The Impact of Climate Change Policy on the Risk of Water Stress in Southern and Eastern Asia

In March 2016 a team of MIT Joint Program researchers published a study in PLOS One that found a high risk of severe water stress in Asia by 2050. An MIT News article on that study led to several stories in media outlets, from CNBC to Voice of America. Since that study was published, the same research team has been working to assess the extent to which climate mitigation and adaptation practices could reduce the future risk of water stress in a region that’s home to 60 percent of the world’s population. Reducing that risk could both save lives and help ensure sustainable growth in the area.

In a paper accepted by Environmental Research Letters, the team focused on the impact of climate change on the risk of water stress in Southern and Eastern Asia (SEA) by midcentury, and how climate mitigation could lower that risk.

Using models that link climate, hydrology, socio-economics and water management, they produced large ensemble projections of future water supplies and use in response to scenarios of climate change and socioeconomic growth by midcentury. These large ensembles were needed in order to capture all plausible outcomes in the regional and global patterns of future climate and socio-economic change. The researchers examined the most likely outcomes of these projections as well as what could occur at the extremes (low-probability cases). They found that while population and economic growth contributes to increased risk of water stress (water-use near or exceeding supply) across the region, unconstrained climate change enhances that risk in China and reduces it in India. They also noted that in the most extreme cases, climate change results in a severe increase in water stress in both nations, where annual freshwater use would routinely exceed supply.   

To evaluate the potential benefit of climate mitigation on water-stress risk throughout the SEA region, the research team considered a large-ensemble scenario under a modest reduction in greenhouse gas emissions (comparable to the current COP21 international agreement). They found that the avoided climate changes eliminate the likelihood of the extreme outcomes described above. Furthermore, the researchers projected that the policy would reduce the additional population (since the year 2000) in the SEA region under threat of facing at least heavily water-stressed conditions from climate change and socioeconomic growth from 200 million to 140 million—a 30-percent decrease.  

Yet even with mitigation, the researchers estimated that there’s a 50 percent chance that 100 million people across the SEA region will experience a 50 percent increase in water stress and a 10 percent chance they will experience a doubling of water stress by 2050. The team maintained that to address these unavoidable risks, SEA nations will ultimately need to implement widespread adaptive measures. And that will be the subject of the researchers’ next study.