About 200 heads of government and state and more than 25,000 delegates from all over the world, will gather at the UN climate conference (COP25) on Monday (2 December) to address the challenges of the climate change.

Establishing rules for carbon markets and finding a common time frame will be the priorities for COP25.

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"In the crucial 12 months ahead, it is essential that we secure more ambitious national commitments - particularly from the main emitters - to immediately start reducing greenhouse gas emissions at a pace consistent to reaching carbon neutrality by 2050," said UN secretary-general António Guterres on Sunday.

The negotiations will focus on article six of the 2015 Paris Agreement, referring to the regulation of carbon markets system that is set to help countries decarbonise their economies at lower cost - this is the last section of the rulebook which remains unresolved.

Governments are also set to update their national contributions plans to reduce greenhouse gas emissions - that they can formally express throughout 2020.

Most of the national climate plans include the use of carbon markets to achieve emissions reductions with different mechanisms, meaning that governments and private sectors can trade emissions reductions.

However, the lack of agreement might undermine the entire accord and even lead to an increase in emissions.

The World Meteorological Organization announced last month that greenhouse gas concentrations reached their highest recorded level in 2018 and the UN warned that the world is currently heading towards a 3.2 degrees temperature rise from pre-industrial levels.

The president of the new commission, Ursula von der Leyen, wants Europe "to become the first climate-neutral content."

However, a new UN environment programme report released this week concluded that global greenhouse-gas emissions need to fall at least by 7.6 percent each year between 2020 and 2030 to keep temperature rises as close as possible to just 1.5 degrees.

Under that scenario, the EU's proposal to increase the targets to 50 percent or 55 percent, compared to 1990, would not be in line with the Paris Agreement objectives to keep global temperatures under 1.5 degrees.

However, a lot depends on G20 countries, who account for around 78 percent of global emissions.

The UN conference will also pave the way for next year's COP26 summit in Glasgow when countries are expected to boost the climate commitments they made in 2015 in Paris.

Venue moved twice

The COP25 was initially scheduled to be held in Brazil. But It was moved to Chile after the Brazilian president Jair Bolsonaro was widely criticised by environmentalists for his policies on the Amazon region.

However, following violent protests and civil unrest in Chile, the government announced at the end of October that the country was ceding the hosting of the UN climate conference to Spain, although Chile remains overall in charge of COP25.

The COP25 will take place days after the European Union collectively declared a "climate emergency" and three weeks after Donald Trump confirmed the United States' withdrawal from the Paris Agreement.

According to a statement, the US will have a diplomatic team but no senior members of Donald Trump's administration at the COP25.

"The United States will continue to participate in ongoing climate change negotiations and meetings - such as COP25 - to ensure a level playing field that protects US interests," the US State Department said on Saturday.

The Alliance of Small Island States (AOSIS) has also voiced its concerns about the risks of small island and low-lying coastal states whose future might depend on national plans of industrialised countries.

However, according to Spain's minister for the ecological transition, Teresa Ribera, "COP25 will reaffirm that multilateralism is the best tool to solve global challenges such as climate change".