Ackman Goes Cold on Tariffs: Warns of 'Economic Nuclear Winter'

​Bill Ackman, the hedge-fund heavyweight who’s usually in Trump’s corner, just hit the brakes on his support. In a fiery Sunday night post on X, Ackman sounded the alarm over Trump’s latest tariff barrage, calling for a 90-day timeout before the U.S. plunges headfirst into what he calls an “economic nuclear winter.”

Why the sudden change of heart? Trump’s new tariffs—blanketing all imports with a 10% tax and hitting allies and foes with even steeper levies—sent the markets into panic mode. Futures were already in free fall Sunday night, and investors braced for a Monday meltdown that could shove the S&P 500 into bear-market territory.

​Ackman warned that if Trump pulls the trigger on these so-called “reciprocal” tariffs come April 9, it won’t just sting—it could paralyze the economy. “Investment will stall, consumers will freeze, and our global reputation will be toast,” he said. His suggestion? Hit pause, negotiate, and dangle the potential for trillions in fresh investment to lure countries to the table.

​The billionaire’s pivot is particularly jarring because, days earlier, he backed Trump’s aggressive strategy, quoting the classic negotiation tactic: “Sometimes the best move is to make them think you’re crazy.” But now that the markets are hemorrhaging, he’s sounding the alarm bells.

While Ackman urged Trump to delay the tariff rollout, Treasury Secretary Scott Bessent brushed off recession fears, boasting that over 50 nations are already reaching out to talk trade. Trump echoed the optimism, saying global leaders are “dying to make a deal.” Still, he hinted that market pain might be part of the cure. “Sometimes you have to take medicine to fix something,” he told reporters from Air Force One.

Not everyone’s buying Ackman’s concern. NYU’s Nouriel Roubini, never shy with criticism, accused him of flipping only when his portfolio started to sweat. Ackman fired back, claiming neither he nor Pershing Square Capital was using risky leverage, and the firm could stomach paper losses without panic-selling.

​Still, with markets in a tailspin, Ackman’s about-face adds fuel to the debate on how far Trump will push his trade war—and what the economic fallout could be.