After more than two weeks of negotiations, delegates from more than 190 countries went home Dec. 15 without reaching an agreement on how to account for carbon reductions and markets under the Paris Agreement on climate change.

Expressing disappointment with the lack of concrete progress at COP25, U.N. Secretary-General António Guterres said in a statement, "The international community lost an important opportunity to show increased ambition on mitigation, adaptation and finance to tackle the climate crisis."

Experts tracking the climate talks heading into the event indicated that properly designed carbon market mechanisms would be critical to ensuring that countries collectively reduce total global greenhouse gas emissions and avoid double-counting reductions. Parties to the Paris accord, which aims to limit global warming to 2 degrees Celsius relative to preindustrial levels, have collectively listed carbon markets as one means of achieving 51% of their combined pledges, according to the World Resources Institute.

Andres Landerretche, COP25 coordinator for the presidency overseeing the negotiations, indicated at a Dec. 13 news briefing that the talks were falling apart. "These negotiations have always been very, very difficult. ... At the end of the day, there are some groups that are asking for more financing, which is fair in order for them to move forward with their adaptation plans."

The formal name of COP25 is the 25th annual session of the Conference of the Parties to the U.N. Framework Convention on Climate Change. The next session, COP26, is scheduled for November 2020 in the U.K. In addition to once again attempting to resolve carbon market issues, a number of countries have a deadline under their pledge in the Paris accord to release plans by the end of 2020 for raising their carbon-cutting ambitions.

Scientists have indicated that the world will need to act quickly to curb annual emissions levels by 2030 and achieve net-zero emissions by 2050 to achieve the goals of the accord, but global emissions thus far have continued to climb and reports have indicated that current ambitions of countries fall far short of the goal.

The EU separately fell short of getting get all EU members, Poland specifically, to agree to be carbon neutral by 2050. Poland gets the vast majority of its power from coal-fired generation. But the EU leaders expressed hope of convincing Poland to agree to the target.

President Donald Trump recently started the process of pulling the U.S. from the Paris accord.