Though some American labor unions, including the auto workers and public employees, supported the original Earth Day protests in 1970, since then organized labor has often been indifferent or antagonistic to environmental and climate concerns out of fear that any action would eliminate jobs at the very moment that unions are declining.

Fossil-fuel executives and lobbyists have fanned this fear, telling the powerful unions in the building and industrial trades—the laborers, pipe fitters, plumbers, electricians, and carpenters—that a shift to renewable energy would throw them out of work, even though the opposite is true. Executives of the American Petroleum Institute have worked diligently to disarm unions by paying for safety and training programs, sponsoring the conferences and meals, providing talking points, and ramming home the view that fossil fuels are essential for jobs and for the American economy.

Despite these efforts, union attitudes are steadily changing, as seen clearly at a recent national gathering of more than 240 union leaders in Chicago. The event was the brainchild of Joe Uehlein, who retired from serving as the secretary-treasurer of the AFL-CIO’s Industrial Division 15 years ago in order to found the Labor Network for Sustainability (LNS). (Disclosure: I am a former board member of LNS.)

Uehlein had participated in previous efforts to bring labor and environmental leaders together, such as the Blue-Green Alliance and the Apollo Project, which failed to achieve their objectives because of their top-down caution. For years, Uehlein and his small staff have instead been painstakingly building a bottom-up approach—visiting local and national leaders, listening to their fears and hopes, building bridges, pointing out the immense benefits that rebuilding America’s energy system would have for workers, and organizing “convergences” of leaders from across the labor movement.

Today unions are no longer locked into resistance to action; indeed, some have already endorsed the Green New Deal. One dynamic new leader, Sarah Nelson, the president of the Association of Flight Attendants, explained that the climate crisis was already harming her members through increased turbulence, on-the-job injuries, and lost income through rising weather delays. “The Green New Deal is the moonshot of our time,” she declared forcefully, “We cannot allow the idea that labor is opposed to addressing climate change to continue to exist.”

Many other union leaders in the room agreed, including those from the Service Employees International Union (SEIU), which had also endorsed the Green New Deal. The SEIU is the second-largest union in America, with nearly 2 million members working primarily in three industries: health care, public services, and property workers (janitors, security officers, and food-service employees).

The conference organizers also invited Cecil Roberts, the combative president of the United Mine Workers. Roberts passionately defended his union’s historic resistance to climate action by pointing to the devastating impact of endless job losses on his home state of West Virginia and beyond. “Tragedy after tragedy after tragedy have swept across those hills and hollers,” Roberts said. The proposed solutions—such as job training or promises of a just transition—had simply not worked. But in a noticeable shift in tone, Roberts promised to keep searching for agreement. “It’s true that we are not in lockstep,” he concluded, referring to the labor movement’s attitudes on climate, “but we agree on 75 percent…[and] I am not going to run away from this.”

Union leaders tend to blend passionate idealism with unsentimental pragmatism—and Roberts displayed both. He particularly needed help with the miners’ most immediate and serious problem—the impending elimination of coal miners’ health insurance and pensions. The callous and inept management of the world’s largest coal companies—Peabody and Arch—had resulted in massive financial losses and declarations of bankruptcy in 2016. This devastated their workforce by killing jobs—and gave coal executives an excuse to ask the bankruptcy court to release them from any obligation to pay for worker health insurance and pensions. Benefits that workers had been faithfully paying for over decades to secure their retirements and health care would suddenly disappear.

In a sign of solidarity that transcended the disagreements over climate, the Labor Network for Sustainability and its allies has been pushing the congressional co-sponsors of the Green New Deal to adopt S. 27, the American Miners Act, to protect the miners’ pensions and health care. By making common cause with the miners on a fundamental issue of job rights, the union supporters of the Green New Deal are laying the groundwork for possible future alignment on climate.

The gathering also brought some long-standing tensions in the labor movement to the surface. On the last morning—in which the sessions had been intended to design and agree on practical strategies that could be pursued jointly—discontent among some of the participants of color erupted. Some of the leaders of color had met the night before and had produced a resolution that they asked the convergence to adopt. Though substantial efforts had been made by a large steering committee to secure a high degree of diversity in the speakers and participants, those who signed the petition felt it needed to be even greater. Michael Leon Guerrero, a Latino man who is the executive director of LNS and who had served the former head of the Climate Justice Alliance, immediately agreed. They also asked for LNS to engage on a broad range of social justice questions, including ending police violence, which are beyond the organization’s mission.

The tension arose in part because the leaders committed to racial and economic justice—like the rest of their union counterparts—are waking up to the vast potential power of the Green New Deal as a set of ideas and as force for political change. They were not rejecting it; quite the opposite. They wanted to be certain that their concerns were not overlooked.

Given the breadth and vision of the Green New Deal, that debate about priorities is now engaged. The question is whether the allies can also find a way to support one another, turning the ideal of solidarity into a force that can transcend differences and build momentum for change.

The challenge could hardly be more urgent, since time is running out. In the same week as the Chicago conference, mussels cooked in their shells on California beaches, a bizarre hailstorm buried a Mexican city under five feet of ice, and a town in France hit 115 degrees Fahrenheit, the highest temperature ever recorded in that country’s history.

Will America’s labor unions—still trying to fend off the battering ram of corporate power and the Trump administration—succeed in uniting with leaders who are fighting racism, fired-up youth who don’t want to hear any more excuses, and the millions who are heartsick about Trump’s dismantling of the American republic? Will they be able—finally—to generate an effective response to the potential collapse of our ecosystem, our economy, and our democracy?

There is a way. The question is whether America, once globally famous for its forward-looking leadership, can finally find the will.