But this was not the moment to bring any such thing up ‘with the Governor. Maybe he had seen that lecture of Leving’s-or maybe he knew something more. But Grieg was bent over the control unit, concentrating on it.Best to pay attention, Alvar told himself.

“This is a simglobe unit,” the Governor said, a bit absently, concentrating on the controls in front of him. “You may have seen one before, or seen a recorded playback from a simulation run on one. But I doubt you have seen one like this. In fact, I am certain of it. It’ s a Settler model, much more sophisticated than our own units. It’s a gift from Tonya Welton-and before you can get suspicious ofthat, it was quite thoroughly tested by our own people, andprogrammed by our people. It has not been rigged in any way.”

“So what will it show me?” Alvar asked.

The Governor finished adjusting the controls and looked up at his guest, his face suddenly grim. “The future,” he answered in a flat, emotionless voice that put a chill in Alvar’s spine.

The windows made themselves opaque, and the room’s lights faded away into darkness. After a moment, a vague, dimly lit ball of light came into existence in the middle of the air between Alvar and Grieg. It quickly came into sharper and brighter focus, to become recognizably the globe of Inferno. Alvar found he was drawing in his breath sharply in spite of himself. There are few sights as beautiful to the human eye as a living world seen from space. Inferno was heart-stoppingly lovely, a blue-white gem gleaming in the void.

It was in half-phase from Alvar’s point of view, the terminator slicing neatly through the great equatorial island of Purgatory. Nearly all the southern hemisphere of Inferno was water, though there had been arid lowlands before the terraforming projects gave this world its seas.

The northern third of the world was given over to a single great landmass, the continent of Terra Grande. Even in summer, the polar regions of Terra Grande sported an impressive ice cap. In the winter months the ice and snow could reach halfway down to the sea…

Just north of Purgatory, a huge, semicircular chunk was neatly sliced out of the southern coast of Terra Grande, the visible scar of an asteroid impact some few million years ago. Hidden by the water, the arc of the landward edge of the crater extended out into the sea, forming a circular crater. Purgatory was actually the central promontory of the half -submerged crater. The huge water-filled crater was called, quite simply, the Great Bay.

Clouds and storm-whirls knotted and twisted about the southern seas, with the greens and browns and yellows of the sprawling northern continent half-hidden beneath their own cloud cover. Dots of lightning flickered in the midst of storms in the northwestern mountains, while the eastern edge of the Great Bay was cloudless in the morning light, dazzlingly bright, the coastal deserts gleaming in the sun, the greenswards of the forests and pastures beyond a darker, richer green.

A bit farther south and west along the coast of the bay, Alvar could just pick out the lights of Hades, a small, faint, glowing light in the predawn darkness.

“This is a real-time view of our world as it is today,” Grieg’s voice announced from the far side of the now solid-seeming globe. “We came to a waterless world with an unbreathable atmosphere. We gave it water and oxygen. Every drop of water in those oceans, we caused to be there. Every breath of oxygen in the air is there because we remade this world. We unlocked water from the rocks and soil and imported comets and ice meteors from the outer reaches of this star system. We put plant life in the sea and on the land and gave this world breathable air. We made this world bloom. But now the bloom is off the rose.

“Next you will see Inferno as it will be, if we merely rely on our own abilities, using just our own terraforming stations and technology, if we go on as we have been. First, to make it easy to observe, I will remove the atmosphere, cloud cover, and the day-night cycle.” Suddenly the half-lit globe was fully illuminated, and the storms and haze vanished. The hologram had seemed like a real world up to that moment, but, stripped of darkness and cloud, it was suddenly nothing more than a highly accurate map, a detailed globe. Quite irrationally Alvar felt a pang of loss even then. Something lovely that had been was suddenly gone, and he knew, beyond doubt, that the surviving image of the world would grow uglier still. “Now let me add a few supplementary graphics,” Grieg’s voice said. A series of bar charts and other displays appeared around the globe, showing the state of the forests, the sea and land biomass, temperatures, atmospheric gases, and other information.

“I will run the simulation forward at the rate of one standard year every ten seconds,” Grieg said, “and I will keep the western hemisphere positioned so you can watch the fate of Hades.” A white dot appeared at the appropriate position on the edge of the Great Bay. “That is Hades’s location.”

The governor spoke no more, but instead let the simglobe tell its own tale, partly in direct images, partly in readouts and graphic displays.

It was the oceans that died first. The predators at the top of the food chain overbred and all but wiped out the mid-chain species, the fish and other creatures that fed on each other and on the various species of plankton, and were in turn eaten by the high-end predators. Their food supply wiped out, the high-end predators died out as well.

With no controls on their reproduction, the plankton and algae in the ocean were next. They reproduced out of all control and the oceans bloomed a sickly, ghastly green. Then the seas turned brown as the algae died as well, having overrun their own food supply and absorbed virtually every molecule of carbon dioxide. With no animal life in the ocean, plant life everywhere,’ on land and sea, was starved for carbon dioxide. The loss of the greenhouse gas meant Inferno could retain less and less heat. The planet began to grow colder.

Alvar watched, an unwilling witness to the forthcoming doom of his own world, watched as the planet Inferno was strangled by ice. Water, water was the key. No living world could survive without it, but it could do no good-and could do great damage-if it was in the wrong state, in the wrong place. Now it was the ice cap that was the problem. The line on the chart displayed the size of the northern ice cap, but Alvar could see the cap itself growing. The ice advanced, and the northern forests fell before it, the great stands of trees dying in the too-cold, carbon-dioxide-starved air. With the atmosphere’ s oxygen content far too high, and drought conditions taking hold, forest fires exploded everywhere, even as the ice pushed southward.

The white ice reflected back far more heat and light than the forests, and the planetary cooling trend locked itself in, strengthened itself, reinforced itself.

But the cooling was not universal: Alvar could see that. As the forest died and the ice advanced and the overall planetary temperature dropped, local temperatures dropped in some areas and rose in others. Wind patterns shifted. Storms grew more violent. Semipermanent snow hurricanes lodged themselves here and there along the southern coast of Terra Grande, while Purgatory became semitropical. But still the ice advanced, creeping farther and farther south, locking up more and more water in snow and ice, water that should have flowed back into the southern ocean.

The sea levels dropped. The oceans of Inferno, never very deep to begin with, receded at incredible speed as the ice grew ever deeper in the north. Islands began to appear out of the southern ocean. Still the waters drew back, until the Great Bay revealed its true form as a drowned crater. Now it was a circular sea, surrounded on all sides by land.