Days after Donald Trump took the oath of office, the Bulletin of the Atomic Scientists reset the Doomsday Clock to 2½ minutes to midnight, in part because of destabilizing comments and threats from America’s new commander in chief. One year later, we move the clock forward again by 30 seconds, due to the failure of President Trump and other world leaders to deal with looming threats of nuclear war and climate change.

The Science and Security Board for the Bulletin of the Atomic Scientists assesses that the world is not only more dangerous now than a year ago; it is as threatening as it has been since World War II. In fact, the Doomsday Clock is as close to midnight today as it was in 1953, when Cold War fears arguably reached their highest levels.

To call the world nuclear situation dire is to understate the danger — and its immediacy. North Korea’s nuclear weapons program appeared to make remarkable progress in 2017, increasing risks for itself, other countries in the region and the United States. Failure in 2017 to secure a temporary freeze on North Korea’s nuclear development was unsurprising to observers of the downward spiral of nuclear rhetoric between Trump and North Korean leader Kim Jong-un. But North Korea’s developing nuclear program will reverberate not just in the Asian Pacific, as neighboring countries review their security options, but more widely, as all countries consider the costs and benefits of the international framework of nonproliferation treaties and agreements.

Global nuclear risks were compounded by U.S.-Russia relations that now feature more conflict than cooperation. The United States and Russia remained at odds, continuing military exercises along the borders of the North Atlantic Treaty Organization, undermining the Intermediate-Range Nuclear Forces Treaty, upgrading their nuclear arsenals and eschewing arms control negotiations.

Tensions over the South China Sea have increased. Pakistan and India have continued to build ever-larger arsenals of nuclear weapons. And in the Middle East, uncertainty about continued U.S. support for the landmark Iranian nuclear deal adds to a bleak overall picture. A related danger is the rise of cyberthreats targeting national infrastructure, including power grids, water supplies and military systems.

On the climate-change front, the danger may seem less immediate than risk of nuclear annihilation, but avoiding catastrophic temperature increases in the long run requires urgent attention now. Global carbon dioxide emissions have not yet shown the beginnings of the sustained decline toward zero that must occur if we are to avoid ever-greater warming. The nations of the world will have to significantly decrease their greenhouse-gas emissions to manage even the climate risk accepted in the Paris accord. So far, the global response has fallen far short of meeting this challenge.

The Trump administration’s decision essentially to turn a blind eye to climate change transpired against a backdrop of a worsening climate, including exceedingly powerful hurricanes in the Caribbean and other parts of North America and extreme heat waves in Australia, South America, Asia, Europe and California. The Arctic ice cap achieved its smallest-ever winter maximum in 2017. And last week, data from 2017 demonstrated a continued trend of exceptional global warmth.

We believe the perilous situation described here would, in itself, justify moving the minute hand of the Doomsday Clock closer to midnight. But there’s also a real threat posed by a fundamental breakdown in the international order dangerously exacerbated by recent U.S. actions. In 2017, the United States backed away from its long-standing leadership role in the world, reducing its commitment to seek common ground and undermining the overall effort toward solving pressing global governance challenges. We hope this resetting of the clock will be interpreted exactly as it is meant: an urgent warning of global danger. The time for world leaders to address looming nuclear danger and the continuing march of climate change is long past. The time for the citizens of the world to demand such action is now. It is time to rewind the Doomsday Clock.

Lawrence Krauss, chair of the Bulletin of the Atomic Scientists Board of Sponsors, is director of the Origins Project and foundation professor of the School of Earth and Space Exploration and Physics Department at Arizona State University. Robert Rosner, chair of the Bulletin of the Atomic Scientists Science and Security Board, is a distinguished service professor in the Departments of Astronomy & Astrophysics and Physics at the University of Chicago.