Lakes, glaciers, and major river basins on the Tibetan Plateau. Endorheic basins are shown in light purple and exorheic basins in light yellow. Bar plots show TWS changes (TWSC) for each basin (only basins with TWS trends ≥ 1.0 Gt/yr are shown) during 2002‒2017, estimated from the GRACE JPL-M solution. Blue bars represent mass gain in TWS, whereas red bars represent mass loss, and bar size represents the magnitude of TWS changes (Gt/yr). Specific values for TWS changes are shown in each basin. Credit: Penn State, Tsinghua University
Key Points:
- Water levels in the Tibetan Plateau are significantly dropping, which will affect almost two billion people.
- If aggressive climate policies are not developed, scientists predict a 100% loss of water availability in some areas within 40 years.
- Scientists reached their conclusions after examining the terrestrial water supply (TWS), which includes water both above and below ground.
Scientists at Penn State, Tsinghua University and the University of Texas at Austin warn that the water supply of almost two billion people is at risk unless bold climate policies are adopted. The scientists directed their attention to the Tibetan Plateau, sometimes called “the roof of the world,” which contains a rich network of streams and rivers that supply drinking water to a large portion of Asia.
The study’s findings are especially important because a detailed look at how climate change has affected the terrestrial water storage (TWS) of the Tibetan Plateau had not been conducted before. TWS is an aggregate of all of the water found in any given habitat. The Tibetan Plateau, in particular, is very susceptible to the effects produced by climate change.
The team found that climate change in recent decades has led to severe depletion in TWS (-15.8 gigatons/year) in certain areas of the Tibetan Plateau and substantial increases in TWS (5.6 gigatons/year) in others, likely due to the competing effects of glacier retreat, degradation of seasonally frozen ground and lake expansion.
Their projections for future TWS under a moderate carbon emissions scenario suggest the entire Tibetan Plateau could experience a net loss of about 230 gigatons by the mid-21st century (2031‒2060) relative to an early 21st century (2002‒2030) baseline.
More specifically, excess water loss projections for the Amu Darya basin, which supplies water to central Asia and Afghanistan, and the Indus basin, which supplies water to Northern India, Kashmir and Pakistan, indicate a decline of 119% and 79% in water-supply capacity, respectively.
The scientists, who published their research in Nature Climate Change, say their projections point to serious consequences even if efforts are made to cut back on carbon emissions.
“The prognosis is not good,” said Michael Mann, professor of atmospheric science at Penn State. “In a ‘business as usual’ scenario, where we fail to meaningfully curtail fossil fuel burning in the decades ahead, we can expect a substantial decrease—that is, nearly 100% loss—of water availability to downstream regions of the Tibetan Plateau.”