Our Nature: The Earth as Home

Climate change debates: a new way of looking at the issue

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Contents

INTRODUCTION
ONE: GEOCENTRIC HOME
TWO: HELIOCENTRIC HOME
THREE: COSMIC / GEOLOGICAL HOME
FOUR: EVOLUTIONARY HOME
FIVE: CHEMICAL HOME
SIX: RADIOACTIVE & QUANTUM HOME
SEVEN: A MODELLED HOME
EIGHT: THE EARTH WE NOW INHABIT
NINE: HOTHOUSE EARTH
TEN: A DAMAGED EARTH
GUIDE TO FURTHER STUDY

Preface

Eons of past time and ceaseless change, embedded in earth’s geology and in the evolutionary biology of species, are the twin factors which provide the best guide to the major risks facing humanity in the present day. The current state of the planetary surface on which we all reside, as well as the many steps in the emergence of homo sapiensfrom its ancestral origins in the hominin tribe, are the results of specific stages during prior times and of new developments.  The history of our planet is a 4.5–billion–year record of violent upheaval, driven by forces deep below its surface, such as volcanic eruptions and marked most dramatically by the push and pull of gigantic continental masses against each other. Its atmosphere too, as well as climatic conditions, have likewise been repeatedly altered, a function of the interaction between the earth’s crust and external factors such as solar radiation, strikes of massive asteroids, the planet’s orbit, the tilt of its axis, and others. Geologists have named the stages in this record: The current one is known as the Quaternary, which has featured the growth and decay of continental ice sheets in 100,000-year cycles. The most recent episode, beginning roughly about 12,000 years ago, is called the Holocene.

            The human counterpart to the first phase of the Quaternary, known as the Pleistocene, was the migration of our hominin ancestors (such as homo erectus) out of their African homeland, which is thought to have begun as much as 1.8 million years ago. We ourselves have been baptized with the term “anatomically modern humans”; we originated in Africa between 300,000 and 250,000 years ago and began to disperse about 70,000 years ago. Because these later treks occurred in the most recent cold glacial cycle, climatic conditions were not conducive to rapid human population growth – until the arrival of the Holocene, the warm interglacial, when temperatures were about 6°C (11°F) warmer than they had been just 7,000 years earlier. And then, in the geologically-brief period of less than 10,000 years, the population of modern humans literally exploded, by which time wandering hunter–gatherers had become settled farmers and herders, and the first civilizations had been born.

            The recent evolutionary success of homo sapiens, therefore, resulted wholly from the fortuitous confluence between the modern geological history of the planet’s land surface, on the one hand, and the formation of a relatively new hominin species, equipped with a large brain and upright gait, prepared to exploit its new environmental opportunities, on the other.

            And exploit them we did: Around 3000 BCE there were an estimated 45 million of us worldwide, and the number reached 1 billion for the first time around 1800 CE. But at that point most people were still living on primitive agricultural holdings, beset by backbreaking manual labor, impoverishment, and the endemic threat of famine and infectious disease.  Then the Industrial Revolution marked another decisive turn, at least as dramatic as the one from hunter–gatherers to farmer–herders more than ten millennia earlier. Arguably, humans were thereby propelled into a new epoch, called the Anthropocene, where we have become so dominant on the planet that we are now influencing the future stages of global climate. And if this is the case, we humans collectively have become responsibile, for the first time in the evolution of our species, for the next stages in our climate history. 

            The scientific argument that human-caused factors are forcing the global climate along a new pathway – one that could bring great harms to human settlements around the turn of the next century – is contested by some who attack the theory and the evidence marshalled in order to support it. But that argument is also resisted by many others who point to the lack of full certainty in the scientists’ predictions, or who refuse to accept the idea that humans could exert much influence on the climate, or who profess to believe that climate scientists are perpetrating a hoax on the public, or who aver that God will decide the outcome. Since 100% certainty is impossible to achieve in predictions of this kind, we are left with a throw of the dice: Does one accept the contentions of climate scientists or not? If it is expected to be costly to say yes, as it probably will be, then why not just wait and see what happens?

            In the pages that follow I have tried to frame the debate over the credibility of climate science in a new way, by putting the issue in the double-perspective of the earth’s geological history and the evolution of species, culminating in the fortunate nexus of the Holocene and modern humanity. 

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