Weather, Climate and Climate Change

Human Perspectives

Greg O'Hare, John Sweeney, Rob Wilby

• Publisher: Routledge
• Year: 2014
• ISBN:
  9781317904816
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Geography
• Index: Geography

A timely and accessible analysis of one of the most crucial and contentious issues facing the world today – the processes and consequences of natural and human induced changes in the structure and function of the climate system.

Integrating the latest scientific developments throughout, the text centres on climate change control, addressinghow weather and climate impact on environment and society.

Chapter 1
Introduction to systems and the climate system

1.1 Early development of climatology

1.1.1 From classical times to the Age of Discovery

As they sailed up the River Nile, the ancient Greeks noticed that it became warmer. Being logical in their search for explanation, they assumed that the earth must slope upwards towards the sun. The word ‘climate’ traces its roots from this now discredited deduction, being derived from a Greek word meaning ‘slope’. But despite writings on climate by authors such as Aristotle and Hippocrates as early as the fourth century bc, progress in the study of the atmosphere was slow for almost the next two millennia. It was only with the Renaissance, when a renewed interest in exploration and overseas trade occurred, that the need to understand spatial variations in climate became obvious once again. In an Age of Discovery based on sailing ships, understanding the vagaries of the winds became vital. Later on, rainfall reliability, and thus water supply, became relevant matters for public health in urban areas. Amassing of large data collections began, aided by improvements in instrumentation. But, data collection alone does not help understanding, and organising and classifying of all kinds of weather data was the obvious next stage. Classification is never the most glamorous part of an emerging discipline and so climatology tended to become the ‘ugly sister’ of meteorology, its bookkeeping arm, until well into the twentieth century.

1.1.2 Determinism and possibilism

Making causative linkages between simplistic classifications of any phenomena can be dangerous, no less so with climate. It is tempting to infer that benign climates with few limitations in heat or moisture will be associated in general with productive agricultural or natural vegetation systems, and ultimately with the creation of an agricultural surplus which in the past provided the security for expansionism and economic development of all kinds. There may be considerable justification for this, especially in societies dependent on the annual harvest for their survival. It is entirely different, and misplaced, however, to extend this logic unquestioningly to issues related to cultural and economic development. Yet this was done widely in the early decades of the twentieth century. Such a philosophy, known as environmental determinism, implied control of human affairs by an external influence, namely the physical environment. Taken to its extreme, it consigned cultural and economic development to spatial and temporal variations in the physical environment. Progress, it was argued by determinists, was based on climate, heredity and culture. Mid-latitude climates, with their seasonal contrasts implying a constant need to plan ahead, were implicitly deemed superior as influences promoting well-being and intellectual development by comparison with their equatorial counterparts. In the aftermath of the Second World War this smacked of ethnic prejudice and was rightly considered totally unacceptable. Environmental determinism was discredited.

The pendulum swung towards possibilism – a denial of the importance of the physical environment. The featureless plains which characterised key economic and geographic models by Von Thunen, Weber and Chrystaller, pointedly played down the importance of the physical environment to the point of virtually ignoring its existence. Climatology, heavily tarred by the deterministic brush, languished. The proportion of articles dealing with weather and climate in key scientific journals fell from about 35 per cent in the second decade of the twentieth century to 4 per cent in the mid 1960s. However, just like determinism, advocates of possibilism also pushed their logic too far.

Awareness that all human endeavours must be accommodated within a physical setting, and within climatic constraints, dawned slowly. A paradigm that believed that technological advances could ‘fix’ the physical environment when required was dominant for long periods and remains deeply embedded in the psyche of some ideologies. Gradually, a more balanced perspective on the role of the physical environment has emerged. Concepts of stewardship, rather than domination, of the environment were learned the hard way. Some spectacular failures in agricultural expansion into marginal areas were instrumental in this. But gradually the relevance of a climatic perspective has become clear in a number of crucial areas. The ‘Green Revolution’, the management of urban air quality, the emergence of the ozone hole, the growing toll of climate-related natural disasters, irrigation schemes, deforestation, soil erosion – all had important unanticipated climatic dimensions to them. But perhaps the clinching issue, which has led to climatology emerging as a vital discipline for humankind, has been the realisation that climate is itself changing over short and long timescales. Far from being prisoners of our climates as determinists suggested, climate is increasingly seen as a prisoner of human actions. The role of human action in contributing to most of the temperature change observed in the last 50 years (Figure 1.1) has now been widely accepted. At the annual meeting of the World Economic Forum, a global partnership of business, political, intellectual and other leaders held in Davos, Switzerland in January 2000, it was declared that climate change is the greatest global challenge facing humankind in the twenty-first century.

Figure 1.1 Global mean annual temperature trends from 1860 to 2002. The year 2002 was the second highest annual temperature recorded for the period with 1998 the highest.

