Climate system

The ocean is an integral part of the climate system. It contains almost 96% of the water in the Earth s biosphere and is the dominant source of water vapour for the atmosphere. It covers 71% of the planet s surface and has a heat capacity more than four times that of the atmosphere. With more than 97% of solar radiation being absorbed that falls on the surface from incident angles less than 50" from the vertical, it is the main store of energy within the climate system. 

DMS has been observed in the marine atmosphere since the early 1970s, but it was not until the mid-1980s that there was interest in this gas as being a natural source for sulfate CCN. Sulfate aerosols are, in number terms, the dominant source of CCN. The major role clouds play in the climate system leads to possible climatic implications if changes to DMS production occurred. Furthermore, the dependence of this production on environment conditions means that scope for a feedback process arises this feedback is called the Charlson hypothesis. ... 

Scanvac. Classified indoor climate system Guidelines and specifications. Swedish Indoor Climate Institute, Stockholm, 1991. 

Climate is often viewed as the aggregate of all of the elements of weather, with quantitative definitions being purely physical. However, because of couplings of carbon dioxide and many other atmospheric species to both physical climate and to the biosphere, the stability of the climate system depends in principle on the nature of feedbacks involving the biosphere. For example, the notion that sulfate particles originating from the oxidation of dimethylsulfide emitted by marine phytoplankton can affect the albedo (reflectivity) of clouds (Charlson et ai, 1987). At this point these feedbacks are mostly unidentified, and poorly quantified. 

In its assessment of climate change, the IPCC (1990) identified five hydrosphere-related feedback mechanisms in the climate system likely to be activated by increased greenhouse gas concentrations in the atmosphere. These feedbacks are briefly described below for more detailed discussion of the climate system, refer to Chapter 17. 

Clouds. Cloud feedback mechanisms are among the most complex in the climate system, due to the many disparate roles played by clouds, which control a large portion of the planetary albedo but also trap terrestrial radiation, reducing the energy escaping to space. To complicate matters further, different t5 es of clouds behave differently in the same environment. In the present climate mode, clouds have... 

Broecker, W. S. (1997). Thermohaline circulation, the Achilles heel of our climate system Will man-made CO2 upset the current balance Science 278, 1582-1588. 

The El-Niho southern oscillation (ENSO) phenomenon is an interannual perturbation of the climate system characterized by a periodic weakening of the trade winds and... 

Fig. 17-1 The global climate system, (a) Energy fluxes, including incoming solar radiation, reflected radiation, emitted longwave radiation (from an effective altitude of ca. 6 km), and atmospheric and oceanic heat flux toward the polar regions, (b) The atmospheric circulation corresponding to part (a). Refer back to Fig. 7-4 and associated text for a discussion of the general circulation.

Keeping in mind the entire set of components in the climate system as depicted in Figs 17-2,4-13, and 17-3, we can now re-examine Fig. 1-2 to emphasize that biogeochemical cycles are coupled with the climate system. The temperature (as inferred from the record of the deuterium to hydrogen ratio in Antarctic ice) covaries with CO2, CH4 and other species that derive from biological processes. Two simple, if extreme, possibilities can be drawn ... 

The biosphere and its processes are an integral part of the physical climate system and are coupled to and have influenced changes in climate. 

It is scenario 3 that is most consistent with the data depicted in Fig. 1-2. Given that the physical climate system is strongly influenced by gases in the atmosphere that absorb and emit infrared radiation (e.g., H2O, CO2, CH4, etc.), and since the amounts of these species in the air depend to some extent (for some, a great extent) on the functioning of the biosphere, it is logical to view the climate of the Earth as a coupled physical, chemical, and biological entity. 

Taken together. Figs 17-2, 4-13, 17-3, and 1-2 constitute a complex image of the Earth s climate system, including most of the factors that are known to be involved. However, such diagrams fail to adequately represent the dynamical nature of the totality of interactions of all of the parts. In order to explore these interactions, the natural variability of climate, and changes due to external perturbations, we must now introduce the key notions of forcings, feedbacks, and responses. 

Fig. 17-2 The web of interactions in the atmospheric part of the global climate system. The strength of the interactions is qualitatively depicted by the thickness of the line. Bidirectional interactions have two arrowheads, unidirectional ones have only one. (From Houghton (1984), reprinted with permission from Cambridge University Press.)...

The Dynamics of the Climate System Forcings, Feedbacks, and Responses... 

The actual workings of the coupled biogeo-chemical and physical climate system, the ways that it responds to external perturbations, and the ways that it approaches or departs from a... 

Changes in the physical characteristics of the Earth that are internal to the climate system can... 

The nature of such processes can be depicted as a feedback loop, as shown in Fig. 17-4. Using the nomenclature in this figure and continuing with enhanced evaporation of water vapor as our physical example of a feedback that is completely internal to the climate system, we... 

While most climate models consider feedbacks as being dependent on temperature (usually Ts), there are many other dependent variables in the climate system that could be involved, for example solar irradiance at the ground or rainfall. However, it is customary to describe these mathematically as functions of Tg,... 

Fig. 17-4 Schematic of the climate system with and without feedbacks, that depend on temperature.

Recent revisions to the boundary conditions (ice-sheet topography and sea surface temperatures) have added uncertainty to many of the GCM calculations of the past two decades. Moreover, all of these calculations use prescriptions for at least one central component of the climate system, generally oceanic heat transport and/or sea surface temperatures. This limits the predictive benefit of the models. Nonetheless, these models are the only appropriate way to integrate physical models of diverse aspects of the Earth systems into a unified climate prediction tool. 

---