Lima - The world's nations gathered in the Peruvian capital Lima on Monday in a renewed push for a deal to roll back carbon emissions threatening future generations.
The 12-day talks under the UN Framework Convention on Climate Change (UNFCCC) take place amid grim scientific warnings and a surge in interest in sealing a pact in Paris in December 2015.
"Never before have the risks of climate change been so obvious and the impacts so visible", said UNFCCC chief Christiana Figueres.
"Never before have we seen such a desire at all levels of society to take climate action."
Figueres, flanked by Peru's environment minister Manuel Pulgar-Vidal, who will chair the conference, attended an interfaith candlelit vigil on Sunday to draw attention to victims of climate change.
About 10 000 delegates, activists, journalists and backroom staff have been accredited for the conference, with some 40 000 police providing security.
Since September, top-level interest has hauled the climate issue out of the doldrums, where it had lingered after a near-fiasco at a summit in Copenhagen in 2009.
In September, UN Secretary General Ban Ki-moon coaxed world leaders into renewing their vows to fight the scourge.
Since then, the three biggest emitters, China, the United States and Europe have sketched their own plans for contributing to the carbon cleanup.
But the Lima talks must clear several hurdles.
They must agree on a clear and transparent way by which countries next year will report national pledges to reduce climate-damaging greenhouse gases.
Without this cornerstone of trust, the voluntary approach that became the UNFCCC's strategy after Copenhagen could founder.
The UNFCCC's 196 parties must also hammer out a workable negotiating text for next year, a draft that is still likely to have big gaps, such as the accord's legal status and how pledges should be policed.
The envisioned 2015 accord would take effect from 2020, placing all nations for the first time into the same arena for tackling carbon emissions.
Right now, measures fall woefully short of keeping warming to 2°C over pre-industrial times, according to the Climate Action Tracker (CAT), an unofficial monitor.
In fact, Earth is on track for around 4 C warming, it says, a scenario that many experts say will be a recipe for drought, flood, storm and rising seas, and the risk of conflict over resources.
"Without collaborative action now, our shared Earth system may not be able to sustainably support a large proportion of humanity in the coming decades", the Earth League, an alliance of leading climate scientists, warned in a joint statement on Monday.
The world's most climate-vulnerable countries small island states and impoverished African countries are lobbying for the UNFCCC to uphold a tougher target of 1.5°C, which comes up for review in 2015.
"Lying two meters [over six feet] above sea level, we have more to lose than anyone from an agreement that falls short", Tony de Brum, foreign minister of the Marshall Islands, told AFP.
"The next 12 months are a chance to get back on track and the Lima COP (Conference of the Parties) must sketch out a process to get us there by analysing and assessing each other's proposed effort and understanding what it all adds up to."
Pressure on funding
Hand in hand with the emissions question is the issue of finance for poor countries, which will be hit worst by climate change but are least to blame for causing it.
To unlock a deal in Paris, developing countries want rich economies in Lima to show specifics on how they will honour promises to muster up to $100bn annually by 2020.
Nearly $10bn has been promised in start-up capital for the Green Climate Fund (GCF), the main vehicle for channelling the money.
Much more is needed, but also work on specific mechanisms for providing the money, say campaign groups.
"Vague promises won't help people to adapt to the harmful effects of climate change or help countries to purse cleaner paths to growth and development", said Winnie Byanyima of Oxfam.