1 Given that the sea level at the end of the last glacial maximum was 120 m lower than that today, estimate the volume of ice in the ice-sheets that covered the northern parts of the American and Eurasian continents.

2 How much energy would be required to melt the volume of ice you have calculated in Question 1? Compare this with the extra summer sunshine north of latitude 60° which might have been available between 18 000 and 6000 years before the present according to the data in Figure 4.7. Does your answer support the Milankovitch theory?

3 It is sometimes suggested that the large reserves of fossil fuels on Earth should be preserved until the onset of the next ice age is closer so that some of its impact can be postponed. From what you know of the greenhouse effect and of the behaviour of carbon dioxide in the atmosphere and the oceans, consider the influences that human burning of the known reserves of fossil fuels (see Figure 11.2) could have on the onset of the next ice age.

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