World population facing water stress could ‘double’ by 2050 as climate warms


The number of people exposed to water stress could double by 2050 if efforts are not made to keep global warming below 2C above pre-industrial levels and future population growth is high, a study finds.

This means an additional 380 million people could face water stress by mid-century, when compared to the number in 2010.

Even if the world does meet the Paris Agreement ’s temperature target of limiting warming to below 2C and population growth is low, the number of people exposed to water stress could still rise by 50% by 2050, when compared to 2010, the research says.

Increases will be concentrated in the Middle East, North Africa and south and central Asia – regions that already face significant challenges as a result of water stress, the lead author tells Carbon Brief.

Running dry

Around two-thirds of the global population – four billion people – face water scarcity for at least one month a year in today’s world.

Water availability is affected by physical processes – such as the amount of rainfall, rate of evaporation and the geology of the land surface and human management, through dams, groundwater extraction and reservoirs. 

For many countries, water availability is also shaped by the actions of other nations that lie further upstream. These shared water resources are described as “transboundary” and include, for example, major rivers that traverse multiple countries.

The new study, published in Earth’s Future , examines how climate change could shape water stress across international borders. “Water stress” is a measurement of the ratio between water use and availability, the authors say. It is specifically a measure of “demand-driven” water scarcity, they explain in their research paper:

“The focus here is on water stress – calculated as a water use-to-availability ratio – because…it captures well a simple intuition about how water use and availability relate: when water is abundant, water use generally has less impact than when water is in short supply.”

Forecasting thirst

For the research, the authors combined data from hydrological models and climate models. To make projections for water stress in 2050, they looked into two possible scenarios.

Glossary

RCP2.6: The RCPs (Representative Concentration Pathways) are scenarios of future concentrations of greenhouse gases and other forcings. RCP2.6 (also sometimes referred to as “RCP3-PD”) is a “peak and decline” scenario where stringent mitigation and carbon dioxide removal technologies mean atmospheric CO2 concentration peaks and then falls during this century. By 2100, CO2 levels increase to around 420ppm – around 20ppm above current levels – equivalent to 475ppm once other forcings are included (in CO2e). By 2100, global temperatures are likely to rise by 1.3-1.9C above pre-industrial levels.

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