The coronavirus outbreak has prompted climate activists to abandon public demonstrations, one of their most powerful tools for raising public awareness, and shift to online protests.

This week, for example, organizers of the Fridays for Future protests are advising people to stay off the streets and post photos and messages on social media in a wave of digital strikes.

“We are people who listen to the scientists and it would be hypocritical of us to not treat this as a crisis,” said Saoi O’Connor, a 17-year-old Fridays for Future organizer from Cork, Ireland.

Greta Thunberg, the 17-year-old Swedish activist who inspired the Friday youth protest group, last week stayed at home and tweeted a photo of herself and her two dogs, with a message calling on protesters to “take it online.”

Similarly, a coalition of climate movements had planned huge protests around commemorations for the 50th annual Earth Day in April. Those have now been canceled or moved online. One group, Earth Initiative and March for Science New York City, plans to live-stream speakers and performers at an online event.

Dominique Palmer, 20, a Fridays for Future organizer in Britain, acknowledged the challenges of protesting online. Hashtags and snappy videos are good, she said, but really making an impact will require more work. Twitter protests in which activists send out messages aimed directly at selected officials, and phone-banking, in which they telephone them en masse, are two of the ideas under consideration.

The new strategy marks a sharp turnaround for climate activists. A year ago this month, more than a million youth activists took to the streets worldwide in a global day of climate action.

It also comes at a crucial time. With a presidential election in the United States this year, activists had hoped to raise the profile of climate change on the public agenda. And, just days after the election, world leaders are scheduled to gather in Glasgow for United Nations-led climate talks where presidents and prime ministers will face pressure to get more ambitious about reining in greenhouse gas emissions.

Fridays for Future called preliminary online protests last week a success. Activists posted from bedrooms, gardens and balconies overlooking empty streets. Families joined in. In one video posted on TikTok, a father tucked his daughter into bed, leaving her alone with a climate monster in her closet.

Some experts, however, said reaching world leaders and the general public would be more difficult now as the pandemic shuts down large parts of public life.

“What you’re going to end up doing is amplifying within an echo chamber, which is really different from what the movement wants,” said Dana Fisher, a professor of sociology at the University of Maryland whose research focuses on activism. Twitter hashtags, like #ClimateStrikeOnline and #DigitalClimateStrike, are far less visible than huge crowds in the streets, she said.

Still, Dr. Fisher noted, the young people leading climate protests are highly effective at using social media to build their movement.

That was echoed by Ms. O’Connor, the Irish activist, who said she had noticed new faces in online protests messages that she hadn’t seen at her group’s weekly gatherings in Cork. She said Fridays for Future organizers were adaptable and prepared to adjust strategy as necessary. “Intersecting crises will be a feature of our times,” Ms. O’Connor said. “We can’t let one stop action on the other.”

Ms. Palmer said she hoped public demonstrations would resume before the United Nations conference in November. If not, she said, respecting advice to stay off the streets for the sake of older people, for whom coronavirus exposure is especially dangerous, would still come first.

“And that’s also how we want the older generation to feel toward young people,” Ms. Palmer said. “We want them to make the effort to save the planet for us in that same way.”

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