Sometimes the most vicious fights occur over the smallest differences. Brutal battles have pitted Catholics that kneel in prayer against Protestant sects that stood before the same God. There’s a (possibly apocryphal) story from the U.S. House of Representatives about a senior politician explaining that internal conflict between Congressional chambers was more important than fights between Republicans and Democrats. “Republicans aren’t the enemy,” the Democratic old timer says in one version of the story. “Republicans are the opposition. The Senate is the enemy.”

The scientists and activists working to reverse climate change are no different. The infighting can be savage.

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It may be a tautology, but “at the most basic level, anyone interested in addressing climate change knows we have to limit greenhouse gas emissions,” said Noah Kaufman, an economist at Columbia University’s Center on Global Energy Policy. The problem is, those who share that goal disagree about the best way to pursue it.

The roughest head-knocking has been between the energy wonks who think we should use whatever power sources necessary to eliminate emissions — nuclear, biofuels, carbon-capture — and those who think renewable energy is the only answer.

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The science historian Naomi Oreskes accused James Hansen, the well-known NASA climate scientist, of engaging in “a new form of climate denialism” for saying the world needs nuclear power. Tisha Schuller, an environmentalist who came to think fracking could help reduce emissions, received regular death threats. Activists even distributed pictures of her children. The fights rage on social media, and recently they spilled into the courts.

In November, Mark Z. Jacobson, a Stanford researcher, renewable-energy champion, and a 2016 Grist 50 member, sued a group of scientists for publishing a critique of an influential paper he had written laying out a path for the United States to run purely on renewables. (He later dropped the suit.)

“People tend to either agree on the goals, or on the means — if you want to get something dramatic done you have to agree on both,” said Jane Long, a senior consulting scientist at the Environmental Defense Fund and one of the researchers who critiqued Jacobson’s paper. “I think the kind of changes we contemplate isn’t the kind we can accomplish without alignment of both goals and means.”

Amid all this rancour, it’s easy to forget that all these people are on one side of a climate fight; they agree about more than they disagree.

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“Even though [the debate] consumes a lot of my time and other people’s time, it’s sort of beside the point,” Jacobson told Grist. “I’d say there’s no disagreement on 90 percent of our plans.”

So where’s the common ground among all these scientists, academics, and advocates who care about climate change? What are the things that we’re going to need no matter what path we take? Here’s a rundown of broad areas of agreement. Consider it a checklist — or rather, a to-do list — for climate hawks.

You pollute, you pay.

How much do you have to pay to use the atmosphere as a dump for greenhouse gases? For most people and businesses, it’s totally free. Make polluting expensive, and it would cut the amount of greenhouse gases people spew.

“We should all be able to get behind tech-neutral policies to reduce greenhouse gases,” Kaufman said. You could do that by putting a price on carbon — as some 40 countries from Denmark to China have done — or by regulating pollution, punishing companies for releasing methane into the atmosphere. Either one encourages the development of better technologies without causing a fight over exactly which technologies should win.

Grist / Alexandros Maragos

It’s a pattern that runs throughout history. People assume they can pollute for free until the pollution builds up and becomes a serious problem. Then — under duress — they start paying for the trouble. Consider regular old trash. When neighbors live far apart from each other, they can toss garbage out the window without worrying about the consequences. But it’s a different story in cities.

In 1866, New York City told residents they needed to stop the “throwing of dead animals, garbage or ashes into the streets.” Soon, New Yorkers started paying to get their waste picked up. Without a free pass to pollute, the carriage operators who had been leaving dead horses in the streets were at a disadvantage when a new technology came along that didn’t produce piles of manure and leave carcasses behind. At the time, nobody worried that this new horseless carriage would dump carbon into the air. But today that carbon is piling up.

Putting a price on carbon emissions is the same as charging people for the dead animals and ashes they toss into the road. A tax or a regulation curbing emissions would have the same result, Kaufman said. Both would raise the cost of polluting and also raise the rewards for any modern-day Henry Fords developing revolutionary technologies.

