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climate change

Climate Projections for Hong Kong

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The Observatory utilizes data of a number of computer climate models in the IPCC Fifth Assessment Report (AR5) and statistical method with urbanization effect on temperature incorporated to project the temperature changes in Hong Kong in the 21st century. Results show that under the high greenhouse gas concentration scenario (RCP8.5), the temperature is expected to rise by 1.5-3°C and 3-6°C in the mid-21st century (2051-2060) and late 21st century (2091-2100) respectively, when compared to the 1986-2005 average of 23.3°C. Under the medium-low greenhouse gas concentration scenario (RCP4.5), the temperature is expected to rise by 1-2°C and 1.5-3°C in the mid-21st century and late 21st century respectively, when compared to the 1986-2005 average.

Projected changes in the annual temperature of Hong Kong

Projected changes in the annual temperature of Hong Kong relative to the average of 1986-2005 under the high (red) and medium-low (orange) greenhouse gas concentration scenarios (solid line plots the mean value while dashed lines show the likely range of projection results). Historical observations are shown in black.

Under the high greenhouse gas concentration scenario, the annual number of hot nights (days with a minimum temperature of 28°C or above) and very hot days (days with a maximum temperature of 33°C or above) are expected to increase significantly in the 21st century, while the annual number of cold days (days with a minimum temperature of 12°C or below) is expected to drop.

Low
concentration scenario
Medium-low
concentration scenario
Medium-high
concentration scenario
High
concentration scenario
Projected annual number of hot nights, very hot days and cold days in Hong Kong under the high greenhouse gas concentration scenario.

Projected annual number of hot nights, very hot days and cold days in Hong Kong under the high greenhouse gas concentration scenario.

» Climate projections under different greenhouse gas concentration scenarios

 

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 in the projections for the future climate are still rather large. This, to a certain extent, reflects that climate projection is still subject to various uncertainties in the simulation of future climate, which depend very much on such factors as future greenhouse gas emissions, the choice of models, the ability of climate models to simulate physical processes, the downscaling methodology, the stability of the statistical downscaling relationship in the future. The technique is expected to continue to improve over time as scientists know more about various physical processes that impact on the climate.