Author and activist Bill McKibben [above] wasn’t only preaching to the choir when he addressed the annual meeting Sunday of the Mass. Climate Action Network, he was among the adoring.

Not only was he accorded several standing ovations during his closing keynote address at MIT’s Stata Center, he was approached by attendees throughout the day and thanked, not only for his leadership in the fight against global climate change but, in the words of one, for just being on the planet. More than 300 attended the conference, and the vast majority stayed until the end so they could hear McKibben speak.

A Lexington native who now lives in Vermont, McKibben split his address between reporting on last month’s worldwide day of action and assaying the next steps in the fight to stabilize atmospheric carbon content at 350 parts per million. That figure, considered the maximum level to ensure climate stability, was the focal point of the Oct. 24 action: Under the umbrella of McKibben’s 350.org, individuals coalesced into 5,200 groups in 181 countries — "pretty much all the countries there are, except North Korea" — to send the message to climate-change delegates meeting six weeks hence in Copenhagen that they want significant action on the issue.

It could be argued that no message was ever stated more broadly. According to McKibben, CNN termed it “the most widespread day of political action in the planet’s history.” That’s an accomplishment, certainly, but it was undercut by the news earlier in the day that President Obama had said the conference would not produce a climate treaty, as activists have long hoped and urged.

At lunchtime, meeting with a group affiliated with the Global Warming Education Network, McKibben alluded to the Obama’s comment when he said, “I got myself through the last 18 months of pushing [by believing that] Copenhagen would be a natural endpoint for some of this, but it’s not true.” During his address, McKibben acknowledged that his own carbon footprint is off the charts, having traveled extensively worldwide to organize the action. He is not paid for his 350.org advocacy work.

One of the goals of Oct. 24 was simply to record its events, to have tangible evidence that a broad, diverse subset of the planet’s citizens consider global climate change a threat, and that they want action. Part of the proof — 24,000 images — is available on 350.org’s flickr page.

Among the relative handful he shared were a photo taken underwater at the Great Barrier Reef, which he said will be dead within 50 years if trends continue, and photo taken at conference-table depth in the Maldive Islands: Ministers in President Mohamed Nasheed’s cabinet gathered around a u-shaped table in the surf to dispatch a resolution to Copenhagen’s delegates calling for decisive action. McKibben said the highest point in the Maldives in only 50-60 feet, putting it among the nations most at risk of a rising ocean.

“We spent the last 50 years adding flags at the UN in the era of decolonization. We may spend the next 50 years taking flags down as countries disappear,” McKibben said.

Playing to the home crowd, McKibben included photos from events held in Boston and Concord. The latter gathering, which drew between 300 and 400, was addressed by McKibben’s mother; he grew up in Lexington.

Taken together, McKibben said, the outpouring showed that “ordinary people could rally around a single data point and proved it could be done without dumbing it down.” He added that the perception of environmentalism as the sole province of affluent white people has been forever undercut.

In response to a questioner, McKibben said he does not expect, or want, to make the worldwide effort an annual one. He said its point has been made, and that future efforts may well require acts of civil disobedience, such as the march he helped lead in Washington last March over Congress’s use of a coal-fired plant to supply its heat. Congressional leaders have said they will convent the plant to natural gas.

“When we did this thing in Washington, Wendell Berry and I said in our invitation that 'you’re going to do this wearing your Sunday best or your not going to do it.' We wanted to say, ‘we’re not the radicals here. It’s the people who are pouring carbon into the atmosphere.'

“Clearly, one of the things we discovered [on Oct. 24] is that there’s a global appetite for working on this. It’s important to figure out how to harness that power and to put it to use against the great powers. Ideas of all kinds are more than welcome; this is an ongoing conversation.”

Following his speech, McKibben led dozens of people carrying banners and candles on a march to Boston Common, where college students have been sleeping out on Sunday nights, not only to bring attention to their cause but to be nearby the state capitol so they can lobby state government on Monday morning.

For the second week in a row, some of them were cited for illegally camping out on the Common. McKibben was one of them.

Disclosure: I am not a member of MCAN, but I represent Sustainable Arlington on an MCAN liaison group. I attended the event on a press pass.