Looking to drive home that the planet faces a dire risk if it does not address the causes and effects of climate change, former U.S. vice president and longtime environmental advocate Al Gore struck a mostly optimistic tone as he led a call to action before a largely receptive audience Tuesday at the Collision tech conference in New Orleans.

“For anybody who doubts that we have the will to change, just remember that the will to change is itself a renewable resource,” Gore, the Democratic nominee for president in 2000, said in a 20-minute keynote address that was part pep talk, part lecture.

Now in its fifth year overall and its third in New Orleans, Collision is known as America’s fastest-growing tech conference. An estimated 25,000 attendees were expected at panel discussions, networking events, speeches and individual meetings through Thursday at the Ernest N. Morial Convention Center.

Addressing the challenges of global warming won't be easy, Gore warned the crowd. 

“If we have to, and we do have the ability to change, we’ve still got to summon the political will to make the large-scale policy changes and technology and business changes and cultural changes” that are needed, he said.

Gore urged the crowd to give serious consideration to finding ways to invest in renewable energy technology, which he said would “put pressure on the entire investment market” to move in that direction.

“The investor community has an enormous role to play,” he said.

Although President Donald Trump has informed the United Nations that the U.S. will withdraw from the Paris climate agreement, Gore said the next president — if elected in 2020 — could get the U.S. back into the pact in short order, since the formal withdrawal process requires roughly four years.

Gore ticked off a list of recent hurricanes and storms that pummeled many areas, including Hurricane Harvey that flooded the Houston area last year and Hurricane Maria, which has left much of Puerto Rico still grappling with widespread power outages and other major problems nearly a year later.

He criticized the federal government’s response to the damage in Puerto Rico, calling it “a disgrace the way we have abandoned our fellow Americans” and equating it with “environmental racism.”

Noting that NASA and NOAA scientists have concluded that 17 of the 18 warmest years since modern record-keeping began have occurred since 2001, Gore said the fact of global warming cannot be disputed.

“Suffice it to say, the answer to that first question about the climate crisis, ‘Must we change?’ is yes. In fact, you could say, ‘Hell, yes.’ It’s pretty dang obvious that we have to change.”

After weeks of speculation, Collision organizers confirmed Tuesday that the conference will move to Toronto next year.

Paddy Cosgrave, the CEO of the company that runs Collision, addressed that decision Tuesday before introducing Gore. On the stage, he presented Toronto business leaders and officials, who alternated between praising the Canadian city as "the safest city in the entire world" and the "most multicultural city in the entire world."

For his part, Cosgrave called New Orleans “perhaps the most unique city in the world. It’s certainly the most unique city in America.”

Follow Richard Thompson on Twitter, @rthompsonMSY.