Climate change is a slow story. The permafrost thaws. The oceans acidify. The cost of solar power falls. And meanwhile humanity keeps adding more greenhouse gases to the atmosphere.

The climate worsens slowly, and it will be solved slowly. Its works in time scales years and decades-long, not days or hours. Yet every so often there is an exceptional moment, and we are in one right now. This may be the single most important week for the climate this decade.

That’s because right now, in a suburb of Paris, global negotiators are in all-day, all-night talks to try and advance the first major global climate agreement since the 1990s. So far, these highly anticipated talks have gone much better than expected. They have avoided the acrimony and impassable “red lines” of previous conventions.

But that’s partly because all the easy problems have been solved. Now only the hard questions remain. Here’s a guide to most of them.

How much should the world limit warming?

The background: In 2009, the world’s nations agreed: The global temperature average should not be allowed to rise more than two degrees Celsius over pre-industrial levels.

Since then, study after study has emphasized the dangers of a two-degree-warmed world and the simultaneous difficulty of actually halting climate change there. When Paris began, some observers expected the UN to abandon the two-degree limit in favor of something more realistic.

Instead, there are some signs it may embrace a more ambitious target. More than 100 countries, including the United States, have announced support for limiting warming to 1.5 degrees Celsius. Many island nations have declared they cannot accept anything more. China has also signaled its endorsement. Were the UN to follow their lead, it would be a triumph for both activists and the most climate-vulnerable nations—even though many scientists, including President Obama’s top science advisor, believe keeping warming below 1.5 degrees to be a near impossibility.

The text: In the December 9 version of the draft Paris outcome, Article 2, Section 1 deals most directly with temperature limits:

This screenshotted excerpt from the UN draft Paris agreement reads: “The purpose of this Agreement is to [enhance the implementation of the Convention and to achieve its objective][further implement the objective of the Convention set out in its Article 2 [through enhanced action, cooperationand support]] so as:(a) To hold the increase in the global average temperature toOption 1: below 2 °C above pre-industrial levels,Option 2: well below 2°C above pre-industrial levels [and to [rapidly] scale up global efforts to limittemperature increase to below 1.5 °C] [,while recognizing that in some regions and vulnerable ecosystemshigh risks are projected even for warming above 1.5 °C],Option 3: below 1.5°C above pre-industrial levels, ”
Text within brackets is still up for debate.

* * *

How quickly will the world abandon fossil fuels?

The background: If humanity hopes to keep warming below 1.5 degrees Celsius by 2100, it must essentially stop emitting greenhouse gases into the atmosphere by 2060, according to a recent study from Nature Climate Change. (Then it must start pulling carbon out of the atmosphere—no easy feat.)

But should the Paris agreement come out and say that? Delegates are less sure. Small island states want forceful language, like the phrases above which call for “zero global [greenhouse-gas] emissions by 2060” or “decarbonization as soon as possible after mid-century.” But Saudi Arabia says that such a goal is a “threat to sustainable development”—which some interpret as meaning a threat to its oil production. (The head of the Saudi climate delegation also advises the country’s Ministry of Petroleum.) According to The New York Times, petroleum-pumping Venezuela is also skeptical of long-term decarbonization language.

The text: In the December 9 version of the draft Paris outcome, Article 3, Section 1 addresses the conference’s collective long-term goal:

This excerpt reads: “1. Option 1: Parties collectively aim to reach the global temperature goal referred to in Article 2 through [apeaking of global greenhouse gas emissions as soon as possible, recognizing that peaking requires deeper cuts ofemissions of developed countries and will be longer for developing countries; rapid reductions thereafter to [40–70 per cent][70–95 per cent] below 2010 levels by 2050; toward achieving net zero greenhouse gas emissions[by the end][after the middle] of the century] informed by best available science, on the basis of equity and in thecontext of sustainable development and poverty eradication.Option 2: Parties collectively aim to reach the global temperature goal referred to in Article 2 through a longtermglobal low emissions [transformation toward [climate neutrality][decarbonization]] over the course of thiscentury informed by best available science,”

* * *

Who should pay for the costs of climate change, and how much should they give?

The background: Surprise, surprise: “Climate finance”—that is, who gets money, and who gives it—is the most controversial issue at the Paris talks.

In order to salvage the 2009 climate talks in Copenhagen, Hillary Clinton pledged that the rich world would “mobilize” $100 billion to help developing countries make their economies more sustainable and prepare for the storms to come. The key word is mobilize: Unlike traditional foreign aid, where government money is redirected to poorer countries, the U.S. and the E.U. would arrange for billions to flow from a variety of sources, public and private.

Does that count? And is the rich world defined strictly as the U.S., E.U., Canada, and Japan? The United States would prefer for China and India—two wealthy, powerful nations that also contain hundreds of millions of people still in poverty—to pitch into that $100 billion target. Yet even as the two talk up their own investment in the developing world at the talks, they blanche at being compelled to join the rich world’s pledge.

The text: A great deal of the December 9 version of the draft Paris outcome deals with money, but here’s a taste, from Article 6, section 2:

Mobilization. Option 1: All Parties shall take action to mobilize, and/or facilitate the mobilisation of, climate finance from a
wide variety of sources, public and private, bilateral and multilateral, including additional sources, as well as
through facilitative policy frameworks, in line with their respective and evolving responsibilities and capabilities,
with developed country Parties taking the lead, noting the significant role of public funds. [Some Parties may
need support in order to take action.]
Option 2: Developed country Parties and other Parties included in Annex II to the Convention shall mobilize
financial resources beyond their previous efforts, supporting country-driven strategies, and taking into account
the needs and priorities of developing country Parties.

