Dirty Words

Writings on the History and Culture of Pollution

Hannah Bradby

• Publisher: Routledge
• Year: 2013
• ISBN:
  9781134058891
• Edition: 1
• Topic: Politics & International Relations
• Subtopic: Political Ideologies
• Index: Politics & International Relations

Did dinosaurs contribute to global warming? What is rubbish theory and what indeed is rubbish? And how did the whale become a cuddly toy? And why did we decide to saturate our land and food with pesticides?

Dirty Words examines all of these questions and also includes a study of pollution in fiction, from the fogs of Dickens to the smog of Chandler, advice on how to be an environmental troublemaker, and a suggestion of our choice of futures: the world as an icebox or a greenhouse.

This entertaining and provocative collection of pieces by a group of environmental experts challenges the reader to take a closer look at the current pollution debate.

Originally published in 1991

CHAPTER ONE

LIFE AND CLIMATE

SIMON F. WATTS

INTRODUCTION

Increasing public awareness of the importance of our environment and climate is well demonstrated by the aftermath of the recent gales which have hit much of the British Isles. Any scientist even remotely connected with climate or environmental research has been bombarded by (it seems) an endless number of journalists all asking the same question: “Are the gales linked to the greenhouse effect?”. We are a society obsessed, although maybe in this case the obsession is neither bad nor untimely.

The study of climate involves a knowledge of the workings of the atmospheric, oceanic and solid earth systems, and their interaction with each other and the biota (living things). The presence of life on Earth has radically changed both the planet and the course of events on it. We live on a wet, warm world that is teeming with life. This happy state of affairs can be contrasted to that on the other planets in the solar system. We are only lately learning how complex and vital a part life has played in our planetary history.

So before we examine the modern climate and what appear to be some of its important mechanisms, it is instructive to survey what has gone before, and the role of life in the system up to now.

CLIMATE AND THE ROLE OF LIFE

The age of the Earth is thought to be nearly five and a half billion (5,500,000,000) years (see Figure 1.1). We do not know very much about the violent time just after the Earth had accreted (formed). It is likely that large meteorites periodically hit the Earth. The surface was probably molten over large areas, there were volcanoes emitting both lava and gases. These gases formed the basis of the primordial atmosphere. After a time, things began to cool down, the crust solidified, and water vapour began to condense as rain. After about one and a half billion years (4 billion years before present), there is evidence that there were oceans. It is in this scenario that the first life appeared on Earth.

It seems that almost as soon as the crust had solidified and cooled to reasonable temperatures, the primordial landscape was colonized by life. That early life probably developed in micro-environments (puddles, ponds, etc.).

The atmosphere and oceans of this ancient Earth were very different from our present system. The Earth was very young, there was much more volcanism than now. The sea contained the same major components as now, along with reduced iron salts, ammonium and vast amounts of organic life molecules (for example, amino acids). The Sun was about 30 per cent less radiant than now, although due to the presence of greenhouse gases the Earth was a good deal warmer. The atmosphere contained mostly carbon dioxide, nitrogen, possibly some hydrogen and only tiny amounts of oxygen. As there was very little oxygen, the sunlight reaching the surface had far more ultra-violet (UV) light in it – it was much harsher than now. In the modern atmosphere, ozone, (a form of oxygen), acts as a filter for UV light.

The first recognizable fossils are prokaryotic bacteria, preserved in pre-Cambrian algal mats: they are thought to be about three and a half billion years old. The fossil record is very incomplete in this period (the Archean), and there is much we do not know. These first prokaryotes were scavengers, feeding on the nutrient-rich sea around them and producing methane and carbon dioxide. It is possible that this methane became a minor component of the primordial atmosphere. Among these scavenger prokaryotes are organisms that are very similar to the modern blue-green algae. These early blue-greens were responsible for the transformation of the early carbon dioxide-based atmosphere to the modern oxygen-based system we have today.

Figure 1.1: Time scale in millions of years since the formation of the Earth

The blue-green algae were the first organisms to practise photosynthesis (using the energy of the Sun, like plants). They fed on the surrounding carbon dioxide to produce the poisonous gas oxygen. Oxygen is very reactive and will add oxygen to or remove hydrogen from most compounds. If oxygen reacts with something, oxidation results, eventually giving ah oxidizing environment. Reaction with hydrogen results in reduction and ultimately a reducing environment. At that time the sea was very reducing. As the oxygen was formed, it reacted in the sea to oxidize and precipitate the iron salts, forming what we now see as the banded iron rocks. Eventually the ocean became oxidized (about one and a half billion years BP), and this vast production of oxygen surged into the atmosphere. Within a short period (about 15 million years) the atmosphere also became oxygenated.

Paleobiologists tell us that because the ancient blue-green algae are so very similar to their modern descendants (they may even be the same species), that they would require similar habitats – warm, shallow seas. So we know that over the first two billion years or so of life, there were warm shallow seas on the earth. Over the billion years or so between now and then, the continents have moved. However, by using the magnetic record in the rocks, we can determine their former positions. Therefore we can reconstruct and approximate the geography of the ancient Earth, or large parts of it.

With some educated guesswork, the type of fossil temperature data above, and analysis of radioactivity from unstable elements (isotope measurements), we can get some idea of the temperatures over parts of that ancient world. This information, and what we know about the way the oceans and atmosphere work, can be used to reconstruct the type of climates that the Earth has had. A generalized temperature record of the Earth appears in Figure 1.2. In the past, it has been much warmer than now, principally due to the initial high atmospheric greenhouse gas concentrations. As life colonized the early earth, the blue-green algae began to consume carbon dioxide. This stabilized and eventually decreased global temperature.

