Last month set the record for Hong Kong Observatory’s tally of number of hours in a month with “reduced visibility” – ie “visibility below 8 kilometres when there is no fog, mist, or precipitation”: a whopping 546 hours – almost 18 hours per day, recorded at HK International Airport.
Records from the HK Observatory (since 1968) and Hong Kong International Airport (since 1997) show highest record monthly totals for hours with reduced visibility are all from 2002: indeed, only one monthly record dates from 2002.
At HK Obs, the numbers of hours with reduced visibillity have increased markedly in recent years. Until 1980, the highest annual total was 388 hours. It wasn’t till 1994 (503 hours) that an annual total exceeded 500 hours; yet since then, the annual total has climbed sharply, first passing 1000 in 2003 (1117 hours), then reaching 1570 hours in 2004 and 1503 hours last year.
At the airport, the annual total for hours with reduced visibility reached 2438 hours last year.
As you might expect, totals are markedly lower in summer, when cleaner southerly breezes tend to blow.
So, Donald Tsang – the government has a few challenges if to make progress with the Action Blue Sky campaign.