Compared with the 1980-1999 average of 23.1ò¾, the annual mean temperature in Hong Kong in the decade 2090-2099 is expected to rise by 4.8ò¾ according to the middle-of-the-road projection. The corresponding low-end and high-end values are 3.0 and 6.8ò¾ respectively (Leung et al., 2007).
As for extreme weather, a study conducted by the Hong Kong Observatory shows that the annual number of hot nights (days with a minimum temperature of 28ò¾ or above) and very hot days (days with a maximum temperature of 33ò¾ or above) are expected to increase significantly in the 21st century. On the other hand, the annual number of cold days (days with a minimum temperature of 12ò¾ or below) will continue to drop (Lee et al., 2011).
Details of the study on the temperature projections for Hong Kong in the 21st century can be found in the following publications :
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Temperature Projections for Hong Kong based on IPCC Fourth Assessment Report, Y.K. Leung, M.C. Wu, K.K. Yeung & W.M. Leung. Bull. HK. Met. Soc., 17, 2007, HKO Reprint No. 764 (2007)
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Projections for Extreme Temperatures in Hong Kong in the 21st Century, T.C. Lee, K.Y. Chan and E.W.L. Ginn, Acta Meteorologica Sinica, 25(1):1-20 (2011) (Link to summary of the study)
Past and projected annual mean temperature anomaly for Hong Kong
based on IPCC AR4 monthly mean data (Leung et al., 2007)
| Parameter |
Average
1980-1999
(Observation) |
Projections |
| 2050-2059 |
2090-2099 |
| low-end |
mean |
high-end |
low-end |
mean |
high-end |
| Annual number of hot nights |
16 |
58 |
96 |
125 |
87 |
137 |
175 |
| Annual number of very hot days |
9 |
20 |
51 |
81 |
29 |
89 |
131 |
| Annual number of cold days |
17 |
1 |
4 |
8 |
0 |
1 |
5 |
Projections for annual number of hot nights, very hot days and cold days in Hong Kong based on AR4 daily data (Lee et al., 2011)
Note:
Climate projection uncertainties
It is important to note that climate projection is very different from weather or seasonal forecasts. Climate projection involves assumptions in future socio-economic and technological developments and greenhouse gas emission scenarios and aims at describing the plausible change in the future climate from a long term perspective, rather than depicting the "day to day" or "year to year" variations in weather.
Although a majority of the model projections suggests in general consistent trends for the changes in the climate of the 21st century, inter-model differences are still rather large with a divergence in the projections for the future climate. This, to a certain extent, reflects that climate projection is still subject to various uncertainties in the model simulation of the future climate, which depend very much on such factors as future greenhouse gas emission scenarios, the choice of models, model skills, the downscaling methodology, the stability of the statistical downscaling relationships in the future. The technique is expected to continue to improve with time as scientists know more about various climate processes and atmospheric processes that impact on the climate.
