After enduring days of scorn for insisting that he had better things to do with his time than attend yet another United Nations-sponsored gabfest on climate change, the United Kingdom’s new prime minister, Rishi Sunak, reversed course Wednesday and announced that he would attend next week’s conference in Egypt after all.

Declaring that there is “no long-term prosperity without action on climate change,” Mr. Sunak said Wednesday he would join the thousands of diplomats, activists, and world leaders jetting off to the Red Sea resort of Sharm el Sheikh between November 6 and the 18th for the 27th such meeting of what in UN-speak is called the Conference of the Parties of the United Nations Framework Convention on Climate Change.

Shortly after taking office, Mr. Sunak announced that he has more pressing domestic issues to deal with, but was later shamed into reversing himself by opposition party leaders who said his absence would send the signal that the United Kingdom is insufficiently committed to addressing what they are now calling a “planetary emergency.”

During his time in Parliament, Mr. Sunak has been viewed as skeptical of the “Net Zero” emissions targets foisted on the world by previous United Nations meetings on the topic. He has supported measures that encourage green energy development via private sector financing and investment, but rejected calls from the more strident sectors of the climate movement to spend immense sums of taxpayer money to force the country away from fossil fuels.

Mr. Sunak will be joined in Egypt by President Biden, the American climate tsar, John Kerry, and as many as 100 leaders from more than 200 other countries. Also on hand will be as many as 35,000 delegates gathering for days of roundtables and discussions on topics as diverse as gender, decarbonization, biodiversity, and civil society.

During the last such meeting, at Glasgow in 2021, the 197 nations represented made all sorts of promises — about deforestation, about greenhouse gas emissions, about gas-powered vehicles, and about coal-fueled power plants — that few have followed through on in the interim. Participants also signed a Glasgow Climate Pact urging rich countries to pay at least $40 billion a year to countries in the developing world coping with environmental disasters such as floods and drought that now are invariably blamed on climate change. Most of that money has yet to materialize.

Given its setting in Africa, this year’s conference is expected to focus on badgering the world’s rich countries into paying what in some circles are being called “reparations” to countries of the Global South that are experiencing floods, heatwaves, droughts, and other natural disasters. Because developed economies emit more greenhouse gasses than less-developed ones, the reasoning goes, those countries should pay to mitigate the effects of climate change around the world.

Ahead of the meeting, the International Federation of Red Cross and Red Crescent Societies was among the dozens of non-governmental organizations calling on the rich world to scale up funding that would allow those in the less-developed countries to cope with what the organization called the “catastrophic impacts” of climate change.

“Our planet is in crisis and climate change is killing the most at-risk. COP27 will fail if world leaders do not support communities who are on the frontlines of climate change,” the group’s president, Francesco Rocha, said. “Families who are losing loved ones, homes or livelihoods cannot afford to wait for vague promises or weak commitments.”

The spectacle of policymakers gathering for days of discussions that rarely, if ever, produce anything concrete, however, is beginning to sour even for icons of the environmental movement. The climate change movement’s chief scold, Greta Thunberg — who attended two previous conferences — said she would not be going this year. During a book tour stop at London over the weekend, the 19-year-old Swede called the meeting nothing more than an opportunity for “greenwashing, lying, and cheating.”