The Impacts and Costs of Climate Change Page: 14
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The Impacts and Costs of Climate Change
to what extent additional water resource options would be available for these cities and hence, to what
extent this finding is robust. This increased water demand from mega-cities may have implications for
environmental flows of water in major rivers of China, India and Tibet if the mega-cities of India and
China decide to seek large scale diversion and impoundments of flows in the region.
Hare's interpretation of the results on millions exposed to potential water stress can be summarized as:
* 1 C of warming or below may still yield high levels of additional risk, particularly in the period to
the 2020s and 2050s, with this risk decreasing due to the increased economic wealth and higher
adaptive capacity projected for the coming century. For the 2020s, most of the current global
climate models imply a level of risk of additional number of people in water shortage regions in
the range 400-800 million for around a 1C warming.
* 1.50C of warming produces quite different but nevertheless substantial levels of risk in the
different time periods under the Parry et al. (2001) analysis, with a peak in the 2050s at over 1,500
million, declining to around 500 million in the 2080s.
* A major threshold change in risk occurs in the Parry et al. (2001) analysis in moving from 1.50C
to 2-2.50C, with the numbers rising from close to 600 million to between 2.4-3.1 billion. As
explained earlier, this is driven by the water demand of megacities in Indian and China in their
* 20C warming and above produces consistently very high levels of additional risk at all time
periods under the HadCM2 scenarios. The range of risk for the current array of models in the
2050s is in the range 662 million to around 3 billion.
* Above 2.50C warming the level of risk begins to saturate in the range of 3.1- 3.5 billion additional
persons at risk.
Above 2 to 2.50C global average temperature increase it is projected that an additional 2.4 to 3.1
billion people will be at risk of water stress23.
One of the most serious effects of climate change will be to increase the risk and possibly the duration
Drought will have negative impacts in southern Europe where projections indicate up to 1 % per
decade decrease in annual precipitation with decreases of 5 % per decade possible in summer (EEA
2004). This reduction in precipitation in southern Europe is expected to have severe effects, including
more frequent droughts, with considerable impacts on agriculture and water resources. These negative
effects can cause very heavy economic losses, for example droughts in 1999 caused losses of more
than Euro 3 billion in Spain (EEA, 2004).
At a global level, higher temperatures and erratic rainfall are the primary causes, while a shift in
circulation patterns, such as extended periods of El Nifios, could see droughts lasting for years and
possibly decades. Although the scenarios of future drought risk are as yet uncertain, the effects would
be serious. The immediate consequences-water stress, food scarcity, reduced plant growth, disease
burdens-can lead to economic, social and even political stresses. The most severe consequences,
such as famine, forced migration and disease epidemics need not be direct consequences of a drought;
however an increase in drought risk with climate change could push some sensitive ecosystems and
economies beyond a threshold of sustainability. The global economic cost of drought has not been
calculated. However, droughts in Africa have cost up to 8% of GDP, primarily due to loss of power
production from hydroelectric plants.24 Annual average losses in the United States due to drought are
estimated at $6 to $8 billion.25
23 Source: Parry et al, 2001
24 Benson, C. and Edward J. Clay. 1998. 'The impact of drought on Sub-Saharan African economies: a
preliminary examination.' Technical Paper, 401. Washington, D.C.: World Bank.
25 'Economic impacts of drought and the benefits of NOAA's drought forecasting services' National Oceanic ad Atmospheric
AEA Technology Environment, August 2005
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Watkiss, Paul; Downing, Tom; Handley, Claire & Butterfield, Ruth. The Impacts and Costs of Climate Change, text, September 2005; Oxford, England. (digital.library.unt.edu/ark:/67531/metadc29337/m1/25/: accessed September 21, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .