Changing Monsoon

Soot from China and India is raising temperatures on the Tibetan plateau, impacting the monsoon

At places, the Tibetan plateau rises five miles above the adjacent Indo-Gangetic plain. At this altitude, the plateau, while much colder than what most of us are used to, is still warmer than air at such heights. The heat from the plateau warms up the surrounding air, creating a current that is one of the factors fuelling the monsoon both in India and East Asia.

According to a paper published in the journal Atmospheric Chemistry and Physics, soot from industrial pollution and the burning of wood in the plains (the increase in population has raised this to levels far higher than in the past) is being deposited on the snow-covered plateau. The ability of snow to reflect sunlight is decreased by this deposition, and so the soot is warming up the plateau.

A computer model suggests that the increase may be as much as 2 degrees Farenheit. Not only is this impacting the severity of the monsoons—increasing them—it also affects the water runoff from the plateau, which is a source of most of the important rivers in the region. According to the US Department of Energy’s Pacific Northwest National Laboratory press release: ‘Soot on snow also stood out when the model investigated water runoff. Smaller changes were observed when just carbon dioxide or soot in the air were examined, but soot on snow by itself increased runoff substantially during the late winter and early spring and then decreased it during the late spring and early summer. With all three scenarios combined, the runoff increased by 0.44 millimetres (or nearly two-one hundredths of an inch) daily between February and April, and then decreased by 0.57 millimetres daily between May and July. These changes provide more water in the winter, when it’s not particularly useful to farmers, but less in the summer when it’s needed to grow crops.’

According to lead researcher Yun Qian, “On the global scale, greenhouse gases like carbon dioxide cause the most concern related to climate change. But our research shows that in some places like the Tibetan Plateau, soot can do more damage.”

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Hartosh Singh Bal