Scientific reality makes clear that the only plausible way to preserve a livable climate — and hence modern civilization — starts with aggressive national and global cuts in carbon pollution by 2030.

But political reality makes clear that such cuts can’t happen instantly — and that global action requires leadership from the United States. After all, the U.S. is the richest country in the world and the biggest cumulative source of heat-trapping emissions over the past century.

With eight years of a pro-science president, Barack Obama, the nation made steady progress on reducing emissions and committing to future reductions, enabling a global climate deal in Paris in 2015. But with just two and a half years of an anti-science administration, national and global progress have both stalled under President Donald Trump, who has begun to abandon the Paris Accord and undermine action here and abroad.

That means November 3, 2020 — the U.S. presidential election — is the deadline for Americans who do not want to destroy the health and well-being of current generations, their children, and future generations. If Trump is reelected, the prospects for the necessary national and global cuts in carbon pollution by 2030 will be gone.

Why are deep cuts by 2030 so important?

Back in October 2018, the nations around the world unanimously approved a landmark report from scientists warning that we must make rapid reductions in global carbon dioxide emissions by 2030 in order to have any plausible chance of averting catastrophic climate change.

That report — published by the U.N. Intergovernmental Panel on Climate Change (IPCC) — led to headlines like “We have 12 years to limit climate change catastrophe, warns UN” by The Guardian, and “The world has just over a decade to get climate change under control, U.N. scientists say” from the Washington Post.

But when freshman Rep. Alexandria Ocasio-Cortez (D-NY) made the exact same point this January — that U.S. millennials fear “the world is going to end in 12 years if we don’t address climate change” — the right-wing and even some in the media pounced.

So, ThinkProgress contacted leading experts on exactly what the science says. They confirmed that, yes, as Ocasio-Cortez said, the world must act fast if we are to maintain any plausible hope of avoiding the catastrophic impacts that come with warming of 2 degrees Celsius or more above pre-industrial temperatures.

For instance, climatologist Michael Mann told ThinkProgress via email in January, “Projected impacts look especially bad beyond 2°C or so of planetary warming.”

“And there is no scenario for stabilizing warming below 2°C that doesn’t require rapid reductions in carbon emissions over the next decade,” Mann added.

The IPCC report noted, for instance, that “Limiting global warming to 1.5°C rather than 2°C is projected to prevent the thawing” of as much as 1 million square miles of permafrost. And that matters because the northern permafrost contains twice as much carbon as the atmosphere does today.

So, we face the very real possibility of a snowballing catastrophe — where global warming of 2 degrees or more thaws a huge area of permafrost, and the resulting carbon emissions released because of this then creates considerably more warming that in turn releases yet more heat-trapping gases from the permafrost.

Andrew Jones, co-director of Climate Interactive, a U.S. think tank that generated some of the scenarios the IPCC used in its report, told ThinkProgress he “definitely” agreed with Mann’s assessment. Rapid reductions means a 30-50% decrease in global emissions by 2030, rather than the 10% increase we are currently looking at.

Into this discussion over rhetoric comes a new article in journal Nature Climate Change, “Why setting a climate deadline is dangerous.” In it, scholars from Japan, the U.K., and Germany argue “a 2030 deadline arises from political (mis)use of science in setting an artificial deadline.”

The article is deeply flawed. For instance, the authors write of the IPCC’s “estimate of the remaining time to reach 1.5°C — a likely range of 12–34 years from 2018. This is where the ‘12 years’ rhetoric originates.”

But that’s not accurate. The ’12 years’ rhetoric does not originate from the fact that we might hit 1.5 degrees Celcius in 2030. It originates from the fact that if we don’t make very deep cuts by 2030, we have no possible chance of keeping below 1.5 degrees — and if we don’t make deep cuts by 2030 we are going to blow past 2 degrees.

Also, the new article’s concerns about deadlines are mostly hypothetical. For instance, one of the biggest problems they allege is that: “A more fundamental problem with deadline-ism is that it might incite cynical, cry-wolf responses and undermine the credibility of climate science when an anticipated disaster does not happen.”

But the people using the 2030 deadline aren’t saying any specific disaster will happen immediately after missing such a deadline. They are saying if we don’t make deep cuts by 2030, then we can’t stop catastrophic climate change in the ensuing decades.

The fact is, all the major climate change impacts — like sea level rise, Dust-Bowlification, and temperature rise — are irreversible over a span of centuries if not millennia. The IPCC made that very clear in its big 2014 “synthesis” report. The summary of that report for policymakers, which was signed off by every major country, mentions “irreversible” 14 times and has extended discussions of exactly what it means and why it matters. Deadlines matter.

ThinkProgress asked Dr. Mann to comment on this new article about deadlines. “We should of course be as clear as possible about what we mean when we talk dangerous warming limits and pathways for limiting warming below them,” he wrote in an email.

“But saying there should be no targets or timelines at all is really just giving a free pass to polluters,” he added. “It’s a welcome message to the forces of denial and delay.” And those forces currently control the highest office in the land.

If the world is to have any plausible chance of saving the climate, we need the strongest possible action by 2030, and that means we need to elect a president in 2020 who understands the urgency, and who understands that deadlines matter in the face of irreversible catastrophe.

This first appeared in Think Progress here.