Make everything run on less energy

For the better part of human history, creating light often meant tons of work and environmental damage. In the past, people managed to get their light by burning beef fat, storm petrels (a fatty seabird), and sperm whale oil. These were really crappy, inefficient, polluting ways of getting illumination. (It would have taken me at least 10 storm petrels to write this piece, I’m guessing.) Modern LED lights, by contrast, require a tiny trickle of electricity.

It wastes a lot of energy — not to mention birds — if you have teams of workers slaughtering storm petrels, drying them, sticking wicks down their throats, and delivering them to markets. Improving efficiency means cutting out that wasted time and money.

The United States wastes 70 percent of the energy that powers it every day. That’s a massive amount of energy just waiting to be tapped. A more efficient way would use more energy without emitting more carbon.

“I don’t think anyone disagrees that efficiency will help,” Jacobson said.

The most obvious example is gas mileage. Back in 1950, the average car could travel 15 miles on a gallon of gas. By 2010, it could travel more than 23 miles on that same gallon. Cars could get a lot more efficient, still — for every 20 gallons you put in the tank, only five gallons turn into the kinetic energy moving the car; the rest gets wasted as heat. Other obvious steps: replace incandescent light bulbs, insulate homes, get low-gas-mileage cars off the roads. And much else.

“Radical efficiency improvements make it easier to address the climate problem,” said Glen Peters, research director at the Center for International Climate Research in Norway. On this, Peters mused, “I suspect we all agree.”

More sun and wind

In 1977, solar photovoltaic panels were for wild-haired inventors and eccentric millionaires. Back then, the cost of buying a one-watt solar panel was $77; today the cost has fallen to 30 cents. Year after year, the price of solar has cratered faster than the experts predicted. The same is true, to a lesser degree, with wind energy. In many places, wind and solar are simply the low-cost option, which means that building more can save money and also reduce emissions.

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There was general agreement among all the climate researchers I talked to that it makes sense to switch to renewables when it’s the cheapest carbon-free option. The fierce disagreement comes when they talk about paying for renewables when they’re more expensive than, say, nuclear power. Jacobson and a few other scientists think that going 100 percent renewable is the cheapest option. But the majority of researchers think that it would get very expensive to build enough renewables to power the entire country through the darkest days of winter.

“I’ve heard people arguing for 50, 60, 80, and 100 percent renewable,” said Melanie Nakagawa, who worked on climate policy in the Obama administration and now heads up climate strategy for a growth equity fund for climate-related technology at the investment firm Princeville Global. “At some point that percentage matters from a policy perspective,” she explained, but worldwide we’re not close enough to any of those percentages to chill the renewables market. Renewables — mainly hydropower and biofuels — currently account for 10 percent of the country’s energy needs.

Electrify (nearly) everything

Back when President Obama was in the White House, it was Kaufman’s job to go through the various climate plans and scenarios coming from different parts of the executive branch and make sure everyone in the administration was up to speed. He noticed that all the plans to reduce emissions advised plugging a lot more of the country into electricity.

Electricity currently powers a quarter of the U.S. economy. The other three quarters are cars and trucks using gasoline, factories using quadrillions of British thermal units to forge metals and refine petroleum, and buildings heated by gas or propane.

Switching more of these cars and furnaces to run on electricity would allow us to tap into low-carbon energy from renewables and nuclear plants. A little over 1 percent of new cars sold run on electricity right now. To have a shot at keeping global warming under 2 degrees C — the goal set in the Paris Agreement — 10 percent of cars on the road would need to be electric by 2030, according to one scenario plotted by the International Energy Agency.

Grist / Martin Pickard / Getty Images

It’s part of a two-step recipe for eliminating emissions that has become almost a cliche among energy wonks. Step one: Add more low-carbon electricity (solar, nuclear, hydro, wind) to the grid. Step two: Electrify everything.

“There’s broad agreement that we need to dramatically expand electricity to transportation and industry,” said Trevor Houser, climate and energy expert at the research firm, the Rhodium Group. There are some debates around the edges about just how much electrification is practical — maybe not everything — but the consensus is mighty broad.

