Thomas S. Bateman is professor emeritus of organizational behavior and leadership at the University of Virginia. He lives in Rockport.

Around many Thanksgiving tables this year, climate change will be on people’s minds but rarely in the conversation. Two-thirds of Americans are worried about global warming, and a majority of voters want Congress and corporations to do more about it. Yet most underestimate how many others share their concern. That mistake holds back climate action.

In an April survey by Yale and George Mason researchers, 77% of registered voters supported regulating carbon dioxide as a pollutant, and nearly two-thirds supported moving the U.S. economy to 100% clean energy by 2050.

Americans underestimate public support for major climate policies by nearly half . Psychologists call this pluralistic ignorance. People who want climate action stay quiet when they assume others don’t share their view, and their silence keeps the false belief alive.

Learning the truth can change minds. In one experiment, economists told Americans that most of their fellow citizens try to fight global warming. Participants, especially climate skeptics, became more willing to act and to support climate policies.

But people misjudge others’ climate actions in the opposite direction. A study published this summer in Nature Climate Change found that people overestimate how many others donate to climate causes or engage in climate politics. In the Yale-George Mason survey, only one registered voter in 10 had contacted a government official about climate change in the past year. The climate majority is both larger and quieter than people think.

We can’t assume enough others are speaking up. New voices speed progress toward tipping points. In online experiments , once about a quarter of a group committed to a new norm, the rest quickly followed.

Maine shows how quickly climate solutions spread when neighbors talk to neighbors. The state hit its goal of 100,000 new heat pumps two years early, and Efficiency Maine’s registered installers have grown from 30 or 40 a decade ago to 585 today. “Most referrals are word of mouth,” Bridget Gifford of Efficiency Maine told me. “Maine is a small town.”

My research has focused on proactive behavior: acting early to head off problems before the damage arrives. Climate change is my Exhibit A for the cost of waiting. Speaking up takes some nerve and is among the most proactive things anyone can do.

The holiday table is one place to start. Ask what others think and what worries them most, listen seriously, then share your perspective. Climate change touches so much of life, from heating bills and severe weather to the fishing and farming so many Maine families depend on, that almost anyone can find a reason to care.

If the moment is right, mention that nearly all climate scientists agree humans are warming the planet; learning this tends to raise concern.

Staying quiet cedes the debate to a determined, well-funded minority. In February, the Trump administration repealed the EPA finding that greenhouse gases endanger public health. Officials will keep treating climate as a losing issue until the majority tells and shows them otherwise.

This month’s elections changed control of Congress and several statehouses , and newly elected officials are setting priorities and hiring staff. In a 2016 survey , senior congressional staffers in both parties underestimated their constituents’ support for climate action. Staffs have turned over since, but the bias probably persists. After Thanksgiving, write or call your state legislators and members of Congress and tell them you want more and smarter climate action.

We need far more climate leaders, and they don’t need titles. Starting a climate conversation, contacting officials and showing neighbors your heat pump or solar panels are acts of leadership.

We understand climate science, we know what to do and majorities want more action. The climate majority holds a stronger hand than most realize. This holiday season, let’s start playing our cards.