I’ve spoken to a lot of people about environmental action and inaction.
While I haven’t done double-blind randomized controlled experiments, I have seen one broad trend:

People who act on their environmental values do so for others.

People who don’t act on their environmental values do so for themselves.

Action

Typical reasons people give for acting include:

“I want to leave the world better than I found it,”

“Other people breathe that air,”

“This beautiful world is a gift and it’s my responsibility to steward it for others,” and

“I want the next generation to have as clean and pure a world as we did.”

Inaction

Typical reasons people give for keeping doing what they’re doing include:

“I don’t have time,”

“It’s not a priority for me,”

“If I act but no one else does, then what difference does it make what I do?”

“I’m trying to get ahead. I’ll get to it when I can,”

“Someone else should solve it—business/government/entrepreneurs/scientists/engineers should make it easier for me.”

Results

People who don’t act seem to feel more guilty. They defend themselves more. They don’t seem comfortable talking about the environment, as if they wished the problem would go away. They tend to blame others and assign others the responsibility to solve things. They want different results from their actions without changing their actions.
People who act seem happier with their results. They don’t seem to feel guilty. They seem more open about their shortcomings. They seem to grow from the experience. They seem humbled by the task before them but challenge themselves to take it on. They take responsibility for the consequences of their actions. They look for ways to change, expecting growth from it.

Examples

Examples of podcast guests who acted seriously—not just a bit of recycling—before doing my show include Bea Johnson, Evelina Utterdahl, Michael O’Heaney, Jared Angaza, Tensie Whelan, Anisa Heming, Elizabeth Kolbert, and Vincent Stanley.
If you haven’t listened to their episodes, I recommend it. Tell me if they don’t stand apart from the average person you meet. Do they sound happier?

Other groups

I should say there are also mixed groups—in particular, those who act ineffectually but think they are acting effectually. For example, they buy lots of things labeled “green” and “recyclable” that they don’t need and end up filling landfills.
I find them frustrating since they increase waste while feeling they are decreasing it. I don’t know what to make of them. They remind me of Martin Luther King Junior’s passage on white moderates from Letter from Birmingham Jail. It may be a better topic for its own post, but I’m quoting that passage anyway:

I must make two honest confessions to you, my Christian and Jewish brothers. First, I must confess that over the past few years I have been gravely disappointed with the white moderate. I have almost reached the regrettable conclusion that the Negro’s great stumbling block in his stride toward freedom is not the White Citizen’s Counciler or the Ku Klux Klanner, but the white moderate, who is more devoted to “order” than to justice; who prefers a negative peace which is the absence of tension to a positive peace which is the presence of justice; who constantly says: “I agree with you in the goal you seek, but I cannot agree with your methods of direct action”; who paternalistically believes he can set the timetable for another man’s freedom; who lives by a mythical concept of time and who constantly advises the Negro to wait for a “more convenient season.” Shallow understanding from people of good will is more frustrating than absolute misunderstanding from people of ill will. Lukewarm acceptance is much more bewildering than outright rejection.

I had hoped that the white moderate would understand that law and order exist for the purpose of establishing justice and that when they fail in this purpose they become the dangerously structured dams that block the flow of social progress. I had hoped that the white moderate would understand that the present tension in the South is a necessary phase of the transition from an obnoxious negative peace, in which the Negro passively accepted his unjust plight, to a substantive and positive peace, in which all men will respect the dignity and worth of human personality. Actually, we who engage in nonviolent direct action are not the creators of tension. We merely bring to the surface the hidden tension that is already alive. We bring it out in the open, where it can be seen and dealt with. Like a boil that can never be cured so long as it is covered up but must be opened with all its ugliness to the natural medicines of air and light, injustice must be exposed, with all the tension its exposure creates, to the light of human conscience and the air of national opinion before it can be cured.