Pulling a worn, yellowed copy of the 1992 UN climate change convention from her handbag, Farhana Yamin points to the paragraph that states its goal: To stabilise greenhouse gas concentrations at a level that would prevent dangerous warming. It doesn't provide any guidance on how to do that. But Yamin does. And, in a historic first, dozens of governments now embrace her prescription. The global climate pact set for adoption in Paris next year should phase out all greenhouse gas emissions by 2050, says the London-based environmental lawyer. "In your lifetime, emissions have to go to zero. That's a message people understand," said the Pakistani-born Yamin, who has been instrumental in getting that ambitious, some say crucial, goal into drafts being discussed at UN talks in Lima this week. Since Yamin launched the idea last year, it has exploded. Papers have been written, seminars held. UN Secretary General Ban Ki-moon, environmental groups and celebrities including Leonardo DiCaprio have backed variations. Critics call the idea unrealistic because it restricts us to two hard options. Either we abandon fossil fuels, our main current source both of energy and greenhouse gas pollution, or we find ways to capture emissions from coal, oil and gas and then bury them underground. "I do not think this is realistic when two billion people do not have access to energy," said Saudi Arabia's chief negotiator in Lima, Khalid Abuleif. "Concepts like zero emissions ... aren't really helping the process." Yamin is a veteran of the UN climate talks - these are their 20th iteration. She has been "island hopping" throughout, advising a range of small island states that fear being swallowed by the rise in sea levels scientists attribute to global warming. In Lima, she is an adviser for the Marshall Islands. She has also worked for the European Union. While scientists have long said the greenhouse gas emissions blamed for global warming need to be phased out, the overarching goal of UN climate negotiations is to stabilise those gases at a level that keeps warming below 2 degrees Celsius, compared with preindustrial times. It was Yamin who urged that a total emissions phase-out by mid-century be incorporated in the Paris deal, whose focus is on more near-term emissions cuts beginning in 2020. "Yamin had the original idea," said Niklas Hoehne, a German climate researcher inspired by her work. In May, she presented it at a symposium in Norway. "That was when this idea started to get more attention," said Aslak Brun, chief of Norway's delegation in Lima. In Lima, Norway is now pushing for a "net zero emissions" goal by 2050, meaning no more carbon emissions than the world's forests can absorb. Other options being discussed at the slow-going talks use different timelines and words like "carbon neutrality". "Some people don't like 'zero' - it's kind of harsh and scary," Yamin said. Chris Field, a scientist on the Intergovernmental Panel on Climate Change, says the net zero emissions goal is consistent with staying below the 2-degree target. US climate envoy Todd Stern said he could imagine a long-term goal in the Paris agreement "but I'm not sure what kind, whether it would be 'net zero emissions' or something else". China, the world's top carbon polluter, hasn't announced its position.