The author of A Million Open Doors (1992) here spins a near- future global catastrophe yarn. By 2028, the worldwide fiber-optic network has become infested with ``datarodents,'' intelligent independent programs designed to capture information and report back to their owners. ``XV,'' a you-are-there, full-sensory-input system, has replaced TV, and the UN has become the world's principal mover and shaker. However, one particular peacekeeping action, a preemptive nuclear strike against some arctic submarine bases built by fractious Siberians, results in the release of vast quantities of methane gas into the atmosphere. The consequent rapid increase in global warming causes gigantic hurricanes, climatic shifts, crop failures, flooding of low-lying areas, and massive human displacement. Barnes develops and explores his disaster scenario and its eventual resolution from a wide variety of viewpoints, including those of President ``Grandma'' Brittany Lynn and her advisers, researcher Diogenes Callere, computer whiz Carla Tynan and her astronaut husband Louie, and patent-hoarder/money- spinner John Klieg. Astonishing speculations combined with brilliant extrapolations. But the present-tense narrative kills off all sense of drama, and the whole impressive enterprise weighs a ton and a half.