The economic arguments put forward by the Airport Authority in support of the third runway project have been criticised for completely ignoring the social and environmental costs.
Such calculations are not usually part of the assessment of projects in Hong Kong but are often cited by environmentalists and economists elsewhere - including those who opposed the now-aborted expansion of London's Heathrow Airport.
WWF Hong Kong believes the lessons learned from London can shed some light on the ongoing debate surrounding the third runway plan.
'We need a paradigm shift now or we face prices too high for us to pay eventually,' climate programme head William Yu Yuen-ping said.
The change Yu refers to is a new approach in dealing with a project by looking at it as a whole, not just the economic benefits but also the social, community and environmental costs. Without taking these costs into account, Yu said it would be hard to tell if a project was as desirable as the proponent suggested.
Citing a report last year by British think tank New Economics Foundation, which advocates social and environmental cost evaluations, Yu said the costs associated with the Heathrow's third runway actually outweighed benefits by GBP5 billion (HK$62.13 billion). British transport officials had estimated a net benefit of ?5.5 billion.
The difference was found after the foundation ran the costs and benefits model using different assumptions such as carbon emission costs and more up-to-date economic forecasts.