Several developments have the potential to move the hands of the nuclear doom clock closer to midnight.
A new U.S. nuclear policy has a chance of destabilizing the balance of terror by creating a larger arsenal of smaller weapons.
Smaller weapons are more tempting to use. The argument for so-called "tactical" nukes is that they would destroy a smaller area and create less fallout, making them more "safe" to use than traditional many-megaton bombs. And that could lead to temptation to use them.
Just as importantly, that could give other nuclear-armed powers the impression that the U.S. would be more likely to use the weapons - a dangerous spiral that could culminate with...the end of the world, literally.
The United States is hardly the only nation adding stress to a system that is always a hands-breadth from tragedy.
Russia's President Vladimir Putin has rattled the nuclear sabre, even threatening to station missiles in annexed Crimea. Pakistan, another nuclear-armed country, is a divided nation with government agencies linked to Islamic extremism and a beef with India. India has a beef with Pakistan and territorial disputes with China.
North Korea is a wildcard with an accelerating nuclear program that may still be getting help from Pakistan - which denies it. Recent tests by North Korea and China's lack of overt response has set U.S. teeth on edge.
In the end, the basic question is whether humanity can have such dangerous toys and not use them.
Incredible as it may seem, at the height of the Cold War the world might actually have been safer, experts say. Neither the United States nor the Soviet Union had a death wish, and those were clearly the stakes.
And, of course, nihilistic militants have no such qualms.