The Geophysical Agency of Humans and Climate Change

Dipesh Chakrabarty

In equating the problem of global warming with the crucial but techno-economic question of transitioning from fossil-fuel based sources of energy to renewables, we sometimes lose sight of how the scientific understanding of “anthropogenic global warming” signals a very fundamental and irreversible shift in human history and human capability.

It was in 1957 that the scientists Roger Revelle and Hans Suess in a paper in the oceanography and meteorology journal Tellus proclaimed that humanity was engaged in a “large-scale geophysical experiment” by returning to the atmosphere and the oceans over a couple of hundred years the concentrated organic carbon that had been locked up in sedimentary rocks for hundreds of millions of years.

By the time the 4th Assessment Report of the Inter-governmental Panel on Climate Change came out in 2007, scientists were coming round to the view that humans had not only conducted an experiment on a vast geophysical scale but had themselves become a “geophysical force” determining the course of the climate of the planet taken as a whole. The Nobel Prize-winning chemist Paul Crutzen, along with Eugene Stoermer went to the extent of proposing in 2002 that a new geological period had dawned in human history, one marked by the geological agency of the humans. They called it “the Anthropocene” in order to distinguish it from the geological age of the Holocene, one that we have been inhabiting for some ten to fourteen thousand years.

The term “Anthropocene” is not a formal term yet and will probably be debated by geologists for some more time before it is accepted or discarded, but the idea that humans collectively – through our numbers and technology – act in the same way as very large-scale geophysical forces do in determining the climate of the planet, has come to stay. This idea has some long-term implications for the future of life on this planet, including humans.

... this is a geophysical capacity that humans never had until the present time.

That humans may have some kind of geological agency is not a new thought as such. The great American environmentalist pioneer George Perkins Marsh expressed this thought in the nineteenth century in his classic, Man and Nature: Physical Geography As Modified By Human Action (1867). But the word “geology” had only regional connotations in his use; it did not signify anything of planetary proportions.

However, when scientists speak of humans as a “geophysical force” acting on the planet today, they mean something different: that our collective emission of greenhouse gases has the same kind of impact on the planet’s climate as a whole as do forces of very large natures – such as those generated by tectonic shifts or the earth’s collision with a giant asteroid that is supposed to have wiped off the dinosaurs. For instance, paleoclimatologists say that human-induced warming of the planet has now effectively put off – with unknown consequences for the planet’s long-term carbon-cycle, its thermostat, as it were – the next ice-age that would have been due in another twenty or so thousand years.

David Archer remarks in his book, The Long Thaw: How Humans Have Changed the Climate of the Planet for 100,000 Years (2009) that “mankind is becoming a force in climate comparable to the orbital variations that drive the glacial cycles.” This is a geophysical capacity that humans never had until the present time.

An interesting fall out of paleoclimatologists’ claim that humans have now become a geophysical force has been a political debate. For the argument has elicited from many social-science scholars and activists the response that since only some humans – the relatively affluent ones – are mostly responsible for the emission of greenhouse gases, it would be wrong to describe either the climate problem as “anthropogenic” or all humans as having a geophysical force. They suggest instead that the capitalist mode of production be itself seen as something that has acquired a geophysical agency in its drive to bring the entire planet under its own sway.

... only reinforce the point that our geophysical agency, considered over scales of time that matter to humans, is now irreversible.

This argument, while justifiably drawing our attention to issues of historical responsibility for the emission of greenhouse gases, is not fully persuasive. The size of human population will increasingly be a very important factor in global energy consumption and hence in climate-related questions as China, India, and other populous countries attempt to lift their standards of living.

The increase of human population has mainly taken place in countries that have, historically, been less industrialized. So the historical responsibility for the population-factor in the climate crisis lies with them. Secondly, one also has to explain why the leaders of these nations today want to follow the same path of economic development that is identified with industrial nations.

These questions apart, some geologists have speculated that sustaining a large human population – say, some nine billion, assuming that a worsening climate does not precipitate population collapses in some parts of the world – at a high standard of living may actually require humans to develop technologies for harvesting additional solar energy in space in order to direct it to the planet to serve human needs. If such seemingly science-fiction scenarios come to pass one day, they will only reinforce the point that our geophysical agency, considered over scales of time that matter to humans, is now irreversible.

Dipesh Chakrabarty is the Lawrence A. Kimpton Distinguished Service Professor of History at the University of Chicago and a Faculty Fellow at the Chicago Center for Contemporary Theory.

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