Aggressive mitigation policy could halve climate-related impacts on exposure to water scarcity by 2100

( -- In a paper highlighted in Nature Climate Change today, Nigel Arnell, Director of the Walker Institute for Climate System Research at the University of Reading, and colleague Detlef van Vuuren from the Netherlands Environmental Assessment Agency found that stringent measures to reduce greenhouse gas emissions could half the adverse impacts of climate change on water scarcity by 2100, although some models suggest impact reductions as low as 15%. The large range exists because climate models do not agree on exactly how rainfall will change in the future.

This study is the first to consider how impacts on are reduced if warming is kept below 2 degrees C, compared with a scenario in which global temperatures increase by 4 degrees C by 2100. International climate negotiations are focused on a target which keeps global temperature rise below 2 degrees.

Professor Arnell said: "Our results show that stringent measures to reduce greenhouse gas emissions help to reduce the adverse effects of climate change on water scarcity, but they by no means remove the impacts altogether. So, adapting to the climate change we can't avoid is as necessary as mitigation measures to reduce greenhouse gas emissions.

"The absolute numbers and locations of people affected vary considerably across the four climate models used in the study."

Even without the effects of climate change, as much as 40% of the world's population will be living under water scarce conditions by 2020. Climate change is expected to influence future water scarcity through regional changes in precipitation and evaporation. Most climate models suggest rainfall is likely to decrease in the subtropics and increase in mid-latitudes and some parts of the tropics, although details vary.

In some water-scarce parts of the world (eg parts of Asia), rainfall is projected to increase under climate change and this could lessen problems of water scarcity (but possibly also bring an increase in flood risk). In these areas, the mitigation scenario could actually reduce the amount of extra water potentially available.

The research, undertaken as a part of the EU-funded ADAM project, compares a ‘business as usual' scenario which leads to an increase in global mean temperature of 4 degrees C by the end of the 21st Century with a mitigation scenario which assumes policies to reduce and leads to a warming of 2 degrees C by 2100. The emission reductions are achieved by using energy more efficiently, increased use of renewable and nuclear power, increased use of carbon capture and storage and reducing other non-CO2 greenhouse gases. As a result, global emissions of greenhouse gases continue to grow until around 2020 and then decrease rapidly to 2100.

The part of the study just published takes the results from four and feeds the results through a hydrological model which simulates river flow. From river flow the authors calculate two indicators of water availability: one which measures amount of water per person and one which measures the ratio of water used to water available. These measures give an indication of exposure to water stress and assume no adaptation.

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More information: Arnell, N.W., van Vuuren, Detlef P., Isaac, M., The implications of climate policy for the impacts of climate change on global water resources. Global Environmental Change doi:1.1016/j.gloevncha.2011.01.015 (2011).
Provided by University of Reading
Citation: Aggressive mitigation policy could halve climate-related impacts on exposure to water scarcity by 2100 (2011, March 8) retrieved 21 July 2019 from
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Mar 08, 2011
Climate sensitivity to a doubling of CO2 is about 0.4 C, so all this hyperventilating about water shortage is for nought. The IPCC predictions of increasing greenhouse effect, rapidly increasing CO2 levels, increasing atmospheric humidity, and increased temperature are simply not happening. Try some other theory to destroy the world's energy supply.

Mar 08, 2011
Great, so lets arm the greenies with our militaries and surrender our national liberties to their plans. Then have them humanely manage our lives for us. Won't that lead us into a harmonious utopia?

Mar 10, 2011
OK, let the greedies take it all, and let those who are hurt by their irresponsible actions get out of the way and find an early grave. Nice. The greedies will be able to take over whatever spots are left habitable and for the rest who cares? Just leave enough little people to mix their cocktails and clean and change their sheets.

Mar 14, 2011
Boy, there are a lot of cranks out there as evidenced by many of the comments in this and many other pieces on this web site. They just throw out disinformation which is totally incorrect. And, yes, we should definately prepare for a four degree rise - the pace of our CO2 emmissions is not slowing and climate change is occurring much more rapidly and abruptly then what the IPCC suggested.

Governments have known about this problem since the first IPCC report in 1990 which concluded then that man was most likely the cause of global warming. All subsequent report further narrowed the causes, which is us.

I personally hold both political parties responsible for what is occurring now and in the future. They have their scientist which have been harking this for decades now. We are now living with the consequences of inaction, and its not going to be pretty. I for one did not expect this threat in my old age. I used to imagine a nice quiet retirement, but not any more.

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