The latest on climate change in Hong Kong
T C Lee
HKCCF
Programme on climate change
21 September 2010
CONTENT
• Background
•
-
Observed changes
Temperature
Rainfall
Sea Level
Severe Weather Events
Other Meteorological Elements
• 21st century projections
• Future research activities
Climate Monitoring in Hong Kong
Hong Kong Observatory Headquarters
Regular meteorological observations
commenced in 1884, including temperature,
rainfall, pressure, sunshine duration (upto1960),
wind speed/direction, etc.
King’s Park Meteorological Station
Daily radiosonde ascents began in 1951.
One of the stations in the Global Climate
Observing System (GCOS) Upper Air Network
(GUAN).
Other meteorological measurements since
1950s include pressure, temperature, rainfall,
sunshine duration, evaporation, etc.
Locations of Key Climatological Stations in Hong Kong
Kowloon
KP
HKO
Lantau
HK Island
Island
WGL
Urban snapshots in Hong Kong
Dense development
Many Skyscrapers
100 - 400m
e.g.
IFC ~ 415 m
Central Plaza ~ 374m
Urbanization effect on temperature
Urbanization effect on wind speed, visibility and evaporation
Observed Climate Change in Hong Kong
Climate change in HK =
Global Warming + Local Urbanization Effect
Element
Trend
Average Temperature
Increase
Annual Rainfall
Increase
Mean Sea Level
Increase
Temperature
Temperature trend in Hong Kong
Annual mean temperature recorded at the Hong Kong Observatory Headquarters
(1885-2009). Data are not available from 1940 to 1946
Annual mean surface air temperature for 1951-2007 in Hongkong (red) and
Guangzhou (green) as well as Macao (blue)
25
G u a n g zh o u 廣 州
Hong Kong 香 港
M a ca o 澳 門
o
o
o
每 十 年 上 升 0 .1 9 C
每 十 年 上 升 0 .1 7 C
每 十 年 上 升 0 .1 0 C
o
o
o
+ 0 .1 9 C /d e ca d e
+ 0 .1 7 C /d e ca d e
+ 0 .1 0 C /d e ca d e
A n n u a l M e a n T e m p e ra tu re
年 平 均 氣 溫 (o C )
24
23
22
21
20
1951
1956
1961
1966
1971
1976
1981
1986
1991
1996
2001
2006
Year 年
(Source : 冯瑞权 吴池胜 王安宇 何夏江 王婷 梁嘉静 黎婉文 梁必骐, 1901—2007年澳门地面气温变化的分析, 《气候变化研究进展》 2009年01期)
Changes in average temperatures in Guangdong
1975-1980
2001-2006
(Source : 广东气候变化评估报告（节选）, 广东省气候变化评估报告编制课题组,广东气象, Vol. 29 (3), 2007.)
Annual Number of Hot Night in Hong Kong (1885-2009)
(Daily Min. Temp >= 28oC)
Annual number of cold days in Hong Kong (1885-2009)
(Daily Min. Temp <= 12oC)
Annual number of very hot days in Hong Kong (1885-2009)
(Daily Max. Temp >= 33oC)
Time dependent return period analysis of
extreme temperature events in Hong Kong
Element
Return period in 1900
Return period in 2000
Minimum Temperature
≤ 4oC
6 years
163 years
Maximum Temperature
≥ 35oC
32 years
4.5 years
(Source : Wong, M.C. and H.Y. Mok, 2009: Trends in Hong Kong Climate Parameters Relevant to Engineering Design.
HKIE Civil Division Conference 2009 : Conference on Engineers' Responses to Climate Change.)
Rainfall
Rainfall trend in Hong Kong
Annual rainfall recorded at the Hong Kong Observatory Headquarters (1885-2009).
Data are not available from 1940 to 1946
Number of rain days in Hong Kong (daily rainfall >=1 mm)
(at HKO Headquarters)
150
140
-1 .1 d a y /d eca d e
N u m b er o f R a in d a y s (d a y )
130
120
110
100
90
80
70
60
1885
1895
1905
1915
1925
1935
1945
Y ea r
1955
1965
1975
1985
1995
2005
Number of heavy rain days (hourly rainfall > 30 mm)
at Hong Kong Observatory Headquarters (1885 – 2009)
i.e. +3 days in a century
Record high hourly rainfall
at the Hong Kong Observatory Headquarters (1885 – 2009)
Extremes becoming more frequent
Changes in frequency of extreme rainfall events based on timedependent return period analysis
Element
Return period Return period
in 1900
in 2000
1 hour rainfall > 100 mm
37 years
18 years
2 hour rainfall > 150 mm
32 years
14 years
3 hour rainfall > 200 mm
41 years
21 years
Long term trend of annual total rainfall
due to heavy rainfall events (R95p)
1800
1600
Trend = + 21 mm per decade
Significant at 5 % level
1400
R95p (mm)
1200
1000
800
600
400
200
0
1884
1904
1924
1944
1964
1984
2004
Year
R95p : annual total rainfall at HKO Headquarters due to events
exceeding the daily 95th percentile of the climatological normal (1971-2000)
Mean Sea Level
SeaLevel
level rise
Sea
Risein
inHong
HongKong
Kong
On average, the mean sea level in the Victoria Harbour has risen at a rate of 2.6 mm per
year during the period 1954 to 2009
Causes of Sea-level Change
Image source: Causes of sea level rise from climate change. (2002). In UNEP/GRID-Arendal Maps and Graphics Library.
