A giant logo of TED Photo: AFP

A TED conference under the theme "The Case for Optimism" on Monday threw down the gauntlet for a return to face-to-face gatherings, despite the daunting challenges of the coronavirus pandemic, climate change and deep political divides.

Even with those dark clouds, speakers ranging from scientists and academics to artists and entrepreneurs took to the TED stage for the four-day event.

"We are trying to juggle it and do it right," TED curator Chris Anderson told the gathering while stressing pandemic precautions.

"We are living through a piece of history. Even though what we've heard is alarming, we can find optimism."

The event at the heart of what has become a global platform for mind-bending concepts aimed at making the world a better place returned to its roots with a scaled-down event on the edge of Silicon Valley.

Proof of vaccination was required, and badges were only given to those who passed COVID-19 tests.

A welcome kit included masks, wipes and sanitizers.

And the annual gathering that had grown to some 1,800 attendees at its venue in Vancouver was limited to about 600 attendees at a Monterey conference center.

Despite none of the attendees testing positive for COVID-19, Anderson urged everyone to wear masks given the highly-transmissible Delta variant.

"I felt the weirdest combination of intense excitement and intense nervousness," Anderson said of the weeks leading up to the conference.

"I want to salute the courage and commitment of each of you to come here; I know it wasn't necessarily easy to come."

TED attendee Betul Kacar, an astrobiologist who is a professor at the University of Arizona, took solace in the turmoil-roiling society.

"Chaos is needed for change to occur, and the world is definitely changing," Kacar said during a break in the talks.

"When things go smoothly, evolution doesn't happen."