Breathing Space: The Natural and Unnatural History of Air

Breathing Space: The Natural and Unnatural History of Air

by Mark Everard


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Product Details

ISBN-13: 9781783603848
Publisher: Zed Books
Publication date: 04/15/2015
Pages: 200
Product dimensions: 5.40(w) x 8.50(h) x 0.70(d)

About the Author

Mark Everard is a visiting research fellow at the University of the West of England, Bristol.

Read an Excerpt

Breathing space

The natural and unnatural history of air

By Mark Everard

Zed Books Ltd

Copyright © 2015 Mark Everard
All rights reserved.
ISBN: 978-1-78360-387-9


Air and the making of the atmosphere

The distinctions between the terms 'air' and 'atmosphere' are hardly airtight, even in scientific terms. Most definitions of 'air' relate to the gaseous content of the outer layer of the Earth. However, the term 'atmosphere' came into being in the seventeenth century as a compound of the Greek words atmos (vapour) and sphaira (sphere). So 'atmosphere' too relates to layers of gases that may surround a material body of sufficient mass, held in place by its gravity, though extending out in the case of planet Earth to include increasingly less dense and more energetic outer layers. For other planets that comprise mainly various gases, it is only the outer layer that constitutes their atmosphere. This book uses the term 'air' to refer to the physical 'stuff' we breathe and 'atmosphere' as the wider gaseous and energetic layers surrounding our home planet, although these definitions are necessarily porous.

The atmosphere is, by orders of magnitude, the largest habitat on our home planet. However, due to its fluidity, invisibility and lack of clear national ownership, it is also the most readily overlooked. The atmospheric system is not merely massive but also diffuse, comprising an immensely complex system of constantly flowing energy, matter and living things. Its frequent omission from our thoughts, and the fragmented way in which we have addressed isolated acute problems while disregarding impacts elsewhere in the air system, pose looming threats that we need urgently to address for our continued wellbeing. But first we need to understand it, and to develop a necessary degree of respect for the generally invisible yet endlessly protective and supportive bubble that we depend upon for our very life and livelihoods every single day.

What is air?

Answers to this deceptively simple question are complex and elusive. Dictionary definitions such as that of the Oxford English Dictionary – 'The invisible gaseous substance surrounding the earth, a mixture mainly of oxygen and nitrogen' – tell us a little more about the nature of air itself. In fact, at ground level, the approximate composition of air today is 78% nitrogen and 21% oxygen, the remaining 1% or so comprising a range of other gaseous substances. However, the properties of air change with altitude above sea level. With increasing altitude, air pressure reduces as the concentration of air molecules decreases, leading to what is called 'thin air', a major contributor to why many people suffer altitude sickness. In the upper atmosphere, where the air is thinnest of all, high in the stratosphere known as the 'ozone layer', there is a higher density of ozone molecules than anywhere else; these serve to block some of the sun's most energetic rays, deflecting potentially damaging radiation back out into space. Air does all of these things, and more, with us being barely aware of its existence.

In the beginning God created the heaven and the earth. And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters.

These familiar words from the first chapter of the Authorised King James Version of the Bible, Genesis 1, articulate one view of the origins of our home planet and life upon it. Although only Creationists now tend to view this as in any way a literal representation of the origins of the Earth and its diverse life forms, the text is interesting in that it commits the same flaw as many subsequent scientific and popular texts: it omits to mention the air. However, as the Latin word spiritus means 'breath' or 'air', perhaps the intended meaning has been lost in translation into the dominant world view of 1611.

Even within the many pages of the United Nation's Millennium Ecosystem Assessment, an authoritative study involving over 1,300 scientists in 95 countries in an assessment of the status and trends of all major global ecosystem types, air receives a relatively light touch. Chapter 13, dealing with 'Air quality and climate', comprises 36 pages within the overall massive 'Current state & trends assessment' report of the Millennium Ecosystem Assessment. A range of atmospheric 'services' are explicitly recognised in the chapter: these include warming; cooling; water recycling and regional rainfall patterns; atmospheric cleansing; pollution sources; and nutrient redistribution. The significant impact of both natural and managed ecosystems on climate and air quality is also recognised. But, in some ways, the air itself is largely a 'ghost at the feast', featuring by inference yet in reality always a fundamental medium linking all of the other 'major habitat types' assessed in the report. However, the wider benefits of the air to humanity are diverse and vital.

The only national-scale ecosystem assessment published at the time of writing, the UK's National Ecosystem Assessment, ploughs a similar track by focusing on key habitats – 'mountains, moorlands and heath', 'semi-natural grassland', 'enclosed farmland', 'woodland', 'freshwaters', 'urban', 'coastal margins' and 'marine' – with no explicit consideration of air.

