Post on 30-Dec-2015
description
The latest on climate change in Hong Kong
T C Lee
HKCCFProgramme 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.
WGL
KPHKO
Lantau Island
Kowloon
HK Island
Locations of Key Climatological Stations in Hong Kong
Urban snapshots in Hong Kong
Dense development
Many Skyscrapers100 - 400m
e.g.IFC ~ 415 mCentral Plaza ~ 374m
Urbanization effect on temperature
Urbanization effect on wind speed, visibility and evaporation
Climate change in HK = Global Warming + Local Urbanization Effect
Observed Climate Change in Hong Kong
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) andGuangzhou (green) as well as Macao (blue)
每十年上升0.17oC
+0.17oC/decade每十年上升0.10oC
+0.10oC/decade
每十年上升0.19oC
+0.19oC/decade
20
21
22
23
24
25
1951 1956 1961 1966 1971 1976 1981 1986 1991 1996 2001 2006
Year 年
An
nu
al M
ea
n T
em
pe
ratu
re 年
平均
氣溫
(o
C)
Macao 澳門 Hong Kong 香港 Guangzhou 廣州
(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 )
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.)
Changes in average temperatures in Guangdong
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)
Element Return period in 1900 Return period in 2000
Minimum Temperature ≤ 4oC
6 years 163 years
Maximum Temperature ≥ 35oC
32 years 4.5 years
Time dependent return period analysis of extreme temperature events in Hong Kong
(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)
60
70
80
90
100
110
120
130
140
150
1885 1895 1905 1915 1925 1935 1945 1955 1965 1975 1985 1995 2005Year
Nu
mbe
r of
Rai
nda
ys (
day
)
-1.1 day/decade
i.e. +3 days in a century
Number of heavy rain days (hourly rainfall > 30 mm) at Hong Kong Observatory Headquarters (1885 – 2009)
Record high hourly rainfall at the Hong Kong Observatory Headquarters (1885 – 2009)
ElementReturn period
in 1900Return period
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
Changes in frequency of extreme rainfall events based on time-dependent return period analysis
Extremes becoming more frequent
Long term trend of annual total rainfall due to heavy rainfall events (R95p)
Trend = + 21 mm per decade
Significant at 5 % level
0
200
400
600
800
1000
1200
1400
1600
1800
1884 1904 1924 1944 1964 1984 2004
Year
R9
5p
(m
m)
R95p : annual total rainfall at HKO Headquarters due to events exceeding the daily 95th percentile of the climatological normal (1971-2000)
Mean Sea Level
Sea Level Rise in Hong KongSea level rise in Hong 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
0
1
2
3
4
5
6
1961 1966 1971 1976 1981 1986 1991 1996 2001 2006Year
Nu
mb
er o
f ty
ph
oo
n l
and
fall
wit
hin
300
km f
rom
Ho
ng
Ko
ng
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 1980-1999.
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 HarbourReturn period (year)
Extreme sea-level based on past data
Extreme sea-level after a mean sea-level rise of 0.59 m
Extreme sea-level after a mean sea-level 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 4.0 4.8
50 3.5 4.1 4.9
Note: mCD = metres above Chart Datum.Chart Datum is 0.146 metre below Principal Datum.
A sea-level of 3.5 mCD similar to that during Typhoon Hagupit, a once in 50 years event,
would become a bienniel event after a rise of the mean sea-level by 0.59 m.
A sea-level of 3.5 mCD similar to that during Typhoon Hagupit, a once in 50 years event,
would become a bienniel event after a rise of the mean sea-level by 0.59 m.
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
Raised mean sea level
Coast Coast
Original 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
TyphoonExtreme sea-level recorded
Extreme sea-level after a mean sea-level rise of 0.59 m
Extreme sea-level after a mean sea-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.)
0
200
400
600
800
1000
1200
1400
1600
1970 1975 1980 1985 1990 1995 2000 2005 2010
Mon
thly
Ele
ctric
ity C
onsu
mpt
ion
per
Cap
ita (
MJ)
Domestic Electricity
Commercial Electricity
Year
1970-2009 Time Series of Seasonal Variation
Variation in electricity consumption in Hong Kong increases significantly in the last 4 decades in both domestic and commercial sectors.
Slope Correlation (r) P-value Significant at 5 %?2000's 2.97E+06 0.79 5.78E-14 Yes1990's 2.28E+06 0.64 4.86E-08 Yes1980's 1.11E+06 0.49 6.41E-05 Yes1970's 4.02E+05 0.37 1.02E-03 Yes
Monthly Electricity vs Monthly Cooling Degree-days (2000-2009)
y = 3E+06x + 4E+08
R2 = 0.6315
0.0E+00
1.0E+08
2.0E+08
3.0E+08
4.0E+08
5.0E+08
6.0E+08
7.0E+08
8.0E+08
9.0E+08
0 20 40 60 80 100 120
Monthly CDD (May-Oct)
Mo
nth
ly E
lect
rici
ty (
pe
r ca
pita
)
Monthly Electricity vs Monthly Cooling Degree-days (1990-1999)
y = 2E+06x + 3E+08
R2 = 0.404
0.0E+00
1.0E+08
2.0E+08
3.0E+08
4.0E+08
5.0E+08
6.0E+08
7.0E+08
8.0E+08
9.0E+08
0 20 40 60 80 100 120
Monthly CDD (May-Oct)
Mo
nth
ly E
lect
rici
ty (
pe
r ca
pita
)
Monthly Electricity vs Monthly Cooling Degree-days (1980-1989)
y = 1E+06x + 2E+08
R2 = 0.2426
0.0E+00
1.0E+08
2.0E+08
3.0E+08
4.0E+08
5.0E+08
6.0E+08
7.0E+08
8.0E+08
9.0E+08
0 20 40 60 80 100 120
Monthly CDD (May-Oct)
Mo
nth
ly E
lect
rici
ty (
pe
r ca
pita
)
Monthly Electricity vs Monthly Cooling Degree-days (1970-1979)
y = 402087x + 1E+08
R2 = 0.1372
0.0E+00
1.0E+08
2.0E+08
3.0E+08
4.0E+08
5.0E+08
6.0E+08
7.0E+08
8.0E+08
9.0E+08
0 20 40 60 80 100 120
Monthly CDD (May-Oct)
Mo
nth
ly E
lect
rici
ty (
pe
r ca
pita
)
During warm months (May-Oct) – Electricity Consumption vs CDD
Sensitivity of electricity use to climate factor increases in recent decades.
2000’s 1990’s
1970’s1980’s
A. Domestic Sector
Correlation is significant at 5% in all 4 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