During his campaign for president, Donald Trump promised to end action on climate change and kill the climate treaty adopted in 2015 in Paris. To truly understand why that’s such a big deal—perhaps the biggest deal ever—you need to think about a few things.

Yes, you need to think about the oft-repeated but nonetheless true and alarming statistics: 2014 was the hottest year ever recorded till 2015 snatched the crown—till 2016 obliterated the record. Last summer featured some of the hottest days ever reliably recorded on this planet: 128 degrees Fahrenheit in cities like Basra, Iraq—right at the edge of human endurance. Global sea ice has been at a record low in recent months.

But you need to think about more than that.

Think about the slow, difficult, centuries-long march of science that got us to the point where we could understand our peril. Think of Joseph Fourier in the 1820s, realizing that gases could trap heat in the atmosphere; John Tyndall in the middle of that century, figuring out that carbon dioxide is one of those gases; and the valiant Svante Arrhenius in the 1890s, calculating by hand how the global temperature rises in lockstep with carbon dioxide levels. Think of Hans Suess and Roger Revelle in the 1950s, fumbling toward an understanding that the oceans would not absorb excess CO 2 —the first modern realization that CO 2 must be accumulating in the atmosphere and hence, as Revelle put it, “human beings are now carrying out a large-scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future.” Think of Charles Keeling in 1958, installing the first real CO 2 monitor on the side of Mauna Loa and for the first time watching the CO 2 level steadily rise. Think of the scientists who built on that work, using satellites and ocean buoy sensors to erect a scaffolding of observations; think of the theorists who used that data and the new power of supercomputers to build models that by the 1980s had made it clear we faced great danger. Think of the men and women who educated those scientists and who built the institutions in which they were educated and who organized the learned societies that supported them. And think of the forums—like the UN and its Intergovernmental Panel on Climate Change—that brought them together from across the planet to combine their knowledge.

The Paris accord would limit the global temperature rise to 2 degrees Celsius—unless the incoming administration dismantles it. Jonathan Raa/Pacific Press/LightRocket/Getty Images

All this, taken together, is one part of what we call civilization.

Now think of the men and women of the diplomatic corps, who over generations have learned to build bridges across nations, to sometimes reconcile disputes short of war. The Paris accord was a triumph for them, not because it solved the problem (it didn’t, not even close) but because it existed at all. Somehow 195 nations—rich and poor, those with oil beneath their sand and those that have to import it—managed to agree that we should limit the rise in temperature to 2 degrees Celsius this century and set up an intricate architecture to at least begin the process. That too is an aspect of what we call civilization.

None of this should be taken for granted. The building blocks of our common home—science and diplomacy and also civility—are hard-won, and history would indicate that they can fade fast. In fact, we now seem likely to start tossing them away based on nothing but the politically useful whim that climate change is a hoax. When Trump announced on the campaign trail that he would “cancel” the Paris agreement, it represented an assault on civilization as surely as announcing that he would jail his political opponent represented an assault on democracy. He’s backed down from the latter plan and, under pressure, said he now has an “open mind” about Paris—though his chief of staff clarified that his “default position” is that climate change is bunk. In any event, he has packed his transition team and cabinet with a small band of climate deniers who have blocked action for years. Already they’ve announced their intention to end NASA’s climate research, which has been a bulwark of the scientific edifice. If they have their way, there will be no more satellites carefully measuring the mass of ice sheets so we can track their melt, no more creative and fascinating “missions to planet Earth” that the space agency has run so successfully. We seem intent on blinding ourselves, on ripping out the smoke detectors even as the house begins to burn.

Trump’s team can’t, by themselves, change everything. Engineers and entrepreneurs have done their jobs magnificently over the past decade, as the price of a solar panel has fallen 80 percent. Because of that work, the potential for rapid change is finally at hand. Denmark generated nearly half its power from wind in 2015, and not because it cornered the world’s supply of breeze. Given the new economics of renewable energy, progress will continue. But the climate question has never been about progress per se; we know that eventually we’ll move to the sun and wind. The issue has always been about pace, and now Trump will add serious friction, quite likely shifting the trajectory of our path enough that we will never catch up with the physics of climate change. Other assaults on civilization and reason eventually wore themselves out—fascism, communism, imperialism. But there’s no way to wait out climate change, because this test has a timer on it. Melt enough ice caps and you live on a very different planet. Either we solve this soon or we don’t solve it. And if we don’t, then the cascading crises that follow (massive storms, waterlogged cities, floods of migrants) will batter our societies in new ways that we are ill prepared to handle, as the xenophobia of this election season showed.

Which is why we need to rise to the occasion. Not only in our day jobs but in our roles as citizens—of city, state, country, planet. Engineers should, by all means, keep developing the next generation of batteries; but that work is merely necessary now, not sufficient. We must not watch idly as Trump takes a hammer to the mechanisms of our civilization, mechanisms that can’t be rebuilt in the time we have. We need to resist in all the nonviolent ways that we’ve learned over the past century and in new ones that the moment suggests. There will be marches and divestment campaigns, pressure to be put on city halls and statehouses. We will not lack for opportunity. If many join in, then civilization will not just endure but will emerge stronger for the testing, able to face our problems with renewed vigor. At best, it’s going to be a very close call.

Bill McKibben* is the Schumann Distinguished Scholar in Environmental Studies at Middlebury College and founder of global grassroots climate campaign 350.org. *

This article appears in the February issue. Subscribe now.