Pretend the Earth’s atmosphere is a bathtub.

On one end of the bathtub is a spigot, and out of that spigot pours all of the carbon dioxide that humans put into the atmosphere, ranging from car exhaust to manufacturing to cattle ranching. On the other end of the bathtub is a drain, and out that drain pours all of the carbon dioxide that humans take out of the atmosphere.

Overflow crowd attended talk at the Katharine Cornell Theatre Thursday night. — Mark Alan Lovewell

What’s wrong with this equation?

The spigot is on, but the drain is clogged. The bathtub is overflowing.

“We have procrastinated for so long about turning off the spigot, that we now have to get the roto-rooter out and unplug that drain,” renowned climate scientist Dr. Philip Duffy told the Martha’s Vineyard Commission and a packed crowd of listeners at the Katharine Cornell Theatre Thursday night.

“This is the urgency. Because it doesn’t get any better. It gets worse.”

A Harvard and Stanford-trained astrophysicist who worked in the Obama administration to pass the Paris Climate Accords, Mr. Duffy is now a researcher at the Woods Hole Research Center who has devoted himself to studying the broad-scale effects of climate change and advocating for solutions.

At the special presentation before the commission Thursday, Mr. Duffy explained the grave state of the global climate crisis, giving a dire prognosis for the planet that has ignored the consequences of its actions for far too long. Even if humans were to have completely turned off the carbon dioxide spigot in 2010, he said, the planet would continue to warm for another three centuries. To reverse the trend, humans won’t just have to become carbon neutral; they’ll have to remove carbon from the atmosphere. It’s a history lesson that goes back for nearly a million years.

“The past tells us a lot, and helps to inform us what we are going to do in the future,” Mr. Duffy said. “In the big picture, the main driver of climate change on Earth, for the past 800,000 years, has been carbon dioxide.”

Ten thousand years ago, the Earth substantially warmed and temperature stabilized, providing humans with predictable, seasonal temperatures that allowed for formalized agriculture, animal husbandry, and, in turn civilization. But over the past two hundred years, greenhouse gas emissions from the industrial revolution have gradually put those temperatures in flux, causing more extreme weather, drought, sea level rise, and the threat of mass human displacement and migration away from the equator.

On a human time scale, the temperature changes, loss of arctic ice sheets and rise in sea level and may not seem significant — less than one degree so far, leading to about 10 millimeters of sea level rise. But on a geological scale, that sort of change is supersonic.

“This is happening a lot faster than anybody expected,” Mr. Duffy said.

Commissioners voted 13-0 to adopt an emergency climate crisis resolution. — Mark Alan Lovewell

He said the projections of future sea level rise have been adjusted upward over time. Ancient permafrost is melting, releasing enormous quantities of methane and primordial greenhouses that were once trapped below the Earth’s crust for millenia. Ice loss is also accelerating faster than scientists predicted, meaning if the planet isn’t able to keep global temperature rise to 1.5 degrees celsius by 2040, then the entire Greenland ice sheet will irreversibly melt, leading to upwards of 20 feet of sea-level rise.

The increase in temperature will also cause increases in extreme weather, Mr. Duffy said, including more tropical hurricanes, polar vortexes and drought in traditionally water-plagued parts of the world like the southwestern United States, Mexico, sub-Saharan Africa and India. All those places, home to billions of people, would also have two more months per year where temperatures are above 95 degrees Fahrenheit. Most of India would have greater than 160 days per year with temperatures over 95 degrees. Millions of people will move, he predicted.

“The number of days where it is dangerous to be outside are increasing,” Mr. Duffy said. “This is an ominous threshold which we have crossed.”

The effects of climate change will also be felt in New England, he said. Scientists have inextricably linked climate change to an increase in instances of Lyme disease and other tick-borne illnesses. There will be more hurricanes, flash floods and coastal erosion. There has already been a 71 per cent increase in extreme rain events in the region. Parts of the Vineyard Haven Harbor could be underwater soon, maps showed.

“Increases in extreme precipitation have occurred throughout the U.S., but nowhere more than here in the northeastern United States,” Mr. Duffy said. “Climate change doesn’t fix itself. If we turn off the tap, it doesn’t get better.”

So how does the planet limit temperature rise to 1.5 degrees Celsius, roto-root the spigot, remove carbon dioxide from the atmospheric bathtub and avoid the most catastrophic effects of climate change?

“Really, we don’t know,” Mr. Duffy said. “Most of the solutions are science fiction . . . the only tech that could work for carbon dioxide removal on this scale is deliberate, large-scale land management.”

The good thing, he said, is that polling shows support for climate activism is widespread, despite a prevailing narrative that suggests otherwise. Solutions in agriculture and re-forestation are hopeful and promising, he said, with old-fashioned methods of trapping carbon dioxide in soil and trees — albeit, done on a global scale — a feasible step toward removing greenhouse gases from the atmosphere. New technology, like artificial meat, plant-based diets, recycling efforts and the sharing economy are also promising developments.

“We need action. We need it now,” Mr. Duffy said. “What’s lacking more than anything else is the will to go ahead and do it.”

The presentation was followed by a robust question-and-answer session among Mr. Duffy, commissioners and Vineyarders, all wondering how could people do their part? Discussion touched on everything from stronger land-clearing regulations, to better insurance policies, to climate equity and social justice. As an Island, Mr. Duffy said, the Vineyard has a unique opportunity to take action.

And on Thursday, the MVC did.

The commission voted 13-0 to adopt an emergency climate crisis resolution, requiring them to develop a framework for factoring climate impacts into its analysis of developments of regional impact. The resolution also supports the nonbinding resolution Island towns will present at their annual town meetings to eliminate the Island’s reliance on fossil fuels by 2040, as well as draft energy and adaptation master plans. Commissioners Clarence A. (Trip) Barnes 3rd and James Joyce abstained.

More than two hours after the presentation began, the crowd applauded the vote.

“It seems like it’s a step,” Mr. Duffy told the commission. “I’m proud of you for taking that step, and I think you should be proud of yourselves.”