He said he rejected the stance that there was no pathway to limit global warming to 1.5 degrees Celsius above preindustrial levels, a goal set in the Paris Agreement to avoid the worst effects of global warming, without nuclear. Masayoshi Iyoda, an activist from Japan with 350.org, an international climate action campaign, cited the nuclear disaster at Fukushima in 2011 and said that nuclear power was a dangerous distraction from decarbonization goals. “It is simply too costly, too risky, too undemocratic, and too time-consuming,” he said in a statement. “We already have cheaper, safer, democratic, and faster solutions to the climate crisis, and they are renewable energy and energy efficiency,” Mr. Iyoda said. All but four of the 31 reactors that have begun construction since 2017 were designed by Russia or China, with China poised to become the leading nuclear power producer by 2030, the International Energy Agency said. This year, Germany shut its last three nuclear plants. Nuclear capacity rose in the 1980s, particularly in Europe and North America, but dropped sharply over the subsequent years after accidents at Three Mile Island in Pennsylvania in 1979 and Chernobyl in 1986. New technology and tighter regulations have been put in place since then. Americans are conflicted about nuclear power, but a growing number favor expansion compared with a few years ago, according to a Pew Research Center study published in August. Jenny Gross is a general assignment reporter. Before joining The Times, she covered British politics for The Wall Street Journal. More about Jenny Gross