New York City might as well be the place for a "bold, new course of action" on climate change, as the conveners of the 2014 Climate Summit hope. 

Channelling his inner Frank Sinatra, UN Secretary General Ban Ki-moon likely thought that if climate change commitments can be made there, they can be made anywhere.

In a rousing display of solidarity, tens of thousands of people marched through New York and other cities worldwide ahead of Tuesday's summit to call for action on reducing greenhouse gas emissions.

Many are gathering on the sidelines of the event to put pressure on world leaders, who are in town both for the summit and the UN's opening session, to reach a global climate deal.

Here are a few things to know about the summit:

1. It's being held at a time of unprecedented awareness of climate change.

The summit comes on the heels of a report by the UN's Intergovernmental Panel on Climate Change that says the world is dangerously close to no longer being able to limit global warming to 2 C over pre-industrial times. It is also coming as the current temperature increases are leading to more extreme weather events, many scientists are saying.

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The 2009 United Nations Climate Change Conference in Copenhagen endorsed the continuation of the Kyoto Protocol but didn't result in a binding agreement. (Pawel Kopczynski/Reuters)

"People have hit the point where they feel they need to do something dramatic," said Gabriela Rappell, the youth programs director for the Sierra Club of Canada, in an interview with CBC News. 

She says the summit is significant, in relation to previous climate conferences, because of the number of "everyday citizens" protesting and publicly displaying their views around the globe.

The summit's location in New York is also important. The city was battered by Hurricane Sandy in 2012, forcing many to experience the effects of environmental disaster firsthand.

"The evidence has just been mounting," Rappell says. "And governments around the world have been dragging their heels, and all of these things have come together to create the perfect storm for citizen action."

2. It will have record attendance, but some notable absences.

More than 120 heads of state and government will discuss their national plans of action — the largest number of world leaders to ever attend a climate conference. 

Just as interesting are the absences.

Prime Minister Stephen Harper is one of a number of leaders to forgo the international gathering. He is in New York to address the UN General Assembly, but has sent Environment Minister Leona Aglukkaq to the summit in his stead, . 

Indian Prime Minister Narendra Modi and Chinese President Xi Jinping, the heads of the world's two most populous nations, will also be sending representatives in their place.

According 2010 data from the U.S. Department of energy, China and India are the first- and third-largest producers of carbon dioxide. The U.S. is second. 

Russia rounds out the top four global CO2 emitters, and Russian President Vladimir Putin will not be at the summit either.

It's "a bit of a slap in the face to other world leaders who are there," said Keith Stewart, a spokesperson for Greenpeace Canada.

U.S. President Barack Obama and Japanese Prime Minister Shinzo Abe (Japan is the fifth largest global producer of CO2) are scheduled to speak.

3. It's not a formal negotiation — that comes later this year.

Stewart said the event is not a formal negotiation on climate change but an "extraordinary meeting to try to jump-start the whole thing and get it back on the rails." 

He said the issue of climate change has fallen off national political agendas over the past few years, and the New York summit is an attempt to lay the groundwork ahead of a UN climate conference in Lima, Peru, this December. CBC News has confirmed that Environment Minister Aglukkaq will represent Canada at that meeting.

The Lima conference is a lead-up to a key conference in Paris in 2015. The goal in Paris is to create an environmental agreement that will come into effect after 2020. The legally binding 1997 Kyoto Protocol to reduce emission targets expired in 2012, and the last climate conference in Copenhagen in 2009 failed to create a binding agreement.

4. Saving the ocean is not on the agenda.

In a column for The Guardian newspaper, David Miliband argued that by not addressing climate change's impact on the world's oceans, the summit is "guilty of a major sin of omission."

Miliband, a former British Labour MP who co-heads the Global Oceans Commission, cited a World Meteorological Organization bulletin that warned of increasing ocean acidification, caused by excess amounts of carbon emissions that the oceans absorb.

Greenpeace's Stewart said the reason for omitting the ocean from the summit might be because "you can't solve that problem in the ocean. It's got to be solved by stopping greenhouse gas emissions."

The eight "action areas" that the talks will tackle are agriculture, cities, energy, financing, forests, industry, resilience and transportation.