The ice mass continued to advance, and the city of Hades vanished under the snow and ice.

Suddenly the simulation froze. “You see this world as it will be, approximately seventy-five standard years from now. For all intents and purposes, by that time there will be no other life on this planet but ourselves. Some small remnant populations of this and that species might well survive in isolated pockets, but the world as a whole will be dead.” Alvar heard a grim graveyard chuckle in the darkness. “By the time the world is as we see it here, I suppose we humans ourselves could be regarded as a remnant in an isolated pocket.”

“I don’t understand,” Alvar protested, speaking to the faceless voice of the Governor somewhere in the dark. “I thought the danger was from the deserts growing, the planet getting too hot, the ice caps baking off.”

“That was what we all thought,” the Governor said bitterly. “Whatever desultory, token efforts my predecessor made to correct the situation were based on calculations and predictions to that effect. The deserts were supposed to grow, the ice cap to vanish completely, the sea levels to rise. There are plans in my files for dikes to be built around the city and hold back the rising water!”

Alvar heard the Governor step out from behind the console. He came around the side of the simglobe to stand by Alvar’s chair and look at the half-frozen world. “Perhaps I am being unfair. The situation is remarkably complex. If one or two variables shifted slightly, itwould be the sea, and not the ice, that would overwhelm the city. In fact, stage one of our revised terraforming plan is to tip the scales backtoward the collapse-into-desert, coastal-flooding scenario-it is a less drastic catastrophe than the ice age we otherwise face. You have not seen the worst of the ice age yet.”

“But why push toward the desert scenario? Why not work toward a stable middle ground?” Alvar asked.

“An excellent question. The answer is that our current situation is aresult of aiming for that middle ground, a middle ground we may well not be able to achieve.”

“I don’t understand.”

The Governor sighed, his face dimly lit by the image of a dying world. “The groundwork for a stable ecology comfortable to humans was never properly laid in the first place, and we are paying the price for it. A properly terraformed world, when disturbed in some way, will always tend back toward that comfortable middle ground. Not here. Life is supposed to be a moderating factor in a planet’s environment, smoothing out the extremes. But life’s hold on Inferno is getting weaker, and a weakened system moves toward extremes. What we would view as a ‘normal’ terrestrial ecology has, on Inferno, become the abnormal,unstable transition point between two stable states-ice age or an overly arid continent with high sea levels. Of the two stable states, we are heading for the ice, and that will kill us.

“Creating an Inferno with a mostly desert, half-flooded Terra Grande may be the best we can do. It will only leave us halt and lame. You see, if we can force the trends back toward desert-spreading, then life would at least survive on this planet even when our civilization collapses!”

“When our civilization collapses!” Alvar cried out in astonishment. “What are you saying? Is that really going to happen?”

Grieg sighed, a tired-sounding noise of resignation. “I suppose I should say ‘if’ instead of ‘when,’ but I have been reading a whole series of classified reports that suggest that collapse is far more likely than anyone imagines. When it gets bad, people will start pulling out. Not everyone will be able to afford it. There will be too few ships available. Prices will be high. Some people will die, and many more will leave. I doubt there will be a large enough population left to keep society functioning, even with the robots. Maybe all the people will die off, but the robots will survive. Who knows?”

The Governor seemed to come back to himself a bit. He drew his shoulders up and looked down at Alvar and spoke in a firmer, more controlled voice. “Forgive me. There is a great deal on my mind.”

Chanto Grieg paced back and forth in front of Alvar once or twice, clearly working to collect his thoughts. At last he spoke. “We are in a knife-edge situation, Sheriff, in more ways than one. Political and social issues are intertwined with the ecological problems. In looking at the ecology, we therefore must plan for the likelihood that whatever survivors there are will not be able to do anything to save the planet, beyond whatever effortswe make. The ice age result is not survivable. The desert result is. So we force the planet back toward the desert pattern, and, if we get the chance, we can try and reterraform from there. That will certainly be preferable to our current future,” Grieg said, gesturing toward the simglobe.

“But the ice age doesn’t look that bad,” Alvar objected.

“Don’t forget that I have stopped the program,” Grieg said. “But yes, all this, wecould survive, even if we ignore the great and terrible crime of allowing the planet to die.” The Governor regarded the globe thoughtfully. “Even the ice overwhelming the city is not an insurmountable problem, viewed on a global scale. We could dome over the town, or burrow underground, as the Settlers do. Butthis is not the end of the story.”

The Governor turned and stepped back into the darkness. Alvar heard the Governor tapping new commands into the console, and found himself struck by the random thought that buttons and switches were a typically Settler way to do things. Why not voice commands, or an interface to allow a robot to handle the machinery?

But he knew his mind was just finding ways to avoid facing the reality of what Grieg was showing him.What does all this have to do with me? he wondered, more than a bit uncomfortably.I’ m just a cop chasing crooks. I’m not running the planet. But even as he told himself those things, Alvar knew there was a larger reality here. And all this might well have a great deal to do with him.

Chanto Grieg set the simglobe controls to move forward in time. The ice caps grew larger, the seas receded farther. “This is the crisis point,” Grieg said, “eighty-five standard years from now. The seas recede enough to expose the south polar highlands.” The simglobe tilted its south polar region toward Alvar, and he could see the polar landmass emerging from the water, instantly forming its own ice cap. “The polar lands have been hidden under the seas, but they are at significantly higher elevations than the surrounding lowlands. When the sea level shrinks enough, the polar continent emerges.

“And that is what will doom us. There has been ice over the southern polar ocean all along, but the water beneath the ice has always been able to flow freely. The circulation patterns are complex, but the effect of the currents is that the Antarctic waters have been able to blend with the temperate-zone and equatorial waters. The warm water cools down and the cold water warms up. But onceboth poles are landlocked, the planet’s ocean currents shift violently. Water no longer flows througheither polar region, and thus the oceans’ currents will no longer be available to moderate the temperature differential between the south pole and the equatorial region. The oceans no longer have any place to dump their heat. What that means is that temperatures in the south polar regions drop precipitously-and equatorial and temperate-zone temperatures go through the roof. The absolute volume of water in the oceans is greatly reduced as well, which means the oceans simply are not able to hold as much heat energy.

“Air temperatures rise. Storms become more and more violent. The water in the oceans boils off while the poles descend into ever-greater cold. Within 120 years of today, the last of the free water on this planet will be locked up in massive ice caps at the north and south poles. It will get cold enough at the poles to form lakes of liquid nitrogen. But the temperate regions and the equator will simply be baked alive.