This coming week, world leaders will descend on New York City to attend the United Nations General Debate. Before the speeches get underway, Secretary-General Ban Ki-Moon will host the U.N. Climate Summit, where he and his officials will pitch climate change as a development issue and environmental reform as an investment opportunity. "This is not about dividing up the pie of pain, but about growing the pie of opportunity,” said Assistant Secretary-General for Policy Coordination and Strategic Planning Robert Orr during a press briefing this week. 

Inside U.N. headquarters, over 120 heads of state and executives from multinational corporations—like Wal-Mart, McDonalds, and petroleum and oil industries—will commit to being more environmentally conscious. Outside headquarters, however, the environmental movement has support from perhaps an even less-likely supporter: unions.

Labor is conventionally seen as an antagonist to “job-killing” environmental measures. In 2011, Laborers International Union of North America (LIUNA) President Terry O’Sullivan accused two unions that opposed the Keystone XL pipeline of being “under the skirts of delusional environmental groups which stand in the way of creating good, much needed American jobs.” “Highly publicized conflicts have led to the perception that environmentalism and unionism do not mix,” write Richard Kazis and Richard L. Grossman in their 1982 book Fear at Work: Job Blackmail, Labor, and the Environment.  

But this antagonism, as Kazis and Grossman show, overlooks some crucial episodes in the environmental movement’s history.

Take the southwestern Pennsylvania factory town of Donoroa, where, in the 1940s, smog was a fact of life. Residents were accustomed to breathing toxic air the consistency of pea soup. They were used to sweeping off layers of dust from their cars and window sills. One week, in late October 1948, the air became even worse. For two days, visibility was so poor that driving was impossible. One father used a flashlight when he walked his little girl to school in the morning. But this was before air pollution was widely understood to be a health hazard, and regardless, the U.S. Steel plant emitting the smog provided jobs. It took a couple days and a rainstorm for the smog to thin, but by then, 20 people were dead, 6,000 of the town’s 13,500 residents were ill, and a few hundred had fled. Calling the dense smog “an act of God,” U.S. Steel refused to admit liability.

Donora’s “killer smog” proved a turning point for United Steelworkers (USW), the union representing the town’s factory employees. Embracing progressive environmental reform, the steelworkers union became a leading voice in the environmental movement, helping to advocate for the passage of the 1970 Clean Air Act. "We refuse to be the buffer between positive pollution control activity by the community and resistance by industry," United Steelworkers president I.W. Ael said. In 1990, USW acknowledged climate change as  “the most important environmental issue of our lifetime.” In partnership with the Sierra Club, USW formed the BlueGreen Alliance in 2007 to promote a positive relationship between unionists and environmentalists.

This happy convergence of labor and the environmental movement is not well known, but there’s no shortage of these stories. Labor’s devotion to environmentalism began in earnest after Donora and predates the modern environmental movement, writes Scott Dewey in the journal Environmental History

In 1963, the AFL-CIO’s director of legislation expressed strong support for the proposed Clean Air Act. Throughout the decade, high-level officials in the union testified in support of air quality regulation before Congress, calling for federal action. A few years later, in February 1970, United Autoworkers (UAW), which was involved with founding Earth Day, sponsored the first environmental teach-in in the United States. In 2007, a Washington Post article quoted the president of the International Association of Machinists (IAM) Tom Buffenbarger saying that the goals of environmentalists and unionists were aligned: "As of late, an awareness has grown that our goals are the same. We want good air, clean water and access to the outdoors."

Today, unions and environmentalists are a natural match, says Senior Strategic Adviser on Climate and Energy for the BlueGreen Alliance Jon Barton. “We all live on this planet, and I think there’s a growing recognition among those in the labor movement that the fight around climate and climate change is everyone’s fight,” he said in an interview. “We have people who believe a job today is worth a dead planet tomorrow,” says Amalgamated Transit Union (ATU) President Larry Hanley. “There aren’t going to be any jobs on a dead earth.” Like the Donora steelworkers, today’s union workers are directly affected by their companies’ environmental practices. To rally against environmental reform would be to vote against their health and future wellbeing, according to labor leaders. 

The U.N. is addressing the fear that there will be no place for today’s workers in tomorrow’s sustainable industries head on. At the 2009 U.N. Climate Change Conference, negotiators considered how to train today’s workforce for tomorrow’s jobs, calling for a “just transition,” i.e., minimal negative impact on the labor force as the world transitions into a low-emissions economy. Though unions won’t be attending the Summit next week, such concerns about a “just transition” are likely front and center.

During the U.N. Investor Summit on Climate Risk in January 2014, AFL-CIO President Richard Trumka spoke about his time working in a coal mine: “It cost money to properly ventilate the mine so it didn’t fill with explosive gas, so they liked to tell us the air was fine, when it wasn’t. And most of all they told us it was healthy to breathe coal dust, when we knew it was killing each of us, and our families.” The experience, he implied, was formative to his role as union leader. “I am here,” Trumka continued, “on behalf of the American labor movement to tell you we remain committed to the task of stopping runaway climate change. This is not easy for us. For millions of workers in the U.S., our livelihoods, our families, our communities are at stake—not decades from now, but right now,” he said.

This coming Sunday, secretary-general Ban, who calls climate change “the defining issue of our time,” will link arms and walk with the People’s Climate March, including members of 1199 SEIU, ATU, and Local 805 Teamsters, and several dozen other unions. Two days later, he’ll host the Climate Summit.