Denis Hayes, the man credited with founding Earth Day, predicted 2020 will be a turning point in the global climate change movement.
"I'm confident that the end is in sight. When conditions are right, people are ready to demand change, and America can turn on a dime," Hayes told reporters Monday during a news conference on Earth Day, which he helped established in 1970.
Hayes said people around the world are demanding change, especially the young, and that makes him optimistic.
"It recently happened in the United States on gay marriage. It more recently happened in New Zealand on gun control. It happened globally on the ozone hole," Hayes said.
Tens of thousands of students around the world skipped school for one day last month to protest inaction on climate change. There were protests in South Africa, India, New Zealand and South Korea. In Europe, students packed streets in London, Lisbon, Vienna, Rome and Copenhagen, among other cities.
Mass climate change protests have been taking place in London for the past week. On Monday, police said they have arrested 1,065 people since Extinction Rebellion began, aimed at paralyzing parts of central London to emphasize the need for sharp reductions in carbon use.
"Most social movements are powered by youth," he told reporters.
Hayes said even though U.S. President Donald Trump has "taken a wrecking ball to international climate treaties, appointed the two worst EPA administrators in history, and pledged to resuscitate the dead coal industry, I'm confident that the end is in sight."