Unseen oceans of gas

Omission of the airspace as a major habitat type is surprising as it is not only important, it is also staggeringly big. Indeed, calculated up to an altitude of 100 kilometres – and including the atmosphere, the stratosphere, the troposphere and the mesosphere – the volume of air surrounding the planet is about 51 thousand trillion (51 trilliard) cubic kilometres, or 51,000 trillion trillion litres. This is about 38,000 times the volume of all of the world's oceans, which total about 1,347,000,000 cubic kilometres. The volume of the planet's air is so great that it eludes meaningful comparison in intuitive terms such as numbers of bathtubs, swimming pools or shopping malls.

Each of us draws in substantially in excess of 20,000 breaths per day, and we live our lives perpetually immersed in the bubble that surrounds the Earth. Yet, for something so immense and familiar to us, air remains incredibly easy to overlook.

That it is colourless, and also generally odourless and tasteless, blinds at least three of our five primary senses to it. We acclimatise to an ambient pressure of around 100 kilopascals (kPa) at sea level, equivalent to a pressure of nearly 14 pounds per square inch (psi). However, amazingly, we are unaware of this vast pressure except when we climb steeply, as our ears 'pop' or we experience altitude sickness, or when we immerse ourselves in the denser medium of water. And, although rapid air movement can be hugely destructive and fast movement through it can give rise to significant frictional drag, we can walk through still air without the slightest sense of its viscosity.

Of the five major senses, that leaves only hearing and the longer wavelength vibrations that we might sense as touch, both transmitted as physical waves. The rush of air is audible as it interacts with hard surfaces such as trees, buildings and ear lobes, and it is the physical structure of air that we depend upon to convey the pressure waves that we know as 'sound'. However, still air is not exactly the most raucous thing we ever experience.

To use a visual metaphor, the invisibility of air means that it is all too easily and frequently taken for granted, both in our daily experiences as biophysical entities and through our diverse industries and other activities.

Air, then, is a vital constituent of our home planet, or at least of the habitable part on the surface where all life lives, and is absolutely essential for virtually all life on Earth from plants to animals to microbes. And, of course, it is essential for us human beings who wade through it, generally unconsciously, every day.

How did all this air get here?

To vastly understate the reality, there is a lot of air about. So how did all this air get here?

The matter from which the solar system formed comprised mainly hot gases and dust circling a central core that condensed to create the sun. Most of the known planets of the solar system condensed from these same gaseous constituents; the best estimates suggest that our home planet Earth formed around 4.54 billion years ago. And that same matter, or at least virtually all of it, is still with us today.

Over geological timescales, heavier fractions began to settle out of this homogeneous amalgam through sedimentation, precipitation and other processes, progressively condensing into an increasingly solid internal structure as the Earth cooled. Due to gravitational forces, the most diffuse gaseous constituents formed an outer layer of the proto-Earth. They still do so today. The substantial size and density of planet Earth and its proportionally stronger gravitational pull, together with our location in the solar system, prevent the gases from becoming too warm and hence too energetic, and therefore enable our home planet to retain a durable atmosphere.

Clearing the air

Exposed as we are to the realities of accumulating waste and pollution stemming from the profligacy and lack of forethought that have shaped so many lifestyles and supporting technologies in the developed world, a common tendency is to think of the natural world as a pure canvas soiled by steadily rising contaminants. Taking a snapshot of the last two-and-a-bit centuries of history, this is undoubtedly true. However, a wholly different picture emerges if we take due account of the longer span of time over which the atmosphere formed.

As we have observed, the proto-planet constituted a largely homogeneous cloud of space dust, which progressively condensed into a solid core and outer layers of lower density. The gaseous composition of the primordial planetary atmosphere is thought to have been 98% carbon dioxide, 1.9% nitrogen and 0.1% argon. The cooling Earth became geologically active, with volcanoes spewing out vast quantities of lava, ash and gases, which then, as now, comprised mainly water vapour, carbon dioxide and compounds of sulphur, nitrogen and chlorine, with some molecules of methane and ammonia. This rich soup of atmospheric gases was conspicuously lacking in free oxygen, which, as we will see later, was a product of evolving life forms. The early atmosphere was therefore rich in what we refer to today as 'greenhouse gases' (the 'greenhouse effect' is described in greater detail later in this chapter), and was also 20 or 30 times as dense as it is today. Cumulatively, this resulted in heating the Earth's surface to temperatures as high as 85° to 110°C. Only as the atmosphere gradually cooled was water able to condense into clouds and then into liquid form as rains fell on bare rock, commencing the water cycle that in time would produce a covering of soil through the actions of both weathering and emerging life. Carbon dioxide would have been entrained by rain drops and also absorbed into early oceans, reducing the degree of warming through the 'greenhouse effect' and kicking off the exchanges of chemicals and energy that are the mainstay of biospheric cycles.

