Nuclear energy’s obituary has been in the works for decades.

And predictions of a nuclear decline were bolstered in June, when Pacific Gas & Electric in California announced its plans to close the state’s last operating nuclear power plant, Diablo Canyon Power Plant.

The decision comes at a time of expanding renewable energy in California, slowing electricity demand and, as The New York Times reported June 21, “after years of public pressure to close the plant … because of safety concerns over its location, near several faulty lines, and its use of ocean water for cooling.”

But elsewhere, the industry is showing signs of life – and support from a small group of climate scientists who believe nuclear must be considered as a possible tool to cut carbon emissions, given what they see as the gravity of excessive warming.

On June 3, the Tennessee Valley Authority’s new $4.7 billion nuclear power plant, Watts Bar Unit 2, came online. The 1,150-megawatt reactor was the first nuclear power plant in the nation to switch on since 1996.

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Meanwhile, Energy Secretary Ernest Moniz has marshaled the Energy Department to find ways to preserve nuclear power’s role in electricity generation as the nation strives toward a less carbon-intensive economy. “We’re supposed to be adding zero-carbon sources, not subtracting,” he said at a May symposium the department convened to explore ways to help strengthen the nuclear industry.

Policy experts, climate scientists, and others remain divided over whether nuclear should have a future in a global energy mix aimed at mitigating climate changes.

In late 2015, a small dust-up played out at The Guardian newspaper in the U.K. when Harvard historian Naomi Oreskes, who has written extensively about the politics and vested interests related to climate change, criticized climate scientists who had earlier argued in the paper that nuclear power is essential if the globe is to take decarbonization seriously. Those scientists, James Hansen, Kerry Emmanuel, Ken Caldeira, and Tom Wigley, argued that in the wake of the December 2015 Paris climate accords, nuclear energy – particularly next-generation “closed fuel cycle” systems that reprocess spent fuel – shows real promise for addressing the intermittency challenge of renewable sources of energy. The group called for “an accelerated deployment of nuclear reactors” – as many as 115 reactors annually between now and 2050. “Nuclear will make the difference between the world missing crucial climate targets or achieving them,” the scientists wrote.

Oreskes argued that an expansion of nuclear power is unnecessary and would detract from a real commitment to “focusing on wind, water and solar, coupled with grid integration, energy efficiency, and demand management.” Paraphrasing a colleague, Oreskes wrote that “nuclear power is an extraordinarily elaborate and expensive way to boil water.”

As these debates continue, it’s worth examining the pros and cons of nuclear power in the context of risky global warming. Here’s a brief rundown.

Pros

Inexpensive relative to fossil fuels: The cost of generating electricity from an existing nuclear energy facility varies according to the particular plant generating the electricity; an older plant can be much less efficient than a newer one, for example. Nevertheless, the Nuclear Energy Institute, an industry group, has reported that in 2015, generating electricity from a nuclear power plant in the U.S. cost an average of 2.4 cents per kilowatt-hour. That was a bit less than the electricity production cost using coal in 2015, about half the cost of gas, and about 10 times less than the cost of oil.

However, as The Economist reported in a story on nuclear energy last October, the declining cost of natural gas threatens nuclear energy’s place as a low-cost leader for electricity generation.

Low levels of greenhouse gases produced: Nuclear power plants provide nearly 60 percent of the nation’s carbon-free power, followed by hydroelectric plants at about 18 percent. That’s a huge portion of the nation’s carbon-free energy, and it’s not at all clear how it could be replaced – at least in the near term. In their piece, Hansen, Emmanuel, Caldeira and Wigley wrote that nuclear power, “particularly next-generation nuclear power with a closed fuel cycle (where spent fuel is reprocessed), is uniquely scalable, and environmentally advantageous.” Over the past 50 years, they added, nuclear power plants have avoided emissions of an estimated 60 billion tons of CO2.

Efficient: Nuclear power plants, which produce power steadily when operating, typically run at more than 90 percent of their capacity – higher than gas, coal, and other types of energy plants.

Resilient to (some) environmental changes: During the frigid winter of 2014 in the U.S., when a polar vortex descended into the lower 48 states, parts of the nation faced shortages in natural gas, and some coal plants shut down because of the extremely low temperatures. But nuclear power plants, with nuclear fuel on-site, kept operating – showing their resiliency to weather extremes. At the same time, as droughts intensify in some parts of the world with continued climate change, nuclear power plants may find it increasingly difficult to gain access to sources of water that they need for cooling.

