Peruvian Minister of Environment Manuel Pulgar-Vidal, left, shakes hands with the Peruvian foreign affairs minister, Gonzalo Gutierrez, after the approval of the Lima Call for Climate Action during the 20th U.N. Climate Change Conference COP20 in Lima. (Cop20 via European Pressphoto Agency)

Negotiators eked out a global agreement to fight climate change during an environmental summit in the Peruvian capital, Lima, early Sunday. The approach taken by this agreement is quite different from that of the more familiar Kyoto Protocol. There are no formal commitments to reduce carbon emissions by a numerical target during a specific time frame. Instead, each state promises to design its own “nationally  determined contribution” that “represent[s] a progression beyond the current undertaking.” There is no clear mechanism to ensure that these national efforts are  meaningful nor an obvious way to enforce these self-imposed obligations.

One may naturally be inclined to skepticism that such a soft agreement will have any effect. As a World Wildlife Fund representative said: “We went from weak to weaker to weakest.” Yet, there are also some research-based reasons for optimism that the Lima Accord may on the margin nudge countries toward greater efforts to curb carbon emissions.

There are some inherent limitations to what any international treaty can do. There is no global legislature that can use a majority vote to pass treaties that are legally binding on all countries. Countries are generally not bound by the treaties they don’t sign or ratify. It is nigh impossible to negotiate a treaty that sets meaningful numerical targets and that all or the most important carbon-emitting states are willing to sign.

The best-known issue is the position of developing countries. These countries were exempted from obligations to cut emissions under the Kyoto Protocol. Since then, countries such as India, China and others have become major polluters. Many developed countries, including the United States, insist that any climate treaty must curb emissions by developing countries. Yet, these countries counter that the wealthy nations have polluted their way to richness and so it is their responsibility to take the lead until developing countries have caught up.

There are also other reasons why centrally imposed numerical emission targets are not always the most effective. Carbon emissions are largely shaped by factors that have little to do with environmental policies. For example, meeting the Kyoto targets is easy for a country that loses much of its heavy industry (like Russia in the 1990s) or that discovers major natural gas deposits (natural gas produces energy at lower emission rates than many other sources). But it is really hard for countries that go through a period of economic growth, as the United States did in the 1990s. So, the 55 countries that remain committed to the Kyoto Protocol have handily met their targets, but that may just be because only countries that could already meet their targets ratified the treaty. Indeed, Canada repudiated the treaty after it became impossible to meet its target.

While new numerical commitments may work for smaller, more cohesive groupings of countries, such as the European Union, the global approach has since shifted to a different strategy, which is based on the realization that the main push for climate-friendly policies must come from within countries. The purpose of international agreements and institutions is to help those domestic groups that favor emission curbs, not to set central standards that the international community can’t enforce. This fits the insights from political scientists that the effect of many treaties depends on domestic politics.

So how does the Lima agreement help domestic groups that favor carbon reductions? A first, and very important, feature is that it brings the issue on the agenda in every U.N. member state. Every country has agreed to develop a national action plan, although the language on what exactly needs to be in that plan was watered down during the negotiations. Still, anyone who has ever participated in or studied an activist movement knows that getting an issue on the agenda is a major hallmark. Delaying decisions to some unspecified point in the future is a time-honored tactic for executives who face competing demands (see: pipeline, Keystone). The Lima Accord has just made that a bit harder. In the next six months, executives everywhere are expected to formulate a plan that details how a government is going to do more than it currently does on climate change. This is a major opportunity for those lobbying for change, although a counter-mobilization is sure to arise as well.

By going through the domestic process, the agreement does not depend on often-weak international enforcement mechanisms but relies on domestic courts and legislatures to ensure that commitments are enforced. This may not help much in countries where legislatures and courts have little independent influence from executives. Yet, there are many large carbon emitters with domestic institutions that can effectively curtail incentives to cheat on the announced policy goals.

Another potential mechanism is shaming. The agreement calls for the U.N. Framework Convection on Climate Change to publish all national action plans on its Web site and for scientists to calculate the contributions these plans make to curbing emissions. Not all governments will be troubled by negative assessments and publicity, but research suggests that shaming (or rankings) can work at least some of the time to encourage governments to do things they otherwise wouldn’t do. Similarly, some governments appear to value the prestige that comes with being a leader in efforts to fight climate change. Publicly available comparative assessments may give incentives to these countries to do even more to top the rankings.

It would be too rich to suggest that Lima is a major breakthrough in the battle against climate change. There will surely be countries that fail to deliver on even the minimal obligation to define a national contribution that goes beyond existing efforts. There will also be major countries that do not meet their self-imposed goals. This agreement is really just a precursor for a more comprehensive agreement that could be reached in Paris next year. The parameters on many tough issues, including the financing of climate projects in developing countries, still need to be negotiated. This agreement can only nudge countries to do better; it cannot solve the problem. Yet, it is hard to see what alternatives there are to the approach taken in Lima given the structural limitations of global law and treaty-making.