Summer surface air temperatures ('C)
One major consequence of rising global temperatures will be an increase in the temperature of the oceans and some melting of the ice at the poles. There is some evidence that sea levels have risen during the twentieth century. The sea level at Brest on the west coast of France, for example, has risen by 10 cm since the Industrial Revolution. Therefore there have been many cataclysmic predictions of the effects of sea-level rise (see Figure 7.24 and Plate 7) over the next 60 years. A rise of 15 cm by 2030 and 50cm by 2100 may not seem much since most people live well above sea level and would not be directly affected. However, nearly half of the world's population lives near coastal regions and some countries (e.g. Bangladesh and the Pacific nations) are little more than l m above sea level. It is quite impractical to consider the construction of sea defences along the whole of their coast line, and even if this was possible the introduction of salt water into the fresh water table would make such defences ineffective as far as protection of agricultural land was concerned.