Introduction

Recent studies on climate change and climate modelling indicate that there is at least a 90% probability that global warming is due to human activities and more specifically to gaseous emissions since the beginning of the industrial revolution in 1750 [1]. Data from various measurement stations around the globe show that gaseous emissions, such as carbon dioxide (CO2) and methane (CH4), have constantly increased since 1850. CO2 concentration in the atmosphere has increased more than 40% since pre-industrial times with an annual increase of about 80% between 1970 and 2003, and there is a trend for systematic increase [2]. Global warming is related

J. Ganoulis (*) and C. Skoulikaris

Department of Civil Engineering, Aristotle University of Thessaloniki, Thessaloniki, Greece e-mail: [email protected]

1850 1900 1950 2000 1850 1900 1950 2000

Fig. 10.1 Comparison between observed and simulated temperature change (a) without and (b) taking into account human gaseous emissions [2]

1850 1900 1950 2000 1850 1900 1950 2000

Fig. 10.1 Comparison between observed and simulated temperature change (a) without and (b) taking into account human gaseous emissions [2]

to the so-called greenhouse effect, in which high concentrations of gases in the atmosphere are responsible for the increase in air temperature in the troposphere.

Atmospheric temperature fluctuations are induced by variabilities and instabilities of different origin, such as air turbulence and density distribution. The following three causes are also responsible for these fluctuations:

• Temporal changes in solar energy

• Volcanic emissions of aerosols, and

• Gas emissions from anthropogenic activities, mainly from fossil-fuel burning.

As shown in Fig. 10.1, climate models are able to predict temperature increase after 1950 only if the man-induced gas emissions are taken into account. Climate change primarily and additionally man-made modifications in land use result in modifications of different components of the hydrological cycle, such as evapotranspiration and precipitation. This is already the case in arid or semi-arid climates like the Mediterranean, where data time series recordings have shown a decreasing trend in precipitation over the last few decades.

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