Robert Downey Jr. doesn't pretend to be a brilliant scientist — even though he's played Tony Stark, aka Iron Man, for the past 11 years.

But on Tuesday night he attended Amazon's new open-to-the-public Machine Learning, Automation, Robotics, and Space (re:MARS) tech conference in Las Vegas — a room filled with artificial-intelligence legends, astronauts, and other dignitaries — as a keynote speaker.

And just when the crowd thought Downey was just there to entertain, he got the audience to cheer: At the end of his talk he announced that he was launching a new initiative called Footprint Coalition.

Its goal is nothing less than to use robotics, artificial intelligence, and technology to clean up the Earth and reverse its carbon footprint in a decade.

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Robert Downey Jr. doesn't pretend to be a brilliant scientist — even though he's played Tony Stark, aka Iron Man, for the past 11 years.

But on Tuesday night he attended Amazon's new open-to-the-public Machine Learning, Automation, Robotics and Space (re:MARS) tech conference in Las Vegas — a room filled with artificial-intelligence legends, astronauts, and other dignitaries — as a keynote speaker.

He delivered a gag-filled talk that somehow weaved together the history of the Marvel Cinematic Universe, the evolution of Stark's Iron Man suits, allusions to his own troubled history with drug addiction, and the actual history of artificial intelligence and its pioneers, along with a bunch of jokes using the Amazon Alexa voice and Matt Damon (including a videotaped guest appearance by Damon).

Read more: An Amazon employee explains why thousands of workers want the company to stop selling cloud services to oil companies, just like it won't sell guns

And just when the crowd thought Downey was just there to entertain, he got the audience to cheer: At the end of his talk he announced that he was launching a new initiative called Footprint Coalition.

Its goal is nothing less than to use robotics, artificial intelligence, and technology to clean up the Earth and reverse its carbon footprint in a decade.

Here's how he told to the story.

Downey at Amazon's re:Mars conference. Business Insider/Julie Bort

"Quick disclaimer, I don't pretend to understand the complexities we face as a species, just because I portrayed a genius in my professional life — my scholastic achievement peaked at a correctional finishing," Downey said, alluding to his troubled past that landed him incarcerated on drug charges until he cleaned up in a court-ordered rehab treatment. Downey also told the audience how he never made it past high school.

"On the flip side, I did play an interesting and iconic character for 11 years, Tony Stark," he said, adding that what he liked about Stark was that he went from a "soulless war profiteer to a man who was willing to sacrifice himself for the good of the community."

Downey also had to personally change, transforming from a troubled youth into a reliable actor and member of an ensemble acting team, as part of the "Avengers" movies' cast.

"Interestingly enough, when you want to change, the universe puts people in your life that facilitate that," he said.

And his fame gives him access to all sorts of people.

"Recently, I was at a table with supersmart, impressive, expert folks about six months ago, and the following statement was made: 'Between robotics and technology, we could probably clean up the planet significantly, if not entirely, within a decade,'" he said, and the room burst into applause.

Read more: Amazon employees were miffed at Jeff Bezos' response to their climate-change proposal: 'This is not the kind of leadership we need'

"Being essentially a 54-year-old child, I said: 'Let's do it! Let's commit to a process, let's form a coalition,'" he said. "And that did not inspire the reaction I expected. It was dead silence."

(He used courser language involving bodily waste and smells in an elevator to describe the reaction he got.)

Those smart intellectuals, who thought the tech could do it, also thought that overcoming bureaucracy, sharing intellectual property, and intergovernmental cooperation would be too difficult to overcome.

But Downey wants to try anyway.

"I know it's a kumbaya-type dream. It's a logistical clusterf---," he said. "I'm down with dedicating myself to maybe one small part of making good on that statement, even in abject failure, it's still the best idea I've ever had."

So at this robotics show, he announced his Footprint Coalition, which is still so new, its website hasn't even been set up. The actor is promising that the organization will officially be off the ground in April 2020 and that he's willing to spend "the next 11 years" working on it.

"I've got to do something — I'm unemployed," he joked, a reference to the ending of the latest "Avengers" movie.