Written By: Emma Websdale
Due to persistent greenhouse gas emissions, the number of people at risk of water scarcity will increase by 40% as the climate warms, says the Potsdam Institute for Climate Impact Research.
According to an international scientific research project, known as the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP), one in 10 people will suffer from absolute water scarcity if the earth warms by 3oC (3.6oF) above pre-industrial levels.
“The steepest increase of global water scarcity might happen between 2 and 3 degrees global warming above pre-industrial levels, and this is something to be experienced within the next few decades unless emissions get cut soon”, says lead-author Jacob Schewe of the Potsdam Institute for Climate Impact Research.
He adds, “It is well-known that water scarcity increases, but our study is the first to quantify the relative share that climate change has in that, compared to – and adding to – the increase that is simply due to population growth.”
Defined as less than 500 cubic meters (132,000 gallons) of water available per person per year, absolute water scarcity is a level that requires great operative water efficiency measures in order for water-struck countries to manage supplies. In comparison, the current global average water consumption rate per person per year is more than double that amount (approximately 1200 cubic meters. This difference suggests how easily absolute water scarcity rates could become outstripped.
The ISI-MIP project compares comprehensive global model projections of interactions of water scarcity, disease, flooding, crop yields and other issues. Its researchers found that climate change, primarily influenced by ongoing greenhouse gas emissions, would increase the risk of water scarcity by 40% by altering rainfall and evaporation patterns.
The report, to be published in the journal Proceedings of the National Academy of Sciences, is a unique community-driven effort run by 30 teams from 12 countries. Its purpose is to show policymakers that they might be underestimating the social and economic impacts of climate change.
“The multi-model assessment is unique in that it gives us a good measure of uncertainties in future impacts of climate change – which in turn allows us to understand which findings are most robust”, says co-author Pavel Kabat of the International Institute for Applied Systems Analysis (IIASA).
He adds, “From a risk management perspective, it becomes very clear that, if human-made climate change continues, we are putting at risk the very basis of life for millions of people, even according to the more optimistic scenarios and models.”
Regions at the highest risk of increased water scarcity include the Middle East, southern United States, the Mediterranean and southern China. Results also indicate that western China, parts of Eastern Africa and southern India are likely to see substantial increases in water scarcity.
Referencing the latest Intergovernmental Panel on Climate Change (IPCC) report, scientists agree that failure to curb greenhouse emissions is likely to increase global temperatures by 2oC by 2100 –an amount that will trigger this 40% rise in water scarcity.
However, the United Nations Environment Programme’s (UNEP’s) 2013 Emissions Gap Report offers some hope on the subject. The UN report states that it is still possible to keep warming below 2oC, provided that annual emissions are reduced by 12% from 2010 levels (to 44 gigatons of CO2 equivalent, or GtCO2e) by 2020. Emissions would then need to be further reduced to 40 gigatons by 2025 and again by 22 gigatons by 2050.