UN scientists have set a goal of preventing a glocal temperature rise of more than 2 degrees Celsius (3.6 degrees Fahrenheit) over pre-Industrial Revolution levels
Paris (AFP) - Diplomats convene in Bonn Monday for the last five-day negotiating session before 195 nations try to ink a global climate pact in December.
The UN talks have made progress, but consensus remains elusive on many crucial points.
Here are some of the outstanding issues:
- Define 'too hot' -
In 2010 the world's nations set a goal of preventing a rise of more than 2 degrees Celsius (3.6 degrees Fahrenheit) over pre-Industrial Revolution levels.
But small island states and poor nations -- which will get hit early and hard by global warming -- are today pushing for a lower ceiling of 1.5 degrees Celsius.
Whatever goal is agreed, exactly how the nations would collectively reach it is also still subject to debate.
- Money, money, money -
In 2009 rich countries pledged to mobilise $100 billion (87 billion euros) per year from all sources by 2020 to help poor countries fight climate change and adapt to its impacts.
A recent report by the Organisation for Economic Co-operation and Development (OECD), an intergovernmental body, said climate finance from all sources hit $62 billion in 2014.
But sharp disagreement remains on how much of the money should be public or private, what accounting methods should be used, and the appropriate split between grants and loans. And climate finance mobilised last year, developing nations point out, is no guarantee of what will be available in 2020 and beyond.
More recently, the world's poorest countries have also pushed for payouts -- beyond the $100 billion -- for "loss and damage" caused by global warming.
The United States and the European Union have balked at the concept of "compensation", but agreed to engage on the issue.
- Slashing emissions -
One pillar of the Paris climate agreement will be the pledges that nearly 150 nations have already made for reducing their greenhouse gas emissions.
China, the United States and the European Union -- which together pump out over half the world's carbon dioxide pollution -- have led the way.
The emissions reduction plans presented so far, however, would still cause Earth to warm by 2.7 degrees Celsius, well past the danger mark, according to an analysis released in early October.
In response, some negotiators have proposed including a mechanism that would encourage countries to re-evaluate and ramp up their efforts over time.
- Blame game -
Built into the negotiations is the principle that rich countries have been the major cause of the problem and are thus more responsible for fixing it.
The talks are taking place under the auspices of the 1992 charter of the UN Framework Convention on Climate Change, which enshrined this principle of "differentiation".
But wealthy countries insist that much has changed since then, and point out that nations once tagged as "developing" have made huge economic leaps and become big polluters in their own right.
China is now the world's number one emitter of carbon pollution, overtaking the US, and India is number four. The extent to which the "differentiation" principle will stymie progress -- as it has in the past -- remains to be seen.