Feedbacks, climate chemical

In the preceding chapters, we have discussed the ocean s pivotal role in the crustal-ocean-atmosphere fectory. For example, the ocean serves as a receptacle for chemical flows originating from land. We have seen that the ocean s ability to either store these chemicals or bury them in the sediments is a crucial component of the global biogeo-chemical cycles that influence climate and, hence, the hydrological cycle and ocean circulation. These and other linkages support feedbacks that act on biological diversity and abundance, terrestrial erosion, and atmospheric composition. 

The on-line integration of meso-scale meteorological models and atmospheric aerosol and chemical transport models enables the utilization of all meteorological 3D fields in ACTMs at each time step and the consideration of the feedbacks of air pollution (e.g. urban aerosols) on meteorological processes and climate forcing. 

It is necessary to highlight the effects of aerosols and other chemical species on meteorological parameters, which have many different pathways (direct, semi-direct, and indirect effects, etc.) and they have to be prioritised and considered in on-line coupled modelling systems. Sensitivity studies are needed to understand the relative importance of different feedback mechanisms for different species and conditions relevant to air quality and climate interactions. A concerted action to mobilise and coordinate research in this area is needed. 

The term weathering implies that chemical weathering is related to climate. This relationship is important both from the standpoint of the potential long-term feedback during much of... 

Snowpack chemical emissions include oxidants and aerosol precursors, that also interact with climate. Oxidants determine the lifetime of greenhouse gases and aerosols impact the atmospheric radiation budget. If snowpack chemical emissions are determined by climate, feedback loops involving snow chemistry also need to be studied to assess the extent of climate change in snow-covered regions. 

The Earth s climate depends among other parameters (see later) on the chemical composition of the atmosphere. Thus, any variation in the composition raises the possibility of climatic change. First of all, the chemical composition regulates the radiation balance of the Earth-atmosphere system. However, since differences in radiation balance in various geographical regions control the atmospheric circulation, there is also a relationship between composition and dynamic processes. In this chapter we shall deal mainly with the effects of compositional variations on the radiation balance. Moreover, the significance of so-called feedback mechanisms will also be stressed. 

Figure 2.1 illustrates one of the many possible feedback scenarios. For example, climate changes, mechanical compaction, or heat transport can cause or change ground-water flow. Groundwater flow brings about advection and dispersion of solutes. Mass fluxes across spatial domains cause changes of chemical concentrations, and perturb chemical equilibrium or a chemical steady state, which leads to chemical reactions. 

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