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Faulty Data Hampers Drive To Cut Pollution

Cheung Chi-fai – SCMP
Jan 10, 2008

Government officials monitoring air pollution in the Pearl River Delta have had to move the goalposts for pollution reduction after estimating that emissions levels in 1997 were twice as high as had been thought.

The Pearl River Delta Air Quality Management Plan review said particulates emission in the delta region in 1997 was 520,000 tonnes, more than double the 245,000 tonnes previously estimated.

A 40 per cent underestimation in sulfur dioxide and nitrogen oxides emissions were also found in the review. As a result, emissions data from 1997 that serve as a baseline for measuring progress towards reducing pollution have been raised, according to the review paper.

As the 1997 data had been underestimated by as much as 112 per cent in the case of particulates, changes to the baselines would have a big influence on determining how far the region was from achieving emission reduction targets.

In 2002, Hong Kong and Guangdong province agreed to pursue pollution target cuts of between 20 and 55 per cent in four major pollutants by 2010 from 1997 levels.

By underestimating the baseline emissions, the extent of emission reductions required by 2010 would be smaller, making it easier to achieve the targets. Overestimates, however, meant more efforts were needed.

Changes to the baseline data, however, would also lead to different maximum allowable emission limits. The review report said the underestimation on the 1997 data was due to factories failing to declare emission levels accurately, mismatches between reported emissions and amount of fuel used, and industrial processes not taken into account.

The paper said an emission calculation methodology in keeping with standards in the United States and European was completed for Hong Kong and Guangdong in 2005. It was then used to review the 1997 and 2003 emission figures – the most up to date data available for Guangdong.

Alexis Lau Kai-hon, an atmospheric scientist at the University of Science and Technology, said updating the baseline data would have an impact on how targets could be met.

“Lifting the baseline not just means more efforts to cut emissions are needed, it also means higher levels of emissions will be tolerated, too,” he said.

Data released by the Environmental Protection Department showed that not only were the 1997 baselines adjusted, the yearly emission data of Hong Kong have also been revised based on the new formula. As a result, Hong Kong was moving faster towards meeting the 2010 targets.

For example, the city had reported nitrogen oxide emissions in 2005 were 15 per cent below the old 1997 baseline but the difference widened to 17.8 per cent against the revised baseline. Figures from 1996 show the city had already met its 2010 target in nitrogen oxide emissions.

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