Hong Kong has seen some uncharacteristically chilly weather in recent weeks. While many have wondered about the necessity of closing primary schools, there was also some agreement that staying indoors or venturing out made little difference when it came to keeping warm.
So why does Hong Kong seem to feel more bitterly cold than it actually is?
‘It’s not humidity – it’s the wind’
Some believe that, just as humid summers are less tolerable than dry summers, humid cold is also more severe than dry cold. However, according to the Hong Kong Observatory (HKO), this is not exactly true.
The HKO explains that water vapour in the air actually conducts less heat than dry air, challenging the belief that humidity always makes Hong Kong’s weather more insufferable. Instead, the wind chill factor is the most influential contributor to how cold one feels.
Unluckily for Hong Kong, strong monsoon wind signals have also added to the “perfect storm” that was January’s cold snap.
The structure of buildings in Hong Kong may also be responsible for the chilly temperatures indoors.
Albert K. H. Kwan, professor in the Department of Civil Engineering in the University of Hong Kong (HKU) told HKFP that “buildings in Hong Kong are not designed for heat insulation. That’s why in the summer time, we waste a lot of energy in air conditioning (cooling) and in the winter time, we have to either switch on a heater or feel very cold indoors.”
Unlike most parts of the world which have standards on insulation, Hong Kong has no such requirement, he added. This also means that we have to spend more energy both cooling and heating our homes.
There is also the fact that you may be wearing lighter clothing indoors and moving around less. “Basically the metabolism is slower. Outdoors you are constantly walking and it makes you feel warmer. More layers of clothing are also a factor.” said Huang Jianxiang, assistant professor in the Department of Urban Planning and Design at HKU.
Huang added that urban planning has some, but not a significant effect, on temperatures in Hong Kong. In the mornings, the city is affected by the cold island effect, which will decrease the urban temperature by “just a fraction of a degree’s difference,” said Huang. The rest of the day, the opposite – the heat island effect – will raise temperatures instead.
Could the increasingly unusual weather in recent years have anything to do with global warming?
Liu Zhonghui, an associate professor in Department of Earth Sciences at HKU told HKFP that it is difficult to ascertain if the phenomenon is indeed due to global warming. He said that scientists still need to observe a few more similar events before judging the underlying reasons.
However, he mentioned that there was a rare weather event in a certain region in the Arctic, “Scientists observed this time that the Arctic warmed from -30 degrees Celsius to about zero degrees Celsius.” He said that it was very unusual, but some scientists think that it was merely a disturbance due to a hot air mass penetrating the cold air mass in the Arctic, letting the cold air travel to the south.
While we can’t yet be certain whether global warming is causing Hong Kong’s weather to be more unstable, we can be sure that the city’s buildings aren’t currently made to withstand the kind of cold we had last weekend. One can only hope that the records for cold weather don’t get broken every year as they often are for high temperatures during Hong Kong’s summers.