The officials from around the world who will gather in South Africa on Monday to convene the latest round of U.N. climate negotiations are facing an uncomfortable fact: The global pact that has dictated greenhouse-gas targets since 1997 may no longer be relevant.

The mandatory targets of the Kyoto Protocol cover less than a third of the world’s carbon output. Major emitters are not bound by it. And, increasingly, the world is relying on a patchwork of measures rather than a universal treaty to lessen the impacts of global warming.

The Kyoto agreement won’t die altogether in Durban; it may be extended for another five years without binding commitments from industrialized nations while programs for international carbon offsets are preserved as a way to compensate for emissions.

Delegates to the U.N. Framework Convention on Climate Change will focus largely on technical details, such as how to administer a future fund to help poor nations adapt to global warming and how to transfer clean technology to developed nations.

But the debates over concrete policies to cut greenhouse-gas emissions over the next decade are happening in places such as the Australian Parliament and California’s Air Resources Board.

James L. Connaughton, who chaired the Council on Environmental Quality under President George W. Bush, said Kyoto’s global, top-down strategy has been replaced by a more incremental approach to tackling emissions.

“The situation has never been weaker for that vision” of a global approach, said Connaughton, now executive vice president for corporate affairs, public and environmental policy for Constellation Energy. “On the other hand, there’s been quite a lot of progress bottom-up, country by country, in terms of setting reasonably ambitious goals and time frames” for cutting greenhouse gases.

In 1997, nearly 200 countries — including the United States — forged an agreement that aimed to cut industrialized nations’ global emissions 5.2 percent compared with 1990 levels by the end of 2012. But 14 years later, the binding targets cover countries that account for just 27 percent of the world’s carbon output. That’s because the United States did not ratify the Kyoto Protocol and the agreement did not cover major emerging economies such as China and India.

Nonetheless, many countries and regions are pressing ahead with strategies to curb their carbon emissions. Australia imposed a carbon tax on several industries that takes effect next year and will transition to a carbon-trading system in 2015.

Several developing countries are adopting what are known as “nationally appropriate mitigation actions.” Mexico is considering legislation to establish a domestic carbon market while developing rules for the cement industry and providing incentives for low-income residents to buy energy-efficient homes. Colombia is working on plans to scrap its aging and polluting freight trucks, promote renewable energy, increase energy efficiency in construction and expand rapid bus transit.

“You’ve got some good things happening,” said Ned Helme, who heads the Center for Clean Air Policy and has worked with several Latin American governments on climate policy. “Look at where we are on the ground and where we’re moving.”

Todd Stern, the U.S. special envoy for climate change, emphasized in a news conference this month that all the major emitters of greenhouse gases established their 2020 climate targets in a political agreement at last year’s U.N. talks in Cancun. The United States pledged to cut its emissions 17 percent compared with 2005 levels, and China has pledged to cut its carbon dioxide emissions per unit of gross domestic product between 40 and 45 percent during that same period.

“We have agreed on something to 2020. Everybody has. That’s Cancun,” Stern said.

An analysis by the Center for American Progress shows that these commitments would bring the world two-thirds of the way toward keeping the global temperature rise by the end of the century to 2 degrees Celsius (3.6 degrees Fahrenheit), the target all parties to the U.N. Framework Convention on Climate Change have endorsed for several years. And if developing nations don’t follow through on their most ambitious goals, even the two-thirds mark will be out of reach, according to a new report by the U.N. Environment Program.

“What is evident is we have a large gap to fill, because of what science tells us we need to do,” said Maria Fernanda Espinosa, Ecuador’s coordinating minister of heritage and a leading climate negotiator.

And although 1,055 American mayors have pledged to meet the original U.S. target of cutting emissions 7 percent from 1990 levels, only four cities — San Francisco, Seattle, Portland and Los Angeles — have said they have reached that goal. Michael Schmitz of ICLEI, which tracks local government climate policies in the United States, said that without a national cap on carbon, “it’s very difficult to achieve the reductions that mayors, frankly, thought they’d be able to do.”

In light of those challenges, the European Union, which is the only Kyoto signatory willing to enter into a second five-year commitment period, has said it will not do so unless countries including the United States, China and India are willing to begin negotiations that could produce a new legally binding agreement by 2020. The E.U. accounts for 16 percent of the world’s global greenhouse-gas emissions.

“It has to be part of a bigger picture of a broader deal. We need a mandate, a road map,” Karsten Sach, Germany’s lead climate negotiator, said in an interview. “I am convinced the E.U. stands firm on that.”

The key countries that would have to endorse a broader deal have yet to do so. The United States argues that it cannot sign on to the prospect of a legally binding pact until it knows what that pact would look like. Major developing countries say that the U.N. process does not bind them to the same rules as industrialized nations and that they will not accept a change in status.

“The formal positions are pretty hard on this,” said Jennifer Morgan, director of the World Resources Institute’s climate and energy program. If negotiators walk away from Durban without forging a clear path forward, she said, “it sends a signal that countries aren’t as serious as they need to be about solving the problem of climate change.”