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Climate Change and the European Water Dimension - Agri ...

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Figure III.4. Projected change in summer precipitation (%) in Europe up to 2080, relative<br />

to average precipitation in <strong>the</strong> period 1961-1990 (based on intermediate ACACIA<br />

scenario; EEA, 2004).<br />

air is precipitated out, thus suggesting that <strong>the</strong> intensity of <strong>the</strong>se events will increase<br />

with <strong>the</strong> availability of moisture. Therefore <strong>the</strong> incidence of heavy precipitation <strong>and</strong><br />

drought events is also predicted to increase, which suggests implications not only for<br />

increased contamination resulting from run-off but also decreased groundwater<br />

recharge <strong>and</strong> an increased incidence of flooding. Moreover, changing precipitation<br />

rates affect rates of chemical wea<strong>the</strong>ring of silicate rocks, <strong>and</strong> hence ultimately <strong>the</strong><br />

carbon dioxide content of <strong>the</strong> atmosphere.<br />

Among <strong>the</strong> anthropogenic factors for climate change are anthropogenic carbon<br />

dioxide <strong>and</strong> aerosols of various origins. Such changes could have a large impact on<br />

<strong>the</strong> hydrologic cycle. For example, sulphate aerosols from volcanic <strong>and</strong><br />

anthropogenic sources in <strong>the</strong> stratosphere <strong>and</strong> in <strong>the</strong> troposphere may increase <strong>the</strong><br />

scattering of sunlight away from space, ei<strong>the</strong>r directly or via effects on clouds.<br />

Aerosols can also produce direct tropospheric heating, with similar effects to CO2 on<br />

<strong>the</strong> hydrologic cycle. Aerosols can also influence precipitations. Already in 1968<br />

Warner (1968) deduced that aerosol emissions from sugar cane fires were affecting<br />

precipitation by examining rainfall records from Western Australia. Aerosol-induced<br />

precipitation suppression has been observed both with in situ measurements (Ferek<br />

et al., 2000), <strong>and</strong> in satellite observations (Rosenfeld, 2000) showing that <strong>the</strong> effect<br />

does in fact occur in <strong>the</strong> atmosphere. If precipitation is suppressed, water that would<br />

have been removed from <strong>the</strong> atmosphere remains aloft <strong>and</strong> can be transported to<br />

o<strong>the</strong>r locations before it is deposited to <strong>the</strong> surface. The same is true for <strong>the</strong> energy<br />

associated with such water—<strong>the</strong> latent heat released on condensation in clouds <strong>and</strong><br />

<strong>the</strong> energy required for evaporation of water from <strong>the</strong> surface. The redistribution of<br />

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