I . ABSTRACTThe hydrological cycle consists of several processes that act as variables for climate andclimate change. Due to this it has been investigated and predicted that climate changemay not only have intense effects on the hydrological cycle, but that the hydrologicalcycle itself may also reciprocate and influence climate change. It is now recognized thatclimate change, or global warming, can directly effect precipitation, evapotranspiration,and soil moisture. It has been predicted, using various models all dependent on GlobalCirculation Models, that the hydrological cycle will be intensified. There will beincreases in evaporation and precipitation, which do not cancel each other out due to theirunequal distribution. When considering the hydrological cycle, aquifer systems are asource of land surface heterogeneity making their features indispensable for regionalscale interpretation, in order to model correct values of runoff and surface temperatures.More focused models present that subsurface saturation both is effected by and has aneffect on climate change.II. INTRODUCTION According to global assessment by the United Nations, already one third of a 5.7billion global population survives under conditions of water stress, and about 450 millionpeople are living under conditions of severe stress. Sustainable water supply to whichhumans have access to is the accumulated river discharge (Q) from mean annual surfaceand subsurface runoff. When considering water demand pushed by irrigated agriculture,domestic and industrial sectors as a fraction of the sustainable water supply, DIA/Q, UNestimates for the percent population (2000) living under water stress conditions aresupported. Table 1 shows the individual estimates. (Vorosmarty et al, 2000) Table 1. World population (2000) living under progressive levels of relative waterdemand. Water stress definition and standards have been set by the UN.Countries experiencing water stress are concentrated in southern and northern Africa,around the Mediterranean and Middle East, southern Asia and Indian subcontinent,Central America, and large parts of Europe. (Ranjan et al, 2006) This is a predominantportion of the land mass and human population on Earth. Figure 1 illustrates how waterstress is apparent across arid and semiarid regions, and densely populated regions ofhumid tropics and temperature zone. (Vorosmarty et al, 2000) Pressures are believed toincrease drastically in Africa and parts of southern Asia and Eastern Europe. (Ranjan etal, 2006) This emphasizes the need for an integrated approach in collaborating climatechange, water resources, and socioeconomic communication in order to strategize for abetter future. Figure 1. Global distribution of areas under water stress condition, which the color red denoting areas of extreme water stress. Climate change did not grow to be of major concern until the last few decades.Post the Industrial Revolution there was observation of soaring concentrations of greenhouse gases, including the birth of synthesized gases known as CFCs. These increases inconcentrations along with residence time are listed in Table 2. Climate change isgoverned by solar irradiance, surface albedo, surface energy fluxes, cloud properties,surface temperature, and greenhouse-gas concentrations. The latter has been the cause ofrecent climate changes and the fear for future climate change. (Loaciga et al, 1995) Table 2. Concentrations and residence times of significant greenhouse gases. (Vorosmarty et al, 1995)In order to understand climate change, knowledge of how Earth’s atmosphereregulates surface temperature must be attained. This “greenhouse effect” is driven by theprimary source of energy that heats Earth, solar radiation (measured in Watts per squaremeter). A solar constant has been measured by satellites to give a range of 1365 to 1372Wm-2. Only a fourth of this goes to work as solar insolation after considering Earth’sspherical geometry, resulting in an average flux of solar radiation of 342 Wm-2. The netinput is 237 Wm-2 because 105 Wm-2 is reflected back to space due to planetary albedo,currently approximated to be 30%. Approximately 169 Wm-2 of this net value is absorbedby surface and about 68 Wm-2 is absorbed by the atmosphere. (Loaciga et al, 1995) Sdown Lup ------------------------------------------------------------------- SH LH Sup LdownFigure 2. Diagram of Earth’s energy fluxes. S is “solar” radiation, L is “longwave” radiation; SH is sensible heat; LH is latent heat. From these values it is evident that Earth’s atmosphere is cooler than the surface,or it is the case generally. The vertical atmospheric profile, Figure 3, depicts howtemperature decreases towards the tropospause. Due to the atmosphere’s relativecoolness, its gas molecules can absorb more energy than emit (Stefan-Boltzmann Law),permitting it to maintain the energy emitted by the surface to warm the surface. Putquantitatively, mean effective radiative temperature is approximately -18ºC, althoughEarth’s surface reads a global mean temperature of approximately 15ºC. This differenceof 33ºC is due to the atmosphere’s greenhouse effect. The surface-atmosphere system iscomprised of emitted surface radiation trapped by the atmosphere’s greenhouse gases,giving a net estimated result of 153 Wm-2 under today’s equilibrium conditions. This isthe greenhouse effect, which is what is subject to being dangerously enhanced because ofincreased concentrations of greenhouse gases. (Loaiciga et al, 1995)Figure 3. Vertical atmospheric profile. (Loaicigs et al, 1995)The change in climate due to increased concentrations of greenhouse gases is notonly complex, but inadequately comprehended. Svante Arrhenius (1896) was the firstscientist to study the effect of increased CO2 concentrations on surface temperatures, afteracknowledging mathematician, Jean-Baptiste Fourier’s, understanding of the greenhouseeffect. Current predictions are compatible with Arrhenius’ results, in which surfacetemperatures increased from doubling CO2 concentrations. (Loaiciga et al, 1995)In order to analyze the effect of the atmosphere’s greenhouse gases,
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