BioEd Online

The Bulletin of Atomic Scientists has moved the hands of its Doomsday Clock to five minutes before midnight the metaphorical marker of the end of humanity.

Two factors prompted the Bulletin's board to move the clock forward by two minutes: the spread of nuclear weapons and, in a first for the group, climate change. "The unthinkable seems closer now, in some ways, than it ever was," says Lawrence Krauss, a physicist at Case Western Reserve University in Cleveland, Ohio, and a member of the Bulletin's board.

Several prominent scientists made the announcement at a press conference held jointly in Washington and London.

The chief reason for the move is the dawn of a "second nuclear age", in which far more countries can acquire nuclear technology. The Bulletin cited North Korea's October test of a nuclear device, the nuclear smuggling network of Pakistani scientist A. Q. Khan, and the diplomatic failure to halt Iran's nuclear programme as examples of the growing threat from proliferation.

It also pointed to the nuclear stockpiles of the United States and Russia, which together possess around 26,000 warheads. Although the threat of global nuclear annihilation has declined, the threat of a regional war that could kill millions has grown, says Martin Rees, an astronomer at Cambridge University, UK: "There is now more chance than ever of a few nuclear weapons going off in a localized conflict."

Branching out

The Bulletin's second concern, climate change, represents a new direction for the organization, which a group of Manhattan Project scientists started in 1945 to warn of the threat of nuclear annihilation. "When we looked at doomsday, we realized that there were other technologies and trends that we needed to include," says Kennette Benedict, the Bulletin's executive director.

After considering several threats, including nanotechnology and bioterrorism, the group decided that the dangers of climate change are almost as dire as those of nuclear weapons.

The Doomsday Clock was unveiled in 1947, set at seven minutes to midnight. Its hands have been moved forward or back 17 times before the latest announcement. It came closest to midnight, within just two minutes, in 1953, when the United States and the Soviet Union tested hydrogen bombs within nine months of each other. "The world has come to the brink of disaster on more than one occasion," says cosmologist Stephen Hawking. "But for good luck, we would all be dead."

The last adjustment was in 2002, when the clock was moved forward two minutes in response to the 2001 terrorist attacks on the United States and the Bush administration's nuclear policies, such as its withdrawal from the anti-ballistic missile treaty.

The decision to move the clock is no surprise, says Daryl Kimball, executive director of the Arms Control Association, a non-profit think tank in Washington DC: "2006 was clearly one of the worst years in terms of trying to stop the spread of the bomb."

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