China’s CO2 emissions over 2000-2013 may have been overestimated by as much as 10.7 billion tonnes, a new study published in Nature magazine found, implying China might be left room to emit more CO2 in the future under a global carbon budget.

The study, carried out by researchers from a number of international institutions, said samples from around 600 Chinese coal mines showed the coal’s carbon content was up to 40% lower than the default values recommended to be used in emission calculations by the UN’s IPCC.

“The problem is that most international datasets go for harmonised assumptions, but this means they miss country specifics. That makes a big difference for China,” said Glen Peters, a researcher at Oslo’s Center for International Climate and Environmental Research.

The IPCC recommends using 0.713 tonnes of carbon per tonne of coal when estimating CO2 emissions, whereas the researchers found Chinese coal only contained 0.491-0.499 tonnes of carbon.

They estimated China’s CO2 emissions in 2013 from coal combustion and cement production at 9.2 billion tonnes of CO2 (2.49 billion tonnes of carbon), 14% lower than the EU’s Emissions Database for Global Atmospheric Research (EDGAR) and some 5.5% lower than BP estimates.

If correct, the study means China’s share of global emissions is smaller than the 29% EDGAR estimated in 2013.

Over 2000-2013, the researchers said China’s cumulative emissions may have been overestimated by as much as 10.7 billion tonnes of CO2 by international sources, even though they also found China’s energy consumption had been underreported by around 10% in the same period.

The miscalculation amounts to the equivalent of three years of total EU output.

China itself uses a carbon content reference much lower than the IPCC’s – 0.518 tonnes – but the study concluded China’s greenhouse gas (GHG) emissions in 2005 – the latest year for which China has reported to the UNFCCC – were 12% lower than the official number.

ROOM TO EMIT MORE? OR LESS?

If China’s historical emissions are lower than previously estimated, that would imply China’s share of the global carbon budget – the theoretical budget for how much each nation can emit in the future if the world is to meet the 2C target – could be increased, the study said.

“Depending upon how the remaining quota of cumulative future carbon emissions is shared among nations, a correction of China’s current annual emissions by 10% suggests a 25% (inertia basis) or 70% (blended basis) difference in the cumulative future emissions that can be emitted by China under a 2C warming target,” it said.

However, if China at some stage agrees to a UN climate treaty that sets absolute limits on its emissions, a lower historical baseline would suggest a lower future cap.

China may push back against the study’s conclusions, as government-led think-tanks have said that falling demand and tanking coal prices from 2013 onwards have led many domestic producers to mine lower-quality coal and blend it with gangue material normally unused after processing, resulting in lower carbon emissions.

“Evaluating progress towards national commitments to reduce CO2 emissions depends upon improving the accuracy of annual emissions estimates and reducing related uncertainties,” the study said.

By Stian Reklev – stian@carbon-pulse.com

Not yet signed up to CP Daily? Subscribe to our free newsletter here