Delegates and leaders from over 190 countries have descended upon Paris for the COP21 conference. Its goal is, for the first time in over 20 years of UN negotiations, to achieve a legally binding and universal agreement on climate, with the aim of keeping global warming below 2 degrees C (3.6 degrees F) between now and the year 2100.

In order to hit this target, it’s estimated that global greenhouse gas emissions have to be reduced by 40 to 70 percent within the next 35 years, and that we only have until the end of the century to reach carbon neutrality.

The delegates have until the last day of the conference — December 11 — to come up with something. To give both large and small countries equal weight, even a single vote can block a final deal.

Even the language used in the agreement can make a huge difference in its success. The draft includes several phrasing options, including over 30 instances of shall vs. should — “shall” is mandatory, but “should” is merely a guideline.

“The fate of mankind is on the agenda at this conference,” said French President Francois Hollande in an interview ahead of the talks. Paris, still reeling from last month’s terrorist attacks that killed 130 people, is under tight scrutiny due to the conference — protestors have placed their shoes in the Place de la République since safety concerns have banned them from marching against climate change. “I can’t separate the fight with terrorism and the fight against global warming,” said Hollande. “These are two big global challenges we have to face up to, because we have to leave our children more than a world free of terror, we also owe them a planet protected from catastrophes.”

Watch a short video from Day One here: https://twitter.com/UNFCCC/status/671724513478881280 

The Prime Minister of India, Narendra Modi, pledged that his country has set “ambitious targets” — by 2030, India aims to reduce emissions by 33 to 35 percent of 2005 levels, and 40 percent of the country’s installed capacity will be from our non-fossil fuels. He also said that India will add 175 Gigawatts of renewable generation by 2022, and will enlarge its forest cover to absorb at least 2.5 billion tons’ worth of carbon dioxide. 

Read more: The Latest Chapter in the Climate Change Saga 

The Prince of Wales — who has blamed climate change as a major reason for Syria’s civil war — spoke on the dangers of deforestation and the transformation of global commodity supply chains. Also representing the U.K. was Prime Minster David Cameron, who said, “Let’s just imagine for a moment what we would have to say to our grandchildren if we failed. We’d have to say, ‘It was all too difficult.’ And they would reply, ‘Well, what WAS so difficult?’”

Russian President Vladimir Putin pledged that by 2030, his country will reduce greenhouse gas emissions by 70 percent when compared with 1990, through “breakthrough technologies and nanotechnologies” (citing “carbon nanotube additives”), which he says Russia is ready to share with the world. Meanwhile, Chinese President Xi Jinping said that developed countries must honor their commitments on finance. 

The Prime Minister of The Bahamas, Perry Christie, pointed out that small island nations such as his are especially in danger of climate change. He cited October’s Hurricane Joaquin as an example — the damage from the storm amounted to nearly 10 percent of The Bahamans’ total budget.

(In related news, research from the University of Leicester warns that the planet’s oxygen levels could dramatically fall if the ocean temperature changes just a few degrees due to global warming — which presents a greater risk than flooding and would suffocate life on Earth.)

U.S. President Barack Obama also spoke at the conference, “as the leader of the world’s largest economy and the second-largest emitter, to say that the United States of America not only recognizes our role in creating this problem, we embrace our responsibility to do something about it.” He said that, over the last seven years, the U.S. has made ambitious investments in clean energy as well as reductions in carbon emissions. Wind power has increased threefold and solar power more than twentyfold, and carbon pollution is at it its lowest levels in nearly two decades.  

Meanwhile, the U.S. House of Representatives has scheduled votes for this afternoon that challenges the president’s environmental policies — a vote could strike down rules on reducing carbon emissions from power plants, both current and future. When asked about the U.S.’s majority support for action on climate change and whether Congress was avoiding public opinion, Speaker of the House Paul Ryan replied, “I don’t think we’re out of step with public opinion wanting jobs, wanting economic growth, weighing the costs and the benefits. I think when you weigh the costs and the benefits against these so-called legally binding obligations they don’t add up. I think it’s very clear people want jobs.” House Majority Leader Kevin McCarthy commented that the House does not agree with the president trying to commit taxpayer money to support an international climate accord. “I don’t think that’s the best use of our money,” he stated, suggesting that a current must-pass year-end spending bill could help block such an effort. The House will vote this week on several pieces of legislation to challenge the president’s climate policies, including trying to curb the Obama administration’s controls on power plant emissions. 

Speaking at COP21, UN Secretary-General Ban Ki-moon listed his four criteria for success:

• “First, the agreement must be durable. It must send a clear signal to markets that the low-emissions transformation of the global economy is inevitable, beneficial and already under way.”
• “Second, the agreement must be dynamic. It must be able to accommodate changes in the global economy, and not have to be continually renegotiated.”
• “Third … an agreement that embodies solidarity with the poor and most vulnerable. It must ensure sufficient and balanced adaptation and mitigation support for developing countries.”
• “Fourth, the agreement must be credible. Current ambition must be the floor, not the ceiling, for future efforts. Five-year cycles, beginning before 2020, are crucial.”

If a deal is reached by Dec. 11, here are some of its possible key elements, according to The Telegraph: 

1. National pledges to cut emissions: Most countries have already submitted “Intended Nationally Determined Contributions” (INDCs), setting out how they plan to limit their emissions in the 2020s. These are not up for negotiation.

2. A long-term goal: A target for global emissions reductions required by 2050 or 2100, to prevent 2 C global warming.

3. Holding countries to account: A clear framework for measuring whether countries are actually carrying out the emissions cuts they have promised.

4. Increasing pledges in future: A mechanism to make countries come back and agree to deeper national emissions cuts.

5. Finance: An agreement that developed nations will help developing countries with the costs of going green, and the costs of coping with the effects of climate change.

Time will tell if these world leaders live up to the things they have promised.