WASHINGTON – “Our Final Hour,” “The End of the World,” “Catastrophe,” “Imagining the… WASHINGTON – “Our Final Hour,” “The End of the World,” “Catastrophe,” “Imagining the Unthinkable.”

These aren’t the ravings of wild-eyed prophets proclaiming the imminent arrival of doomsday. Rather, they’re titles in a recent spate of scientific books and reports calling attention to various perils facing our planet.

In the book “Catastrophe,” Richard Posner, a judge on the U.S. Court of Appeals in Chicago, wrote: “The number of extreme catastrophes that have a more than negligible probability of occurring in this century is alarmingly great and their variety startling.”

In his 2003 book “Our Final Hour,” British Astronomer Royal Martin Rees declared, in a statement some scientists think excessive: “I think the odds are no better than fifty-fifty that our present civilization on Earth will survive to the end of the present century.”

“Imagining the Unthinkable,” a worst-case study that the Pentagon requested last year, warns that a sudden shift in the world’s climate “could potentially destabilize the geo-political environment, leading to skirmishes, battles and even war.”

Some of these scary scenarios are plausible, perhaps inevitable, within the lifetimes of our children or grandchildren. Others are too improbable or remote in time to lose sleep about. Some potential calamities discussed in the scientific literature threaten one city or region – others, the whole world or universe.

Among the more likely hazards are biological or nuclear terrorism, rising sea levels that flood coastlines, the loss of many of the world’s forests and living species, and a smallpox or flu pandemic.

As many as 100 million people could die in a “worst case” outbreak of Asian bird flu, an official of the World Health Organization warned Monday.

Far down the probability scale – but not ruled out in the distant future – are a sharp plunge in temperature that could turn the oceans into ice, a killer asteroid smashing into Earth and a takeover by super-intelligent robots.

Two years ago, the prestigious National Academy of Sciences formed the Committee on Abrupt Climate Change. The committee reported that rapid rises or falls in temperature – by as much as 28 degrees Fahrenheit – have occurred repeatedly in the past, sometimes within a single decade. A recurrence is “not only possible but likely in the future,” the report said.

“The biggest potential catastrophe that we, our children and our grandchildren face is that of climate change,” Sir Crispin Tickell, chancellor of the University of Kent in Canterbury, England, and a former British ambassador to the United Nations, wrote in an e-mail.

David King, the chief scientific adviser to the British government, has called global warming “more serious even than the threat of terrorism.”

Richard Alley, the chairman of the Committee on Abrupt Climate Change, said gradual global warming is tolerable, but the world may be nearing a “tipping point, like someone leaning over in a canoe.”

“A little warming is all right,” said Alley, an earth scientist at Pennsylvania State University in University Park, Pa. “If it comes slowly, you can get ready for it, but if it comes fast, you can’t.

“That’s the `The Day After Tomorrow’ scenario,” Alley said, referring to the recent movie showing New York City encased in ice from a frozen Atlantic Ocean.

Of course, people have been predicting disasters since the dawn of civilization. Most have been false alarms.

In his book, published this fall, Posner scoffed at “scientific doomsters” who make horrifying forecasts that turn out to be false alarms. In 1970, for example, Paul Ehrlich, a prominent biologist at Stanford University in Palo Alto, Calif., predicted that food and water would have to be rationed by 1980 and that 65 million Americans might starve to death in the 1980s. Neither happened.

Similarly, unfulfilled fears of widespread computer breakdowns marked the approach of the year 2000, the dreaded “Y2K.”

“After enough false prophecies of doom, people stop paying attention,” Posner said. Exaggerated predictions produce a backlash and disbelief about genuine risks, he warned.

At a conference on “Doomsday Science” in Goettingen, Germany, this fall, scholars reviewed the long line of apocalyptic books, art, philosophy and religion.

“There are real dangers and profound fears,” Mark Walker, one of the conference speakers and a historian of the nuclear age at Union College in Schenectady, N.Y., said in a telephone interview. “Unfortunately, we don’t seem to be scared of the things that are really dangerous, such as a lethal virus or global warming.”

Margaret Kosal, a researcher at Stanford’s Center for International Security and Cooperation, thinks “the biggest catastrophes – 100 million people or more being drastically affected in a short period – will be completely unintended and unforeseen.”

In an e-mail interview, Kosal worried about the rapid spread of germs that resist even the most powerful antibiotics. “We as a nation and as a world should be seriously concerned with increasing antibiotic resistance,” she said.

She also expressed concern about a terrorist raid on a chemical factory or railroad car filled with chlorine, or a biological attack by “a lone or deranged scientist.”

Two years ago, Rees, the British astronomer, bet $1,000 that a mistake in a laboratory or an act of biological terrorism will have killed a million people by the year 2020.

“I fervently hope to lose this bet,” he wrote. “But I honestly do not expect to.”

Perhaps the strangest – and most horrifying – of the doomsday scenarios in recent scientific literature is a new form of matter known as a quark-gluon plasma. It’s already been and will again be the subject of experiments in high-energy physics laboratories.

Collisions of these subatomic particles might create extremely dense objects called “strangelets,” which would have the fearsome ability to keep growing until all matter was consumed.

As Rees described it, “that would rip the fabric of space itself. … The entire galaxy and beyond would be engulfed. … That would be a cosmic calamity, not just a terrestrial one.”

“These scenarios may seem bizarre, but physicists discuss them with a straight face,” he added. “We cannot be sure that the risk is zero.”

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(c) 2004, Knight Ridder/Tribune Information Services.