Calamities, be they natural or man-made, often come with little or no warning. Climate change, however, is different.

Scientists and some forward-thinking military, political, business and other leaders in other fields have been warning the world about the ecological, economic and security threats posed by a warming planet for decades. Now the alarm is amplified by a searing report from the Intergovernmental Panel on Climate Change (IPCC) that depicts a much more ominous and accelerated impact from climate change that could come not in the distant future, but in just 22 years.

Indeed, if by 2040 greenhouse-gas emissions continue at their current trajectory, it likely would result in a warm-up of more than 2.7 degrees Fahrenheit (1.5 Celsius) above preindustrial levels. Among the potential impacts are more extreme droughts, food scarcity, poverty and damage to coastlines and coral reefs.

The cost of inaction is steep. Environmentally, for sure, but also economically: Damage could top $54 trillion. The cost of trying to keep temperatures below these thresholds is technologically possible but not cheap. “Limiting global warming to 1.5 degrees Celsius would require rapid, far-reaching and unprecedented changes in all aspects of society,” the IPCC said. But “there is no documented historic precedent” for such substantial changes.

Then again, nor was there any precedent for marshaling allies to defeat fascism in World War II, or for the ambitious timeline of landing a man on the moon. Yes, it would take an extraordinary, coordinated effort, but mitigating the worst impacts of climate change can and should be done.

Ideally, such a global endeavor would be led by the U.S. in a true example of American exceptionalism. But President Donald Trump has called climate change a Chinese hoax, announced his intent to withdraw from the Paris Accord and negated Obama-era environmental measures. And most Republican congressional leaders similarly deny or denigrate the scientific consensus and are afraid to challenge the president or, more profoundly, the country to accept necessary policy and lifestyle changes.

Trump’s bluster on global warming may embolden other leaders to negate the necessary global response to the crisis. Brazil, for instance, may also withdraw from the Paris pact if the nation elects right-wing populist Jair Bolsonaro as president. Elsewhere, particularly in Europe, the rise of authoritarianism may accelerate if unabated temperatures trigger mass climate-change migration, a destabilizing dynamic that has long worried Pentagon planners.

The dearth of presidential leadership doesn’t mean America can’t act, however. Some states, including Minnesota, have led admirable efforts on renewable energy. Some cities have acted, too. Business leaders can continue to push toward a more sustainable future. And individuals can do everything possible to blunt the dire outcomes of uncontrolled climate change, including changing their own behavior and choosing elected officials willing to acknowledge and act upon this direct threat to the world.

“This report invites us to think about what does it mean to strive in the face of adversity as a society — we cannot pretend this situation is rosy,” Jessica Hellmann, director of the Institute on the Environment at the University of Minnesota, told an editorial writer. But the sooner action is taken, Hellmann added, “the more cost-effective it is, and the more likely it is to be successful. And the longer we wait, the harder it is, the more expensive it will be and the bigger the magnitude of the warming.”

The science, the threat and now the immediacy of climate change are real. Regardless of politics, an effective response is imperative.