It is quoted (via The Guinness Book of Answers, 8th ed., pp. 92-93; Van der Leeden, Frits. The Water Encyclopedia, p. 203) as 10.4%. In 2020, despite worrying reductions ascribed to global warming, the proportion is still approximately the same. The calculations of glacial ice include glaciers, ice caps, and the ice sheets of Greenland and Antarctica.