The carbon ice-age cycle

The drifting continents
Clash and pull apart
As the pulsing polar ice-caps
Beat on like a heart

Expanding as the carbon drops
And shrinking as it rises
This carbon linked great cycle
Is one of earth’s surprises

Driven by great algal blooms
That peak in times of cold
And die away to little
As the seas grow hot and old

The earth and its biosphere are intimately linked. The ancient dance of ice-ages and interglacial warmth cycle on and on in response to Milankovich orbital cycles or the episodic rising and falling of atmospheric carbon dioxide levels.  Sharp falls in atmospheric carbon dioxide levels can occur when massive oceanic algal blooms suck up billions of tonnes of CO₂ . This could occur for many reasons including continental drift modifying ocean currents, volcanic eruptions or fractures in the earth’s crust releasing billions of tonnes of natural gas.  This in turn can trigger an ice-age which reinforces itself with the albedo of marching glaciers and is accompanied by dramatic drops in sea-level. But as the nutrients in the ocean slowly deplete the algal blooms reduce and atmospheric carbon-dioxide levels start to rise. The world begins to warm and rain returns to shrinking drought stricken continents reducing the volume of iron-rich dust settling on the oceans.  The oceans become clearer as the continental vegetation flourishes and the ice-caps retreat.

 The massive release of carbon from the burning of billions of tonnes of fossil fuel by our industrial world is, unfortunately for us occurring at and intensifying the hot part of the cycle. To a large extent the rapidity of the current rise is uncharted territory. It may not, as the geologists tend to argue, make too much difference in the longer term but the short term impact if left unmitigated will be profound and include both mass extinction of species and the potential collapse of our civilisation.  Time will tell if we, like our ancestors who repeatedly abandoned and reinhabited places like the Unite Kingdom through the ice-ages, can also adapt.  We probably can but there won’t be many of us left.

But we do have the option of mitigating the degree of global warming by reducing our emissions and we also have the option of artificially triggering oceanic algal blooms through the addition of iron to upwelling zones to reduce atmospheric CO₂ levels.  We have to be careful before launching global bioengineering initiatives as the consequences of this are not fully predictable but it is something which should be looked at and business as usual no longer an option.

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