illions 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 400th part 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. For hundreds of millions of years the 400 ppm lodged warm and immobile in the Earth’s strata. It was once in a tree fern, drowned in the Carboniferous. Warmed, folded and compressed it became peat and then anthracite. Rendered immobile, it was fixed and then fossilised, bonded in a series of complex molecules. It was suddenly destratified a few years ago. Torn from the ground by sharpened steel in an open cast coal mine in the Appalachians. Crushed, jostled and exposed to the sun it was shipped to a power plant and swiftly oxidized. Long-standing geological bonds were severed in a spectacular burst of heat and light just outside Pittsburgh. Now mobile, gaseous and with two new oxygen atoms the 400 ppm drifted East, brushing over the cornfields of Ohio. It was briefly inhaled by a Blue Dasher dragonfly on the shores of Lake Erie, before being cast high into the upper atmosphere by a summer tornado. At this altitude movement was quick and smooth. At speeds of up to 25m/s it crossed the continent, was blown out over the ocean, before making its now famous sojourn up Mauna Loa.

I encountered our famous atom a few weeks after its trip to Hawaii. Once discharged from NOAA’s carbon dioxide analyser, the 400 ppm caught the polar jet stream. It was swiftly carried back West, over Canada and the Atlantic at heights that averted its oceanic dissolution. It touched down in my garden in Oxford last week, on a bright and windy June day. Settling gently it brushed against the leaf of a strawberry plant and in a flash of sunlight was photosynthesised. Parted from its oxygen travelling companions the 400 ppm was fixed as sugar – a hexagonal molecule of glucose dissolved in water. It thence travelled slowly through the leaf, down the pedicel and into the ripe red fruit. I picked it this morning; the first of the summer and it sits in a bowl in front of me as I write. I will eat it now and let the sweet juice seep through my gums and into my blood. I wait. My heart pumps. I feel the rush as the glucose speeds to my hungry brain. I tap and so the 400 ppm comes to energise this piece, this thought. Perhaps this dot.

Carbon, as Primo Levi (2000) reminds us in the essay that inspires this story, is ubiquitous, promiscuous and generous. All life is entangled by its destratification, circulation, metabolism and sequestration. We humans are interdependent, connected by carbon pathways. Developments in isotope analysis help disclose the geological provenance of increased carbon dioxide concentrations, but individual carbon atoms remain indeterminate and untraceable. The identification and attribution of specific destratifications and entanglements is an engaging, perhaps illustrative, but nonetheless fictional exercise. In aggregate, all life has mineral roots. Modern humans are (perhaps uniquely) indebted to the prehistoric gift of fossilised fuel, oxidized through multiple generative reactions. We cannot live without carbon, nor do we currently seem able to live well with its geological generosity. 


Levi P (2000) Carbon. In: P Levi The Periodic Table. London: Penguin, pp 188-95.