Climate change: a new twist on a very old story

David Robertson

By: David Robertson

More than 80 percent of adults in the United States now believe that climate change (i.e, global warming) is happening. However, only slightly more than 50 percent believe that humans are responsible (Pew 2018). Despite the established scientific consensus that our current climate crisis is the result of human activity, nearly half of the adult U.S. population still don’t believe it! And yet, there is more to this story; much more. I suspect that only a very small percentage of people know that humans have been contributing to climate change in significant (and positive) ways for thousands of years.

Who is responsible for our climate?  Most people who believe in human-induced climate change probably think that it is a recent phenomenon resulting from the activities of wealthy people and developed countries during the past seven decades of the Great Acceleration, or the past several centuries since the Industrial Revolution. They are partly correct一our current climate crisis is largely attributed to these specific people and societies. But, according to the Ruddiman hypothesis (originally published by William Ruddiman in 2003, and defended by him and others in 2007 and 2013), anthropogenic climate change has a much longer and more interesting pedigree, dating to the origins of agriculture, approximately 10,000 years ago.

Ruddiman summarizes his argument this way: “We live in a world in which peak interglacial warmth has persisted only because of the inadvertent impact of early farming. […] The natural downward trends in CO 2 and CH 4 were overridden by human intervention thousands of years ago, and much of the natural cooling that would have occurred was thereby prevented. […] A world largely free of human intervention did exist in the early Holocene, when the last of the northern ice sheets were melting […] but the climate system has been continuously altered by human interference ever since.” In other words, as Ruddiman asserts, humans are, and always have been, climate makers, but only recently our climate management has begun to produce negative outcomes. This new view of climate, and our ability to manage it, should give us hope for the future.

[Image ©️ Yale University Press]

Our human planet  Simon Lewis and Mark Maslin elaborate on the Ruddiman hypothesis and its implications in their recent book The Human Planet: How We Created the Anthropocene. According to them, 10,000 years ago, the Earth was in an interglacial phase and slowly cooling, sliding gradually toward another glaciation: “This means that without human interference ice sheets should now be growing and the next glaciation should happen anytime between now and 1,500 years in the future. But the ice sheets are not growing… because of the greenhouse gases released by early agriculturalists. Slowly, subtly and inadvertently, the new mode of living that emerged 10,500 years ago managed to delay the next glaciation event, a truly global-scale environmental impact. […] Yet the most important impact of farming was more subtle than postponing the next glaciation. The greenhouse gas emissions resulting from farming almost perfectly offset the long global cooling seen in previous interglacials. This new way of living helped generate a period of climatic stability lasting thousands of years. These conditions meant agriculture was viable in the long term. Without it complex civilizations and empires might never have formed.”

 

In other words, humans are, by definition, climate makers, and the “stable climate” of the past 10,000 years is an artifact (albeit an “inadvertent” by-product) of our own making, just as we are the product of it. One might argue that humans and climate as such have a symbiotic and co- creative relationship.

Ruddiman’s hypothesis in three graphs  

Figure 1 (Ruddiman 2007)  Human activity during the late Holocene caused increases in (a) CH 4 [due to wet rice cultivation] and (b) CO 2 [due to deforestation/agriculture] in contrast to downward trends of previous interglaciations. (c) Anthropogenic greenhouse gases preventing much of the natural cooling that occurred in previous interglaciations.

 

Stories can change the world  This little-known Ruddiman hypothesis is not the story most of us have been told or like to tell ourselves about the historic or the current relationship between humans and climate. While the hypothesis has some details and elements that remain controversial (for the public and the scientific community), the overall story is compelling: humans are climate makers. As both my mother and, allegedly, Mark Twain, like to say, “Don’t let the truth [or in this case, the details] get in the way of a good story.”

According to a recent book by Erle Ellis, titled Anthropocene, “Recent climate simulations have confirmed that greenhouse gas emissions by early agricultural societies had the potential to alter Earth’s climate trajectory, though the amount of this change and its timing remains a subject of active research. Major agricultural emissions of carbon dioxide from about 7,000 years ago remain a plausible if controversial hypothesis. However, early methane emissions from rice production are now widely accepted as the cause of a substantial rise in atmospheric methane concentrations approximately 5,000 years before present.”

Regardless of some of the yet-to-be-resolved details, the bigger message has profound implications for humans, our sense of who we are, and our responsibility for managing the global climate system. In this new story, humans are both heroes and villains. For thousands of years prior to our current crisis, humans unwittingly contributed to a stable climate. We might call this earlier period the “good Anthropocene.” But then, during the past few hundred years, humans turned the tides and gave rise to an entirely new era, what most of us would agree is a really “bad Anthropocene.”

[Source: Nature]

 

We are climate makers  At the beginning of their book, Lewis and Maslin quote Aristotle: “What it lies in our power to do, it lies in our power not to do.” This is a telling start to a powerful new narrative about humans and climate. We may be to blame for our current climate crisis, but we are also responsible for the “relatively stable climate” and “unusually stable environmental conditions” of the last 10,000 years. This new science-based origin story should give us pause to reconsider who we are as a human species and what we are capable of: we are climate makers.

Our current climate crisis is overwhelming and can be depressing. This may be inevitable considering how little most of us know about the history of climate and our ability to shape it (for better or worse). But we should not lose hope! Despite widespread climate fatalism and perceptions regarding the ineffectiveness of individual action and the lack of political will to address this most wicked of challenges, the Ruddiman story should give us a great deal of courage and confidence about what we have the power to do in the future. Humans have been contributing to climate change in significant (and often positive) ways for thousands of years. We can continue to do so.

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Dr. David Robertson directs Virginia Tech’s Executive Master of Natural Resources program, advises students, and teaches courses in sustainable development and urban ecology. Also, he conducts research on green infrastructure systems and sustainable development strategies and has published research in journals such as Society & Natural Resources, Conservation Biology, Ecology & Society, Environmental Management, and Environmental Science & Policy.