As another round of United Nations climate talks starts, most scientists agree that potentially catastrophic climate change can’t be stopped except by keeping global temperatures from rising more than 2 degrees Celsius above their pre-industrial average. Yet even if each country cuts emissions as much as pledged, temperatures are projected to increase by almost twice that amount.

Still, experts haven’t given up hope. Bloomberg View asked leaders in energy, science, government policy and innovation to name the most promising way to keep global temperatures from passing the 2-degree threshold. The answers ranged from the simple to the technical, and all but one start from the premise that, with sufficient effort, this problem can be fixed:

By Bob Inglis: Want to win conservatives? Use a carbon tax.

The best way to curb emissions is using market-based mechanisms, mixing the lightest touch by government and the maximum amount of liberty. It’s free enterprise innovation that’s going to make clean energy work. World leaders should consider a carbon tax, paired with cuts to existing income taxes so that there’s no growth of government. They should also apply that tax to imports from countries that don’t price carbon, to avoid sacrificing economic competitiveness and to give their trading partners an incentive to introduce similar taxes. If the fight against climate change incorporated accountable price signals, American conservatives could enter the conversation.

Until now, they’ve felt excluded as the preferred solutions have involved a growth of government and a loss of liberty. While conservative support for a carbon tax may look impossible at the moment, the impossible may become inevitable. Rather than fickle tax incentives, clumsy government mandates or expensive regulations through cap-and-trade and the Clean Power Plan, energy optimists and climate realists believe a free and entrepreneurial society can deliver on Pope Francis’ leadership and implicit blessing of the “spirit of enterprise.”

(Bob Inglis, a former S.C. Republican congressman, is executive director of republicEn, an energy and enterprise initiative at George Mason University.)

By Bard Harstad: People like to procrastinate — take advantage of it.

First, agree on a ratcheting mechanism of national commitments that is automatic, binding, and legally sanctioned. Future periodic negotiations should deal with modifying these commitments, rather than arguing over how to set them in the first place.

Take advantage of leaders’ desire to push costs into the future. Just as politicians tend to prefer the delayed expense of climate change to cutting emissions today, they may also prefer agreeing to reductions later (even if they ratchet up over time) to cuts today. The challenge is to entrench those commitments in a credible, legally binding way.

Second, ban drilling for oil in the Arctic. Those reserves are the most costly to extract, and are thus the first reserves humanity should conserve indefinitely.

Third, pay developing countries to protect instead of cutting down their tropical forests, because they can keep huge amounts of carbon out of the atmosphere.

(Bard Harstad is a professor of economics at the University of Oslo.)

By Christina Back: The future is (still) nuclear.

The largest source of clean, sustainable and reliable energy available remains nuclear power. But to play a bigger role in reducing carbon emissions and air pollution, future advanced reactors must address four core challenges: They must be safer. They have to produce less radioactive waste. They need to pose lower risk of weapons proliferation. And they need to be less expensive.

General Atomics has a new reactor designed to meet each of these concerns, called the Energy Multiplier Module. It uses ceramic materials that are irradiation-resistant and can survive temperatures more than twice what current metallic fuel rod materials can withstand. Tthese new materials are cooled with inert gas, which means an explosion like the one at Fukushima, caused by the buildup of hydrogen gas, can’t happen. This new type of reactor produces 60 percent more electricity from the same amount of fission. It can run on uranium, thorium or even used nuclear fuel. That means lower construction costs and cheaper power.

(Christina Back directs fission and inertial fusion programs for General Atomics.)

By Howard Herzog: Trapping carbon works — now make it cheaper.

The most direct way to curb emissions of carbon dioxide, if not necessarily the simplest or least expensive, is to catch it before it enters the atmosphere. That process, called carbon capture and storage, traps the carbon produced by combustion of fossil fuels and then stores it, often in deep geologic formations. The primary targets for CCS are large, stationary sources, chiefly coal and natural gas-fired power plants, as well as industrial facilities including refineries, cement plants and petrochemical facilities.

CCS works with our fossil fuel infrastructure and can avoid stranding hundreds of trillions of dollars of fossil fuel assets. When the source of power is trees or crops, which pull carbon from the air, burning it at a facility that uses CCS can create negative net emissions. The problem thus far is cost. Wide-scale deployment of carbon capture and storage requires strong climate policy. That includes technology support policies, such as the type of tax credits that have been successfully applied to renewables.

