The lifestyle of the world's richer countries is much dependent on fossil fuels. Table 2.2 shows that our worldwide use of energy for heating, cooking, transport, operating factories and so on, is about 20 times that of the food we eat. Most of it comes from fossil fuels. The world's resources of fossil fuels are finite, but predicting how long they will last is notoriously difficult. If the present rate of use of coal and oil is compared with known reserves that are likely to be extractable, this suggests that coal will last 1-2 centuries and oil about half a century (UN Energy Statistics Yearbook 1995). However, the world's total coal is estimated to be at least 10 times as much as the 'known recoverable'. The size of known stocks of oil tends to depend on how much money and effort the oil companies spend on exploration, so there are likely to be reserves not yet discovered. In any case, it may never be possible to use all these reserves, because of the effect the released C02 would have on the world's climate. This chapter considers that topic in detail, first the changing carbon balance of the world and the increase in atmospheric C02, then the predicted effects of increases in C02and other gases on climate. That section makes substantial use of a fat book called Climate Change 1995, written by numerous experts belonging to the Intergovernmental Panel on Climate Change (Houghton et al. 1996). A slimmer book by Houghton (1997) summarizes many of the key facts. The final main section of this chapter will then draw on many sources of information to consider how living things (crops and wild species) may respond to these changes in C02 and climate.
During the 19th and early 20th centuries it was obvious that burning coal released soot and other pollutants, which affected the atmosphere of cities. It was known that C02 was released as well, but there was no obvious reason to worry about it. The world's atmosphere is so large, surely any extra C02 would be so much diluted it could not possibly have any effect? This assumption has proved to be incorrect. To measure whether the C02 concentration in the atmosphere is changing requires very accur-MeasuringC02 ate equipment, carefully used. Reliable continuous measurements in the atmosphere started in 1958, on Mount Mauna Loa in Hawaii and subsequently at other sites. We also now know C02 concentrations before 1958, back over more than 200 000 years, by measurements on small bubbles of air extracted from ice cores several kilometres deep from Greenland and Antarctica (Moore et al. 1996, Fig. 3.21). In these cores there are annual layers visible, caused by the different falls of snow in winter and summer, so the bubbles can be dated accurately. Figure 2.1 shows how the COz concentration has changed since 1750. In 1750-1800, in the early years of the industrial revolution, the concentration was about 280 |nl l1 and rising slowly. During the 1990s it was rising at about 1.5 fil l-1 per year, and by 2000 it has passed 360 jxl H.
Because this increase will affect living things (as will be explained
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