Global Issues

Sections 6.4 to 6.6 discussed the increases in concentration of atmospheric greenhouse gases and aerosols due to anthropogenic pollution since the Industrial Revolution, and the accompanying global changes in radiative forcing. There is now considerable model-based evidence that indicates a causal relationship between the net positive global-mean radiative forcing and […]

During the early Palaeozoic, about 530Ma, the Northern Hemisphere was entirely oceanic north of about 30N palaeolatitude. Most of today’s Southern Hemisphere continents (India, Antarctica, Australia, Africa, South America) had formed into a super-continent known as Gondwanaland. Sea levels were at or near an all time high, perhaps reflecting increased […]

If the climate system responds to enhanced greenhouse forcing in a manner that has been projected by climate models, the Earth is likely to experience a number of detrimental impacts. Obviously, much depends upon the magnitude of the climate sensitivity, a variable as yet poorly constrained by the present understanding […]

Cloud feedback is the term used to encompass effects of changes in cloud and their associated radiative properties on a change of climate, and has been identified as a major source of uncertainty in climate models (Cubasch & Cess, 1990). This feedback mechanism incorporates both changes in cloud distribution (both […]

The Cenozoic Era is divided into the Tertiary (65 to 2Ma) and Quaternary (2Ma to present) periods. The climate of the Quaternary is reviewed in section 5.3. In this section, the climatic deterioration and global cooling of the Tertiary Period is investigated. The ensuing discussion will serve as a useful […]

Relatively small climatic variations can create large problems for water resources, especially in arid and semi-arid regions. However, the climatic impacts on hydrology at the regional scale are uncertain, and will be influenced by a complex mix of temperature, precipitation, evaporation, soil moisture availability and run off changes. For many […]

All models must simplify what is a very complex climate system. This is in part due to the limited understanding that exists of the climate system, and partly the result of computational restraints. Simplification may be achieved in terms of spatial dimensionality, space and time resolution, or through parameterisation of […]

Let us consider first the atmospheric gases. Table 1.1 illustrates the average gaseous composition of dry air below 25km. Although traces of atmospheric gases have been detected well out into space, 99% of the mass of the atmosphere lies below about 25 to 30km altitude, whilst 50% is concentrated in […]

Periglacial features are morphological features which are associated with continuous (permafrost) or discontinuous (diurnal or seasonal freezing) periods of sub-zero temperatures. Such features on which palaeoclimatic inferences can be based include: fossil ice wedges; pingos; sorted polygons; stone stripes; and periglacial involutions. Detailed descriptions of these features may be found […]