The report — titled "The Role of China in Mitigating Climate Change" — published in the journal Energy Economics, compares the impact of a stringent emissions reduction policy with and without China's participation. It finds that China's actions are "essential."
"As the largest greenhouse gas emitter in the world, without China, climate goals — like the 2 degrees Celsius target that most agree is necessary to prevent serious irreversible consequences — are out of reach," says Sergey Paltsev, the lead author of the study and the assistant director for economic research at MIT's Joint Program on the Science and Policy of Global Change.
Specifically, the study finds that with China's help the global community is able to limit warming to 2 degrees Celsius, relative to pre-industrial levels. But without China, we miss that mark by about 1 degree Celsius.
Not only will it be close to impossible to achieve the 2 degrees mark without China's participation, but emissions reductions will also be more expensive because substantial costs would shift to only some countries. That is why the researchers argue for a global economy-wide greenhouse gas tax that spreads the burden of responsibility.
But even in this best-case scenario, reducing emissions comes with a steep price tag. China could experience substantial GDP losses by the end of the century under the most stringent policy cases. These losses come from higher energy prices, which influence consumption and export dynamics.
"While strong reductions may turn out to be costly in China and may require some incentives from developed countries," Paltsev says, "that doesn't make China's actions any less important."
The researchers stress, however, that reaching that 2 degrees threshold with China's participation is only possible in the most optimistic case. And these days, there isn't much cause for optimism.
The researchers tested various levels of emission reduction plans — a global carbon tax of $10, $30 or $50. The various taxes would slow warming to 3.5, 2.4 and 2 degrees, respectively, by the end of the century, according to their analysis. With no global policy, the increase in warming is projected to be about 5.5 degrees Celsius.
These scenarios show that, "Even more modest and realistic goals require near universal participation of major greenhouse gas emitters," Paltsev says.
Top energy user today, climate leader tomorrow?
The importance of China's participation in a global climate treaty increases with each year, as the country's population, economy and energy use continue to grow rapidly.
From 2000 to 2010, China's energy use grew 130 percent. That's up from a growth of just 50 percent the previous decade. With a growing, wealthier population, China has become the world's largest energy consumer — and with it, the world's greatest source of greenhouse gas emissions.
China's share of global energy-related CO2 emissions has increased in just eight years from 14 percent in 2000 to 22 percent in 2008. Eighty percent of those emissions came from coal, making China the consumer of about half the world's coal.
But China is on a path toward doing something about their rapidly escalating energy use and emissions. They've recently announced they will be testing a pilot cap-and-trade program in select major cities in 2013, and plan to make the program national by 2015.
John Reilly, the co-director of the Joint Program on Global Change, pointed out recently the irony behind the plan. While the United States created the idea of cap and trade, he says, "just as many of our best innovations are produced in China, they may beat us in implementing such a system ... we're really being left behind."
Paltsev agrees that the system would be "a very good start" for China, allowing the country to reach its goal of reducing carbon intensity by 40 percent relative to 2005 and increasing the share of non-fossil fuels by 15 percent by 2020. But, he says, "these actions are still not enough, making almost no substantial difference in reducing global emissions."
In fact, the change, taken by China alone, would only reduce global temperature by about 0.1 degree Celsius in 2020.
But Tim Yeo, who chairs the United Kingdom Parliament's energy committee, recently told The Financial Times that if China did impose a national cap and trade system, "It's game over for the rest of the world ... Everyone will have to do it, including the U.S."
Paltsev agrees. "While the system would only be a start for China, as the country would still have a long way to go in reducing emissions, it would likely influence other countries — like the U.S. — to follow. But time is really of the essence."