A New Geological Epoch?
For the first time in the 3.5-billion-year history of life on Earth, a single species, humans, has gained the capacity to effect major change in the entire biosphere.
The Case for the Anthropocene
Geologists have worked out a system of naming large segments of Earth’s time. They call short periods of thousands of years “epochs,” longer ones that last tens of millions of years “periods,” and really long ones lasting hundreds of millions of years “eras.” The longest measurements of time are called “eons.” Geologists refer to our current epoch as the Holocene, which started about 10,000 years ago, when the temperature stabilized at a new level of warmth after the last ice age. The word Holocene comes from Greek roots: holo meaning “whole” and cene meaning “new.” Hence, Holocene means “wholly new.”
In 2000 a Nobel Prize–winning Dutch chemist, Paul Crutzen (1933– ), suggested that we are in a new geologic epoch, which he proposed calling the Anthropocene. He believed that the state of human domination over the planet, which has drastically altered the Earth from its pre-industrial condition, warranted the name change. Anthropo is the Greek root for “human.”
Geologists have an authority, the International Commission on Stratigraphy (ICS), that is the official keeper of the geologic time scale, the scale for expressing the history of Earth. Stratigraphy is the study of the order of strata, which are the layers of sedimentary rock and soil — each with characteristics that distinguish them from other layers.
In 2008 some geologists proposed to the ICS that it designate the Anthropocene as a formal geologic unit of time. An informal poll taken in 2010 showed that about half the members of the ICS thought the case was strong enough to adopt this new epoch. No official vote has been taken, but an Anthropocene Working Group continues to study the issue, and many geologists have begun to use the term; indeed, in 2011 the Geological Society of America called its annual meeting “Archean to Anthropocene: The Past Is Key to the Future.”
Evidence of Change
What kind of evidence could demonstrate that humans have begun to dominate and alter the life systems of Earth? The most prominent answer is by now a familiar one: climate change.
Plants and animals are moving northward; glaciers are melting; storms and droughts are increasing in severity; and weather patterns are changing. Behind these weather patterns are changes in the Earth’s atmosphere that scientists can track over geologic time. A tiny part of Earth’s atmosphere is so-called greenhouse gases, which hold in heat reflected from Earth and do not let it escape into space. One of these greenhouse gases is carbon dioxide (CO2). During the glacial/interglacial cycles of the past million years the CO2 varied approximately 100 parts per million (ppm) — from 180 ppm to 280 ppm — due to processes not affected by humans. Since the Holocene and the beginning of human agriculture, the atmospheric concentration of CO2 has risen from 280 ppm to about 390 ppm, much faster than ever before. This has happened mostly due to humans burning fossil fuels in the last 250 years.
Leading scientists are now saying that we must reduce this concentration of CO2 to 350 ppm and that global emissions must be cut by 4.8 percent every year until 2050 in order to keep our climate from a devastating warming. Instead, in 2011 emissions of CO2 increased almost 6 percent; the two biggest producers are China, with 24.6 percent of the total, and the United States, with 16.4 percent.
One might think that natural changes in climate would proceed slowly and gradually, but it doesn’t always happen that way. Sometimes, like at the end of the last ice age, change speeds up because positive feedback cycles accelerate the process. For example, when glaciers at the poles melt, there is less area of whiteness to reflect some of the Sun’s heat back into space. Instead, the heat is absorbed into the land and water, warming it and causing more melting of the glaciers, which then reflect even less heat; the feedback cycle continues.
Not only has the atmosphere been changed by CO2 emissions, so too has the chemistry of the oceans. The oceans are absorbing extra CO2 from the atmosphere. The extra CO2 makes the water more acidic, endangering the life of creatures that form calcium shells, which disintegrate under too much acid. Runoff from fertilizers and pesticides contributes as well, causing strange blooms of harmful algae, while widespread overfishing threatens marine species worldwide.
More than just sea life is under threat; the biodiversity of all sectors of the planet is declining faster than the usual background rate (the normal rate of change). Reports peg the present rate of decline as somewhere between a hundred to a thousand times the background rate. Up to half of all species face extinction in the 21st century, and many biologists believe the current extinction will rank as one of Earth’s six major ones before it is over.
Another way that humans are changing Earth’s systems lies in our ability to synthesize artificial chemicals, like drugs, pesticides, plastics, and synthetic fabrics. Earth is absorbing these chemicals, with unknown side effects.
For example, humans now “fix” more nitrogen artificially than all the world’s plants do. (Fixing nitrogen means converting nitrogen from the atmosphere (N2) into ammonia (NH3), so that it is usable in biologic processes.) Most plants cannot convert nitrogen from the air and need to have it added to the soil. But a few kinds of plants, such as legumes, can fix nitrogen with the help of common bacteria that use plants to help it extract nitrogen from the air, which is then stored in the plants’ roots. People fix nitrogen by burning oil or gas to synthesize ammonia from atmospheric nitrogen and hydrogen. For example, synthetic ammonia fertilizers made by burning fossil fuels contribute to increased food production. Human synthesis of nitrogen is altering Earth’s whole nitrogen cycle.
Another power that humans have gained control over is that of nuclear energy. The United States dropped two atomic bombs on Japanese cities (Hiroshima and Nagasaki) in 1945 to end World War II. Since then, a handful of nations have tested bombs and several major peacetime accidents at nuclear plants have occurred. But, so far, nuclear power has not been used destructively on a massive scale. Large numbers of bombs exist, and some are on alert to be launched within 15 minutes. Multiple deployments could annihilate millions of people and send large-scale debris up into the atmosphere, blocking the Sun’s rays long enough to produce a “nuclear winter” that would be as destructive to life as the asteroid of 65 million years ago that wiped out the dinosaurs.
