What’s it going to take to win American independence from dirty energy?

The Fourth of July seems like a good time to ask — especially as we celebrate the first Independence Day under an administration whose motto might as well be “Make America Suck Coal Again.” (Now watch, Trump will put that on a hat.)

But beyond that, it’s also a good time to ask because of a … let’s just call it a spirited debate that recently broke out between two groups of scientists who work on climate and energy. Both want to see the United States fight climate change, ditch polluting fossil fuels, and ramp up renewables. But there’s a bitter disagreement between them over how it can happen.

The whole thing started in 2015, when Stanford professor Mark Jacobson and some colleagues published a paper arguing that, by mid-century, the United States could be powered entirely by clean energy sources — and by clean, he meant the really clean stuff (wind, solar, hydropower), not the only-somewhat-cleaner-than-coal stuff like natural gas, nuclear energy, and biofuels.

As you can imagine, that got the kind of folks who get excited about clean energy pretty excited. (Bernie Sanders, Mark Ruffalo, big green groups, Grist vet David Roberts. And we were no exception — our editors put Jacobson on the inaugural Grist 50 list of game changers and planet savers.) Better still, Jacobson’s blueprint started to inform policy discussions, with serious people taking the idea of 100 percent renewables pretty seriously.

Still, it’s a long way to go in a relatively short period of time (add up wind, solar, and hydro, and it’s currently just 13 percent of the U.S. energy supply). Many experts sweated the details of the sunny picture that Jacobson and his colleagues presented.

Last month, they did it with the scientific equivalent of a switchblade. Twenty-plus researchers published a study in the Proceedings of the National Academy of Sciences arguing that Jacobson’s original paper (published in the same journal — ouch) “used invalid modeling tools, contained modeling errors, and made implausible and inadequately supported assumptions.”

Those are fighting words for research-types, and Jacobson struck back, which elicited yet another reply. The whole thing probably looked pretty bad to outsiders. In fact, to anyone not enmeshed in the details, it probably looked like a fight over whether it’s even possible to convert the entire United States to clean energy and combat climate change.

Except it wasn’t. Regardless of whether Jacobson took some shortcuts on his road map, both sides agreed that the goal of weaning ourselves off fossil fuels and shutting off greenhouse gas emissions is possible. The question is: What’s the best route to follow?

So rather than continue to focus on an internecine squabble, we talked to six of the smartest energy experts around and asked them to program the GPS coordinates for America’s clean energy future. Here’s how they responded.

It’s too late to stop clean energy

Ramez Naam

, former Microsoft computer scientist, technologist, and science fiction author

It’s true: Wind and solar are intermittent. So how do you deal with that? You really have three choices:

One, build so many wind turbines and solar panels that you can fulfill America’s energy need even when there’s barely any wind or sun. The problem with that is, it’s expensive. You have a lot of capacity you don’t need most of the time.

Two, you build storage for that wind and solar energy. But we don’t really have a viable technology for seasonal storage. [Editor’s note: Folks are working on it.]

Your third option is to keep something that’s not wind or solar running — some nuclear, or maybe some natural gas.

If we had to go off the economics and the technology we have today, we’d say it’s cheapest to take the third option. In the future, the declining cost of tech might change those economics, but overcoming climate change is too important to bet entirely on that.

Here’s my best guess of what the clean energy world of the future looks like: a lot of wind turbines in the Great Plains and Texas, and some offshore. A lot of solar in the West, the Southwest, and the South. Together, solar and wind are providing 70 percent or more of our electricity. Hydro is another 10 percent or more. And we’ve built a lot of long-range transmission.

People think that wind and solar mean getting off-grid or less dependent on the grid, but the opposite is true. You need more grid investment and more movement of energy from the sunniest and windiest places (where it’s cheapest and most reliable to produce) to the places the energy is consumed.

Possibly, in the future, we’ve solved the long-duration storage problem. More likely, there are still nuclear plants running, and there may even be some natural gas plants lingering in the system — not running at full capacity, but they have the ability to power up quickly when there’s not a lot of sun or wind. Along the way, we’ve electrified most of the things that currently run on fossil fuels.

Many people are concerned Trump is dooming us. I don’t think so. We’ve missed the window where policy makers could really stop clean energy. The biggest drivers of clean energy in the United States right now are economics and the states. The congressional districts that produce the most clean energy in the country are almost all Republican. Climate change is hugely polarizing, while clean energy is bipartisan and loved across the board.

The question is no longer if we’ll get to a mostly clean grid, it’s a question of when.

The shiny future

Krishna Kolluri

Varun Sivaram, acting director of the Council on Foreign Relations energy security and climate change program (and member of this year’s Grist 50)

In the United States, wind and solar power just cracked the 10 percent threshold for energy use. (And we are at far more than 10 percent clean energy use, thanks to nuclear and hydro.) But fossil fuels still account for the majority of both electricity use and primary energy use overall, and at no time in the near future will that change.

So we’re not aiming for 100 percent renewable. We’re aiming for near-zero greenhouse gas emissions, or “deep decarbonization.” The target we tend to look at is an 80 to 100 percent reduction in electricity sector emissions by 2050. That’s a goal that we can get our heads around. The strategy looks something like: Make electricity nearly zero-carbon, and then electrify as many end uses as possible. Make transportation run off electricity, make industry run off electricity, and voila, you’re going to get to deep decarbonization of the whole economy.

It’s not feasible with today’s technologies. It could be feasible if we invest in innovation. That can be technological innovation: better nuclear reactors, better forms of energy storage, better solar panels. We could reimagine the way the power grid works. Instead of today’s AC power grid, we could have a bunch of networked DC microgrids that are super efficient. We could have a massive supergrid. We could have…