Thursday, August 20, 2015

Harvard scientist and lead author of new CO2 study says UN IPCC global carbon dioxide number needs to be revised downward significantly-BBC, Nature Letter, 8/19/15

Scientists find significant overestimation of global CO2, around 10% of total in any one year 2000-2013. Lead author Harvard's Liu says, "IPCC emissions factor number needs a revision and that should be at the global level." 8/19/15, Nature Letter

8/19/15, "China CO2 emissions: 'Coal error' caused wrong calculations," BBC, Matt McGrath

"Confusion over the types of coal being burned in Chinese power stations has caused a significant overestimation of the country's carbon emissions. Researchers, published in the journal Nature, say existing CO2 calculations had used a globally averaged formula.

But when scientists tested the types of coal actually being burned in China, they found they produced 40% less carbon than had been assumed.

The study says the error amounted to 10% of global emissions in 2013.

China's drive for economic growth over the past 15 years has seen the rapid expansion of coal burning for the production of energy.  

Indeed, the widely quoted statistic about the country building a new coal power station every week was actually exceeded in 2006, when one and a half such plants were constructed on average. 

That rate of expansion has fallen away but this reliance on coal means that China's emissions of carbon dioxide topped the rest of the world for the first time back in 2007, a position it has retained ever since."...

[Ed. note: Not so: China topped world "back in 2006" not 2007 per above link: "China passed the US by 8% [in 2006]" (parag. 5, above link)."]

(continuing): "China routinely publishes energy statistics but it doesn't produce regular information on carbon emissions....

This new study looked at the actual carbon content found in over 4,000 coal mines in China and in lab tests of 602 coal samples. The emission factors based on these tests were on average about 40% lower than the default values used by the IPCC and others. 

"For most of the developed countries, coal has been comprehensively washed but in China the process is not so comprehensive," lead author Dr Zhu Liu from Harvard University told BBC News....
The researchers say the discrepancy is significant. Over the period 2000-2013, they found that China emitted almost three gigatonnes of carbon less than previous estimates, which is around 10% of the global total in any one year. 

"The findings do have very significant global implications as China accounts for one-third of global total emissions. If we reduce China's emissions by 15%, we get a 5% less global total," said Dr Zhu.

"The IPCC emissions factor number needs a revision and that should be at the global level."...

The team behind the new study says that whatever the global picture, its work has implications for many other countries where information on the mix of coal being burned is unclear. 

"China is one of the biggest coal users in the world. There are also others like India, Indonesia and South Africa that haven't a very robust system for collecting data and verifying the statistics," said Prof Dabo Guan, another author of the paper from the University of East Anglia.

"There is huge, even greater uncertainty for India and Indonesia - this is a starting point for the global south.""


China topped world in CO2 in 2006, per 2007 article linked in above BBC article:

6/19/2007, "China overtakes US as world's biggest CO2 emitter," UK Guardian, John Vidal, David Adam

"Our findings suggest that overestimation of China’s emissions in 2000–2013 may be larger than China’s estimated total forest sink in 1990–2007."... 

8/19/15, "Reduced carbon emission estimates from fossil fuel combustion and cement production in China," Nature Letter, Zhu Liu et al.

"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 China1, 2. Yet estimates of Chinese emissions remain subject to large uncertainty; inventories of China’s total fossil fuel carbon emissions in 2008 differ by 0.3 gigatonnes of carbon, or 15 per cent1, 3, 4, 5. The primary sources of this uncertainty are conflicting estimates of energy consumption and emission factors, the latter being uncertain because of very few actual measurements representative of the mix of Chinese fuels. Here we re-evaluate China’s carbon emissions using updated and harmonized energy consumption and clinker production data and two new and comprehensive sets of measured emission factors for Chinese coal. We find that total energy consumption in China was 10 per cent higher in 2000–2012 than the value reported by China’s national statistics6, that emission factors for Chinese coal are on average 40 per cent lower than the default values recommended by the Intergovernmental Panel on Climate Change7, and that emissions from China’s cement production are 45 per cent less
than recent estimates1, 4. Altogether, our revised estimate of China’s CO2 emissions from fossil fuel combustion and cement production is 2.49 gigatonnes of carbon (2 standard deviations = ±7.3 per cent) in 2013, which is 14 per cent lower than the emissions reported by other prominent inventories1, 4, 8. Over the full period 2000 to 2013, our revised estimates are 2.9 gigatonnes of carbon less than previous estimates of China’s cumulative carbon emissions1, 4. Our findings suggest that overestimation of China’s emissions in 2000–2013 may be larger than China’s estimated total forest sink in 1990–2007 (2.66 gigatonnes of carbon)9 or China’s land carbon sink in 2000–2009 (2.6 gigatonnes of carbon)10."

Supplementary information 


Authors of 8/19/15 Nature Letter:


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