Leaders from a group of 43 countries most vulnerable to the impacts of climate change called on the first day of UN climate talks for a new deal that puts the world on track to limit global warming below 1.5 degrees Celsius.

To achieve that goal - which is tougher than the expected 2 degree Celsius cap at the talks - would require cutting carbon emissions to zero and adopting 100 per cent renewable energy by 2050, the nations said.

Meeting it would demand much higher ambition at the talks than is now on the table, with experts saying current pledges from over 180 nations to curb planet-warming emissions add up to a temperature rise of at least 2.7 degrees Celsius.

Global warming is expected to hit 1 degree C this year.

Costa Rica's Minister of Foreign Affairs Manuel Gonzalez said his country's experience was that committing to reduce emissions could boost rather than harm economic growth.

"Keeping warming to a minimum of below 1.5 degrees won't simply deliver safety and prosperity, it will also deliver justice," he said.

A declaration from countries in the Climate Vulnerable Forum (CVF) said global emissions should peak as soon as possible, and at the latest by 2020.

The group includes middle-income, least-developed and small island developing states, from the Philippines, Bangladesh and Costa Rica to Ethiopia and the Maldives.

Saleemul Huq, director of the Dhaka-based International Centre for Climate Change and Development, told a gathering on the sidelines of the Paris negotiations that sticking to an internationally agreed warming limit of 2 degrees Celsius meant roughly 100 million people would "fall between the cracks".

Philippine President Benigno S. Aquino III said Climate Vulnerable Forum countries are estimated to be suffering economic losses from climate extremes of at least 2.5 per cent of GDP each year - even though they account for less than 2 per cent of global emissions.

His country was experiencing climate change "in the starkest possible terms", through powerful storms and flooding, he said. The Philippines suffers an annual average of 50,000 deaths from weather disasters, he added.

Money channeled into emergency spending to deal with the crises was money the country might otherwise be spending on its development, he said.

"Building back better is becoming less and less of a guarantee, given the new (climate) normal might still be replaced by an even newer normal that is even more destructive if we fail to act," he told the event.

QUALITY OF LIFE

The Climate Vulnerable Forum declaration also called for the Paris agreement to enshrine an international mechanism to address unavoidable climate-linked "loss and damage", such as the effects of rising seas and creeping deserts.

This is a sticking point in the negotiations, as rich nations fear they will be forced to foot the bill for permanent harm caused by climate change.

The Climate Vulnerable Forum said developed countries should continue to take the lead in providing funding to poorer nations, from a floor of $100 billion per year by 2020.

But finance ministers from 20 vulnerable countries have also set a target of mobilising $20 billion in new investment for climate action by 2020 themselves, drawing on all sources including international, domestic, regional and private finance.

In addition, the forum called for faster progress towards an equal split in financial backing for emissions reductions - which now get the bulk of cash - and measures to cope with climate change.

Whether the agreement that comes out of the Paris summit is ambitious or not is a "key difference for all of you and many others", UN climate change chief Christiana Figueres told members of the forum.

She said she had yet to see them working together "in an articulate and coordinated fashion" for a new UN agreement.

"The quality of the Paris agreement equals the quality of life of the most vulnerable in every community - that is the simple equation, that is the stark challenge that brings us here today," she said. – Reuters