Emissions future evolution

Indeed, the most important factor that affects the future estimates of climate is the (anthropogenic) emissions of greenhouse gases and all kind of aerosols. The amount of these products released into the atmosphere depends upon the socio-economical and technological development of humankind. Thus, different hypotheses about these evolutions are assumed, resulting in several emission scenarios. The scenarios used in the IPCC AR4 derive from a Special Report on Emission Scenarios (SRES) published earlier [2]. All these scenarios can be grouped in four families (storylines) that are named Al, A2, Bl, and B2. 

Because of decreased SO2 emissions, the importance of nitrogen for freshwater acidification becomes more and more determinant. Therefore, uncertainties in the evolution of nitrogen emissions make it difficult to predict future trends in freshwater recovery. On the other hand, climate warming may increase the number of alkaline rain episodes (containing Saharan dust) and enhance weathering reactions, which buffer better acid precipitation, increasing alkalinity and pH. 

The apparatus has recently been used for a study of exclmer emission In poly(styrene) and poly(1-vlnylnaphthalene) (42), results of which are discussed below. Systems of this sort have great promise for the study of the time evolution of excited species within polymeric materials, and should be used Increasingly In the future. A feature not yet exploited Is the fact that the exciting radiation Is plane-polarized, which has great potential for use In rotational relaxation measurements (see Section V). 

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