High above, yet invisible, the layers of carbon dioxide formed a barrier, blocking off the escaping heat. Temperature medians had gone haywire. While some parts of the globe had increased by ten degrees and more, others had drastically cooled. Parts of Africa that had never seen a snowflake now had blizzards. Siberia was turning into jungle. The equatorial belt was a steamy, airless no-man's-land, mimicking the conditions of five million years ago.
Mexico City had been the first of the world's great cities to become uninhabitable. In the early years of the twenty-first century it had a population of thirty-two million, making it the largest city on earth. Chase remembered seeing documentary film of conditions there that reminded him of the Nazi death camps in World War II. The film showed rotting bodies in the streets, the city dumps piled hundreds deep. Public utilities and services had collapsed completely and untreated sewage ran in the gutters and formed huge stinking lakes in the plazas and marketplaces. Plague had swept through the city and there were packs of rats roaming through the shops and department stores.
From the faces of those who managed to survive it was apparent that they were suffering from the early stages of anoxia. Pinched, their lips blue-black, they slumped in total exhaustion, mouths sucking in the depleted air. Oxygen content was nearly forty percent lower than normal, equivalent to an altitude of fifteen thousand feet.
Chase recalled the profound shock felt by the scientific community. It had always been assumed that such a decline would take decades, yet Mexico City had slid into ecological nightmare in just a few years. It became a poisonous and decaying wasteland, a memorial as well as a dreadful warning of things to come.
At the entrance to the Tomb he was met by one of the guard corps, a tall loose-limbed boy with a drawling southern accent whose breast patch identified him as "Buchan." Although Chase had been loath to employ armed guards, the threat of attack left little choice.
"Morning, sir." Buchan touched the steel rim of his camouflaged helmet. "How's it look topside?"
His concrete cubbyhole contained a chair, table, a few tattered magazines, and on the crude walls an even cruder patchwork of naked women in bizarre contortions. From the ceiling extended the polished tube of a periscope, through which Buchan surveyed the surrounding terrain. Aboveground had been left completely undisturbed, so that the site, even from fifty yards away, was virtually undetectable. This was their greatest defense.
"All quiet on the western front," Chase reported. He nodded toward the periscope. "Don't you get eye strain peering through that all day?"
"Naw, ain't too bad." Buchan gave him a gap-toothed grin. "Standing orders say you gotta do a sweep every fifteen minutes. Reckon nothing could get near inside of that without being spotted."
"Except a helicopter."
"Yeah, I guess so," Buchan conceded with a shrug. "But we'd pick 'em up on radar, wouldn't we? I think we're pretty safe from a sneak attack," he said confidently.
Chase went down in one of the freight elevators to the mess hall. Seventy feet underground he passed the large board listing the various departments on the different levels.
Marine Geology. Marine Chemistry. Geochemistry. Meteorology. Physical Oceanography. Botany. Biology. Atmospheric Physics. Microbiology. Biological Oceanography. Physiological Research. Marine Ecology. Geophysics and Planetary Physics. Neurobiology. Physiological Psychology.
Altogether, counting technical and laboratory staff, there were about two thousand people. There was space in the Tomb to accommodate many more--twenty miles of tunnels in this section alone. The complex actually stretched much farther, two hundred miles of tunnels in all, though the rest of it had been sealed off from the Tomb itself.
As he ate his scrambled eggs and toast and sipped his coffee, Chase found himself hoping fervently that Buchan's confidence was justified. There were nine access points, each one closely guarded, but even so, the fear of discovery was never far from his mind.
Over his second cup he read the teletext editions of the
