For a brief few hours in the outskirts of Paris Monday, the world seemed to set aside old grudges and rally around a unifying cause.

Heads of state from across the globe called for a strong climate agreement on the opening day of this year's much-anticipated United Nations climate summit. Representatives assembled here in suburban Le Bourget have no shortage of issues to divide them, and tensions are sure to flare as negotiations unfold over the next two weeks. Still, Monday's remarks by world leaders offered a rare moment of commonality among nations as diverse as the United States, China, Russia, France, and dozens of other countries.

It is a modest respite from conflict for a city still recovering from the terrorist attacks that killed 130 people in central Paris just earlier this month.

"[F]or all the challenges we face, the growing threat of climate change could define the contours of this century more dramatically than any other," President Barack Obama said Monday in remarks that would overlap with calls for climate action made by Chinese President Xi Jinping, Russian President Vladimir Putin, French President François Hollande, and many others.

"What should give us hope that this is a turning point, that this is the moment we finally determined we would save our planet, is the fact that our nations share a sense of urgency about this challenge and a growing realization that it is within our power to do something about it," Mr. Obama continued.

The goal of this year's Paris climate conference is to develop an international strategy for addressing climate change once current pledges run their course in 2020. Heat-trapping emissions from fossil fuels and other sources continue to rise despite more than two decades of talks under the United Nations Framework Convention on Climate Change, which seeks to limit dangerous human interference with Earth's climate. This time around, 183 nations representing 98 percent of the world's emissions have already submitted climate plans to the UN.

Many questions linger over the details of the agreement being finalized outside Paris this month. To what extent will the developed world help finance climate projects in the developing world? What parts of the agreement will or won't be binding? How can negotiators build accountability and transparency into the agreement?

Still, participants in the process say they are hopeful that Paris can succeed where past efforts to rein in emissions have failed. What's more, the global economy is stronger than it has been in years, and the costs of alternatives to fossil fuels continue to plummet dramatically. That makes undertaking a global shift to low- and zero-carbon fuels seem more obtainable.

"The transition has begun," UN Secretary-General Ban Ki-moon said in opening remarks Monday. "Enlightened investors and innovative businesses are striving to create a climate-friendly economy. But they need your help in accelerating this essential shift."

The arrival of high-profile figures at the opening of the Paris talks is a departure from standard operating procedure in international summitry. Typically, world leaders prefer to come at the end of negotiations, when all that's left to do is finalize the details. But if there's been one consistent theme in this year's climate summit so far, it has been to try things differently. Observers hope that having heads of state come at the opening of the conference will give negotiators a much-needed opening push, and avoid any of the top-level, last-minute politicking that has bogged down previous negotiations.

The high-level presence made for a busy scene Monday in the sprawling complex that is the conference site in Le Bourget. Officials burst down corridors flanked by aides and trailed by lights and cameras. Multiple languages and modes of dress were on display, all participants sharing only a light blue lanyard – not unlike the UN's iconic helmets of a similar hue. The site itself still feels like a work in progress, and one that won't last forever. False floors moved in unexpected ways, and interior structures made heavy use of particle board.

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The temporary nature of the talks, which last from Nov. 30 to Dec. 11, are one reason officials are already emphasizing the importance of what happens after everyone leaves Paris.

"In many ways, that’s when the real works begins," US Secretary of State John Kerry told the Monitor in written responses to a survey last week. "An agreement in Paris won’t solve this challenge in and of itself – but it will lay the groundwork for a global solution."