China's carbon count not as high as feared
The use of poor-quality coal in Chinese power plants means that the
carbon dioxide emissions of the world's biggest polluter are 10% less
than previously thought.
- cdn.phys.org |
Calculations on how much carbon dioxide China produces have been
wrong for more than 10 years because the official bodies that calculate
it have assumed the country's power stations burn high-quality coal.
In fact, the world's biggest polluter uses coal with a lower carbon
content than power stations in Europe and the US, and so produces less
carbon dioxide per tonne - around 14 per cent less according to experts
from 18 research institutions.
Getting the total quantities of CO2 emitted by each country correct
is crucial if the world is going to reach agreement on tackling
dangerous climate change at the UN conference in Paris in December. One
of the stumbling blocks to agreements in the past has been politicians'
need to have a fair system of sharing the burden of cuts.
Calculating how much pollution each country produces has been largely
based on the quantities of fossil fuels burned in electricity and heat
production and in motor vehicles. This has not taken into account the
amount of carbon in coal and oil varies according to its quality, and so
an average figure has been used, which turns out to be unfair in the
case of China.
Appalling air quality
One of the ironies of the finding is that while the carbon content of
the coal may be less, its impurities means it emits more of other kinds
of pollution. This is what has made air quality in Chinese cities so
appalling, and has started a big debate in China about whether the
country should seek to burn better-quality coal to avoid killing its
citizens with bad air.
The revised estimates of China's carbon emissions, published in the
journal Nature, were produced by an international team, led by
researchers from Harvard University, the University of East Anglia (UEA),
in England, the Chinese Academy of Sciences and Tsinghua University, in
collaboration with 15 other international research institutions.
The team re-evaluated emissions from the burning of fossil fuels and
cement production from 1950 to 2013. They used independently-assessed
activity data on the amounts of fuels burned, and new measurements of
emissions factors - the amount of carbon oxidised per unit of fuel
consumed - for Chinese coal.
Because the amount of coal burned in China is so vast, the size of
the error is also huge. It means there are 2.9 fewer gigatonnes of
carbon in the atmosphere. That is more than the total amount of carbon
stored by China's forests over roughly the same period.
It is particularly important because nearly three-quarters of the
growth in global carbon emissions from the burning of fossil fuels and
cement production between 2010 and 2012 occurred in China. Lead
researcher, Prof. Dabo Guan of UEA's School of International
Development, said the key contributor to the new estimates was fuel
quality, which for the first time was taken into consideration in
establishing emission inventories - something the Intergovernmental
Panel on Climate Change (IPCC) and most international data sources had
not done. "China is the largest coal consumer in the world, but 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," Prof. Guan says.
"China is one of the first countries to conduct a comprehensive
survey for its coal qualities, and a global effort is required to help
other major coal users, such as India and Indonesia, understand their
physical coal consumptions as well as the quality of their coal types.
"Our results suggest that Chinese CO2 emissions have been
substantially over-estimated. Evaluating progress towards countries'
commitments to reduce CO2 emissions depends upon improving the accuracy
of annual emissions estimates and reducing related uncertainties."
Total consumption
The discrepancy would have been even greater if China more accurately
counted its coal consumption. According to researchers, total energy
consumption was 10 per cent higher between 2000 and 2012 than reported
in China's national statistics.However, even taking that into account,
emissions were still less than previously believed because emissions per
tonne were on average 40 per cent lower than the levels assumed by the
IPCC.This alters substantially the estimates of the Carbon Dioxide
Information Analysis Centre(CDIAC) in the US and the Emissions Database
for Global Atmospheric Research (EDGAR) in the EU, which are the
official data sources for the IPCC Fifth Assessment Report (AR5) -
providing scientific evidence for the climate change policy negotiations
in Paris later this year.
The figure is also about 10 per cent less than the estimate given for
China in the most recent publication of the Global Carbon Project, which
annually updates global carbon emissions and their implications for
future trends.
Prof. Corinne Le Quéré, Director, Tyndall Centre for Climate Change
Research at UEA, co-leads the publication of annual updates of emissions
for the Global Carbon Project, says: "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."
- Climate News Network |