United Nations officials say it's historic, part of a "gathering momentum" for action on climate change. Over 160 countries, including Canada, are expected to sign the Paris Agreement on climate change at a ceremony at the UN in New York today.
The agreement was reached in Paris last December but April 22 — Earth Day — is the first day countries can actually sign the agreement.
Warming global temperatures since the Paris conference may be helping spur the momentum.
The year 2015 broke 2014's record for the hottest year ever, and the first three months of 2016 have already eclipsed the prior record highs for those months. In fact, March makes it a string of 11 monthly records for that month's hottest, according to the U.S. National Oceanic and Atmospheric Administration.
That data adds to doubts that meeting the national targets for the Paris Agreement will be enough to achieve its goal of limiting the warming of global temperatures to well below two degrees Celsius, and ideally below 1.5 degrees, from pre-industrial levels.
Global temperatures are already one degree above pre-industrial levels and rising.
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So what's the big deal about signing the Paris Agreement?
Over 160 national governments are expected to sign the agreement today. The others have a year to add their signatures. About three-quarters will be represented at the signing ceremony by their heads of state, Selwin Hart, director of the Secretary General's Climate Change Support Team, told a media briefing on Tuesday.
He termed the ceremony historic, because it will easily surpass the record of 119 signatures on the opening day for signing an international agreement. That record was set in 1994 for signing the Law of the Sea treaty.
Hart said the ceremony is part of "gathering momentum" for action, "a good sign that political commitment remains strong and countries are committed to ensure that this agreement enters into force as soon as possible."
Signing the agreement is just symbolic, though. What really matters is ratification. Hart expects about 10 countries to also deposit their "instruments of ratification" at the signing ceremony.
He said the process "is happening faster than anyone anticipated," adding that Secretary General Ban Ki-moon has asked the countries to indicate in their remarks today when they intend to ratify the agreement.
When does the agreement enter into effect?
Thirty days after at least 55 countries, which together produce at least 55 per cent of the world's greenhouse gas emissions, confirm their ratification or agreement to the UN secretary general, the Paris Agreement goes into effect.
The two biggest emitters, China and the U.S., issued a joint statement on March 31, indicating they would ratify the agreement this year, "with a view to bringing the Paris Agreement into force as early as possible."
They account for about 38 per cent of global greenhouse gases, followed by Russia, India, Germany and Japan. Together, those six countries account for over 55 per cent, according to the UN Framework Convention on Climate Change.
What is Canada doing?
Prime Minister Justin Trudeau is in New York for the signing ceremony, along with Environment Minister Catherine McKenna.
McKenna says the government will first prepare its own climate plan before ratifying the Paris pact this fall. "We need to have a plan to meet our international obligations, and we have six months to do that," she told CBC News this week.
Her government went to Paris with a plan drafted by the previous Conservative government.
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What happens after the Paris Agreement takes effect?
No one should have come away from the Paris talks expecting that the national commitments would be enough to keep global warming below two degrees, not to mention 1.5 degrees.
However, the agreement commits countries to become more ambitious in their targets and sets out a process to achieve that. Every five years, countries will take stock of their progress toward limiting the temperature increase to less than two degrees, starting in 2018.
Nevertheless, Kevin Trenberth, a senior scientist at the National Center for Atmospheric Research, told the New York Times this week, "I don't see at all how we're going to not go through the 1.5 degree number in the next decade or so."
While temperature records get broken, what progress has there been since the Paris conference?
The Washington-based World Resources Institute lists these "signs of progress":
- $286 billion US invested in renewable energy worldwide, a record high and more than twice the amount committed to fossil fuel power plants.
- Energy-related carbon emissions have stalled while the world economy continues to expand, according to the International Energy Agency. So far this century, 21 countries have recorded a reduction in their annual greenhouse gas emissions while growing their economies.
- Clean energy investment soared in China last year, while coal consumption fell.
- The U.S. and Canada agreed to significantly cut methane emissions from existing oil and gas operations.
- Following the Paris talks, more than 500 new commitments have been recorded in a database that tracks climate commitments by non-state actors.
Do the Republican front-runners support the Paris Agreement?
Donald Trump and Ted Cruz reject the scientific consensus on climate change, so the agreement could be in trouble if one of them wins the U.S. election in November.
In March, Trump told the Washington Post's editorial board that he's "not a big believer in man-made climate change."
While chairing a hearing of the U.S. Senate's subcommittee on space, science and competitiveness in December, Cruz said, "There has been no significant global warming for the past 18 years." He has said advocates of the "pseudo-scientific theory" of climate change are using it to bring about "massive government control of the energy sector, the economy and every aspect of our lives."