Fireworks.

In a tense, truncated meeting at the Ted Countdown Summit in Edinburgh on Thursday, Scottish climate activist Lauren MacDonald, a member of a group dedicated to stopping the development of the Cambo oilfield, was joined onstage by Ben van Beurden, CEO of Royal Dutch Shell, one of the world’s largest public oil and gas companies. Shell has a 30% stake in the potential Cambo development.

Chris James, founder of Engine No.1, the small investment firm that famously redrew Exxon Mobil’s board earlier this year, also joined the session, which was moderated by Christiana Figueres, one of the main architects of the 2015 Paris Agreement. It comes at a tense moment: just two weeks before COP26 in Glasgow, the delayed climate conference that is expected to mark a turning point in global action on climate.

“We share the anxiety of what is going on at the moment,” said van Beurden, the first of the three to speak. “We want to be on the right side of history.”

Van Beurden, who has pledged that the energy giant will reach net-zero emissions by 2050—including the emissions of its customers, known as Scope 3—said that the company was working to “dislodge oil and gas.” But he added that it could not immediately be stripped out, arguing that the world remained dependent on fossil fuels and that Shell still needed the legacy business to fund its transition toward renewables.

MacDonald, in response, said that Shell and van Beurden bore a large amount of the personal responsibility for climate change, accusing the company of greenwashing and calling him personally evil. She also questioned him over the company’s involvement in the Cambo development field, off the coast of Scotland, and the company’s appeal of the May climate ruling from a Dutch court that it must move faster to lower its emissions.

MacDonald then left the stage, as climate activists held up banners decrying the use of fossil fuels.

The moment represented a breathtakingly public clash between the numbers and strategy behind the energy transition, as seen by an oil and gas executive, versus the sense of desperate urgency and pain felt by many in the room over years of slow action—or little action at all—on climate change. It was also a meeting of two players in the debate over the pace of climate action who rarely meet, at least in such a public forum.

There had been early signs of protests at the event over van Beurden’s appearance, with local environmental activists staking out the front of the event space and questioning attendees over Shell’s appearance. Once MacDonald made her way off the stage, chants and cheers from activists echoed through the hall outside the stage.

Figueres, an iconic figure in the push for action on climate action, appeared to be choked up as she acknowledged what she said was the clear pain and frustration of MacDonald and many in the room, but asked for her return so the dialogue could continue. She did not.

The moment represented a telling generational divide. Although many of the people at the conference have been working on climate action, science, and technology for decades, the influence of young climate activists—and the extent to which they will bear the brunt of climate change—has been repeatedly referred to at the event. For many, they readily acknowledged, the connection was their own children and grandchildren.

Van Beurden also referenced his own four children, three of them daughters, and their anxiety about climate change; James of Engine No.1 has spoken in the past—including to Fortune’s Alan Murray—about how his own children influenced his decision to switch his investing strategy, ultimately abandoning a coal investment.

For some young activists, those acknowledgements have run hollow. One young activist, Melati Wijsen from Indonesia, referenced in her talk earlier in the week the “youthwashing” she claimed many companies were engaging in to get young climate activists on side, and said companies needed to include young people in meaningful consultations and board discussions.

Once MacDonald had left the stage, however, the grilling of van Beurden ultimately fell to James. Noting that he did not think “the whole oil and gas industry was the same,” he added that he thought the industry suffered from “insular” thinking and added that it had not done itself favors through the past embrace of industry lobby groups that have worked against climate policy.

“Because of that, there’s deep mistrust out there,” he said. He also questioned whether Shell was the right company to manage renewable projects which may have different skill sets and rates of return than traditional oil and gas businesses.

Van Beurden, meanwhile, said that the company could manage those returns, but added that the business also could not move substantially faster than demand. He also answered MacDonalds’ earlier question on Shell’s appeal of the Dutch court ruling, arguing that it singled out just one company and went further than the EU’s own Fit for 55 emissions standards. That legislation is based around 1990 emissions, while the court ruling baselines Shell against 2019 emissions. But van Beurden said the company would nonetheless try to meet the goal.

The company had “said goodbye” to the oil and gas business long term, he said—he just needed to fund the shift, he argued.

James, closing out the session, argued against divesting from fossil fuels, or stopping engagement, and said that activists should push companies—including through proxy votes.

“I think people should be angry,” he said. “If you’re angry, vote.”