Source: Hadley Centre

Key ideas

• 1. A reactionary backlash to the philosophy of environmental determinism stifled the growth of modern climatology until recent decades.
• 2. Awareness of the central importance of atmospheric and climatic considerations in key areas of human endeavour has now grown enormously. This has particularly been demonstrated by the need to address pressing problems of climate change.

1.2 A systems approach

1.2.1 The nature of systems

Complex phenomena can often be better understood using a powerful conceptual tool known as systems theory. As one of the most complex natural phenomena known, the atmosphere has for long been subjected to a systems-based analysis, and conceptualising climate itself as a system provides a means both of understanding its functioning and predicting its potential changes.

A system is an ordered group of interrelated components, linked by flows of energy and material. A clear demarcation between what is inside and outside the system must also exist. Though this sounds complicated, we are only too familiar with everyday examples of the concept, such as a plumbing system or an electrical system, or a central heating system. In each case an organisational entity can be identified with component parts, or even subsystems integrated into the larger entity. Energy and material are moved around between the components and a power source drives the operation.

Systems seldom exist in a totally self-contained manner. Truly isolated systems, with no interchange of energy or materials with their surroundings, do not occur in the natural world. Even closed systems, with energy transfers, but not materials transfer, with their surroundings are scarce. The earth–atmosphere system can be thought of as a closed system, with energy in the form of sunlight (solar radiation) entering and heat (terrestrial and atmospheric thermal radiation) leaving, and negligible interchange of matter between the earth and space involved. Most natural systems are, however, open systems with both energy and matter transferred across the system boundary. The climate system is an excellent example of such an open system (Figure 1.2). Understanding the pathways and the dynamic response of the climate system to forcing pressures, is central to managing it. Such understanding is as yet elusive, though great advances have been made in recent years.

1.2.2 System regulation

Figure 1.2 The climate system.

Source: Hadley Centre

When the average condition of a system is relatively constant over time, an equilibrium exists which reflects the system’s ability to cope with forces either external or internal seeking to disturb it. This ability to self-regulate is a characteristic of systems and is frequently controlled by internal readjustments known as feedback mechanisms. Two kinds of feedback mechanisms can be identified. Negative feedback operates to minimise the effect of any disturbance and seeks to return the system to the pre-existing status quo. This ‘damping’ effect characterises systems or parts of systems resilient to change. For example, it might be hypothesised that global warming would lead to more evaporation and cloud cover. The latter would reflect more incoming solar energy, promoting a tendency for cooling, i.e. negating temperature rises somewhat. Positive feedback, on the other hand, amplifies the effect of a disturbance and may have the effect of destabilising a system. Again it might be hypothesised that global warming might lead to more water vapour in the air. Since water vapour is a greenhouse gas this might be expected to encourage more trapping of outgoing terrestrial radiation, exacerbating the temperature rise. Further examples of both of these types of feedback are discussed in Chapter 6, while the difficulties they pose for climate modelling are discussed in Chapter 7.

Systems-based approaches offer windows on how the atmosphere functions, and how climate might respond to forcing either by natural or human agencies. The conceptual model must never be mistaken for the real thing, however, and the complexity of the atmosphere will ensure that incorporating its processes fully into system models is destined to be an elusive objective for a long time. For the moment we can make informed guesses in answer to the ‘what if’ questions using a systems approach incorporated into powerful computer models. But uncertainty remains, and just like the imperfect classifications of climate in former times, imperfect atmospheric models will always exist, calling for a cautious approach to managing the atmospheric/climatic system.

Key ideas

• 1. Systems are conceptual tools composed of elements with linkages between them, along which flows of energy and materials take place. An external power source provides the driving force for systems.
• 2. Systems are characterised by integration between their components such that a disturbance of any individual component has consequences throughout the system.
• 3. Systems have a capacity to regulate themselves such that they can adjust to a change imposed either externally or internally. This is accomplished by feedback mechanisms.

Further reading

Christopherson, R. (1995) Elemental Geosystems. Prentice-Hall, New Jersey, 540 pp.

Lewthwaite, G. R. (1966) Environmentalism and determinism: a search for clarification, Annals Assoc. American Geographers, 56(4): 1–23.

Phillips, J. D. (1999) Earth Surface Systems: Complexity, Order and Scale. Blackwell, Oxford, 320 pp.

Chapter 2
Mass components of the climate system

2.1 Atmospheric composition

According to Greek mythology, Icarus escaped imprisonment using wings of feathers and wax made by his father to fly out of the island of Crete. Not taking heed of his father’s warnings though, he flew too close to the sun whereby his wings melted and he perished. The myth exemplifies how little was known in ancient times about the atmosphere above the ground – it is one of the most difficult, and dangerous, areas to explore or monitor without sophisticated technology – and it is only in relatively recent times that detailed information about the envelope of gases surrounding the surface...