New London — If the “radically insufficient” response to the threat of climate change thus far is going to be transformed into significant action, ordinary people who care about humanity and the Earth need to start organizing.

So said John Conner, founder of The Grassroots Coalition, a group formed in 2006 to bring churches, universities and social justice groups together to push for reductions in the greenhouse gas emissions causing warming global temperatures, melting of the Arctic, rising sea levels, more intense storms and other effects.

“If life is going to survive, something has to change,” he said. “It has to be a shift of economic and political power.”

Conner, whose group is based in Shade Gap, Pa., spoke to 17 people gathered Monday evening at St. Mary Star of the Sea Church in New London, and will address students and others in the library of Harkness Chapel at 3 and 7 p.m. today in a talk sponsored by The Catholic Community at Connecticut College. The meetings are in response to Pope Francis’ call for action on climate change in his recent encyclical, “Laudato Si,” and in appearances last month in the United States, timed to call attention to the issue before meetings of world leaders on climate change in Paris later this fall.

Conner urged those in the room to educate themselves about climate change, and then decide how to reach out to other churches, colleges, environmental and activist groups in the region as well as to individuals who are inactive to make political leaders aware that they want concrete steps taken. Only if sufficient numbers of people get involved in grassroots activism, he said, will the inertia around the issue change.

“Numbers, numbers,” he said. “Size matters.”

The Rev. Robert Washabaugh, who organized the meeting at St. Mary, said the coalition that could be formed should be nonpartisan, so that the issue itself rather than particular political agendas is advanced.

“It makes sense to bring people of all political stripes into it,” he said.

Two parishioners who listened to Connor’s talk said it may take one or more severe storms and other tragedies caused by changing climate conditions to stir a mass movement around climate change. The danger with waiting for that to happen, Connor said, is that by the time that occurs it may be too late to reverse the damage.

One parishioner, who declined to give his name, questioned whether the effects of rising carbon dioxide levels on the climate have been exaggerated by the computer models used by scientists, citing a recent analysis he found on the Internet.

The majority of the group, however, were more focused on figuring out what they could do in response to climate change.

Deborah Connors, pastoral associate at St. Mary, reminded the group that working to find solutions to climate change will help protect the planet for future generations.

“I have a four-month-old grandson,” she said. “What kind of world are his grandchildren going to grow up in?”

She urged the group not to give up.

“Eventually, the people we’ve elected will start to listen,” she said. “There’s a possibility for real positive change.”

j.benson@theday.com

Twitter: @BensonJudy