If last year's landmark Paris climate agreement enters into force this year or early next year, it will likely do so without the help of one of its strongest supporters.
That's because the European Union, which carried the torch for international climate action for two decades before playing a leading role in brokering the agreement last year, is not to be found on the growing list of countries pledging early adoption ahead of next week's signing ceremony in New York City.
There's almost no scenario where the European Union doesn't eventually become a party to the deal reached last year outside the French capital. In fact, more than 50 European leaders, including French President François Hollande and Ecology Minister Ségolène Royal, will attend next week's signing.
But for logistical reasons internal to the 28-nation compact, it is expected to do so in 2017 or 2018 -- likely after other countries cause it to take effect.
"If I were writing up a list of the countries that I needed to get this into force this year, would I be relying on the Europeans? No." said Nathaniel Keohane, vice president of global climate at the Environmental Defense Fund. "But would I expect that they're good for it in 18 months or something? Of course."
The deal is likely to take effect much earlier than 2020 and possibly as soon as this year. It's not impossible that it could be in force when parties meet in Marrakech, Morocco, late this year for the next high-level summit. To get there, the deal requires 55 countries to formally adopt it with a secondary stipulation that it be ratified by nations responsible for 55 percent of the world's greenhouse gas emissions.
Countries are lining up to help meet that threshold. More than 130 national representatives are expected to be on hand on April 22 when U.N. Secretary-General Ban Ki-moon opens the agreement for signatures in New York.
28 parliaments add confusion
The United States and China pledged late last month that they would be parties by the end of the year, their combined 38 percent of world emissions edging the deal within striking distance of its greenhouse gas emissions threshold. China and its fellow major developing nations pledged a week later to sign the deal on opening day and then "to initiate necessary domestic processes for ratification, acceptance or approval as soon as possible with a view to facilitate the timely entry into force of the agreement."
If India, Brazil and South Africa join the United States and China in rushing toward ratification, perhaps joined by Canada and a handful of other significant emitters, that threshold will be easy to achieve. Smaller emitters like the four island nations that have already taken steps to ratify the deal -- Fiji, Palau, the Maldives and the Marshall Islands -- are also lining up to meet the 55-nation threshold.
Europe has a more difficult task ahead of it. The union can't ratify an agreement without giving all 28 member parliaments time to do their work.
"Although the E.U. negotiates in the [Conference of the Parties] as a single entity, the ratification process requires actions in individual countries and their parliaments," said Robert Stavins, director of the Harvard Project on Climate Agreements. "And Europe is heterogeneous."
The European Parliament and the council are expected to vote by this summer on a tightening of the Emissions Trading System (ETS), which covers the utility sector and heavy industry. Reductions from sectors that fall outside the ETS -- building emissions, transportation and others -- will be allocated on the basis of gross domestic product to countries across the compact, with wealthy countries making the deepest cuts. The parliament and council will be asked to consider that "effort-sharing" legislation before summer, as well.
Then in the fall, Brussels will float policy proposals for how countries might opt to deliver their share of the reductions by boosting renewable energy use, beefing up efficiency or taking other steps. Proposals for greening the power grid and transportation system will also be unveiled. This multi-pronged policy aims to deliver the union's combined Paris pledge to cut emissions 40 percent compared with 1990 levels by 2030.
Not all Europeans want action
Countries then have the task of obtaining the approval of their respective parliaments -- a process that varies from country to country and is likely to extend into 2017. The European Parliament will need to do the same. Only when all 29 parliaments have completed their work will the member states, alongside the European Union, join the Paris Agreement by notifying the United Nations of their consent to be bound. At that time, they will also have to notify the United Nations of the individual emissions limits each member state will contribute to the European Union's collective target.
Stavins notes that regional politics and economic conditions will also play a role. While what he calls the "core countries" of Europe -- France, Germany and the United Kingdom -- are strong proponents of climate action, nations in the south are experiencing serious economic trouble. And countries in Eastern Europe -- particularly Poland -- rely heavily on coal and are more resistant to policies that constrain its use.
All of that means Europe will not be an early adopter. But Europeans stress that this slower trajectory is intrinsic to their system of government and does not show less commitment. Indeed, with domestic policies in place to support Paris, E.U. nations might be less likely to back out of the agreement than, say, the United States, which will join the deal on the president's authority alone and could as easily back out of it under a Republican president.
But questions persist about how the European Union -- which has frequently played the role of the world's conscience on climate change -- might be treated if the deal enters into force without it.
Decisions could be made at the next U.N. summit that the European Union would not have a formal hand in. The union is an important source of climate aid, and observers say other countries are unlikely to use the situation to push through rulemakings that would be hostile to Europe.
"It's hard to imagine a situation where parties to the Paris Agreement would not very much want the E.U. to be part of the decisionmaking process for the critical rules under the agreement," said David Waskow, international climate director at the World Resources Institute. "So I think a way forward will be found in order to ensure that kind of participation."
Europe would likely hold an "observer" status until it ratifies the agreement, with the right to submit formal comments on drafts of negotiating text and to make statements during the process.