Far beyond the Arctic circle, an army of tracked vehicles make their way, powered by their internal nuclear piles, trundling slowly to their destination to begin their work.
At a point determined by the thickness of the Earth's crust, geological stability, access to the coast and railheads, and predicted
climatic conditions over the next millenium, they meet in a clearing. At other locations splayed roughly equally around the North Pole, in Scandinavia, Siberia, Alaska, Greenland and Iceland, another army, each a mirror of this one, has also gathered. There is a pause, as if for a moment of cybernetic reflection.
The six largest snow making machines ever constructed, and the largest wood chipper ever conceived, set out upon their planet saving endeavour. Like the giant bucket excavators that first tore the ancient carbon from the earth and flung it into the burning gullet of civilisation, they dwarf the accompanying host of supporting machinery, thousands of engineers, technicians and labourers, and the slew of dignitaries and scientists.
Conveyer belts, pipelines and railways stretch beyond the horizon to the south.
Further south, robotic tree harvesting machines set to work in Belgium-sized plantations. Their mighty jaws rip whole fir, spruce and pine trees from their roots, and transfer them to the flatbed carriers waiting alongside.
Out in the warmer waters of the north Atlantic and Pacific, gigantic automated algae farms have been working for years already, pulling down gigatons of carbon dioxide from the atmosphere. Floating processing plants have extracted cellulose fibres from the algae, spun them into thousands of miles of rayon thread, and woven it into mile after mile of fabric.
Parallel plants have produced algae-derived paper in equal prodigy. Giant barges have been inflated around the enormous rolls of cellulosic geotextiles, so they can be kite-sailed and towed into the harbours of Vladivostok, Anchorage, and the northern ports of Canada, and airlifted - by Zeppelin of course - to the waiting roll-laying machines.
Thousand kilometer bobbins of carbon fibre thread sit atop their carriers. Under heavy military guard from the Mitsubishi/Raytheon Space Elevator Corporation, the world's largest stockpile of carbon nanotube thread glistens like spun diamond as the first light of dawn peeks over the forest.
Under more casual guard is the world's largest stockpile of waste paper.
Between them are mountainous stacks of whole trees; firs, spruce, pine, complete to the last twig, needle and root bundle; bamboo poles, polystyrene packaging, used dental floss, disposed chopsticks, toothpicks, fraying fishing nets and long lines, rotting tatami and seagrass matting, sugar cane waste and corn stalks, kelp, and pellets of plastic harvested from the Great Pacific Garbage Patch.
A signal flare comets brightly skyward. And it begins.
With a thunder, the fountain of snow begins to emerge from each of the snow-blowers. Water is one of two essential resources for this endeavour for which Nature has furnished its own transport mechanism - the atmosphere. Extracting water in situ from the air, they gulp down cubic miles of it, like howling baleen whales, cool it, and jet forth torrential snowstorms upon the landscape.
The chipper, dubbed Chippersaurus by her keepers, screams into life, with a sound like a billion grade school teachers dragging their fingernails down a billion chalkboards in a billion hurricanes. The celebrity contingent choose to depart, backload for the waiting cargo Zepellins.
Dump trucks, dozers, cranes, helicopters, conveyors and reconstituted Siberian mammoths push, pull, drag, drop and haul the assembled, variform biomass and carbonaceous waste material into the center of the snow/sawdust storm. Rolling machines plough back and forth, back and forth, layering paper, cloth and thread through the snow, and compacting it under their weight.
In the center, a mound begins to form. As it grows, the seven giants begin their dance. They circle the center - Chippersaurus seems to lead the snowblowers in some eldritch Arctic witchcraft, infinitesimaly crawling their way widdershins, almost imperceptible to human observers, except the patient, the exhausted, and the lazy.
Over the weeks, months and years - indeed the century - to follow, the barrowmound rises. Service vehicles trundle up and down its slopes and burrow beneath it. At seven kilometers radius, it holds around 110 cubic kilometers of ice - equivalent to a film a mere third of a millimeter thick removed from the surface of the world's oceans.
Yet as volume grows as the cube of radius, by the time the mound is 150 kilometers from side to side - and a staggering 70 kilometers high, it has frozen in place a meter's worth of sea level rise, saving millions of square kilometers of the world's most productive, most inhabited land, at a loss of a mere 200-odd square kilometers of Arctic rock and tundra. The seven sister sites together have mitigated a seven meter rise.
Now comes the clever bit:
A long ramping tunnel leads from the surface of the mound, down into a facility called the Sarcophagus, an enormous cavern at - or even below - the base of the mound. Other tunnels, pipes and chambers, laid down as the mound was constructed, lead at various bearings and elevations from the Sarcophagus to the outside. The entire mound, the Sarcophagus, ancilliary voids, and the tunnels between them, form a gigantic, geothermally powered atmospheric fractionation engine.
Such a huge artificial icecap will of course trap rising geological heat underneath it. Unless that heat is diverted or put to good use, it threatens the lifespan of the whole mound.
Air is drawn continuously down the main tunnel, deep into the sarcophagus. Some of the tunnels and voids are arranged as a giant Stirling engine to drive the whole process. Others form a massive heat exchanger, venting the geological heat to enormous heatsink farms on the dark, northward slopes of the mound.
The air at the base of the stack is so cold that carbon dioxide condenses, falling as a snow of dry ice. It can be sequestered in situ, beneath the mound. Manual gathering of carbonaceous waste can begin to taper off, as the howling caverns of the Mound distill raw CO2 out of the skies. As the dry ice snow fills the cavern, the winds slow in proportion, providing a self-regulating negative feedback.
After a century or two, it is stifled altogether. Gigatonnes of CO2 sit frozen beneath the mound like the chewy toffee center of an icecream, safely entombed for generations.
Earth's climate stabilises. Agriculture, industry, nature and man resume their course. We can get on with the 21st century's tasks - liberating the poor, colonising the stars, fixing that death thing.
At the summit, 70km above the Earth's surface, powered by stratospheric winds and near continuous sunlight, is a kick-ass spaceport and ski resort.