Q1.
Part of the Tibetan Plateau. These satellite pictures are from 1987 and 2021 respectively. What differences do you notice?
Answer
Two changes stand out when the 1987 picture (left) is set beside the 2021 one (right).
- Far less white. In 1987 a broad sheet of white snow and ice covers most of the ridges across the upper half of the picture. In 2021 that white has almost gone; the same ridges now show as bare brown and grey rock, with only small patches of snow left.
- The lakes are bigger, and some have joined up. In 1987 the dark lakes are separate — a large blue lake at the lower left, a dark lake beside it, another long lake to its right, with strips of land between them. In 2021 those same lakes have spread outwards until they touch, forming one long, connected sheet of water, and one or two new small lakes have appeared where there was dry ground before.
Why it happens: the two changes are one change. As the climate warms, the snow and ice that used to sit on the plateau all year melt away — that is the vanished white. The meltwater has to go somewhere, and the Tibetan Plateau is a high basin with very little drainage out to the sea, so the water simply collects in the hollows already holding lakes. The lakes rise, spill sideways and merge. The chapter states it plainly: with climate change, snow-melt has led to the expansion of existing lakes and the creation of new ones.
Did you know? This matters far beyond Tibet. The plateau is called the ‘Third Pole’ because it holds the largest reserves of freshwater outside the polar regions, and it feeds the Indus, the Brahmaputra and the Yangtze. Ice released as lake water is water no longer stored for the dry season, on which hundreds of millions of people downstream depend.