* * *

How often should nations check and reassess their emission reductions?

The background: Two different mechanisms apply here.

The first is stock-taking, when countries will announced how they’ve reduced carbon emissions. The draft Paris agreement now says global stock-takes will take place every five years. It also says that the first stocktake will happen in either 2023 or 2024, though the United States wants them to start earlier. The New York Times reports that the U.S. is angling for the first stock-take to come in 2019 or 2021—both non-presidential election years.

The second is ratcheting, when countries will announce more ambitious emissions reductions. India hopes for ratchet sessions to come every 10 years, saying its short term goal must be lifting its people out of poverty. The U.S. and the Pacific island nations wants countries to ratchet every five years.

The text: Article 10 of the the December 9 draft Paris outcome deals with global stocktaking, as do a few other sections:

1. The CMA shall periodically take stock of the implementation of this Agreement to assess the collective progress
towards achieving the purpose of this Agreement and its long-term goals. It shall do so in a comprehensive and
facilitative manner, considering mitigation, adaptation and the means of implementation and support, and in light
of the best available science [and equity].
2. The CMA shall undertake its first global stocktake in [2023][2024] and every five years thereafter unless
otherwise decided by the CMA.
3. The outcome of the stocktake shall guide and inform Parties in updating and enhancing their actions and support,
in a nationally determined manner, in accordance with the relevant provisions of this Agreement, as well as in
enhancing international cooperation for climate action.

* * *

Who should make sure nations meet their reduction goals?

The background: The United States wants an outside agency, perhaps similar to the International Atomic Energy Agency, to make sure nations keep the promises they made before the Paris talks to cut emissions. China, India, and other developing countries are skeptical of third-party oversight. In the Times, a former Clinton climate advisor says that the U.S. has increased its climate-finance money to try and gain leverage on the issue, but that the two rapidly developing powers are happy to wait the talks out.

The text: Right now, mention of an outside agency does not appear in the Paris draft text.

* * *

Who is responsible for the loss and damage caused by climate change?

The background: As climate change worsens, it will assault not only coastal cities and settlements, but also rural farmers and fishers who depend on predictable seasons and reliable ocean currents. Who should pay for all the infrastructure deluged and harvests lost? In 2013, a UN climate conference began establishing an international loss and damage mechanism to address these concerns.

The United States and other developed countries—which, after all, have emitted most of the greenhouse gases in the atmosphere right now and thus are responsible for that warming—say they want to help. But they cannot abide what would amount to climate reparations. “The U.S. clearly acknowledges that these impacts are being felt, but it does have a red line around increases of compensation and liability,” says Rachel Cleetus, the lead economist at the Union of Concerned Scientists.

The text: In the December 9 draft of the Paris outcome, a standalone Article 5 addresses loss and damage:

Article 5
Option I: The following text to be included as Article 5 (Loss and Damage)
Option II: The following text to be part of Article 4 alongside adaptation provision
1. [The Warsaw International Mechanism for Loss and Damage associated with Climate Change Impacts shall
serve this Agreement.
2. Upon the completion of its review at the twenty-second session of the COP,9
the Warsaw International
Mechanism shall be subject to the authority and guidance of the CMA and supported through the Financial
Mechanism of the Convention.
3. A climate change displacement coordination facility shall be established under the [Warsaw International
Mechanism][CMA] to help coordinate efforts to address climate change induced displacement, migration and
planned relocation.
4. A process to develop approaches to address irreversible and permanent damage resulting from human-induced
climate change will be initiated under the [Warsaw International Mechanism][CMA] with a view to completing
this process within four years.]

* * *

Who bears responsibility for protecting the climate, anyway?

The background: In 1992, the world adopted the United Nations Framework Convention on Climate Change. This document has guided all future climate diplomacy: This climate convention in Paris formally meets under its auspices. The framework convention establishes the principle of “common but differentiated responsibility” for protecting the climate system: That is, everyone has a role to play in keeping the world safe, but highly developed countries have the most responsibility.

Now, many developed countries want to make sure this principle is adhered to: the differentiated as much as the common. There’s no single blurb of text to point to that demonstrates this principle, said Cleetus, but developing countries want it to be a common thread through the text.

“Mitigation commitments, finance commitments—developing countries were asking for these issues to be seen together,” she told me. They needed “to be decided together under the convention rather than as one-off agreements on specific pieces of it.”

In particular, she said, they want any ratchet mechanism for emissions reduction to be tied to increases in finance from developed countries. Developing countries “won’t agree on an outcome where they’re making agreements to emissions reductions and are not seeing commensurate increases in finance,” Cleetus said.

The text: Again, no single portion of the December 9 Paris draft outcome addresses these issues. But I was struck by these two adjoining resolutions in the preamble. They’re both bracketed, which means that neither has a secure place in the final agreement. But they seem almost to argue and rebut each other:

[Noting that the largest share of historical global emissions of greenhouse gases has originated in developed
countries, that per capita emissions in developing countries are still relatively low and that the share of global
emissions originating in developing countries will grow to meet their social and development needs, Recognizing that Parties should take action to address climate change in accordance with evolving economic
and emission trends, which will continue to evolve post-2020, ]

The first clause declares: The most developed countries, the global North, are responsible for what became of the climate.

But wait, says the second clause: Wouldn’t the global South like to follow the North into prosperity? That means it will bear more responsibility soon. And it means, too, that both sides together must decide what the climate becomes now.