A growing number of leaders are openly acknowledging that a 2015 international agreement to avert catastrophic global warming will surely fall short of what's needed to achieve that goal.

But another consensus is also forming among top U.S. experts: that shortfall is OK, as long as the deal puts all major climate polluters on a serious, upward and transparent path to cutting greenhouse gases.

"The big question the public is going to ask is: Are all the major emitters participating? And are they doing enough to help solve this challenge?'" said Peter Ogden, director of international climate and energy policy at the Center for American Progress and a former chief of staff to U.S. Special Envoy for Climate Change Todd Stern.

The new agreement to be signed in Paris, to take effect in 2020, will essentially replace the 1997 Kyoto Protocol. Unlike Kyoto, the Paris deal will demand action from everyone, and not just from wealthy industrialized countries. But in order to make that palatable for governments, negotiators are moving away from a traditional top-down approach in which scientists dictate what is needed to save the planet and countries are allotted targets accordingly.

Instead, consensus has built around a more voluntary approach in which governments figure out how much they can cut and offer it up as a pledge. Those "intended nationally determined contributions" are due early next year.

In interviews with former negotiators and longtime observers of the U.N. climate negotiations, not one person expressed confidence that the sum of countries' targets will be enough to keep rising global temperatures below the internationally agreed 2-degree-Celsius "guardrail" between dangerous and extremely dangerous warming.

"If that were the case, it would be a stunning surprise. I don't think anyone expects that," said Joy Hyvarien, executive director of the U.K.-based Foundation for International Law and Development (FIELD).

Recently, the Massachusetts Institute of Technology used a sophisticated climate model to come to the same result.

Studies show a continuing emissions rise
In a report, "Expectations for a New Climate Agreement," researchers reviewed the likely pledges and found that instead of greenhouse gas emissions scaling back dramatically, they would actually result in levels of carbon dioxide equivalent in the atmosphere exceeding 580 parts per million by the end of the century.

"At least in what's likely to be agreed in [Paris], it won't put us on the path that the IPCC [Intergovernmental Panel on Climate Change] says is consistent with the 2-degree target. It's going to bend the curve; we believe that. But it's not going to bend the curve enough to meet with what the IPCC says is required," said Henry Jacoby, lead author of the study.

Jacoby argued that reality is something that needs to be acknowledged by leaders openly, well before the Paris meeting.

"It doesn't seem to us that we're having the conversation we should be having. We should be more openly talking about what countries are going to be willing to do, and more open about what the structure of the agreement is going to be. This is all not known yet," he said.

"If it becomes generally recognized that this round of negotiations is not likely to put us on the path [to 2 degrees], what happens then? We treat this as if this negotiation was going to complete something, and it's one step in a very long process," he added.

Several ideas already are being floated to help bridge the gap between what countries are likely to deliver and what scientists say is actually needed to steer the planet to safety.

In a recent blog post, Hyvarinen of FIELD advocated that diplomats carve out a special additional category open only to countries that put forward ambitious targets.

Giving gold stars, and possibly some type of special benefits to the best actors, she said, "could help counter the weakness of a bottom-up agreement." She like many other analysts also argued for a strong review mechanism that would allow countries to strengthen their targets over time.

But can a Paris deal that does not keep temperatures below 2 degrees still be considered a success?

Harvard University economist Robert Stavins says yes. Even if the sum of emissions cuts countries offer is insufficient to attain the 2 degree goal, he argues, it would still be a monumental step to have all major polluters on board for a new deal.

Wanted: a foundation for an effective solution
"What I anticipate coming out of this is that we will have an agreement in 2015 that will have the right foundation, the right set of countries participating ... and we will begin to build the foundation that we ought to have begun to build at the time of Kyoto," he said. "I think what's important is the right foundation for moving forward, as opposed to the actual numbers that are in the agreement."

Nigel Purvis, a lead U.S. climate negotiator in the Clinton administration and now CEO of the consultancy group Climate Advisers, said there is "no chance" the Paris targets will be consistent with the 2-degree goal. But like Stavins, he said that getting the new agreement right will ultimately be more important than the initial targets.

"It would be a major step forward for there to be an agreement where all countries were committing to taking action and where there was clarity about how we would know they were on track to do what they promised," Purvis said. That, along with a mechanism to enable countries to increase their ambition, he said, "would be a significant step beyond Kyoto and beyond Copenhagen."

Environmental groups have not been as sanguine about the prospects of a treaty that falls short of 2 degrees.

"If the numbers don't add up, it's not a political failure only. It's a physical failure," said Wael Hmaidan, director of Climate Action Network (CAN) International, told ClimateWire earlier this year. "If you want to get to New York and you only get to New Jersey, you failed, right?" (ClimateWire, Jan. 14).

Others, though, argued that the Paris deal cannot afford to be weighed down with outsized expectations like those for the 2009 summit in Copenhagen, Denmark, where diplomats tried and failed to produce a new treaty. The deal in 2015 will be a big deal, they argued, but not the final solution to global warming.

Said Ogden, "To meet the credibility test, we must show a meaningful deviation from the catastrophic course that we had been on, and continue to bend that emissions curve. It will not be the final word, but it will be the absolutely critical next step, knowing that there will have to be steps after that."

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500