Despite the Paris terrorist attacks that killed 130 people, there was no question of canceling the United Nations climate change conference scheduled to open on Monday (30.11.2015), according to French President Francois Hollande.

"Not only will the climate change conference be held," Hollande told the Congress bringing together both chambers of parliament on November 16, "but it will be a moment of hope and solidarity."

Heads of state expected to sketch compromise

US President Barack Obama, Chinese President Xi Jinping, Russian President Vladimir Putin and Indian Prime Minister Narendra Modi are all among the leaders set to address the conference on its opening day.

Representatives from nongovernmental organizations familiar with the negotiation process expect leaders to outline in their speeches possible compromises for those aspects of a climate treaty that remain contentious.

Global climate treaty to limit global warming

The grand goal of this UN climate change conference, the 21st Conference of Parties (COP21), to negotiate a global climate treaty to enter into force in 2020, in which all countries commit to curbing greenhouse gas emissions and to limiting global warming to below 2 degrees Celsius (3.6 degrees Fahrenheit) by the end of the century (compared to pre-industrial levels).

The 2-degree-target was adopted by the international community at the climate change conference in Cancun, Mexico, in 2010. Scientists agree that if global warming were limited to less than 2 degrees Celsius, its effects could be kept manageable.

"We can't differentiate precisely between what's going to happen when the world warms by 1.5 degrees, or when it warms by 2 or 2.5 degrees," said Anders Levermann, a physicist with the Potsdam Institute for Climate Impact Research. But he added: "What we can say is that the risks involved get bigger with each degree of global warming."

Under business as usual, Levermann told DW, "We are on a path that would take us to a world warmer by 5 degrees."

"That would mean losing mountain glaciers worldwide, having the Arctic sea ice melt away completely, and losing all of the coral reefs, upon which 600 million people worldwide depend for their livelihoods."

2-degree-goal already out of reach?

However, it is clear that even if leaders of the more than 190 nations that will gather at the Paris conference agree on a treaty, this will not limit global warming to below 2 degrees.

Climate pledges submitted by nations in the runup to COP21 are not enough: According to UN estimates, the world would warm by 2.7 degrees even if all these pledges were implemented unconditionally.

Review needed - but when?

For this reason, some parties want to push for a "ratchet-up" mechanism reviewing every five years whether countries are doing enough to reduce greenhouse gas emissions.

"The big question is when this review should take place for the first time," Germany's chief negotiator Karsten Sach told Deutsche Welle.

Many states, including the European Union, have set targets for 2030 for planning reasons, Sach explained. "But since we already know that we are not on track to limiting global warming to below 2 degrees, the European Union as well as the United States and small island states want the first review to take place already before 2020," he continued.

That way, countied could improve on targets for 2030, if necessary, Sach continued. He added that "some big nations" were opposed to this idea, and that he was expecting "tough negotiations" on this issue.

Transparency also divisive

The question of how transparent such a review process would be also remains contentious.

"We need clear rules that ensure that a ton of CO2 in China is equivalent to a ton of CO2 in India or in Germany," said Christoph Bals, policy director at the nongovernmental organization Germanwatch, and a seasoned observer of climate change conferences. He added that this was not the case at all at the moment.

"Some countries are factoring in their forestry, others are not," he said. "Some countries use different emission factors for different fossil energies, others do not."

But in its push for more transparency, the EU is set to encounter opposition from major emerging economies.

"China and India are not exactly big fans of transparency," said Sabine Minninger, who is in charge of climate politics at the Protestant Development Service, also called Bread for the World.

"They are among the worlds' biggest emitters of greenhouse gases, and if they made themselves subject to review, that could entail other responsibilities as well."

Issue of finance close to hearts of poor countries

Developing countries, particularly the world's poorest countries, are especially concerned about other aspects of the climate deal to be struck in Paris: including that of climate finance.

Climate financing refers to financial assistance for poor countries, for both facilitating their economies to embark on a low-carbon growth path, as well as to adapt to the effects of climate change.

In the Cancun climate change conference, the international community had finalized an agreement to make $100 billion per year available for this by 2020.

But it was not specifically agreed how the international community is to arrive at this sum, or which country is going to contribute what amount at which time.

The NGO Oxfam estimates that public climate finance provided by developed countries was only around $20 billion per year on average in 2013 to 2014.

According to Sabine Minninger, developing countries will push for stronger commitments for the period after 2020. "What we need is long-term reliability," she told Deutsche Welle.

"The numbers are not even all that important - but what is important is that we have a path detailing the scaling-up of climate finance."

Addressing 'loss and damage'

Beyond financing adaptation and mitigation, there is also the issue of the impacts of climate change too severe to allow for adaptation - like that of islands being washed away by rising sea levels.

In UN climate negotiating language, such effects are being described as "loss and damage" - a reference that had not been included in a first draft of the agreement.

Developing countries along with small island states succeeded in adding an article on loss and damage to subsequent draft text - a paragraph they are expected to push strongly to keep in the final text.

This paragraph includes the call for a facility to help coordinate efforts to address the displacement of people as a result of climate change.

Suffice to say, industrialized countries are not thrilled by the prospect of rather vague, extra damage that would be difficult to put a price on, and could run very expensive. As such, this represents another potential sticking point.

Optimism against all odds

Despite divergent views on many of the issues connected with striking a global climate agreement, observers are optimistic.

When the international community attempted to agree a global climate deal at the climate change conference in Copenhagen in 2009, the result was a dismal failure.

"Then, the US and China were hopelessly at loggerheads," says Christoph Bals, adding that the situation is completely different now.

Jennifer Morgan of the World Resources Institute agrees: "You have the US and China acting domestically with significant climate action, and internationally," she said. "Also, both leaders are personally committed, and I think that makes a big difference."

Positive developments in 'real world'

And then, observers add that much has changed in the world over the past six years. "Developments in the real world are much more favorable than before Copenhagen," said Bals, pointing for example to increasing investment in renewable energies.

"Renewables are [economically] competitive," said Morgan. "It's not seen as a competition between environmental protection and the economy anymore - they can go hand in hand, and that's a major breakthrough."

"Paris just needs to accelerate the pace," Morgan concluded.

And if the French presidency of the climate conference is to be believed, that's exactly what Paris is set to achieve.

"Paris can't fix everything," said ambassador Berengere Quincy, "but Paris can be a turning point."