The UN climate conference opens in Dubai on Thursday with nations urged to increase the pace of action on global warming and phase out fossil fuels, amid intense scrutiny of oil-rich hosts UAE.

The two-week-long climate negotiations being held this year in the glitzy Gulf city come at a pivotal moment, with emissions still rising and this year likely to be the hottest in human history.

Britain's King Charles III, world leaders, activists and lobbyists are among more than 97,000 people expected to attend what is being billed as the largest climate gathering of its kind.

The UN and hosts the United Arab Emirates say these talks, known as COP28, will be the most important since Paris in 2015, when nations agreed to limit global warming to well below 2 degrees Celsius since the preindustrial era, and preferably to a safer limit of 1.5C.

Scientists say the world is not on track to achieve these targets and nations must make faster and deeper cuts to emissions to avert the most disastrous impacts of climate change.

On the eve of the summit, UN Secretary-General Antonio Guterres said the conference should aim for a complete "phaseout" of fossil fuels, a contested proposal supported by many nations and scientists that has dogged negotiations past. 

"Obviously, I am strongly in favour of language that includes (a) phaseout, even with a reasonable time framework," Guterres told AFP before flying to Dubai.

A central focus will be a stocktake of the world's limited progress on curbing global warming, which requires an official response at these talks.

"Right now, we're taking baby steps where we should be taking great leaps and great strides to get us to where we need to be," said UN climate chief Simon Stiell on Wednesday.

On Friday and Saturday, about 140 heads of state and government — Pope Francis had to cancel at the last minute due to the flu — are expected to articulate their ambition after a year of devastating floods, wildfires and storms across the globe.

Hosts under pressure

On Thursday, nations are expected to formally approve the launch of a "loss and damage" fund to compensate climate-vulnerable countries after a year of hard-fought negotiations over how it would work.

But it remains to be filled, with rich nations urged to make contributions so the money can start flowing.

The UAE sees itself as a bridge between the rich developed nations most responsible for historic emissions and the rest of the world, which has contributed less to global warming but suffers its worst consequences.

But the decision for it to host has attracted a firestorm of criticism, particularly after the appointment of Sultan Al Jaber — the head of UAE oil giant ADNOC — to steer the talks as COP president.

The 50-year-old Emirati, who also chairs a clean energy company, has defended his record and resisted pressure from European and US lawmakers to stand aside.

Fears of a conflict of interest were given fresh life on the eve of COP28 when Jaber was accused of using the presidency to pursue fossil fuel deals in meetings with governments — accusations he strenuously denied.

Guterres said Jaber was in a better position to tell the oil industry that the "solution of the climate problems requires the phaseout of fossil fuels" than "if he was the member of an NGO with a very solid pro-climate record."

Thorny issues

Nations will navigate a range of thorny issues between 30 November and 12 December, and experts say geopolitical tensions and building trust could be a huge challenge.

Israeli President Isaac Herzog and Palestinian Authority leader Mahmoud Abbas may cross paths on Friday, as they are scheduled to speak within minutes of each other.

Neither US President Joe Biden nor Chinese President Xi Jinping — heads of the world's two biggest polluters — are attending, though Washington and Beijing did strike a rare common note on the climate this month that spurred optimism going into COP.

Sonia Dunlop, CEO of the Global Solar Council, said it was hoped that more than 100 countries would agree to triple renewable energy by 2030 — a flagship proposal being put forward by the COP hosts.

Rallying a common position on the future of fossil fuels will be more challenging.

Any decisions at COP are made by consensus, meaning nearly 200 nations — whether dependent on oil, sinking beneath rising seas or locked in geopolitical rivalry — must traverse these fault lines to reach any agreement.

"In the end, the proof is in the pudding," US climate envoy John Kerry said Wednesday.