400Ppm: Exit Holocene, Enter Anthropocene

Introduction by
The Editors

On 10 May 2013, 400 parts per million of CO2 concentration in the atmosphere was recorded at the Mauna Loa Observatory, Hawaii.


n 10 May 2013, 400 parts per million of CO2 concentration in the atmosphere was recorded at the Mauna Loa Observatory, Hawaii. This seemingly innocuous number failed to grab the attention of mainstream media, but it inadvertently signaled a quiet earth revolution – a geohistoric moment of “wild destratification”, as Deleuze and Guattari would have it. At the start of the Industrial Revolution (and the designated origins of the Anthropocene), atmospheric CO2 was at 280 ppm. The last time CO2 levels hit 400 ppm was in the Pilocene (between 2.6-5.3 million years ago). In light of these potentially seismic changes in the atmosphere and society, Society and Space invited some interdisciplinary reflections on 400 ppm.

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400Ppm: 400 Ppm And The Ages Of The Earth

What does the recent passing of the 400 parts per million (ppm) threshold in atmospheric carbon dioxide mean, in terms of the history of the Earth? It’s tempting to answer this question by simply taking a graph of atmospheric carbon dioxide concentrations over geological time, and drawing a horizontal line back to see when it was last at the current level.

400Ppm: Regime Change In Geo-Social Formations

In other words, the assumption is still that human subjects mobilise themselves to move across an immobile Earth. But have we been too short-sighted, too horizontal, too human-centred in our imaginings of borders?

400Ppm: Geographies Of A Global Experiment

The wavering, saw-toothed plot of atmospheric carbon dioxide levels pushed determinedly over the threshold of 400ppm, tracing a line from the global space of the atmosphere to the hermetic spaces of geoscientist Charles Keeling’s early CO2 observations. As one of millions of virtual witnesses to this traversal, I was reminded that Keeling’s deployment of his 5-litre flasks was not the first time that a glass orb had changed science and, with it, the world.

400Ppm: Passing A New World Threshold

When coming across the figure of 400ppm, I was struck by how difficult this was. 400ppm – what is one supposed to do with this figure? Tellingly, it is not only the mediators and audiences of science, but the scientists themselves that are struggling.

400Ppm: The 400th Part Per Million

Millions of carbon dioxide molecules passed through the Mauna Loa measuring equipment on the 9th May 2013 to generate the milestone daily average of 400ppm. I will focus on one – the 400thpart per million – and the story of its carbon atom. There are many such science fictions that could be told; this one is indicative and personal.

400Ppm: Riding The Keeling Curve

Do you remember where you were when you first heard the news? I was invigilating in an examination with a physical geography colleague. About halfway through the examination my colleague was consulting his iPad when he turned the screen to me saying, “this is not good!”

400Ppm: Wither Carbon Accounting?

In the year of 400 ppm, the politics of carbon accounting seem to have reached a dead end. However, rather than interpreting this historical juncture as the failure of climate politics, we may use it to foster more productive political imaginaries.

400Ppm: Symbolism, Dread, And Panic

The concentration of carbon dioxide in the atmosphere has never before in human evolutionary history exceeded this level. But what does 400 ppm symbolise? And why might it cause dread and panic?

400Ppm: Coping With Abundance Rather Than Scarcity

The symbolic threshold of 400ppm is a poignant reminder that we are well past the point where climate change response can be a planned, gradualist transition. It is much more likely that profound and unwanted change in the next few years (perhaps not even decades) will make a mockery of current policies on climate change and other issues.

400Ppm: We’re Lucky It’s Not 500 Already

Amongst all the hubbub about CO2 concentrations at Mauna Loa reaching 400 parts per million, another important point is being overlooked—were it not for the fortuitous presence of natural carbon sinks, the CO2 concentration would already have been much higher. We are being buffered from the full impact of our CO2 emissions, but this may not continue indefinitely.

400Ppm: Critical Climate Change Scholarship

The fact that, in mainstream environmentalism, nature appears increasingly as a set of dynamic, creative, and resilient social-ecological processes is symptomatic of a moment of real possibility for the creation of alternative future natures – and one that, we would argue, a critical project must actively embrace.