In December, delegates from 195 nations meeting in Paris approved a remarkable global climate agreement. It calls for all countries to reduce emissions of greenhouse gases substantially.

Most of these emissions come from the burning of fossil fuels — coal, oil and natural gas — and the message couldn't be clearer: We need to change the way we generate and use energy, and do so quickly.

The United States set a modest goal: cutting emissions by 26 to 28 percent from 2005 levels by 2025.

In the face of persistent congressional opposition to climate change policy, President Barack Obama has used executive authority to move toward that goal, most notably through the Environmental Protection Agency's Clean Power Plan, which will regulate coal-fired power plants and new vehicle fuel economy standards.

The question now is what additional policy actions will most help in meeting — or preferably, exceeding — the target for emission reductions.

Should we rely on a revenue-neutral carbon tax that returns all new fees to citizens by lowering other taxes? What about a cap-and-trade system that many U.S. states now use? Both are very appealing but face political resistance.

Another approach may be more realistic. This is to expand and redirect investment in energy technology to favor low-carbon or no-carbon energy sources, among them nuclear power and renewable energy, and to greatly improve energy efficiency.

China understands this strategy. It plans to double its nuclear power capacity, and has 24 new plants now under construction. But China also is investing heavily in wind and solar power, as it has been for years.

Should the U.S. do the same? Yes, but only in part. Currently, our 99 nuclear reactors generate about 19 percent of electrical output, yet only about 8 percent of total energy consumption. The lion's share of the energy we use, about 81 percent, comes from fossil fuels.

Nuclear power will have an important role to play, but it is unlikely to replace much fossil fuel use. It is still too expensive and too risky.

A better bet is to invest in renewables and energy efficiency, which most of the world is now doing.

Despite construction of new reactors by China and other Asian nations, global nuclear electricity production has been leveling off while wind and solar power are soaring. There are good reasons for these trends.

One is cost. The nuclear plants under construction in the U.S., the first after more than three decades, are expected to cost $8 billion to $9 billion each, possibly more, and the eventual decommissioning of reactors remains expensive.

These very high costs make it difficult for private utilities to increase nuclear power generation despite generous federal loan guarantees. They see more promise and lower costs in natural gas-powered plants or in turning to renewable energy.

Other reasons include dealing with waste and safety. Even if the industry can reduce costs through improved technology and reactor design, what do we do about high-level waste disposal, for which no acceptable solution is in sight? And how should we address public concerns over reactor safety after the Fukushima disaster?

A better way forward is to invest heavily in renewables as well as in energy conservation and efficiency, which can cut energy demand sharply.

This includes improved building design, greater reliance on public transit, enhanced transportation efficiency, modernization of the electrical grid and storage technologies, and better lighting, heating and cooling systems.

We also should put more funds into research on promising energy technologies to speed up innovation and commercial development, as Bill Gates and the Breakthrough Energy Coalition have advocated.

The federal government has long favored and heavily subsidized nuclear power and fossil fuels. For the past decade, renewables and efficiency finally have begun to receive significant support. We should accelerate that trend.

Michael E. Kraft (kraftm@uwgb.edu) is professor emeritus of political science and public and environmental affairs at the University of Wisconsin-Green Bay.