(Inside Science) -- This week the U.S. and China announced an agreement to reduce their respective emissions of carbon dioxide, the greenhouse gas that drives the majority of human-caused climate change across the globe. Many praised the move, using strong words such as "landmark," "a game changer" or "a significant shift" (albeit one that is "only the first step on a very long road"). But a global agreement is still needed to limit future warming to levels that experts deem acceptable. Research on negotiations suggests that getting all countries to agree on an overall agreement is still a big job.
China and the U.S. account for about 40 percent of global emissions of carbon dioxide, which makes the deal important, as long as both countries do follow through with their commitments. This may be difficult due to the legislative environment in the U.S., among many other variables. But, both countries will probably need to make additional cuts in the short and long terms in order to reduce warming in the decades and centuries ahead, experts suggest. Also, other countries will have to join in.
Major climate talks are scheduled in the coming year, and while many countries had doubted that China and the U.S. would subscribe to any agreement, research based on game theory suggests that this new pact could affect future negotiations -- and the consequences may not all be positive.
I'll get back to the research, but first, here are the details of the agreement.
The Climate Deal
In the new deal, the U.S. pledged that by 2025 it would cut its emissions by at least 26-28 percent below its emissions levels in 2005. China set a target that its emissions would peak by 2030, that they would strive to make that peak happen sooner and that they will boost the amount of energy generated from sources that are not fossil fuels to about 20 percent.
Numerous commentators view this as a huge step in climate change policy.
Here's an excerpt of meteorologist Eric Holthaus' article in Slate:
"It’s impossible to overstate the deal’s significance for the rest of world. The announcement was made at a roundtable of Asia-Pacific countries. Later this week, leaders from the G20 group of major industrialized nations will assemble in Australia, and Wednesday’s announcement all but ensures that climate change has shot to the top of the agenda. Next month, climate negotiators from around the world will meet in Lima, Peru, in the last major meeting before an expected global climate agreement in Paris in 2015. The U.S.-China deal is sure to motivate additional pledges and actions by other countries."
Because the two largest carbon dioxide emitters did something, it suggests that attempts at a global climate accord are not in vain, suggests James Fallows in The Atlantic:
"As the collapse of the Copenhagen climate talks five years ago showed, the rest of the world is likely to say, 'To hell with it' if the two countries at the heart of this problem can't be bothered to do anything.
"We see our own domestic version of this response when people say, 'Why go through the hassle of a carbon tax, when the Chinese are just going to smoke us to death anyway?' This new agreement does not mean that next year's global climate negotiations in Paris will succeed. But it means they are no longer guaranteed to fail."
Still, climate change is a complex issue. Even if all emissions stopped today, the Earth would still get warmer because of the carbon dioxide already in the atmosphere. Many scientists think the goal of a comprehensive agreement should be to prevent average temperature from growing by more than 2 degrees C -- that's 3.8 degrees F. Writing on Vox.com, Brad Plumer wrote that much more action will be needed to truly cap the global warming that scientists expect to develop over the next century:
"As climate modeler Chris Hope points out, this deal in isolation still puts the world on course for a likely 3.8°C (6.8°F) rise in temperatures by 2100. 'These pledges are only the first step on a very long road,' he concludes."
The stakes are high. Will the new agreement be the catalyst needed to develop a global plan? How do these countries find a common ground, given that they share some goals, but also have at least some competing interests? Is the very process of negotiation an obstacle to an agreement between the scores and scores of countries involved?
Rory Smead, a professor of philosophy at Northeastern University, in Boston, is a researcher who can provide insights about questions like these. In his research, he uses idealized mathematical models to develop insights about behavior. This spring, in a paper in Nature Climate Change, Smead and three colleagues examined climate change negotiations from the perspective of a discipline called game theory.
The research begins with the assumption that countries want to protect against future climate change, Smead told me this spring.
"Everybody wants to solve the problem," he said. "What they disagree about is how to do it."
In the model climate negotiations take the form of what is called a Nash bargaining game, named after the mathematician John Nash, who was featured in the book and film "A Beautiful Mind." The researchers simulated the interactions between countries, each of which want to solve the emissions problem, as they attempt to find a mutually agreeable solution. The countries would each make claims about how much emissions they want to produce, and adjust their claims after each session, or round of bargaining. If the countries sense that an agreement is likely, they'll keep talking. But if they feel that an agreement is unlikely, they'll stop negotiating.
"In the model we know that there are solutions that all the agents would like. The problem is that they can't reach it based on the fact that each of them is trying to do what's in their own interests, given what everybody else is doing," said Smead.
One interesting and now very relevant finding in the paper is that agreements among small groups of countries can make it easier to find a much larger global agreement. But, small agreements can also hamper larger talks. This spring, when I asked Smead about agreements, he explained one hypothetical situation in which two countries agreed to cut emissions by 20 percent, and the potential consequences of that at the bargaining table.
"Now, if by cutting 20 percent you are now more likely to demand that others cut 20 percent first before you're willing to consider more, that's actually going to hurt the process," said Smead. "You can't be unwilling to consider further cuts. You can't even be less willing to consider further cuts than the other guys."
A New Landscape
The day of the U.S.-China agreement, Smead answered a few questions about its potential impact on global climate negotiations in an email exchange with Inside Science. He explained that he thinks this announcement makes it "a little easier" to develop a global agreement.
"My only reservation, as we discussed in our paper, is that agreed reductions now may (possibly) make the parties more reluctant to agree to further reductions if further reductions are necessary to reach a global agreement," he wrote.
Additionally, as the two largest economies, the U.S. and China have built-in advantages that may make it easier for them to make the reductions, than it will be for other countries. But, even these cuts may not be enough, he said.
"[E]ven with respect China and the U.S., we may need to make even more cuts or reductions in order to avoid environmental problems and future cuts may be harder than the first cuts."
The European Union previously announced a plan to cut emissions by over 40 percent from 1990 levels by 2030. That agreement and the one between the U.S. and China means that many of the top emitters have now expressed plans to cut emissions in the coming decades. But it's important not to leave out the many, many countries remaining, said Smead.
"[W]e argue that agreements between many minor emitters may be more effective for reaching global agreements than agreements between a few large emitters," he wrote. "This is not to say that agreements between the large emitters is bad or counterproductive, only that the reaction from other smaller emitters may be very important for whether or not we can reach some kind of global agreement."
In sum, he wrote, "This is a step in the right direction, but it is really just a step and there is a long way to go yet."
This story has been corrected to reflect the correct baseline year for the European Union's plan to cut carbon dioxide emissions by over 40 percent from 1990 levels by 2030.