Peruvian Minister of Environment Manuel Pulgar-Vidal (L), shaking hands with Peruvian Foreign Affairs Minister, Gonzalo Gutierrez (C) during the plenary session of the 20th UN Climate Change Conference COP20 held in the city of Lima, Peru, 13 December 2014. (Cop20 Handout/EPA)

EVER SINCE negotiators failed to agree on a climate accord in Copenhagen five years ago, diplomats have been trying for a big, international do-over. Talks in Lima, Peru, this month put this effort on track to conclude an agreement in Paris next year. The trade-off is that the accord will be insufficiently ambitious and difficult to enforce, in part because of the intransigence of developing countries. It cannot be the final word on the global response to climate change — just an early step. But it’s preferable to no deal at all.

In Copenhagen, negotiators tried to build a legally binding accord that dictated strict emissions cuts to various countries, particularly developed ones. This was always an unrealistic strategy. The failure of the 1997 Kyoto Protocol showed that getting rich, developed countries to honor a strict, centralized and binding global treaty was nearly impossible. Getting developing nations to make legally binding international emissions commitments was even more difficult. Though they have become major emitters, they have insisted that the West bear much or all of the emissions-cutting burden. In Copenhagen, world leaders managed to scrape together only a few last-minute pledges, saving face but not the planet.

Since then, climate negotiators have tried a more bottom-up approach, encouraging governments to bring whatever they can to the table. That approach got its fullest articulation yet in Lima this month. One hundred ninety-six countries agreed that each of them — not just developed nations — would submit some sort of emissions pledge over the next six months. The document negotiated presses governments to be as specific as possible, including with information that would make it easy to compare one pledge to another and to justify why they shouldn’t or can’t do more.

There are serious drawbacks. Developing nations such as India balked at requiring extensive information on pledges — their time frames and emissions measuring methodologies, for example. Third-party observers likely will be able to fill in many of those gaps. But they won’t be able to conduct adequate monitoring and verification of reported emissions reductions — a necessity that must be worked out.

In addition, pledges likely to come in over the next half-year will almost certainly be too modest to ensure that the world keeps its temperature rise below 2 degrees Celsius. Later rounds of talks and pledges will have to increase the world’s ambition.

The flexibility of the broad, voluntary plan leaves room for growth and improvement. More important, the scheme stands a chance of doing what no U.N. climate effort has accomplished: institutionalizing the expectation that all major emitters stake their international reputations on contributing. If it becomes the first of many rounds of meaningful international agreement, it will be a success.