Today, we can broadly divide the solid Earth sphere into four layers. At the centre is a solid inner core, the hottest part of the planet comprising mainly iron and nickel at temperatures of up to 5,500°C. Surrounding this is the outer core, a liquid layer again largely made up of iron and nickel, and at temperatures similar to those of the inner core. The mantle lies around this; at approximately 2,900 kilometres thick, this is the widest section of the Earth. The mantle is formed of semi-molten rock called magma. While the rock forming the upper mantle is hard, the rock of the lower mantle is soft, much of it at the point of melting. The Earth's thin surface layer, between 0 and 60 kilometres of solid rock, is known as the crust. The terrestrial section of the Earth's crust is known as the continental crust, whereas regions covered by water are referred to as the oceanic crust. The oceans, though vast to our eyes, provide only a thin moist surface when compared with the sheer scale of the solid Earth, and they are dwarfed by the atmosphere above. The whole crust is made up of a network of tectonic plates that are in constant motion, and it is at the boundaries between these plates that most earthquake and volcanic activities ocur. All environmental media – earth, water and air – interconnect and play key roles in the great geochemical and energy cycles forming the 'biosphere': the domain in which life occurs and which life shapes.

It is within the solid matter of the planet that many substances we would now consider pollutants are locked away from the air and the cycles of matter and living processes above the Earth's crust. A great deal of this sequestration has occurred through sedimentation processes in which particles fall out of suspension in gas or air, sometimes flocculating first and then accumulating against a solid substratum. Over geological time, layers of sedimented particles consolidate into depositional landforms, progressively firming up into sedimentary rock. Mineralisation processes also lock various substances into solid forms that can become immobilised as rock. These mineralisation processes include the hydrothermal deposition of metals, many of them now economically important, into ores or 'lodes'. Hydrothermal circulation predominantly occurs close to heat sources in the crust of the Earth, including in proximity to volcanic activity; in such areas, granite intrudes in the deep crust due to orogenic processes, whereby land is uplifted at the intersections of tectonic plates. Hydrothermal deposits are also the result of metamorphic processes in which the properties of minerals change under the influence of heat, pressure and the introduction of chemically active fluids.

Together, these processes lock substances such as metals, phosphorus and other micronutrients into solid, buried strata of rock, effectively immobilising them and partitioning them off from free circulation in the biosphere. The net result is that, as the Earth has evolved, the biosphere has become progressively 'cleaner'. As concentrations of toxic and other biologically and climate-active substances have gradually declined, the biosphere has become increasingly more suitable for the emergence and evolution of complex life forms.

The structure of the atmosphere

The atmosphere's complex layers of magnetic and electric fields are subject to various scientific definitions and conventions. In most classifications, the different layers of the atmosphere are divided by major changes in temperature.

The inner layer of the atmosphere, from sea level to a mean approximate altitude of 12 kilometres (39,000 feet), varying with latitude, is known as the troposphere. This is the densest layer of the atmosphere, the weight of upper layers pushing down to create air pressure. Consequently, the troposphere contains 75% of all the gases in the atmosphere. The troposphere is also the layer that is habitable, taking into account the fact that there are no hard surfaces to live on at higher altitudes. It is also where weather patterns form, and hence the medium through which most natural water and other chemical and energy cycles occur. Nevertheless, there is considerable heterogeneity within the troposphere as, with increasing altitude, there is not only decreasing air pressure but also a decline in temperature of approximately 6.5°C for every kilometre elevation.

In addition to its gaseous composition, the Earth's atmosphere also contains a diversity of aerosols. Aerosols comprise colloids (fine particles normally invisible to the naked eye and suspended in another fluid medium) that include both solid and liquid droplets. These aerosols are of various types and concentrations, including both inorganic matter (such as fine dust, sea salt and water droplets) as well as organic materials (smoke, pollen, spores, viruses and bacteria, for example). Fine airborne particles that are either living organisms or are released by them are more commonly known as bioaerosols, shorthand for 'biological aerosols'. All aerosol particles are very small, ranging from less than 1 micrometre to 100 micrometres (a micrometre is one millionth of a metre), and so they remain suspended in the air for a long time, possibly indefinitely, reacting to air currents and potentially moving quickly and over long distances. Natural aerosols contribute to phenomena such as clouds and haze. The atmospheric load of aerosols therefore plays a significant role in water circulation, weather systems, the reflection of incident solar radiation due to the albedo (reflective quality) of clouds, the circulation of matter, and the distribution of and interactions between living organisms, climate and human health.


Excerpted from Breathing space by Mark Everard. Copyright © 2015 Mark Everard. Excerpted by permission of Zed Books Ltd.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Table of Contents

1. Air and the making of the atmosphere
2. Living in a bubble
3. What does air do for us?
4. Abuses of the air
5. Managing our impacts on air
6. Thinking in a connected way
7. Rediscovering our place in the breathing space
8. Resolution for integrated management of the air space
Annex : Ecosystem services and the Ecosystem Approach

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