It's considered the meeting before the meeting, the gathering to do the legwork ahead of crunch climate talks in Paris next year.
Representatives from almost 200 nations are gathered in Peru to forge some measure of consensus on a deal to limit rising greenhouse gas emissions.
Any deal, if agreed in Peru, would be signed off on in Paris, and climate change officials are keen to ensure the France summit isn't a repeat of the UN climate gathering in Copenhagen in 2009.
Back then, officials were to formalise a framework for climate change mitigation laid out in the Bali Road Map. What resulted was a watered down political statement that was not legally binding.
The 12-day meeting in Peru, under the auspices of COP20, is tasked with steering the 196 parties toward the most ambitious climate pact in history - "the matrix for managing climate issues for the next 30 years," according to French climate negotiator Laurence Tubiana.
Due to take effect from 2020, the accord would roll back carbon emissions and ease the threat of misery, ecosystem damage and species loss for future generations.
Given the UN's shaky record on climate change, the challenge is vast.
The last climate treaty was the Kyoto Protocol, inked in 1997. The bid to follow it up in Copenhagen was a near fiasco.
But in recent months, the political tone has changed, strengthening hopes that the creaking negotiations may finally yield a result.
The gathering in Peru has been bolstered by the recent pledges by China and the United States to curtail their greenhouse gas emissions, with Beijing agreeing to a timeframe for the first time.
The "historic" China-US pact acclaimed by climate scientists is an attempt to breathe new life into action against global warming ahead of Paris.
Under the deal, China has set a target for its greenhouse gas output to peak "around 2030", whilst US President Barack Obama committed the US to cutting its own emissions by 26-28 per cent from 2005 levels by 2025.
"The broad outlines of a deal have begun to emerge and the three largest emitters (including the European Union) have stepped forward early and encouraged others to follow suit," says Elliot Diringer of the Center for Climate and Energy Solutions, a US think tank.
"We're in about as good a shape in these negotiations as I think we've been for some time."
Key details are still fuzzy, but the announcement should raise the stakes next year when all countries are meant to put pledges on the table.
Money, too, has added a dose of goodwill. Rich countries have promised contributions to the Green Climate Fund, the main vehicle for channelling help promised to poor nations in Copenhagen - a total of $100 billion annually by 2020.
At the same time, the Peru summit will also see a quieter push to secure more of the limelight for efforts to adapt to the unavoidable effects of climate change. These include building more resilient infrastructure, putting in place disaster warning systems and teaching farmers to harvest rainwater.
Another potential hot topic in Lima is whether countries should include adaptation efforts in their contributions to the new deal. Those contributions are supposed to be put on the table early next year but some industrialized nations have argued the offers should cover only emissions reductions.
But for less developed countries, they are a way of linking their current and future plans for adaptation with the amount of financial and technical support needed to implement them.
This will vary according to how much effort is made to keep global temperature rise to an internationally agreed limit of two degrees Celsius or less, they argue, and should be subject to the same review process as mitigation efforts.