Mature technology: Nuclear energy has been in operation for nearly 60 years, and nuclear physics is well understood. This is particularly true in some European countries, such as France, where nuclear power is the dominant source of electricity. Meanwhile, technological advances now in development may lead to safer and more efficient nuclear power.

Cons

Unstable fuel and a finite resource: Fuel for nuclear reactors, specifically uranium that undergoes fission, is highly radioactive and deadly to humans. No other source of fuel – coal, natural gas, oil, wind or solar – poses the same dangers.

Meanwhile, uranium, a very heavy metal mined in the ground, is a finite resource. The U.S. has increasingly relied on foreign imports for uranium fuel. “During 2015, owners and operators of U.S. nuclear power reactors purchased 57 million pounds of uranium,” the EIA reported on June 1. “Nearly half of these purchases originated from two countries, Canada and Kazakhstan, providing 17 million pounds and 11 million pounds of uranium, respectively.”

U.S. production, which began in 1949 and peaked in 1989, has been at historic lows, partly as a result of environmental concerns associated with mining uranium. Total 2016 production is on track to be just 2.3 million pounds – slightly higher than the low of 2 million pounds produced domestically in 2003.

Aging and costly power plants: Of the nation’s 99 reactors, nearly a third are more than 30 years old and near retirement. The cost to replace them will depend on the number of individual reactors, location and other factors. As mentioned above, the Watts Bar Unit 2 reactor in Tennessee was built at a cost of $4.7 billion.

On July 28, The New York Times reported on plans by the French utility EDF to build the first nuclear power plant in Britain in a generation. The $23.6 billion plant, known as Hinkley Point C, is to have two 1.65 gigawatt reactors that will generate enough power for six-million homes. Its future is not certain, however, as the British government has postponed a final decision on the plant, The Guardian reported July 29.

Meanwhile, the Nuclear Energy Institute, the industry group, reported in a 2016 white paper that in 2015, the average total generating cost for nuclear energy was $35.50 per megawatt-hour; this cost includes capital, fuel, and operating costs. The white paper noted that generating costs have declined since 2012, but over the decade prior to that costs had been steadily increasing. “Between 2002 and 2015, fuel costs increased 21 percent, capital expenditures by 103 percent, (and) operating costs by 11 percent (in 2015 dollars per megawatt-hour),” the report stated. “Total generating costs are up 26 percent in the last 13 years.”

Environmental concerns: Nuclear power plants require huge amounts of water. As a result, nearly all plants in the U.S. are situated on the shores of lakes, rivers or on the coast and rely on submerged intake pipes to draw in billions of gallons of water for cooling and to condense steam after it has turned a plant’s turbines. Intake systems kill wildlife and outgoing heated water can damage aquatic environments near a power plant.

A growing nuclear waste problem: Spent nuclear fuel is highly radioactive, and must be sequestered from the environment in perpetuity. In 2002, Congress approved long-studied plans to construct a permanent repository deep inside Yucca Mountain in the Nevada desert. But federal funding for the project ended in 2010 under the Obama Administration, in the wake of strong opposition from the general public and influential politicians. As a result, more than 70,000 tons of radioactive spent nuclear fuel is stored, within dry concrete casks, in giant pools of water, and by other means, at the nuclear power plants that used the fuel. That fuel is piling up, and experts generally agree that a more long-lasting, ideally permanent, solution will ultimately be needed.

Vulnerability to natural disasters and terrorism: Look no further than the 2011 Fukushima Dai-ichi disaster for an example of a catastrophic failure of a nuclear power plant after a natural disaster. The incident has contributed to a retreat from nuclear power by Japan, Germany, and other nations.

Every energy facility and distribution system is vulnerable to terrorism. But the consequences of a successful attack on a nuclear facility could be especially grim. The 9/11 Commission has reported that nuclear power plants were potential targets of the September 11, 2001, attacks on the U.S. Nuclear terrorism is, and will remain a major concern. A major nuclear disaster – such as at Fukushima Dai-ichi or at Chernobyl in Russia – has devastating and long-lasting impacts on a regional ecology and on people living nearby.