Making a rapid transition to clean, renewable energy is a solution to battling climate change, but it will take upwards of $4 trillion a year for the next 30 years, according to former Secretary of State and current Special Presidential Envoy for Climate, John Kerry.

"We're not even close to one trillion," Kerry said. He joined Jim Braude on Greater Boston following the latest UN Convention of Climate Change called COP27.

"No government in the world has enough to plug the hole of those trillions," Kerry said, noting that the investment will need to come from the private sector, especially banks and other large financial institutions.

Kerry, speaking about COP27, said not enough countries are following through on their climate change promises such as implementing measures to keep global warming at or below 1.5 degrees celsius.

"We are on a track right now that could lead us to 2.5 degrees of warming or more and that's obviously catastrophic. So we have a huge turnaround that we still need to accomplish," Kerry said.

However, he expressed optimism about a better, brighter and healthier future for the planet and the economy, as companies take matters into their own hands and move faster than politicians on going electric.

Watch: Sec. John Kerry: Switching to clean energy will take trillions of private sector funding