And for the last time, she foreknew.
2
Laurinda Ashcroft did not much revise her global braodcast later that day. It was one among several by well-known interfaces, intended over a period of years to make the danger clear and explain Terra Central’s plan for coping. She had prepared most of it beforehand, the usual visuals plus occasional virtuals to invoke every sense.
Watching, you saw Earth revolve around the sun. You saw her orbit drawn in three dimensions, a golden track against blackness and the stars. You saw how she, her moon, and her sister globes interplayed a dance through billions of years, wherein gravitation called the measures, subtly but inexorably. You saw the slow cycle of changeable eccentricity and obliquity, how it set the patterns of lightfall across the planet and how she responded with her air, seas, clouds, rains, snow, and ice.
Since the Arctic Ocean became landlocked, the glaciers had come and gone and come again. In the great winters, northern Europe, half of North America, and huge tracts elsewhere lay under ice whose cliffs reared as high as two kilometers; drowned lands rose anew as sea level dropped a hundred meters; forests withered and died while south of them marshlands came into being and new forests overran the savannahs. Yes, life adapted. If some species suffered, others flourished. But this was on a millennial timescale, scant help to humans and their works.
The next glaciation was overdue. They had unwittingly delayed its beginnings with their emission of greenhouse gases. Now that was past, together with the overpopulation that brought it about, and in any event would not have sufficed. Now more snow fell in winter than melted in summer. Meter by meter, faster each year, the glaciers crept down from the Pole and the mountains.
“You have surely heard what we must do, and soon, before it is too late. Thicken the greenhouse. Thin the clouds. Darken the snows. Make Earth keep more of the sun’s warmth than she can unaided. But perhaps you don’t yet know the magnitude of this, the number of the centuries, or the delicacy and exactness underneath the enormous forces we will call on. Let me show you a little.”
Again, visuals and virtuals. Carbon black strewn over the Arctic, tonne after colloidal tonne, repeated year after year as the layer washes away or sinks from sight. Immense electric discharges high aloft, to force rainfalls so that less light is cast back into space. Mats of brown algal weed carpeting the seas by millions of square kilometers; the care and feeding of these living artifacts. Underwater detonations to break up beds of methane hydrate and release the gas into the atmosphere. Forests set afire and afterward only grasses allowed, for they store less carbon than trees do. Holes drilled down into the very mantle of the planet; nuclear explosions to goad volcanoes into spewing forth carbon dioxide and water vapor more copiously than fossil fuels ever did. The new industries required, their claim on resources, their constructs and monitors everywhere.
“Yes, this will be an Earth very different from the Earth we thought we had restored for ourselves.” Laurinda leaned forward, as if each person watching sat before her in the flesh. “But it will be far less changed than the Ice Age would change it. Our world will still be green, rich, kindly, from rim to rim of the Polar oceans. We will keep many of our woodlands, open waters, pure snowpeaks. And on the new prairies, what wildflowers will bloom, what herds will graze!”
She gave them the images, the sounds, the sense of wind and fragrances, simulated but as vivid as reality. Idealized, yes. But not dishonest. We can have such places.
“Please bear in mind, this will not happen at once. The work must go slowly, piecemeal, in pace with the astronomical cycle, constantly observed and measured, constantly adjusted to hold the giants of climate and weather under control. It will take thousands of years. Then finally, as Earth tilts back sunward, it will be undone, just as gradually and carefully. Most of us will notice little of it in our lifetimes. To our children and children’s children, hundreds of generations, it will be natural, a part of their universe like the moon and stars.”
“That’s the worst,” Omar said. “To them Terra Central will be what God was to their ancestors. Oh, I don’t suppose they’ll worship it. But they’ll know how utterly dependent on it they are. And meanwhile it will be doing what God never did, evolve itself till it’s beyond all human comprehension. What then, Laurinda?”
Earlier, she had not meant to give his viewpoint as much voice as she now did. However, this might actually be the wisest course. He and his fellows were making their protests widely known. By taking them seriously, she, a designated speaker for the artificial intelligence, could perhaps better show why they were wrong.
“Doubtless most of you have heard that certain people think this whole concept is mistaken.” She left out Omar’s Disastrously mistaken. The more so because it’s millennially slow and all-pervading. She smiled. “They are not fools. They have studied the situation and done scientific analyses. Let me discuss their position as I see it. They are right when they say there is an easier, cheaper, and far less disruptive way to stop the Ice.”
Robots in space. Asteroids mined, the stuff of them refined, nanotechnic assemblers forming titanic mirrors to precisions of micrometers, the judicious orbiting of these—no simple task, but well within present-day capabilities. Governed by mathematics and monitors less complex than in the rival scheme, the mirrors’ shine added sunlight onto Earth at the times, places, and intensities needed. The glaciers retreat, climates stabilize, the system stands guard through the necessary era and stands in reserve forever after.
“It would
