(a) Study Fig. 6.1, which is information about melting ice. When Glacier National Park in the USA was established in 1910, there were 150 glaciers (a glacier is a slow moving mass or river of ice). Since then the number has decreased to fewer than 30, and most of those remaining have shrunk in area by two-thirds. Most scientists believe that human activity, in particular the burning of fossil fuels, has caused the atmosphere to become warmer and caused ice to melt. The ice on Mt Kilimanjaro has reduced by more than 80% since 1912. Glaciers in parts of the Himalayas are retreating so fast that researchers believe that most central and eastern Himalayan glaciers could virtually disappear by 2035. Arctic sea ice has thinned and its area has reduced by about 10% in the past 30 years. When temperatures rise and ice melts, more water flows to the seas from glaciers and ice caps. Rising temperatures also cause ocean water to warm and expand in volume. This has increased average global sea level by between 10 and 20 centimetres in the past hundred years. [Figure 6.1]