More electric storage and transmission

Electricity has no shelf life. Unlike a can of tuna that can spend years in hiding, electricity needs to be bought the moment it’s made. Make more electricity than people want at any particular moment, and you can cause fires. Make too little, and you can cause brownouts. That’s why big batteries are so appealing. But even the giant batteries that Tesla is building look tiny if you consider the amount of storage we need to keep the lights on when the sun goes down.

People are trying all kinds of crazy ideas to store energy. They’re forcing air into underground caverns then using the breeze to power turbines when it comes gushing out. They’re using excess electricity to drive trains full of rocks up a mountain, then recapturing some of that energy when they come back down.

If someone figures out a way to extend the shelf life of electricity on the cheap, it will help in every carbon-cutting scenario, whether it’s 100 percent renewable or 100 percent nuclear.

The other way to handle the mismatch between electric supply and demand is to send electricity farther afield. If it gets really windy in Wyoming, and the turbines there start producing too much juice, the state could send that extra electricity to big cities in California.

Well, it could if a major power line connected the two states.

“The transmission system we have today wasn’t built to get to zero carbon,” said Dan Kammen, Director of Renewable and Appropriate Energy Laboratory at the University of California, Berkeley. “Those power lines don’t go to the best wind areas in the mountain states, they don’t go to the best solar areas in the Southwest.”

Most clean-energy scenarios rely on new transmission wires to connect the places with too much electricity to the places with too little, balancing things out.

Source: U.S. Energy Information Administration, High-Voltage Direct Current Transmission Report

More research

Everyone I talked to agreed that the government should be spending more money researching the most challenging problems that stand in the way of weaning ourselves off carbon. It might help to think of climate change as a national security issue, many of them say.

A few years ago, Constantine Samaras, who studies solutions for climate change at Pittsburgh’s Carnegie Mellon University, pointed out on the New York Times’ Dot Earth blog that the government budget doesn’t treat climate change like a true threat. “In the aftermath of the terrorist attacks of September 11, 2001, the R&D budget for counterterrorism grew to almost $2.7 billion in 2003,” he wrote, more than a 500 percent increase in two years. The research and development budget for energy technology and climate change was flat. “We correctly reacted to counterterrorism with enhanced R&D after 2001,” Samaras wrote. “Yet on energy and climate change we’re effectively just muddling through.”

Where should research money go? There’s widespread agreement that we should look into a low-carbon solution for air travel and trucks making long-distance hauls. That appears to be where the agreement stops. When I asked what else deserves funding, I heard a long list of options including advanced nuclear reactors, fusion, and turning air into liquid fuel. The consensus fractured.

Looking forward

Ideally, climate and energy experts could sit down and hash out a consensus on a master plan that would, say, allow us to build only the power plants we really need. But experimentation, failure, politics, and infighting seem to be inescapable elements of any ambitious human endeavor. Success is forged in the crucible of conflict, I guess.

But if we get too wrapped up in these captivating fights — all over how we produce electric power — we’ll miss some big opportunities. “We’d be better off if we took some of the creative energy expended on that debate in the power sector and applied it to other sectors — which, by the way produce 75 percent of the emissions,” the Rhodium Group’s Houser said.

That’s exactly the issue: These disagreements concern just a quarter of the pollution problem that’s driving climate change. The sooner we can agree on a way forward, the quicker we can move on to the rest of the problem. And there’s so much agreement among these experts already: They all are trying to cut greenhouse gases, and would like to put a price — or a penalty — on emissions. They’re all for efficiency, electrification, storage, and better power lines. They support renewables that bring down prices. They all want more money to start working on the next generation of innovations.

So … Kumbaya, right?

Not quite. We can’t simply bury the divisive debates. But maybe we can make those debates more fruitful. The EDF’s Long thinks it would help if we stopped talking so much about specific technologies — 100 percent renewable versus nuclear reactors — and started talking more about the things we need those technologies to do: generating heat, supplying inexpensive energy, delivering electricity that can surge on and off to in fill the gaps.

“If we do that, people will be able to see better that there are problems with every choice,” Long said. “So what poison do you pick?”

And like that, sidestepping one debate plunges us into another one, just as crucial and inescapable. Still, the people on all sides told me that, as they debate their choice of poisons, they’d rather not choose poisonous rhetoric.