He has announced plans to launch a new organisation that will use robotic technology to help save the planet.

In the speech at Amazon's re:MARS conference in Las Vegas, USA, Downey Jr. said the group would be called the Footprint Coalition.

The group, set to start in April 2020, will use robotics and nanotechnology to help tackle climate change.

Nanotechnology allows scientists to work at a very small level, where they can control individual atoms and molecules.

Downey Jr. says the coalition will "clean up the planet significantly, if not entirely, in the next decade".

The actor, who said he came up with the idea after a dinner with experts, has also credited his time working on the Marvel movies as the reason why he has a better understanding of modern technology.

Robert Downey Jr. has set up the Footprint Coalition group to tackle climate change

 

"Being essentially a 54-year-old child. I said, 'Let's do it! Let's commit to a process, let's form a coalition."

"For the last 11 years or so I've been steeped in the actual history of Artificial Intelligence and space stuff as it happened and is happening in reality."

At the moment there are few details about the Footprint Coalition's specific plans. But, Downey Jr. told the crowd that he's alarmed at the state of the environment and that even making a small dent would be important.

After hanging up his Iron Man helmet for good, the actor joked: "I've got to do something. I'm unemployed."