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Three million jobs lost. More than a trillion dollars in uncompensated care. Twenty million people losing health insurance, or maybe it's 52 million.

Supporters of the Affordable Care Act have floated an armada of disaster scenarios as triumphant Republicans in Congress promise to immediately repeal President Barack Obama’s signature health care reform legislation.

A man fills out an information card during an Affordable Care Act outreach event hosted by Planned Parenthood for the Latino community in Los Angeles, California September 28, 2013. JONATHAN ALCORN / Reuters file

Report after report from advocates and independent researchers alike have been outlining harms in apocalyptic detail.

The latest, out Friday from the Milken Institute School of Public Health at George Washington University and The Commonwealth Fund, predicts as many as 3 million jobs would be lost by 2021 if key aspects of the Affordable Care Act (ACA) are rescinded.

“Of the 3 million jobs that are lost, about 1 million are jobs lost in the health care field,” said Leighton Ku, who directs GWU’s health policy research center. Other jobs would be in construction, retail and finance as people who lose their jobs or who lose health insurance spend less money themselves, Ku said.

Related: Replacing Obamacare Will be Hard and Repealing it Just as Hard

Obama himself weighed in, calling the repeal-first, replace-later approach "reckless" and "irresponsible."

“Rather than jeopardize financial security and access to care for tens of millions of Americans, policymakers should develop a plan to build on what works before they unravel what is in place,” Obama wrote in a commentary rushed online into the New England Journal of Medicine Friday.

"This approach of ‘repeal first and replace later’ is, simply put, irresponsible — and could slowly bleed the health care system that all of us depend on,” Obama added.

“If a repeal with a delay is enacted, the health care system will be standing on the edge of a cliff, resulting in uncertainty and, in some cases, harm beginning immediately,” he said.

“If we make that money go away, there are going to be consequences."

The team from George Washington University and The Commonwealth Fund used a computer model and plugged in a moderate Obamacare repeal scenario to gauge its impact.

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“The most common theme we have seen is they want to cancel the Medicaid expansion, cancel premium tax credits and cancel the individual mandate,” Ku told NBC News.

Related: Repeal Obamacare? Maybe Not, Says Trump

These are provisions that helped get health insurance to an estimated 20 million people, most of whom did not have coverage before. The federal government paid for 31 states and Washington, D.C. to expand the Medicaid program to more people. Nineteen states have declined to do so.

The federal government also subsidizes health insurance premiums to the tune of $32.8 billion for people using the Obamacare exchanges to buy private, individual health insurance, and the law requires almost everyone to have health insurance or else pay a small tax.

“If we make that money go away, there are going to be consequences,” Ku said. Not only will people losing health insurance spend less on health care; they’ll spend less on everything.

Related: How Much do You Know About Obamacare?

The left-leaning Urban Institute released a separate report Thursday that projected $1.1 billion in “uncompensated care” if the law is repealed.

It’s a fuzzy and hard-to explain concept that boils down to charity care, said John Holahan, who wrote the report. “It’s a loss of revenue. It has to be paid for somehow,” he said. It ranges from hospitals providing free care to people without insurance, to doctors treating people without payment, or for payments that don’t cover their real expenses. Ad it includes medical care that patients have to pay for out of their pockets.

“What’s going to be in the repeal bill? What will be repealed? When will it be repealed? It’s all really up in the air."

The nonpartisan Congressional Budget Office said in 2015 that an Obamacare repeal would drive up the U.S. budget deficit by as much as $353 billion over 10 years and projected that 24 million people would lose their health insurance.

Joe Antos of the right-leaning American Enterprise Institute scoffs at the idea that anyone can predict even what the GOP-led Congress will do, let alone what the effects will be.

“What’s going to be in the repeal bill? What will be repealed? When will it be repealed? It’s all really up in the air,” he said.

Related: More than 6 Million Sign Up for Obamacare

But the doubt itself is causing disruption, said Ceci Connolly, president and CEO of the Alliance of Community Health Plans and a longtime health policy expert.

“I think it’s incredibly difficult to forecast the implications of where we are headed,” Connolly told NBC News.

For instance, health insurance companies could just drop out of the markets if they see an uncertain future. Or people with health insurance may stop paying premiums, and lose coverage, if the next few years look uncertain.

“I am concerned that they are deadly serious about overturning the Affordable Care Act as quickly as possible without having a plan for replacing it. I think those promises were made loud and clear and politicians feel the need to deliver on that promise. And it’s sad because some of the neediest in our society may pay the price during what could be a very disruptive, chaotic period.”

“If you wait until everything is settled, then it is too late. We want to inform the debate."

Most Americans have coverage through an employer, and another big chunk get Medicare or standard Medicaid. Fewer than 10 percent are covered directly by Obamacare’s individual insurance market or by its expansion of Medicaid.

But that’s still 20 million people. And more are affected by its provisions that stop insurance companies from capping their coverage, or refusing to cover “pre-existing” conditions. The non-partisan Kaiser Family Foundation, which studies health care issues, said last December that 52 million Americans have pre-existing medical conditions that, pre-ACA, insurance companies could often refuse to cover.

Related: Obamacare Premiums Are Going Up

There’s no doubt that Obamacare has not fixed the flawed U.S. health care system. Insurance premiums, which started rising long before the law took effect, are still rising. Health insurance can be hard to navigate and medical care costs more in the U.S. than anywhere else.

“I am the first to say we can make improvements,” Obama admitted in his commentary. “For example, allowing Medicare to negotiate drug prices could both reduce seniors’ spending and give private payers greater leverage.”

That’s why Antos predicted that cooler heads will eventually prevail and prevent the disasters that other think-tanks are predicting.

“Unfortunately, we have had eight years of extreme statements from both sides. It is time for everybody to calm down,” he said.