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The latest on climate change in Hong Kong

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The latest on climate change in Hong Kong T C Lee HKCCF Programme on climate change 21 September 2010 Annual total number of hours with visibility at HKO Headquarters ... – PowerPoint PPT presentation

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Title: The latest on climate change in Hong Kong


1
The latest on climate change in Hong Kong T C
Lee HKCCF Programme on climate change 21
September 2010
2
  • CONTENT
  • Background
  • Observed changes
  • Temperature
  • Rainfall
  • Sea Level
  • Severe Weather Events
  • Other Meteorological Elements
  • 21st century projections
  • Future research activities

3
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. Kings 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.

4
Locations of Key Climatological Stations in Hong
Kong
5
Urban snapshots in Hong Kong
Dense development Many Skyscrapers 100 -
400m e.g. IFC 415 m Central Plaza 374m
6
Urbanization effect on temperature
7
Urbanization effect on wind speed, visibility and
evaporation
8
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
9
Temperature
10
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
11
Annual mean surface air temperature for 1951-2007
in Hongkong (red) and Guangzhou (green) as well
as Macao (blue)
(Source ??? ??? ??? ??? ?? ??? ??? ???,
19012007????????????, ???????? 2009?01?)
12
Changes in average temperatures in Guangdong
1975-1980
2001-2006
(Source ??????????(??), ????????????????,????,
Vol. 29 (3), 2007.)
13
Annual Number of Hot Night in Hong Kong
(1885-2009)(Daily Min. Temp gt 28oC)
14
Annual number of cold days in Hong Kong
(1885-2009) (Daily Min. Temp lt 12oC)
15
Annual number of very hot days in Hong Kong
(1885-2009) (Daily Max. Temp gt 33oC)
16
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.)
17
Rainfall
18
Rainfall trend in Hong Kong
Annual rainfall recorded at the Hong Kong
Observatory Headquarters (1885-2009).Data are
not available from 1940 to 1946
19
Number of rain days in Hong Kong (daily rainfall
gt1 mm) (at HKO Headquarters)
20
Number of heavy rain days (hourly rainfall gt 30
mm) at Hong Kong Observatory Headquarters (1885
2009)
i.e. 3 days in a century
21
Record high hourly rainfall at the Hong Kong
Observatory Headquarters (1885 2009)
22
Extremes becoming more frequent
Changes in frequency of extreme rainfall events
based on time-dependent return period analysis
Element Return period in 1900 Return period in 2000
1 hour rainfall gt 100 mm 37 years 18 years
2 hour rainfall gt 150 mm 32 years 14 years
3 hour rainfall gt 200 mm 41 years 21 years
23
Long term trend of annual total rainfall due to
heavy rainfall events (R95p)
R95p annual total rainfall at HKO Headquarters
due to events exceeding the daily 95th
percentile of the climatological normal
(1971-2000)
24
Mean Sea Level
25
Sea Level Rise in Hong Kong
Sea 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
26
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.
27
Severe Weather Events
28
Number of Thunderstorm Days from 1947 to 2009 (as
observed at HKO Headquarters)
29
Annual number of tropical cyclones making
landfall along the south China coast within 300
km of Hong Kong from 1961 to 2009
30
Annual number of typhoon making landfall along
the south China coast within 300 km of Hong Kong
from 1961 to 2009
31
Other Meteorological Elements
32
Annual mean daily solar radiation recorded at
Kings Park Station (1958-2009)
33
Annual average of 12-hr 10 minute mean wind speed
at Kings Park and Waglan Island (1968-2008)
34
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)
35
(No Transcript)
36
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/perfor
mance.
37
Magnitude of Extreme Sea-levels
Extreme sea-levels (mCD) at Victoria Harbour Extreme sea-levels (mCD) at Victoria Harbour Extreme sea-levels (mCD) at Victoria Harbour Extreme sea-levels (mCD) at Victoria Harbour
Return 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
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.
Note mCD metres above Chart Datum. Chart Datum
is 0.146 metre below Principal Datum.
38
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

39
  • 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.

40
Thank You
41
Storm Surge Sea-level Rise
Original mean sea level
After sea-level rise, storm surges will bring
more frequent sea flooding to coastal low-lying
areas.
42
What would happen in past storms?
Extreme sea-levels (mCD) at Victoria Harbour Extreme sea-levels (mCD) at Victoria Harbour Extreme sea-levels (mCD) at Victoria Harbour Extreme sea-levels (mCD) at Victoria Harbour
Typhoon Extreme 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.
43
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.)
44
Variation in electricity consumption in Hong Kong
increases significantly in the last 4 decades in
both domestic and commercial sectors.
Year
1970-2009 Time Series of Seasonal Variation
45
A. Domestic Sector
During warm months (May-Oct) Electricity
Consumption vs CDD
2000s
1990s
1970s
1980s
Correlation is significant at 5 in all 4 decades.
Sensitivity of electricity use to climate factor
increases in recent decades.
46
Past and projected annual mean temperature
anomaly for Hong Kong (based on IPCC AR4 annual
mean projection data)
47
Past and projected changes in annual rainfall for
Hong Kong
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