by IAN ANGUS
Some 2.8 million years ago, the level of carbon dioxide in Earth’s atmosphere dropped, triggering an Ice Age. Since then, long-term changes in Earth’s orbit and tilt, called Milankovitch cycles, have produced global temperature swings every 100,000 years or so. In the glacial (cold) phases, kilometers-thick ice sheets covered most of the planet; in shorter interglacial (warm) periods, the ice retreated toward the poles. For the past 11,700 years, we have lived in an interglacial period that geologists call the Holocene Epoch.
Under normal circumstances, the glaciers and polar ice caps would now be slowly growing. As recent research shows, “if not for the effects of increasing CO2, glacial inception would reach a maximum rate within the next 11,000 years.”1 Instead of global heating, the Earth’s future would be global freezing, but only in the distant future.
However, as anyone even slightly aware of environmental issues knows, the world’s glaciers and ice caps are not expanding; they are shrinking — fast. Between 1994 and 2017, Earth lost 28 trillion tons of ice, and the rate of decline has increased by 57 percent since the 1990s.2 Even if greenhouse gas emissions are rapidly reduced, conditions preventing the return of continental ice sheets will likely persist for at least 50,000 years. If emissions do not stop, the ice will not be back for at least half a million years.3
In short, as a direct result of greenhouse gas emissions caused by human activity, the Ice Age has been canceled.
This is concrete proof of one of the most radical conclusions of twenty-first century science: “The earth has now left its natural geological epoch, the present interglacial state called the Holocene. Human activities have become so pervasive and profound that they rival the great forces of nature and are pushing the earth into planetary terra incognita.”4
The scientists who first reached that conclusion named the new epoch the Anthropocene. An overwhelming volume of evidence shows that a new stage in Earth system history has begun, one characterized by major changes to many aspects of the natural world, heading toward conditions that humans may not survive. They have shown that many of the largest changes are irreversible on any human timescale. They have dated the beginning of this radical transformation to the mid-twentieth century. They have also shown that physical records of the change can be seen in geological strata.
To any reasonable observer, the case is irrefutable. Yet, some prominent scientists deny that a qualitative change has taken place, and one of the world’s largest scientific organizations has voted against formal recognition of the new epoch. The research and debates that led to this perverse result help to illuminate the challenges facing scientists and ecosocialists in our time.
Earth System Science
During the 1970s and ’80s, increasing numbers of scientists came to the conclusion that traditional scientific methods focusing on local or regional issues were insufficient for understanding environmental problems — that Earth as a whole had entered a period of extreme crisis caused by human activity.
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