New calculation suggests China's greenhouse emissions have been overestimated

New estimates show that for more than a decade China’s greenhouse gas emissions have been overestimated by international agencies, while the country’s energy consumption has been underestimated.

The research, published today in Nature, shows that from 2000 to 2013 China produced 2.9 gigatonnes less carbon than previous estimates of its culmulative emissions, meaning that its true emissions may have been around 14% lower than calculated.

Meanwhile, with a population of almost 1.4 billion, China’s energy consumption grew 10% faster during 2000-12 than reported by its national statistics.

As the world’s biggest greenhouse gas emitter, China’s recent pledge to peak its emissions by 2030 has been praised as responsible leadership on the climate issue, but its faster-than-expected energy consumption growth means meeting this target may present an even bigger challenge.

The researchers, led by Dabo Guan, of UEA’s School of International Development, used independently assessed data on the amount of fuel burned, and new measurements of emissions factors to re-evaluate emissions of two major sources of China’s carbon dioxide emissions – the burning of fossil fuels and cement production – from 1950-2013.

Guan said the new estimates were compiled by considering fuel quality when establishing emissions inventories – something that had previously been overlooked by the Intergovernmental Panel on Climate Change (IPCC) and most international data sources.

“While China is the largest coal consumer in the world, it burns much lower-quality coal, such as brown coal, which has a lower heat value and carbon content compared to the coal burned in the US and Europe,” said Guan.

Counting coal

Pep Canadell, Executive director of the Global Carbon Project at CSIRO, who was not involved in the study, said a lack of research resources meant that estimates of China’s emissions relied on default values from global databases.

Guan’s research team “visited thousands of mines and by actually exploring the coal they found there was less emissions,” Canadell said.

This is a process done by many countries, but for developing nations like China the important task of compiling detailed emissions inventories has historically been too expensive.

“The default values can be quite far away from the real values,” Canadell said. “In the future we would need real values for other places such as India.”

Corinne Le Quéré, director of the UAE Tyndall Centre for Climate Change Research, said there were a lot of uncertainties in China’s data, especially given the discrepancies between national and provincial figures.

“The strong message here is that as we refine our estimates of carbon emissions we get closer to an accurate picture of what is going on and we can improve our climate projections and better inform policy on climate change.”

The good news and the bad news

The new findings are a positive step towards accurately measuring emissions, but their effect on climate policy requires acknowledging the negatives – China’s rapidly growing energy needs.

Frank Jotzo, director of the ANU Centre for Climate Economics and Policy, described continued work on primary data as important but said the findings that emissions were overestimated does not change the challenge China faces in moving away from coal.

“For global climate change mitigation to succeed, a shift from coal to other energy sources in China is essential.” he said. “China is making good progress towards that goal.”

With the Paris meeting of the UNFCCC in November this year, China’s pledge to peak emissions from all activities by 2030 requires addressing its demand for electricity generation in production, transport and industrial systems.

According to Canadell, cement production accounts for about 5% of global greenhouse emissions, but because China is “building so much” it is a much bigger fraction. China produces more than half of global production of steel and cement.

“I don’t think this news is making it easier or harder [to meet climate targets]; the most important thing is to measure the speed and trends of energy consumption,” he said.