5.3 The Early Anthropocene Theory (EAT)

Ruddiman's hypothesis.jpg

The Earth transitioned into the Holocene era about 12,000 years ago, an interglacial period of remarkable climactic stability, which allowed organized human civilizations to flourish[16]. Environmentalists and climate scientists have mainly attributed this remarkable climactic stability to good fortune. Then, they typically lament that we have squandered this good fortune in the recent past. For instance, Bill McKibben wrote in his book, Eaarth[17],

“For the ten thousand years that constitute human civilization, we’ve existed in the sweetest of sweet spots. The temperature has barely budged; globally averaged, it’s swung between 58 and 60 degrees Fahrenheit. That’s warm enough that the ice sheets retreated from the centers of our continents so we could grow grain, but cold enough that mountain glaciers provided drinking and irrigation water to those plains and valleys year round... We have built our great cities next to seas that have remained tame and level or at altitudes high enough that disease bearing mosquitoes could not overwinter… But we no longer live on that planet. In the four decades since, that earth has changed in profound ways ... We’re every year less the oasis and more the desert. The world hasn’t ended, but the world as we know it has—even if we don’t quite know it yet. We imagine we still live back on that old planet, that the disturbances we see around us are the old random and freakish kind. But they’re not. It’s a different place. A different planet. It needs a new name. Eaarth.”

McKibben dates our intransigence as beginning in the 1970s, when ecologists such as Paul Ehrlich warned us all about human overpopulation and political leaders such as Prime Minister Indira Gandhi of India attempted to forcibly sterilize people. Some others have timed our intransigence at the start of the industrial era, about 200 years ago, when we began using fossil fuels in earnest.

Enter Dr. Bill Ruddiman, a Paleoclimatologist and Professor Emeritus at the University of Virginia. In 2003, he published the Early Anthropocene Hypothesis (EAH), claiming that the remarkable climactic stability in the Holocene era was not natural, but due to early human interference in the Earth’s climate. He pointed out that we have been deforesting and denuding land for thousands of years and the greenhouse gas emissions from such agricultural land use changes would have prevented the Earth from retreating into another ice age. It is no coincidence that the vast contiguous desert in the mid-equatorial latitudes of the Earth today is where most well known ancient civilizations of the world arose. The desert that begins with the Sahara at the western edge of North Africa extends all the way into India as the Thar desert of Rajasthan and into China as the Gobi desert. This vast contiguous expanse is the result of desertification caused by the Egyptian civilization, the Sumerian civilization, the Babylonian civilization, the Persian civilization, the Indus Valley civilization and the Chinese civilization, combined. Even today, we can witness the desertification occurring on the ground primarily due to human activities, in places like Rajasthan, India. Therefore, human beings have been impacting the environment tremendously since the agricultural revolution began. In fact, Prof. Ruddiman estimates that the net greenhouse gas emissions from land use changes over the past 10,000 years exceeds the net greenhouse gas emissions from all fossil fuel combustion in the industrial era, combined!

EAH is a hypothesis that dramatically alters the prevailing narrative and therefore, it has received considerable criticisms. However, all the scientific criticisms of the EAH published between 2004 and 2010 have been refuted by subsequent work. In his recent plenary lecture at the annual meeting of the American Association of Geographers, Prof. Ruddiman presented a blow-by-blow account of the main criticisms and their refutations[18]:

“A model simulation of global methane (CH4) sources claimed that anthropogenic emissions were not needed to explain the CH4 increase after 5000 years ago, but archaeobotanist Dorian Fuller and colleagues showed that the spread of irrigated rice explains 70% of the CH4 increase, and livestock will likely explain much of the rest. Initial simulations by land-use modelers suggested minimal pre-industrial carbon emissions, but landscape ecologist Erle Ellis, ecological modeler Jed Kaplan and I found historical records of larger per-capita land-use in pre-industrial time. Kaplan and colleagues published a historically validated land-use simulation indicating large Carbon DiOxide (CO2) emissions closer to those in the EAH. Geographer Ralph Fyfe and colleagues showed deforestation of Europe before industrial times based on pollen. Geochemists claimed that changes in the d13C composition of CO2 rules out large pre-industrial carbon emissions. But large terrestrial carbon burial in boreal peats compiled by paleoecologist Zicheng Yu invalidated their mass-balance analysis. Geochemists claimed that the closest interglacial analog to the Holocene (stage 11) disproved the EAH, but palynologist Chronis Tzedakis and colleagues showed that stage 11 is not a valid analog and that the best analog (stage 19) shows a CO2 decrease like that predicted in the EAH.”

It is now safe to say that after thirteen years of corroboration, the Early Anthropocene Hypothesis has earned the right to be treated as a theory, the Early Anthropocene Theory (EAT). Therefore, far from being fortuitous, it is almost certain now that our human ancestors had been actively involved in maintaining the remarkable climactic stability over the past 10,000 years, though unwittingly. In fact, through the ice core records, we can even pinpoint the time when human impact on the Earth’s atmospheric greenhouse gas composition began to show its signature in the atmospheric composition of CH4 and CO2. It began to occur around 5000-7000 years ago, and in that sense, the world as we know it today was indeed “created” at that time!

However, while our ancestors were unknowingly contributing to the stability of the Earth’s climate in the Holocene era, it is only over the past 200 years, in the industrial era, that the human impact on the environment has reached such epic proportions that the Earth's bio-geophysical processes are becoming precariously unbalanced. It is now the scientific consensus that the systems of human civilization will need to come into conscious alignment with the Earth's planetary life support systems and play an integral part in the Earth's evolution into the future.

[16] https://en.wikipedia.org/wiki/Neolithic_Revolution

[17] McKibben, Bill, Eaarth: Making a Life on a Tough New Planet, St. Martin’s Griffin, Mar 2011, ISBN-13: 978-0312541194, http://amzn.to/1XoQxQV

[18] Quote is taken from Bill Ruddiman’s lecture abstract: http://bit.ly/1NCCbul