Roughly two-thirds of the way through last week’s Democratic debate in Brooklyn, things got interesting. The night to that point had been a rehash of every other debate, with Bernie Sanders and Hillary Clinton hollering from their respective ramparts the same arguments we’ve heard over and over. As a wraithlike Wolf Blitzer presided over the spotlit chasm between the candidates, Sanders advocated a complete rupture with the dark-money-engorged American politics as we know it while Clinton, implicitly at least, asked voters to enshrine it. Then, in the midst of this ceremonial shaking of fists, the conversation turned to climate change.

“Let me start by saying we need to talk about this issue,” Clinton opened, only to have Bernie, who’s been talking about it for years, lambaste her. As he often does, Sanders went after Clinton’s inscrutable relationship with fracking interests, with the oil and gas lobbyists who bundled donations to her campaign, and with the large financial institutions with substantial energy holdings that have given her millions. (Hedge fund D.E. Shaw, to name one, ponied up $1.5 million to her campaign and owns $470 million in shares of oil refinery behemoth Marathon Petroleum.)

Then Sanders turned to the carbon tax — the plan to charge air polluters a fee for each ton of emitted CO2 — and finally we had a show.

“Are you in favor of a tax on carbon so that we can transit away from fossil fuel to energy efficiency and sustainable energy at the level and speed we need to do?” Bernie asked his opponent.

The moment stretched on; a subdermal twitch darted across Clinton’s face. Then she gave this a whirl: “You know, I have laid out a set of actions that build on what President Obama was able to accomplish, building on the clean power plan, which is currently under attack by fossil fuels and the right in the Supreme Court, which is one of the reasons why we need to get the Supreme Court justice that President Obama has nominated to be confirmed so that we can actually continue to make progress.”

Sanders waved off the smoke bomb. “Are you for a tax on carbon or not?” he demanded, as if there were any hope of getting a straight answer. (He didn’t.)

Decades of tobacco-style obfuscation and legislative timidity — both purchased outright by the fossil fuel industry — have virtually guaranteed that the Antarctic ice shelf will collapse by mid-century and plunge coastal cities beneath three feet of seawater by this century’s end. Temperature increase has become a matter not of if, but when, and how much: The 3.6-degree rise seen as the upper limit for containable climate change is already considered a sure thing within most scientific circles. Now the question is whether agricultural and urban infrastructures will be able to withstand the resulting savagery of destabilized weather systems. Insurance companies are already suing local governments over their complete unpreparedness for floods and high winds. More frequent historic droughts, and their attendant crop failures and mass migrations, have forced the Pentagon to reconsider the national defense strategy. Many observers expect a pestilence of violence on top of the biological plagues epidemiologists say will flourish in this coming new normal. In fact, there are plenty of signs it has already begun.

Clearly, the time for advocating an incremental approach to global warming has long since passed. Yet when it comes to averting the greatest catastrophe technological civilization has ever faced, Clinton’s fabled realism makes like the polar ice caps and quickly melts away.

Ironically, the carbon tax is one of the lower-hanging policy fruits — versions already exist in nearly forty countries. Finland was the first national government to adopt it, in 1990. An attenuated cap-and-trade system, which allows companies to receive rebates from the state for lowering their emissions, is currently in place in California. And although the exact price of a carbon tax is still a matter of debate — the U.S. Interagency Working Group on the Social Cost of Carbon, a White House initiative, recommends assessing $12 to $129 for every ton of carbon dioxide — even a modest levy could deliver huge benefits to both the economy and the environment. A study by Tufts economist Gilbert Metcalf calculates that just $15 per ton would cut domestic greenhouse gas emissions by 14 percent and raise $82.1 billion in tax revenue; if the top twenty emitting economies charged $57 a ton by 2020, global emissions would be down 11 percent — all but meeting the goal set by the U.N. Environmental Programme.

Not to mention, a carbon tax is the economic policy preferred by actual economists. In 2013, Gregory Mankiw, the conservative Harvard economist who shaped President George W. Bush’s fiscal policy and advised on candidate Mitt Romney’s, called it a “no-brainer”: “I am confident that the economics profession has it right,” he wrote in the New York Times. “The hard part is persuading the public and the politicians.”

Sanders has bludgeoned the Clinton campaign with the charge that Hillary is in thrall to the fossil fuel industry, a claim she has denied repeatedly. And yet when Bernie put the carbon tax question to her, she simply sidestepped it. Such is the state of modern obscurantist politics: The closest we may ever get to seeing the influence of money on Clinton’s position was that moment, that twitch, that bridling against the tax’s inexorable logic. In her refusal to admit the obvious, overwhelmingly agreed-upon, scientifically sound solution — in that moment of muteness — she proved Sanders right.

Shining a light on the accommodation that takes place between money and policy, so insidious as to be almost subconscious at times, is a slippery thing. But I saw that dynamic clearly at the National Audubon Society, a national bird conservation nonprofit where I was once an editor at the in-house magazine. During my tenure, reporters and editors were discouraged from aggressively promoting a carbon tax. And when we produced an entire issue devoted to climate change, after Audubon announced that the subject would be central to its mission going forward, we were forbidden by CEO David Yarnold from mentioning a carbon tax anywhere in it, for fear of alienating the great middle of the donor base. Just like the Clinton campaign, it was cash über alles.

In its lacerating interview with Sanders a couple of weeks back, the New York Daily News grievously wounded him, exposing the Bern’s tendency toward naïve sloganeering. It also raised the likelihood, already high, that Hillary will eventually take the nomination. Should she ultimately take the White House itself, she will bring with her an expedient environmental incrementalism that we can no longer afford. Bernie’s magical thinking may be his downfall, but it’s nobler than Hillary’s compromise politics. Pragmatism is no virtue when it fails to produce a solution; when it makes things worse, it’s venal.

The mental and moral seizure Clinton experienced at the debate is the same one keeping our larger politics in irons. Only when the influence of wealth is stripped from the political order will we be able to make headway once again. But at this rate, we’re going to need a bigger boat.