Retrieved March 11, 2010 from http://maps.grida.no/go/graphic/causes-of-sea-level-rise-from-climate-change.
Severe Weather Events
Number of Thunderstorm Days from 1947 to 2009
(as observed at HKO Headquarters)
Annual number of tropical cyclones making landfall along the south China coast
within 300 km of Hong Kong from 1961 to 2009
Annual number of typhoon making landfall along the south China coast
within 300 km of Hong Kong from 1961 to 2009
N u m b e r o f ty p h o o n la n d fa ll w ith in 3 0 0 k m fro m H o n g
Kong
6
5
4
3
2
1
0
1961
1966
1971
1976
1981
1986
Year
1991
1996
2001
2006
Other Meteorological Elements
Annual mean daily solar radiation recorded at King’s Park Station
(1958-2009)
Annual average of 12-hr 10 minute mean wind speed
at King’s Park and Waglan Island (1968-2008)
Annual total number of hours with visibility at HKO Headquarters
below 8km from 1968-2008
(relative humidity below 95% and not counting rain, mist or fog)
Projections for Hong Kong in the 21st century
Temperature : the increasing trend will continue. The mean temperature in the
decade 2090-2099 is expected to rise by 4 to 5 oC relative to the period 19801999.
Rainfall : will increase during the latter half of the 21st century with about 10%
increase relative to the 1980-1999 average.
Sea level : The sea-level at the South China Sea including Hong Kong is likely
to be close to the global average in the long run.
•
•
According to IPCC AR4, the global average sea-level will rise by 0.18 to 0.59 m at
the end of 21st century relative to the period 1980 to 1999.
Recent studies by some research groups suggest higher projections
Uncertainties : there are still large uncertainties in the model simulation for the
future climate, depending very much on the future forcing emission scenarios
and local urbanization effect as well as the model characteristics/performance.
Magnitude of Extreme Sea-levels
Extreme sea-levels (mCD) at Victoria Harbour
Return Extreme sea- Extreme sea-level
period level based after a mean sea(year) on past data level rise of 0.59 m
Extreme sea-level
after a mean sealevel rise of 1.4 m
2
2.9
3.5
4.3
5
3.1
3.7
4.5
10
3.3
3.8
4.7
20
3.4
50
3.5
A sea-level of 3.5 mCD similar to that during
Typhoon
50 years event,
4.0 Hagupit, a once in4.8
would become a bienniel event after a rise of
0.59 m.
4.1 the mean sea-level by
4.9
Note: mCD = metres above Chart Datum.
Chart Datum is 0.146 metre below Principal Datum.
Future Work on Climate Research
• Future trends of extreme temperature and rainfall events
based on IPCC AR4 (daily model data)
• Update projections of Hong Kong climate in the 21st
Century base on IPCC AR5 model data
• Urbanization effects on Hong Kong climate
• Weather and Health (Rotavirus, RSV, etc.) – collaboration with
CUHK
• Climate and Ecosystem / Other social impacts
Summary
•
Significant changes in the climate in Hong Kong were observed
in the last century, including the increase in average
temperatures and total rainfall as well as the rise of mean sea
level.
•
Studies of past occurrences of extreme temperature and rainfall
in Hong Kong revealed that cold episodes have become rarer
while very hot days and heavy rain events are becoming more
frequent
•
Looking into the future, Hong Kong can expect even warmer
weather, more variable rainfall, and a sea level that keeps
rising.
•
Climate change research is an on-going process.
Thank You
Storm Surge + Sea-level Rise
Waves caused
by Typhoon
Coast
Coast
Original mean sea level
Raised mean sea level
After sea-level rise, storm surges will bring more
frequent sea flooding to coastal low-lying areas.
What would happen in past storms?
