on fossil fuels. So wind power in developed countries can increase dramatically without substantially changing its proportion in the total.
The second hard truth in the 2007 NPC study is that:
The world is not running out of energy resources, but there are accumulating risks to continuing expansion of oil and natural gas production from the conventional sources relied upon historically. These risks create significant challenges to meeting projected energy demand. (p. 5)
Estimates of oil capacity from both conventional and unconventional sources, such as heavy oil or oil shales, remain large. Humans have used about 1.1 trillion barrels of oil since the dawn of the oil age, Nelson said. Conventional supplies of oil exceed 3 trillion barrels, and the use of unconventional sources of oil could add a substantial amount to that (Figure 4.2). “Quite a bit of oil [is] still left in the ground,” said Nelson. “The more you explore, and the more you learn about the earth, the more you find.”
However, oil production is the more relevant measure, Nelson acknowledged. The NPC study (NPC, 2007) looked at projections for 2030 made by different organizations, which ranged from 85 million barrels a day (approximately today’s level) to 130 million barrels (Figure 4.3). “Reasonable people