Living in Deep Time

The Anthropocene epoch offers a way to understand the present environmental crisis in the context of deep time, the realms of the distant geological past. And as a strange recent tendency in environmental news reporting shows, current generations are being plunged into deep time, like it or not, by the once-in-a-million-year environmental changes that are taking place around them. Climate change deniers share with some well-intentioned environmentalists a damaging and unrealistic view of the planet's deep past as an essentially static state of affairs. But since the end of the eighteenth century the sciences of the earth have developed a very different way of looking at the distant past, a perspective that has grown ever more clearly defined thanks to some major developments in geological thought during the last few decades. In this alternative view, geological time is historical through and through. Tracing its story reveals a dynamic narrative of floods, climate changes, and unpredictable evolutionary development. The birth of the Anthropocene epoch is best seen as the latest turning point within the swirling history of deep time. But if the story of the earth has always been so lively, one might wonder whether present-day change is in fact all that noticeable in the grand scheme of things. What, then, is the real scale of human-induced changes to the earth's systems as a whole?

THE LONG MOUNTAIN

Early in May 2013, at an observatory on the black volcanic slopes of Mauna Loa, Hawaii, the daily average concentration of carbon dioxide measured in the atmosphere rose above 400 parts in every million. The level declined by some 7 parts per million over the next few months as CO2 was drawn from the sky by summer vegetation across the Northern Hemisphere, before it began to rise again in the autumn. The following year, the 400 ppm threshold was crossed in March. A year later, it was crossed in January.

The air of Mauna Loa, the "long mountain" that ascends from the middle of the Pacific, has long been closely monitored. The mountain's remoteness, and the lunar barrenness of its upper slopes, mean that its bright clean air can serve to indicate the state of the whole planet's atmosphere. And because the chemical composition of the atmosphere has been an intensely political issue ever since the beginning of public concern about greenhouse gases in the late 1980s, the first crossing of the 400 ppm limit at the Mauna Loa station was widely reported. The rapidly increasing carbon dioxide level was understood to be the consequence of human activity, and to be cause for concern about the changing state of the climate. The newspapers that reported the story also felt the need to supply some historical context. As recently as the middle of the eighteenth century, journalists explained, CO2 concentrations stood at around 280 ppm. Thus, given that no other factors can plausibly explain the increase, three-tenths of the current CO2 level is attributable to the development of industrial society since the late eighteenth century.

In the complex field of climate science, what story could be clearer than this? After all, explanations of the contemporary world that look back as far as the late eighteenth century are perfectly familiar. That is most obviously and especially the case in the United States, where two documents written shortly before 1800, the original Constitution of the United States and the Bill of Rights, still frame a remarkable proportion of everyday political discussion. It is also true more widely, however. The last decades of the eighteenth century were a formative period for European colonial expansion, so the influence of that era can still be seen in the basic shape of the modern world, its unequal distribution of wealth and poverty. Moreover, the period of the Industrial Revolution also witnessed the French Revolution, the founding event of the modern liberal state. Asked about its impact in the 1970s, the Chinese statesman Zhou Enlai is often – although perhaps mistakenly – said to have replied, "It is too soon to tell." Authentic or not, Zhou's aphorism is admired as a telling expression of a plausible idea: that the impacts of the French Revolution are still playing out, and that contemporary politics still takes place partly in the shadow of 1789. But what if Zhou had said the same thing about (for instance) the formation of the Isthmus of Panama – the clasping of hands between North and South America, which divided the Pacific from the Atlantic three million years ago? What sort of political event, if any, might realistically be placed in a framework that stretches back not hundreds of years, but millions?

That question arises because the newspapers that reported on the phenomenon at Mauna Loa did not look back only as far as the eighteenth century. The journalists writing up the story evidently felt that their readers would be poorly informed if they were confined to such a short-term perspective. What was so special, after all, about the carbon dioxide levels of the mid-eighteenth century, just before the rise of industrialism? To explain that, the New York Times broadened its purview spectacularly. "For the entire period of human civilization, roughly 8,000 years, the carbon dioxide level was relatively stable near [280 ppm]." No doubt many of the Times' readers in May 2013 felt that, as conscientious modern citizens, they should be able to appreciate the significance of the climate change story on the front page of their daily newspaper. But it seemed as if in order to manage that, they would need to take on board not a mere couple of centuries of historical background but eight thousand years. Or rather, even doing that would get them no more than a hundredth of the way to understanding the story.

As the Times coolly told them: "From studying air bubbles trapped in Antarctic ice, scientists know that going back 800,000 years, the carbon dioxide level oscillated in a tight band, from about 180 parts per million in the depths of ice ages to about 280 during the warm periods between." Ice ages, in the plural! The mountaintop sages of Mauna Loa began to sound like those Hindu scholars who reflect on the hundreds of thousands of solar years that make up a yuga, each one a part of the maha-yuga cycles that form one seventy-first part of a twenty-ninth of a day in the life of Brahma. But the Times' reporter went further still. He finally set the morning's news from the Pacific in its proper context when he observed that "the last time the carbon dioxide level was this high was at least three million years ago, during an epoch called the Pliocene."

The New York Times was not alone. In Britain, the Guardian wrote up the story with an explanation that the new CO2 level had "not been seen on Earth for 3-5 million years, [since] a period called the Pliocene." Brazil's O Globo noted that carbon dioxide had not reached the "marca simbolo" of 400 ppm for "3,2 milhões de anos." In France, Le Nouvel...