(Howard Herzog is a senior research engineer for the Massachusetts Institute of Technology’s Energy Initiative.)

By Mark Jacobson: Forget technology — the solution is information.

The greatest barrier to dealing with climate change isn’t technology but information. As policymakers and the public realize they can get clean, low-cost renewable energy — along with the side benefits of new jobs, stable energy prices, less international conflict and the reduced risk of terrorist attacks on large centralized power plants — they’ll become more likely to change course.

At the Solutions Project, we’ve offered detailed plans for how all 50 states and 139 countries can power their electricity, transportation, manufacturing, agricultural and residential sectors entirely from wind, water and sunlight by 2050 — and get 80 percent of the way there by 2030. Kentucky, the heartland of coal, can get 90 percent of its power in 2050 from solar energy while creating almost 200,000 40-year jobs.

The U.S. can get 47 percent of its 2050 power from various types of solar power, 31 percent from onshore wind turbines and another 18 percent from turbines offshore — and cut average per-person electricity costs by $443. The benefits are even greater overseas. Once people realize how much they can gain from fighting climate change, they’ll demand their governments take action.

(Mark Jacobson runs Stanford University’s Atmosphere and Energy Program and is a co-founder of the Solutions Project.)

By Joyce Penner: Geoengineering can work — just not by itself.

As the world struggles to address global warming, some propose geoengineering — intentionally altering the planet’s atmosphere — as a way to lower temperatures.

The most studied technique would work by adding sulfate particles to the stratosphere, which is similar to what happens as a result of large volcanic eruptions. Those particles reflect solar radiation, preventing some of the sun’s rays from warming the Earth.

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While this type of solution sounds promising, it must never be considered in isolation. Without agreements to significantly decrease carbon dioxide emissions, we would have to continue pumping more and more sulfur dioxide into the stratosphere, perhaps for millennia. We don’t know the consequences of such large and prolonged tampering.

Another problem: Curtailing the injection of sulfur would quickly return the Earth to the high temperatures caused by the continued accumulation of carbon in the atmosphere. Only through a concerted effort to decrease those carbon emissions could we return to the normal skies of a sulfate-free atmosphere.

(Joyce Penner is a professor of atmospheric science at the University of Michigan and a member of the U.N. Intergovernmental Panel on Climate Change.)

By Richard Branson: Business can’t wait for governments to act.

A powerful and legally binding global agreement in Paris would provide an urgently needed lynchpin for all efforts to reduce global warming. But business leaders can and should play a crucial role as well by making bold commitments to transform their industries.

There are number of initiatives across the Virgin Group of companies that aspire to achieve net-zero carbon emissions by 2050, either through far-reaching emission reductions or offsets. 2014 was the first year that Virgin Atlantic successfully decoupled business growth from carbon growth, with an overall 12 percent reduction in carbon dioxide or equivalent emissions from aircraft operations between 2007 and 2014.

Over the past decade Virgin has invested more than $150 million in renewable energy ventures. Not all have worked, but we remain committed to investing our capital in developing the power sources of the future.

(Richard Branson is the founder of the Virgin Group.)

By Oren Cass: Staying below 2 degrees is hopeless (without war).

However compelling the arguments for holding global warming below 2 degrees, here’s the problem: Doing so is plainly incompatible with the economic aspirations of the developing world. Even if rich nations halted emissions tomorrow, other countries would need to slash emissions by half immediately and hold there indefinitely. That course would preclude rapid economic growth, which is why developing nations are refusing to contemplate it.

Despite impressive progress, low-carbon technologies remain nowhere near capable of providing affordable, baseload power at the scale required. Instead, the world is currently experiencing a “Renaissance of Coal.”

Dramatic cuts depend on technological breakthroughs that a developing economy might prefer to fossil fuels. The best chance will come if focus shifts from today’s wind farms and solar panels to spurring whatever innovations might come next.

(Oren Cass is a senior fellow at the Manhattan Institute.)

Christopher Flavelle is a columnist for Bloomberg View.

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