Diplomats and activists have gathered in Germany for two-week talks on implementing the Paris agreement to fight climate change.

The 23rd conference of the parties, or COP23, was opened Monday by Fiji's Prime Minister Voreqe 'Frank' Bainimarama. The Pacific island nation is already suffering the impacts of global warming.

Negotiators will focus on thrashing out some of the technical details of the 2015 Paris accord, which aims to limit global warming to 1.5 degrees Celsius.

The two-week meeting is the first major conference on climate change since President Donald Trump said that the U.S. will pull out of the Paris accord unless his administration can secure a better deal. Other nations are vowing to press ahead with the accord.

Who's coming, what are the key debates about and how green will this meeting be? Five things to know about the UN conference known as COP23, which runs from Nov. 6-17.

Germany Climate Talks

'The need for urgency is obvious,' said Fiji's prime minister Frank Bainimarama at the opening of the COP 23 Fiji UN Climate Change Conference. 'Our world is in distress from the extreme weather events caused by climate change.' (Martin Meissner/Associated Press)

Who's coming to Bonn?

Up to 25,000 people are expected to attend the talks, which will be presided over by Prime Minister Frank Bainimarama of Fiji — the first time that a small island nation will be at the helm of a major international climate conference. Participants will include diplomats from 195 nations, as well as scientists, lobbyists and environmentalists.

The United States, which has announced its intention to pull out of the landmark Paris climate accord, will be represented by Undersecretary of State for Political Affairs Thomas Shannon.

Key countries to watch during the talks are the emerging economic powers China and India. Other nations — Estonia, Peru, Ecuador, Iran, Mali, Ethiopia and the Maldives — will also be in the spotlight for leading major international groupings.

French President Emmanuel Macron, German Chancellor Angela Merkel and other leaders are expected to fly to Bonn toward the end of the summit to give the talks a final push and signal their commitment to fighting climate change.

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Barbara Hendricks, Germany's Minister for the Environment, Nature Conservation, Building and Nuclear Safety, poses for a picture with traditional dressed Fijian warriors during the COP23 UN Climate Change Conference 2017, hosted by Fiji but held in Bonn, in World Conference Center Bonn, Germany, November 6, 2017. (Wolfgang Rattay/Reuters)

What are the big climate change topics now?

The 2015 Paris accord set a target of limiting global warming to 1.5 degrees Celsius (2.7 degrees Fahrenheit) — or 2 degrees at the most — by the end of the century.

But diplomats didn't agree on the details of how their nations will reach that ambitious goal. The Bonn talks will flesh out the rule book that countries have to abide by.

This includes coming up with international standards for how to measure carbon emissions, to make sure that one nation's efforts can be compared to another's. A second debate centres around how countries take stock of what's been achieved and set new, more ambitious goals for curbing carbon emissions after 2020.

The third big issue concerns money. Experts agree that shifting economies away from fossil fuels and preparing countries for some of the inevitable consequences of climate change will require vast financial resources — including some from the U.S. administration of President Donald Trump, which is doubtful about man-made climate change.

Germany Climate Talks

A man in a polar bear costume walks between the delegates during the opening of the COP 23 Fiji UN Climate Change Conference in Bonn, Germany, Monday, Nov. 6, 2017. (Martin Meissner/Associated Press)

Why Bonn?

Organizing a massive global conference in Fiji would have strained the Pacific nation's resources and posed a travel nightmare for thousands of delegates. Germany offered to host the talks in Bonn, the country's former capital, because it has ample conference space and is already home to the UN climate change agency.

Still, they are going to miss the sunshine of Fiji. The weather in Bonn is generally dreary at best in November.

How green will the conference be?

Germany says the two-week talks will as be environmentally friendly as possible. The country is setting aside part of the €117 million ($136.3 million) budget for a fleet of bicycles and electric buses to ferry people between venues.

Each participant will receive a bottle to fill with tap water — a move organizers say will save half a million plastic cups.

Germany's environment ministry is also investing in renewable energy projects to compensate for the greenhouse gas emissions caused by people from all over the world flying into Bonn for the talks.

Germany Climate Talks

Delegates pass by a poster of the Fiji Islands in Bonn, Germany, Monday, Nov. 6, 2017. (Oliver Berg/dpa via Associated Press)

And what about Germany's coal usage?

Germany likes to portray itself as a leader in the fight against global warming and Merkel's reputation as the "climate chancellor" is partly built on the pivotal role she played during past negotiations.

But environmentalists note that Germany still gets about 40 per cent of its electricity from coal-fired plants — one of the most carbon intensive sources of energy. And German highways are also virtually unique in having no general speed limit, despite the fact that auto emissions rise dramatically at higher speeds.

If prosperous Germany fails to meet its own emissions targets, as current predictions suggest, critics say that would send a bad signal to the rest of the world.