2008 - climate change
Broadly speaking, Hong Kong started cold and ended warm in 2008.
It was cold(1) for 24 consecutive days between January and February, making it the longest cold spell in 40 years. In contrast, towards the end of the year, September-November turned out to be the warmest autumn in more than a century (2). Taken overall, the annual mean temperature (3) ranks the 20th highest since records began in 1884. I should remark that, while the cold spell was long, the lowest temperature recorded during the period viz. 7.9oC was on the high side compared with the winters of decades ago.
At the global level, the Secretary-General of the World Meteorological Organization expected that 2008 would be the 10th warmest year globally since instrumental records began in 1850(4). This year is slightly cooler than the last few years mostly due to the La Niña phenomenon at the beginning of the year. La Niña is said to occur when the sea-surface temperature in the eastern part of the equatorial Pacific is below normal. The Secretary-General also highlighted the fact that the summer sea ice coverage in the Arctic Ocean was the second lowest since satellite monitoring began in 1979. This reinforces the continuing falling trend in the last three decades, which reflects the seriousness of global warming. The conditions in 2008, both in Hong Kong and globally, are consistent with the broad global warming trend.
I was myself a doubter of climate change. I did not believe that human beings could cause the global climate to change. However, in 2002 I got hold of a copy of the Third Assessment Report of the UN Inter-governmental Panel on Climate Change (IPCC). I found in that report data and arguments so convincing that it was no longer defensible to refute that proposition. After reading the 4th Assessment Report issued by IPCC in 2007, I realize further that we are facing a problem of great seriousness and human beings must wake up and take actions immediately.
Because I was a doubter, I could understand to some extent why some people still do not believe in climate change. It is because they have not had the opportunity to read key data or because they have not encountered any weather phenomenon which has resonance with their personal experience. Here, I present a perspective which hopefully would help people in this category to appreciate the warming trend in Hong Kong. Figure 1 shows the average annual number of hot nights(5) computed for different decades over the last century or so.
Figure 1 Variation in the annual number of hot nights in Hong Kong
Before the sixties of the last century, there were few hot nights. When I was a kid, all that one had to do on hot nights would be to go and sleep on the rooftop or out in the street. After the sixties, hot nights became much more frequent. Now there is no escape from the heat even at night. I hasten to add that the warming in Hong Kong has arisen from two overlapping factors viz. global warming and local urbanization.
On global warming, IPCC has a very nice figure illustrating the situation. It is shown below:
Figure 2 Variation in global temperature in the past centuries
(Source: 4th Assessment Report, IPCC)