Germany’s ambitious plan to eliminate nuclear power over the next decade has energized environmentalists, but the country faces a tricky task if it wants to keep its promise to reduce greenhouse gases that cause global warming, analysts say.

History has made many Germans cautious about the destructive power of technology, and the decision that ended the decades-long debate over nuclear power opened a new one about the impact on emissions. Chancellor Angela Merkel said Thursday that Germany would need more fossil-fuel power plants to fill the gap.

The industrial powerhouse gets almost a quarter of its electricity from nuclear power plants, which emit limited greenhouse gases. If Germany turns to smog-belching coal power plants, emissions could worsen. Environmentalists say that move won’t be necessary, but many analysts aren’t so sure.

“If we want to quickly get out of nuclear power and into renewable energy, we need fossil-fuel power plants,” Merkel said in an address to Germany’s Parliament. “There is no way around.”

More than a dozen new coal-burning plants were already planned around Germany over the next several years, many of them cleaner replacements for old plants that have reached the end of their life spans. Several investment firms said they expected that the country would emit hundreds of millions more tons of carbon dioxide over the next 10 years, driving up price forecasts for European-wide carbon-emissions permits.

Even as Merkel promised to hold to emissions targets, she said she wanted to greatly expand the generating capacity of fossil-fuel-burning plants.

“At least 10, more likely 20, additional gigawatts have to be built in the next 10 years,” Merkel said — more than a tenth of the country’s current capacity.

She reiterated a pledge that Germany would meet its emissions targets and its nuclear deadline. Environmentalists in Germany — some of whom say the nuclear phaseout is not happening quickly enough — compare the scale of the plan’s ambitions to those of the Apollo project in the United States.

“It’s going to be a bit of a make-or-break experiment, which everyone is watching extremely carefully on a global basis,” said David Baldock, executive director of the London-based Institute for European Environmental Policy. “It’s quite brave.”

A quarter of Germany’s electricity is generated by nuclear power plants, slightly more than the United States but far behind France, which gets almost 80 percent of its power from nuclear energy. But the disaster at the Fukushima plant in Japan, which barely caused a stir in France, exacerbated long-held fears about the technology in Germany.

Germany’s Green Party was organized to combat nuclear energy shortly after the Three Mile Island disaster in the United States in 1979. It just took over the government in Baden-Wuerttemberg, a wealthy, conservative region in southern Germany.

Many Germans ascribe their country’s nuclear aversion to the devastation and shame of World War II, which made many here cautious about atom bombs and atomic energy.

Aiming for efficiency

Renewable energy makes up 17 percent of Germany’s power supply, with aggressive subsidies that have encouraged development over the past decade. But because of that preexisting push, some of the easiest steps have already been taken, analysts say. The bigger savings, if Germany is to meet its emissions-reduction goals — a 40 percent reduction by 2020 and a 70 percent cut by 2040 — would come by cutting the demand for electricity by increasing efficiency and changing habits, analysts say.

A plan approved this week will channel money toward renovating old homes to improve energy efficiency, and some legislators want to tighten building requirements for new construction as well. Many areas require residents to sort their recycling to reduce waste; they are likely to become more vigilant about enforcing rules as efficiency goals tighten, analysts say.

“When you look at what you can do to reduce your [carbon dioxide] emissions, a large percentage of it is in buildings, and a large percentage is where you’re generating electricity,” said Sharon Squassoni, director of the Proliferation Prevention Program at the Center for Strategic and International Studies. “If anybody can really make continued strides in efficiency, it’s certainly Germany.”

The presumed advances in technology and efficient production that will come from the increased investment would be a boost to the German economy as other countries follow in its path, further strengthening its already robust export sector.

“What is fascinating about this whole project is the extent to which Germany sees this as its future. How do you lay the groundwork for future industries?” said Miranda Schreurs, director of the Environmental Policy Research Centre at the Free University in Berlin and a member of the commission that advised Merkel about the nuclear phaseout. She said the decade-long transition period was realistic, if challenging.

But others remain skeptical of the plan’s chances for success, noting that Germany could be forced to import electricity from nuclear power plants in neighboring France and the Czech Republic to meet demand, thus undermining the goal of reducing overall nuclear consumption inside or outside Germany’s borders.

Merkel’s rapid turnaround

Critics also note the political motivations behind Merkel’s rapid turnaround on the topic in an election year when her Christian Democratic Party is being drubbed at the polls by the Greens and Social Democrats, who favor more traditionally environmentalist agendas. Last year, Merkel’s party advocated extending the life of Germany’s 17 nuclear power plants by 12 years on average, and she faces conflicts within her party about the switch in positions.

“My personal feeling is that it is not the wisest decision we have always made,” said Michael Fuchs, the vice chairman for economy and industry in Merkel’s party, who has been a leader for nuclear policy within the German Parliament. “The Germans are very sensitive as far as nuclear is concerned, much more so than anywhere else in the world.” He said he was concerned about rising costs and rising emissions as a result of the shutdown.

Some scholars look at Germany’s plan with a mixture of interest and concern.

“If they really push the phaseout, there will be a positive fallout in the sense of vastly accelerated research and development, because Germans will clearly make a big contribution,” said Charles Ebinger, director of the Energy Security Initiative at the Brookings Institution. “To try to do it in a decade is not very wise.” He said there was “no question” that carbon dioxide emissions would go up as a result of Germany’s shift.

Switzerland also said in recent weeks that it would gradually shut down its nuclear power plants. The plans have been criticized by other countries in Europe, who worry that energy costs will rise, as will emissions. French Prime Minister Francois Fillon said last week that there was “no way” for the European Union to meet its emissions targets without nuclear power.

Special correspondent Alexandra Gdanietz contributed to this report.