Two years after the Paris Agreement, representatives from 197 countries are to gather for the 23th UN Climate Change Conference in Bonn, Germany, from November 6 to 17, with 23,000 delegates, scientists and activists expected to attend the largest-ever international conference on German soil.
Here is what you need to know about the COP23:
Who will be present in Bonn?
Apart from the politicians engaged in climate change issues, the experts and the environmental activists, there will be heads of state and government and celebrities.
French President Emmanuel Macron has announced that he will attend, alongside German Chancellor Angela Merkel.
Hollywood star Leonardo DiCaprio, who has long campaigned on climate issues, will be there, as will former US vice president and Nobel Peace Prize laureate Al Gore.
California's veteran governor, Jerry Brown, who has committed the state to curbing carbon dioxide emissions while profiling himself as an opponent of US President Donald Trump on climate change, will be on hand, as will Brown's predecessor, Arnold Schwarzenegger.
Why Bonn, when Fiji is presiding?
UN climate conferences usually take place in the presiding country, and it was the turn of an Asian country. Choosing Fiji, an island nation in the Pacific particularly threatened by climate change, is seen as sending a signal.
But organising a conference of this size and significance would have challenged Fiji's resources, and Germany has stepped into the role of "technical host."
Moreover, the secretariat of the UN Framework Convention on Climate Change is based in Bonn, where a conference was held in 2001.
And the first Conference of the Parties (COP1) was held in this west German city in 1995, when Merkel was the country's environment minister.
The Paris Agreement was adopted two years ago - what still has to be done?
The Paris Climate Agreement, adopted in December 2015, was seen as a major breakthrough. Thus far 169 parties have ratified it, including individual countries and blocs like the European Union. But implementation remains the key issue, and the details have yet to be thrashed out.
In principle the signatories have committed to their own targets for reducing greenhouse gas emissions. The effects of these measures on climate change are to be checked every five years, with the aim of making the commitments progressively more ambitious.
Other important aspects are adaptation to climate change and coping with the damage caused, including rising sea levels and extreme weather conditions.
Does that mean that the targets set thus far are inadequate?
The aim of the Paris Agreement is to curb global warming at significantly lower than 2 degrees, and 1.5 if possible.
Even this limited warming will have far-reaching effects, in the view of experts. These include more frequent drought and heavy rainfalls, rising sea levels and the melting of permanent ice.
But even if the commitments made by the parties to the agreement are met, this will still result in a temperature rise of 3 degrees, by comparison with the pre-industrial era, according to the UN Environment Programme (UNEP). There is thus a lot still to be done.
What precisely should take place in Bonn?
The politicians have to agree to a regulatory framework that allows national climate targets to be compared and monitored. If the conference manages to come up with a draft - even one with disputed sections and several versions - this would be seen as a success. But if there is nothing in writing, this would pose a problem in the view of Oxfam climate expert Jan Kowalzig, as then the time pressure would increase.
The first dialogue on monitoring kicks off in 2018 with the aim of checking whether the various countries are on the right track. One of the controversies concerns the differences between highly industrialised countries - responsible for much of the emissions in the past - and developing countries.