Past and future hosts of the UN climate negotiations the United Arab Emirates, Azerbaijan and Brazil announced Wednesday they would cut their own emissions in line with limiting global warming to 1.5 degrees Celsius.

Nations have been under pressure to keep this warming limit alive by pledging to accelerate their efforts to slash greenhouse gas emissions in a new round of climate pledges due in the coming months.

The United Nations climate chief last week stressed that the new round of commitments -- as well as upgrades to existing pledges for this decade -- were essential to keep the world from blowing past 1.5C and to ensure the "safety and prosperity" of people around the world.

The 2015 Paris Agreement saw countries agree to cap global warming at "well below" 2C above preindustrial times -- with a safer limit of 1.5C if possible.

It also requires countries to submit increasingly deep emission cutting plans every five years, known as Nationally Determined Contributions (NDCs), with the third round of pledges due by February 2025.

In a letter, the so-called troika of the UAE, Azerbaijan and Brazil jointly pledged to align their own climate plans with a warming cap of 1.5C, and urged others to follow suit.

"As three developing countries representing different geographic regions of our world, the COP28, COP29, and COP30 Presidencies will demonstrate our commitment by submitting 1.5C-aligned NDCs", they wrote.

The UAE hosted last year's COP28 conference in Dubai, while Azerbaijan will host this year's summit followed by Brazil in 2025.

Taking into account current climate pledges, the world is still on track to warm between 2.5 and 2.9 degrees Celsius over this century, according to UN estimates.

Warming of 1.5C will probably be reached between 2030 and 2035, according to the Intergovernmental Panel on Climate Change (IPCC), which stresses that every fraction of a degree of temperature rise that is avoided will be safer for people and planet.

"Earth's issuing a distress call," UN Secretary-General Antonio Guterres said Tuesday as the World Meteorological Organisation issued a fresh warning over a slew of climate extremes that lashed across the planet last year as global temperatures hit a record high.

- Critical moment -

The announcement by the troika nations -- all fossil fuel producers -- raised some eyebrows.

UAE's investment in hydrocarbons is growing, and its national plan has been deemed "highly insufficient" by Climate Action Tracker (CAT), an independent think monitor, while Brazil's was declared "insufficient".

Azerbaijan, which only published its climate action plan in October, has not been assessed.

But its share of renewable energy barely moved in the 11 years to 2022, rising from 15 percent to 17, according to its own NDC.

It has promised to reduce emissions by 35 percent by 2030 compared to 1990 levels, and 40 percent by the middle of the century.

Harjeet Singh from the Fossil Energy Non-Proliferation Treaty Initiative said there was "stark contrast between the troika countries' public embrace of climate leadership and their simultaneous plans to expand fossil fuel production".

"These countries must disentangle themselves from fossil fuel interests and lead climate action by example, pressuring wealthier nations that continue to shirk their historic and moral responsibilities," he told AFP.

The first of a series of meetings on national climate goals will be held in Copenhagen Thursday and Friday, with ministers and negotiators from some forty countries expected, including the new United States climate envoy John Podesta.