Extreme sea-levels (mCD) at Victoria Harbour
Typhoon
Extreme Extreme sea-level Extreme sea-level
sea-level after a mean sea- after a mean searecorded level rise of 0.59 m level rise of 1.4 m
Wanda (1962)
3.96
4.55
5.36
Hagupit (2008)
3.53
4.12
4.93
Koppu (2009)
3.02
3.61
4.42
Note: mCD = metres above Chart Datum.
Chart Datum is 0.146 metre below Principal Datum.
Possible inundation around the Pearl River Delta caused by a sea level rise
sea level rise of 0m
sea level rise of 1m
(Source : Wong, K.M., K.H. Lau, J.P. Gray. (2007), Impact of sea level rise on Hong Kong and the Pearl River Delta, presented in
International Conference on Climate Change, May 2007, Hong Kong.)
M o n th ly E le c tric ity C o n s u m p tio n p e r C a p ita (M J )
Variation in electricity consumption in Hong Kong increases significantly
in the last 4 decades in both domestic and commercial sectors.
1600
1400
D o m e s tic E le c tric ity
1200
C o m m e rc ia l E le c tric ity
1000
800
600
400
200
0
1970
1975
1980
1985
1990
Year
1995
1970-2009 Time Series of Seasonal Variation
2000
2005
2010
A. Domestic Sector
During warm months (May-Oct) – Electricity Consumption vs CDD
1990’s
M o nthly E le ctricity vs M o nthly C o o ling D e g re e -d a ys (2 0 0 0 -2 0 0 9 )
M o nthly E le c tric ity vs M o nthly C o o ling D e g re e -d a ys (1 9 9 0 -1 9 9 9 )
9 .0 E +0 8
9 .0 E +0 8
M o n th ly E le ctricity (p e r ca p ita )
M o n th ly E le ctricity (p e r ca p ita )
2000’s
8 .0 E +0 8
7 .0 E +0 8
6 .0 E +0 8
5 .0 E +0 8
4 .0 E +0 8
3 .0 E +0 8
2 .0 E +0 8
1 .0 E +0 8
0 .0 E +0 0
0
20
40
60
80
M o nthly C D D (M a y-O ct)
100
8 .0 E +0 8
7 .0 E +0 8
6 .0 E +0 8
5 .0 E +0 8
4 .0 E +0 8
3 .0 E +0 8
2 .0 E +0 8
1 .0 E +0 8
0 .0 E +0 0
120
0
20
y = 3 E +0 6 x + 4 E +0 8
40
60
80
M o nthly C D D (M a y-O c t)
2
R = 0 .4 0 4
1970’s
M o nthly E le ctricity vs M o nthly C o o ling D e g re e -d a ys (1 9 8 0 -1 9 8 9 )
9 .0 E +0 8
9 .0 E +0 8
8 .0 E +0 8
8 .0 E +0 8
M o n th ly E le ctricity (p e r ca p ita )
M o n th ly E le ctricity (p e r ca p ita )
120
2
R = 0 .6 3 1 5
1980’s
100
y = 2 E +0 6 x + 3 E +0 8
7 .0 E +0 8
6 .0 E +0 8
5 .0 E +0 8
4 .0 E +0 8
3 .0 E +0 8
2 .0 E +0 8
1 .0 E +0 8
0 .0 E +0 0
M o nthly E le ctricity vs M o nthly C o o ling D e g re e -d a ys (1 9 7 0 -1 9 7 9 )
7 .0 E +0 8
6 .0 E +0 8
5 .0 E +0 8
4 .0 E +0 8
3 .0 E +0 8
2 .0 E +0 8
1 .0 E +0 8
0 .0 E +0 0
0
20
40
60
80
M o nthly C D D (M a y-O ct)
100
120
0
y = 1 E +0 6 x + 2 E +0 8
20
40
60
80
M o nthly C D D (M a y-O ct)
2
100
120
y = 4 0 2 0 8 7 x + 1 E +0 8
2
R = 0 .2 4 2 6
R = 0 .1 3 7 2
S lo p e
C o rre la tio n (r)
P -va lu e
S ig n ific a n t a t 5 % ?
2 0 0 0 's
2 .9 7 E + 0 6
0 .7 9
5 .7 8 E -1 4
Yes
1 9 9 0 's
2 .2 8 E + 0 6
0 .6 4
4 .8 6 E -0 8
Yes
1 9 8 0 's
1 .1 1 E + 0 6
0 .4 9
6 .4 1 E -0 5
Yes
1 9 7 0 's
4 .0 2 E + 0 5
0 .3 7
1 .0 2 E -0 3
Yes
Correlation is significant at 5% in all 4 decades.
Sensitivity of electricity use to climate
factor increases in recent decades.
Past and projected annual mean temperature anomaly for Hong Kong
(based on IPCC AR4 annual mean projection data)
Past and projected changes in annual rainfall for Hong Kong