As momentum for the Green New Deal grows, so do its detractors. The ambitious plan to fight climate change introduced by Congresswoman Alexandria Ocasio-Cortez and Senator Ed Markey last week has been called everything from “brainless” to “delusional” by conservatives. President Donald Trump said it sounded like “a high school term paper that got a low mark.” Some Democrats have criticized the Green New Deal, too, saying that its goal of net zero carbon emissions by 2030 is unachievable. Others believe the plan doesn’t go far enough.

What, then, do these critics propose instead? What should America do to drastically reduce greenhouse gas emissions and slow catastrophic global warming?

Most Republicans don’t have an answer to that question because they deny that anything needs to be done at all. But as New Yorker staff writer Osita Nwanevu noted on Twitter, those who accept the dire reality of climate change aren’t helping by offering empty critiques.

Some conservatives are getting frustrated with the lack of alternative proposals from the Republican Party, too. “The ‘Green New Deal’ is a bad idea,” Eddie Scarry wrote recently for the Washington Examiner. “But it’s an idea, nonetheless. And the country has shown it’s willing to try new things if it might make lives better. Republicans should learn that quickly, or lose.” Mike Cernovich, the male supremacist and conspiracy theorist, made a similar argument on Twitter.

It’s a strange day when an alt-right troll admits that climate change denial is a losing strategy. But Cernovich is right. Americans increasingly recognize that the world needs to decarbonize quickly. To prevent the planet from warming by 2 degrees Celsius, which many scientists consider the tipping point, the world must become carbon neutral by 2070. How can it meet that goal without the kind of massive government intervention that the Green New Deal proposes? I put that question to the plan’s critics.

The Green New Deal is based on the idea that the only way to solve a problem as enormous as climate change is to change the way society works: to reform American capitalism itself. That’s why, in addition to transitioning the country to 100 percent renewable energy and installing a high-speed rail system to reduce our reliance on cars, Ocasio-Cortez and Markey’s resolution calls for universal health care, a federal job guarantee program, and affordable housing for all. It also says the public should have “an appropriate ownership stake” in the achievements of the Green New Deal.

The latter policies are what bother Joseph Majkut, the director of climate policy at the Niskanen Center, a think tank that describes itself as a group of “globalists” who support “economic and social inequality” but also a “belief in the wealth creating power of free markets.” “[The Green New Deal] is a whole portfolio of things that aren’t necessarily aimed at reducing greenhouse gas emissions,” he said. “I understand the perspective that this is supposed to be a reorganization of the social and political economic order, and climate is a part of that. But to me it feels like climate is just one part of this larger progressive reorganization of society.”

Majkut and the Niskanen Center argue that a federal climate plan should stick to climate-specific policies. He advocates for a nationwide carbon tax; investment in “advanced research and development” for reducing carbon emissions from industry and agriculture; more government subsidies for low-carbon energy sources like wind and solar; and stricter efficiency rules on buildings.

But will those policies be enough to achieve net-zero carbon emissions within several decades? Majkut said he’s not sure, but added that he’s not sure how the Green New Deal would do it, either. “I don’t see how having Medicare for All makes it easier to achieve decarbonization,” he said.

How, I asked, can we make it easier to achieve decarbonization?

“I have absolutely no idea, man,” Majkut said. “Climate change is really hard.”

Ramez Naam, who lectures on energy and environment at Silicon Valley’s Singularity University, outlined similar policy ideas to Majkut in a viral Twitter thread on Friday. But he argued that significant research investments in zero-carbon agriculture and zero-carbon manufacturing—along with government incentives for the technology that emerges—would be enough to achieve decarbonization. “We can figure out how to take agriculture, which is currently 25 percent of our emissions, and do it in a zero carbon way,” he told me. “Then government policy can shape the market and encourage deployment of this new technologies.”

Decarbonization is possible, Naam argued, if the U.S. government invested enough resources in low-carbon agriculture, manufacturing research, and new technologies. “American companies would be the ones exporting the technology for carbon-free cement, carbon-free steel, carbon-free factories, and that would be a huge opportunity,” he said. “I think it will have even more impact than the Green New Deal, because the Green New Deal only decarbonizes the United States. We would only reduce global carbon emissions by 15 percent, and that’s not enough.”

Critics of Naam’s plan might argue that it’s far too risky for a problem as dire as climate change. It relies on scientists’ developing miracle cures for our highest-emitting sectors within just a few years—and then it relies on industry to successfully deploy those cures across the planet. The plan does not seek to reduce excessive consumption, but to somehow make excessive consumption sustainable.

The Green New Deal seems less risky by contrast, since it would mandate the transition to low-carbon energy sources that already exist. The are a lot of questions surrounding the Green New Deal—first and foremost whether it could ever become law—but at least it doesn’t rely on miracle cures. It’s an almost impossible solution to an almost impossible problem.

And yet, even the Green New Deal may not be enough. “We can’t just seek to decarbonize America,” Naam said. “The ultimate climate policy is policy that makes it easier for other countries to decarbonize.” He cited a tweet by Vox’s Matthew Yglesias that called not for a Green New Deal, but a Green Marshall Plan. That frame isn’t exactly right, Naam said: “We shouldn’t be going to countries and building their infrastructure for them.” But it’s the seed, at least, of a potential alternative to the Green New Deal.