Talousnobelisti Jean Tirole käsittelee kirjassaan Economy of Common Goods myös ilmaston muutosta, joka on globaali yhteismaan ongelma, jonka ratkaisu vaatii näin globaaleja talkoita ja kansainvälistä sopimusta. Tirolen mukaan ilmastosopimus ei käytännössä toimi, jos se perustuu pelkkiin lupauksiin. Sopimuksen pitää perustua sanktioihin. Vapaamatkustajan ongelmaan ei ole helppoa ratkaisua, mutta tärkeintä että ongelma otetaan huomioon alusta asti.
The Kyoto Protocol failed to create an international coalition for a carbon price in proportion to its social cost. It was also a perfect illustration of the instability of international agreements that do not take the free rider problem seriously.
Tirole ehdottaa paria vaihtoehtoa vapaamatkustajan ongelman ratkaisemiksi:
Government debt is an instructive analogy. Sanctions against a country in default are limited (fortunately, gunboat diplomacy is no longer an option), which has led to concerns about whether countries are willing to repay debt. The same goes for climate change. Even if a good agreement were reached, there would be limited means to enforce it. The public debate about international climate negotiations usually ignores this reality. That said, we have to pin our hopes on a binding agreement, a genuine treaty, and not an agreement based only on promises. ... There is no perfect solution to the problem of enforcing an international agreement, but we have at least two tools.
First, countries value free trade; the WTO might consider that the nonrespect of an international climate agreement is equivalent to environmental dumping, and impose sanctions on those grounds. In the same spirit, punitive taxes on imports could be used to penalize countries who do not participate. This would encourage hesitant countries to join the agreement and would make it more likely that a global coalition for the climate could be stable. Clearly the nature of the sanctions could not be decided by countries individually—they would quickly seize the opportunity to set up protectionist measures that would not necessarily have much connection with environmental reality.
Second, a climate agreement should be binding on a country’s future governments, like sovereign debt. The IMF could be a stakeholder in this policy. For example, in the case of a tradable emissions permits system, a shortage of permits at the end of the year would increase the national debt, and the conversion rate would be the current market price. Naturally, I am aware of the risk of collateral damage that could result from choosing to connect a climate policy with international institutions... but what are the alternatives?
YK:lla Tirole ei näe suurta roolia. vaan ehdottaa ilmastokoalitiota:
Although it is important to maintain a global dialogue, the UN process has shown predictable limits. Negotiations between 195 nations are incredibly complex. We need to create a “coalition for the climate” that brings together, from the outset, the major polluters, present and future. I don’t know whether this should be the G20 or a more restricted group: in 2012, the five biggest polluters—Europe, the United States, China, Russia, and India—represented 65 percent of worldwide emissions (28 percent for China and 15 percent for the United States). The members of this coalition could agree to pay for each ton of carbon emitted. At first, no attempt would be made to involve the 195 countries in the global negotiation, but they would be urged to join in. The members of the coalition would put pressure on the WTO, and countries that refused to enter the coalition would be taxed at borders. The WTO would be a stakeholder on the basis that nonparticipants are guilty of environmental dumping; to avoid undue protectionism by individual countries, it would contribute to the definition of punitive import duties.