The human ecology of climate change - Climate Change: Biological and Human Aspects - page 385

(c)

World

60

Coal

Coal
Oil
Gas
Renewables
Nuclear

50

Oil

40

30

20 Gas

10

Renewables

Nuclear

0

1950 1960 1970 1980 1990 2000 2010

Year

Fig 7.8 (continued)

The global energy picture that emerges has been one of diversification. There was
a proportional decline in the importance of coal over the last half of the 20th century
(see Figure 7.8c), before a resurgence in the early 21st century. The proportion of
global energy demand met by oil over this time increased to around 46% by 1980
when price and energy-security concerns began to cause a shift to other energy
sources such as nuclear power and gas. Most of the global energy diversification has
been at the expense of coal, much in the way that fossil fuels replaced wood in the
USA and much of the New World, and a little later less-developed nations, in the
late 19th and early 20th centuries. However, longevity of individual energy resources
(the economically recoverable ones) will, as we shall see in the next chapter, determine
the economic sustainability of respective fuels.
At the end of the 20th century nearly all countries were dependent on fossil fuels
for the majority of their energy needs, although nuclear and renewable energies, as a
proportion of the total, were beginning to grow.
Although a look at the breakdown of a nation's (or the global) commercial energy
budget informs as to fuel-switching and is suggestive of new fuel-introduction lead
times, it does not indicate how much carbon dioxide will be generated in the future:
it all largely depends (higher energy per carbon methane notwithstanding) whether
the total fossil energy consumed remains constant, increases or decreases. In fact,
commercial energy consumption overall has been increasing globally with time, and
markedly so (see Figure 7.9). This exerts a pressure to increase fossil fuel con-
sumption in the absence of new non-fossil energy resource deployment. Indeed, by
the end of the 20th century most of our global commercial energy consumption
(around 87%) came from fossil fuels, this having increased by more than 350%
since the middle of the century. Even though the contributions from nuclear and
renewable energies have grown slowly, their growth - as a proportion of the global
commercial energy budget - has increased the annual non-fossil contribution only