With fewer than 300 days until the long-awaited signing of a global pact to curb climate change, the world's nations remain deeply divided on fundamental issues.
- The goal -
Most parties agree that overall global warming must be limited to two degrees Celsius (3.6 degrees Fahrenheit) over pre-Industrial Revolution levels, though small island states at highest risk of climate change-induced sea level rise want a lower ceiling of 1.5 C.
What parties don't agree on at all, is how to get there.
One proposal in the framework text approved in Geneva on Friday is to reduce greenhouse gas emissions by 40-70 percent from 2010 levels by 2050 and near-zero emissions by 2100, as advised the UN's Intergovernmental Panel on Climate Change.
Other options see deeper cuts, sooner, while some would set no numerical target.
- Who does what? -
The issue that permeates everything, "differentiation" is about how to share responsibility between rich and developing nations for cutting climate-damaging greenhouse gas emissions.
Developing nations want rich economies that are bigger polluters to shoulder a bigger burden. Wealthy countries, in turn, point to the rise of emerging giants like China and India as massive emitters of carbon from burning fossil fuel to drive their explosive growth.
- Money -
Developing nations want the 2015 Paris pact to contain a commitment from rich nations on financing and other assistance for the costly switch to greener energy, and for projects to help threatened communities adapt to unavoidable global warming-induced risk.
But rich countries are loathe to take on binding long-term engagements in an economically unstable world with fast-changing national circumstances.
- The legalities -
Will the pact be a protocol that needs to be ratified by national parliaments, or a mere political declaration? To what degree will a country's emissions target be binding under international law and failure subject to censure or penalties?
Will there be a mechanism for measuring, reporting and verifying a country's actions?
These crucial questions all await answers, suggesting a bumpy road to a universal agreement in Paris in December.