It’s no secret that China holds a huge amount of leverage on the future of CO 2 emissions. Its incredible economic growth over the last 20 years was accompanied by a boom in greenhouse emissions. Actions to reduce that boom (as well as other pollutants) are in progress, but they haven't had any appreciable effect as of yet.

At the Copenhagen talks, China pledged a lower-carbon economy—reducing the CO 2 emitted per unit of GDP (also known as “carbon intensity”) by 40 to 45 percent below 2005 levels by 2020. And China’s current Five Year Plan (2010-2015) set a goal of reducing carbon intensity by 17 percent while still growing GDP eight percent per year.

But between 2002 and 2009, China’s carbon intensity increased by three percent. What drove that? A new study led by Dabo Guan digs below the national level to take a look at the trends behind carbon intensity. The study suggests that, while huge progress is being made, it's still being swamped by massive growth in capacity.

If your aim is to reduce carbon intensity, there are a few fundamental ways to get it done. Obviously, you can switch to energy sources that don't release carbon. But you can also increase the efficiency of each sector of the economy so that more is produced for the same amount of carbon emissions. Alternatively, you could decrease the prevalence of carbon-heavy sectors (like steel production) in the economy, moving instead toward low-carbon sectors.

Over half of China’s provinces lowered their carbon intensity between 2002 and 2009—mainly the wealthier ones. Guangdong and Jiangsu achieved this by improving efficiency and shifting to lower-carbon industries. Those were the only provinces where carbon-heavy sectors didn’t grow to a larger economic share.

Inner Mongolia, for another example, made massive gains in efficiency, but they were nearly offset by the growth of carbon-heavy industries. Economic activity there is focused on mining and smelting. While small, inefficient facilities were replaced by more modern ones, production also boomed. Capacity for smelting metals and producing cement, for example, increased 14 times over.

In provinces like Guizhou, much-improved efficiency was swamped by the growth of dirty industries. Turning coal into coke for things like steel production is big there, and the efficiency of this industry increased 60 percent. Production, however, rose by a factor of 11.

The researchers also analyzed general trends to see which were most important. On the positive side, lower-carbon industries are definitely taking over for dirtier ones, but only in the wealthiest regions. Additionally, Industries are becoming more efficient as they grow and mature.

Unfortunately, the emissions-increasing trends had a much larger impact. The problem is that the largest sectors of regional economies were the ones that made the least progress. The researchers write, “This is probably due to these large—and thus important—sectors experiencing less political pressure to reduce their carbon intensities. In many cases, their carbon intensities increased in the dash to raise or maintain high provincial growth rates.” Carbon-heavy industries, which already accounted for a large part of the economy, grew the fastest.

In other words, when growth rate goals conflict with carbon-reduction goals, growth has won.

The researchers point out that China could do a lot more to press emissions-reducing technologies into service. The country has been building more renewable and high-efficiency tech than most of the rest of the world, but that has mainly gone into the wealthiest provinces. It could make a big difference in other regions.

As part of its recent pledges, China is piloting an emissions-trading scheme. However, because it will be structured around carbon intensity goals rather than carbon emissions goals, the researchers worry that this won’t succeed in turning things around. They write, “The recent past has convincingly shown that implementation of intensity targets were not able to slow down overall carbon emissions growth… [I]t may not even be possible to meet those carbon intensity targets when governments are at the same time providing strong incentives to sub-national governments to improve their growth performance, which is then often achieved in a very carbon-intensive way.”

Nature Climate Change, 2014. DOI: 10.1038/NCLIMATE2388 (About DOIs).