In his letter headlined 'Genuine change?' (South China Morning Post, November 29), your correspondent J. Lee noted the rising temperature trend at the Hong Kong Observatory headquarters and asked if such a trend was also observed at other nearby sites like King's Park. Analysis has shown a slow increase in temperatures at the observatory since measurements began in 1884. Over the past 50 years, the annual average minimum temperature at the observatory has risen by just over one degree Celsius. The annual mean temperature also shows a rising trend, but at a slower rate. This is characteristic of the effects of urbanisation. On the contrary, at Cheung Chau, a site much less affected by urbanisation, both the annual mean minimum and annual mean temperatures between 1976 and 2000 do not exhibit any significant changes. The effect of climate change or global warming is not obvious. As for our site at King's Park, the long-term temperature trend follows closely the pattern of that of the observatory. King's Park is as much affected by urbanisation as the observatory. In passing, it should be noted that six years is too short a period for trend analysis as it may be affected by shorter term events. For example, 1997 and 1998 were the two warmest years on record in Hong Kong due to the strong effects of El Nino. Readers interested in temperature data at Cheung Chau, King's Park or other stations are invited to read our online publication 'Summary of Meteorological Observations in Hong Kong' ( http://www.weather.gov.hk/ publica/pubsmo.htm). W. M. LEUNG for Director of the Hong Kong Observatory