Our Sun is a main sequence star, which means that its output behaviour with time is amenable to prediction. Over the time between early life and the present day (about three and a half billion years), the Sun’s output has increased considerably. This increase, translated into global average temperatures, means that the Earth should now be about 20 degrees hotter than it was then, (see Figure 1.2). It is clear that not only is the earth much cooler now than one might expect, but also that its mean surface temperature has stayed relatively constant over the past three billion years in a context of changing external factors. So the presence of life has not only had the effect of cooling the planet, but also of keeping the temperature within a certain range.

Figure 1.2: Change of temperature and carbon dioxide concentration with time since the formation of the Earth

Of course, this is a very simplified view. The Earth-ocean-atmosphere system is very complex. It is highly likely that effects other than carbon dioxide/greenhouse gases were also involved; for example, cloud cover, decrease in optical density of the atmosphere, changing amounts and patterns of volcanism.

It is this seeming temperature regulation by life, apparently for its own benefit, which leaves one in some difficulty. An animate creature or person can effect an act – for example, I can put the kettle on. But here we are talking about an assemblage of different life forms with no overall identity or purpose. It is beyond doubt that the presence of life has cooled the Earth. After all, the initial cooling, which offset some of the Sun’s heating, was achieved by the blue-green algae consuming the carbon dioxide and methane atmosphere (both are greenhouse gases). Models of an abiotic (lifeless) Earth produce a Venus-like planet with none of the cooling or temperature homoeostasis that we know has occurred over the last three billion years. It is still not known why the system works as it seems to.

Conventionally, Earth is thought of as being composed of three components: the solid earth, the oceans, and the atmosphere. Life in the form of the various species has simply colonized the available space or niches in or amongst these three systems. If for some geological, meteorological or oceanographic reason, conditions change such that they are inimical to that life, then the biota would simply disappear. The very existence of life was seen to be at the mercy of “the elements”. Although not the original view of scientists, this is seen now as the “traditional” view.

Examination of this idea of the biota in an environment or matrix which it can adapt to, but do nothing to modify, is very interesting. A closer look at the three inorganic “elements” shows that in fact, all three have been extensively altered or modified by the biota.

The atmosphere was originally composed of mainly carbon dioxide, nitrogen and hydrogen. We have already noted that the biota were the force that transformed this atmosphere into its present oxygenated form. It is instructive to examine the atmospheres of the most Earth-like planets in our solar system. They are all close to their thermodynamic equilibrium: that is, composed of carbon dioxide and a little nitrogen. The Earth’s atmosphere, however is wildly out of equilibrium, with oxygen and methane co-existing, and almost no carbon dioxide. The Earth is the only planet in our solar system on which there is life. That life has dictated the composition of the atmosphere.

The surface of the solid earth has also been modified in a major way by the presence of life. For example, the cliffs of Dover were formed by algae (coccolithophorids) which utilize the carbon from atmospheric carbon dioxide and incorporate it as calcium carbonate into their shells (liths). When the organisms die, their liths fall to the bottom of the ocean. After sedimentation and further physical and chemical processes, they are transformed into chalk and limestone.

Finally, the ocean has also been extensively modified by organisms. Although the gross composition, i.e. the concentrations of major ions, is dictated by chemistry, the tracer metals and organic load are biota-controlled. It is these trace components and organics which are the working parts of the ocean. They mediate the photochemistry, affect the efficiency of the biota-mediated pumping and production of atmospheric gases.

The fact that the biota have directly affected, and in some cases dictated, the composition of these surroundings undermines the idea that life is at the mercy of the elements, but does not totally discredit it. After all, bacteria growing in a culture affect the composition of their culture medium, but this does not necessarily mean that they prosper because of it. The fact that life has so massively altered its global environment is important, and it forces us to reassess very carefully the “traditional” view of the Earth.

THE GAIA THEORY

With this and other evidence in mind, Professor James Lovelock went a stage further, and proposed what has come to be called “The Gaia Theory”. He viewed the Earth as one unified system, and treated it using systems theory. It is rather like the human body, composed of many parts, but operating as one unit. He is at pains to explain that this does not imply any teleology on the part of the biota, and shows how the control of climate is an emergent property of the global system. He gives an example of specialist doctors knowing all there is to know about the different organs and components of the human body. They have a conference about what the assembled body will look like and what its properties will be. Although they could be expected to predict many things about the assembled body, it is very difficult to see how they would be able to predict the critically important emergent properties, for example, that the body will maintain a constant temperature and pH value. In the human and global systems, temperature stasis is an emergent property of the system, something that is not apparent from the individual system components. In short, the whole is greater than the sum of the parts.

In terms of global climate, regulatory mechanisms as envisaged in the Gaia Theory (these include temperature homoeostasis), require the following:

— a biologically-controlled parameter (for example, carbon dioxide concentration) which affects some climatically sensitive parameter (for example, temperature).

— a feedback mechanism (for example, temperature or some other climate parameter) to affect the biological process.

This type of system is called a feedback loop, and a common example of it is an oven. One sets the gas control at a certain temperature. The flames light and heat up the oven. The temperature in the oven is monitored by a thermocouple. When the oven has reached the set temperature the thermocouple switches the gas off. As the oven cools down so the thermocouple switches on the gas again to heat up the oven, and so on. Hence the oven is maintained at a constant temperature. In this example, the thermocouple is the feedback mechanism (i.e. it is sensitive to temperature) and the gas flame is the parameter which affects the temperature.

GLOBAL CLIMATE CONTROL MECHANISMS

At the outset it should be remembered that the global system is very complex, and the most that can be done is to highlight a few of what are maybe the more important mechanisms. In reality, climate is probably affected by many processes working in concert and/or opposition rather than one mechanism exclusively.

The Greenhouse Effect

Conventional thought has identified atmospheric carbon di...