The foregoing evidence may convince biologists and climate scientists, but geologists have a very specific method of periodization. They look for evidence in the rocks, or at least in layers of mud that will become rock. They are finding that proof. Worldwide sediments contain the radioactive signature of atomic bomb testing in the 1960s. Similar evidence of chlorine from bomb testing and of mercury associated with the burning of coal also exists in ice-core samples.
Environmental historians support the claims of geologists. For example, scholar John McNeill, in his environmental history of the 20th-century world, Something New Under the Sun, asserts that “the human race, without intending anything of the sort, has undertaken a gigantic uncontrolled experiment on the Earth.”
There are differing opinions as to what these changes might bring and how humans might be able to overcome them. James Lovelock (1919– ), an English independent scientist, believes that humans have passed the point at which they can control change. Non-human processes are now in control and will bring the planet back into some kind of equilibrium, which may not support much human life. The best we can do, he feels, is to try to adapt to the changes.
Others believe that humans have been in tight fixes before and have always been able to figure a way out, using their unique abilities of collective learning to generate new ideas, new technologies, and new solutions. If only a few thousands or millions of humans could do this at previous crises, why can’t seven billion do it now?
Geologists continue to debate other questions: Do we date the Anthropocene from 8,000 years ago, or from 2,000 or 200 or 100? How do we know when we have reached the critical point of human influence on the Earth? Whatever geologists decide about the name of this epoch, the mere consideration has been a productive way for scientists to try to get a handle on the scale of contemporary change.
Meanwhile, people have to align themselves with this decisive period in planetary history. Human decisions made in the near past and those made in the near future will determine the direction of life on our planet. Many leading scientists and journalists believe that we have at most 10 years in which both to rally ourselves to change our destructive behavior and to implement new technologies. Otherwise, humans could face a looming breakdown in our planet’s current life-support systems. Many people trust that human ingenuity will be able to get us through this decisive period, but it will take the commitment, innovation, and cooperation of a large portion of all humans on the planet to accomplish this.
By Cynthia Stokes Brown
For Further Discussion
What evidence would convince you that the biosphere has entered a new epoch, the Anthropocene? What claim testers helped you determine your answers? Share your answer in the Questions Area below.
Christian, David, Cynthia Brown, and Craig Benjamin. Big History: Between Nothing and Everything. Preliminary Edition. New York: McGraw-Hill, 2010.
Hertsgaard, Mark. Hot: Living Through the Next Fifty Years on Earth. Boston and New York: Houghton Mifflin-Harcourt, 2011.
Kolberg, Elizabeth. “The Anthropocene Debate: Marking Humanity’s Impact.” Yale Environment 360. May 17, 2010.
McNeill, J. R. Something New Under the Sun: An Environmental History of the Twentieth-Century World. New York: Norton, 2000.
Ruddiman, William F. Plows, Plagues and Petroleum: How Humans Took Control of the Planet. Princeton, NJ: Princeton University Press, 2005.
Want to join the conversation?
- How should climate change deniers be influenced to pay attention to the evidence?(5 votes)
- I think a better question to ask is if that will help in a significant way. There are many corporations, governments etc. that are temporarily benefiting from this situation. Our focus should be on them. It doesn't seem likely that you can argue people into believing in climate change: there is a huge amount of evidence already.(1 vote)
- What more can we do to raise the consciousness of people to the importance of taking care of our environment?(1 vote)
- Definitely the global warming epidemic has convinced me that the biosphere is becoming weaker i belive that with these chemicals we are using and creating things will only get worse for earths occupants and earth its self. From the wild life acting stranger and migrating to other places to even the plants changing forms, also the heavier storms and the colder winters even the hotter summers plus the weird climate changes in places where it is uncommon.(0 votes)
- I think people or scientist should find out other ways to help change the climate. It is not taken seriously and what other things can we improve on in our environment?(0 votes)
- The evidence that convinced me that the biosphere has entered a mew epoch is that the oxygen, carbon dioxide and many other natural components have changed and started things such as global warming and many other things. Humans have introduced things to the environment that would never have formed naturally such as certain chemicals and other things that have damaged wildlife, plant life, and our air.(0 votes)
- What evidence would convince you that the biosphere has entered a new epoch, the Anthropocene? What claim testers helped you determine your answers?
The scientists around the world are saying that the world is warming and getting too warm. To support this, where I live we used to get a bit of snow every year, but as I have gotten older the temperature during winter has increased we don't have anywhere near as much snow as we used too. Because of this I do believe that we are in a new epoch, the Anthropocene.(0 votes)
- This is good work, but I wonder if you intended to post it here, for all KA learners around the world. Does it belong in your Google Class or somewhere like that for your teacher to see? If so, you should post it there, too.(1 vote)
- I would say that the proof that lead me to believe that we are currently in the anthropogenic epoch was the assertion that our CO2 emmissions have increased almost exponentially in the last ten thousand years. Before it took millions of years for the CO 2 emmissions to go from 100ppm to roughly 280ppm but in the last 10000 or so years we have increased the output of CO2 to roughly 390ppm in the atmosphere which in turns clouds the atmosphere heating up the earths surface which cause global warming a melting of the ice caps and therefore further global warming as the Suns rays have nothing reflect off of. All due to our increased use of fossil fuels and innovations.(0 votes)
- The test Stratigraphers use is what can be seen in the geological record. And much can be. CO2 increases, Hg, Coal burning sediment. Now, the debate is if these markers are durable enough to to signal a new epoch. My guess is that they will be. The common suggested time frame is from 1950-...(0 votes)