Scientists must step up to avert a nuclear breakout

Nature

by Karen Hallberg

February 25, 2026

AI-Generated Deep Dive Summary

The expiration of the New START treaty on February 5 marks a significant escalation in nuclear risks between the United States and Russia, two of the world’s largest nuclear powers. This agreement, which had capped both countries’ arsenals and provided critical transparency and stability for over three decades, is now gone. The absence of this binding treaty increases the likelihood of a renewed arms race, global proliferation, and potential nuclear conflict—a scenario that scientists, policymakers, and the public must address with urgency. Historically, treaties like New START have been instrumental in reducing the global nuclear arsenal from 70,000 warheads in the mid-1980s to approximately 12,300 today. These agreements not only curbed the number of deployed strategic warheads but also fostered a framework of mutual restraint and verification that has kept nuclear risks in check for decades. Now, without New START, both nations operate without these critical guardrails, raising concerns about predictability and transparency in their nuclear strategies. To mitigate this growing threat, US and Russian leaders could unilaterally commit to a one-year moratorium on exceeding the treaty’s limits, as proposed by Russian President Vladimir Putin last year. This step would demonstrate a shared commitment to stability and set the stage for broader negotiations on a modernized security framework. It would also reinforce the principles of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), particularly its Article VI mandate to pursue disarmament. Scientists, too, have a vital role to play in addressing these risks. The Bulletin of the Atomic Scientists’ recent move to set the Doomsday Clock

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Originally published on Nature on 2/25/2026