy technologies

What to watch:

Solar energy technology breakthroughs make this clean source of power cost competitive.