Water and climate change
B.Y. LeeDirector of the Hong Kong Observatory
May 2010
Global warming :
“Most of the observed increase in globally-
averaged temperatures since the mid-20th century
is very likely due to the observed increase in man-
made greenhouse-gas (GHG) concentrations”
(United Nations Intergovernmental Panel on Climate Change (IPCC),
Fourth Assessment Report (AR4), 2007)
Very likely = 90%
About 10% increase relative to the 1980-1999 average of 2324 mm
About 5% or 120mm less than the 1980-1999 average
( 相片來源：水務署 Photo from Water Supplies Department)
香港極香港極端少雨端少雨和極和極端多端多雨的年數雨的年數Number of extremely dry years and extremely wet years in Hong KongNumber of extremely dry years and extremely wet years in Hong Kong
( 相片來源：水務署 Photo from Water Supplies Department)( 相片來源：水務署 Photo from Water Supplies Department)( 相片來源：水務署 Photo from Water Supplies Department)( 相片來源：水務署 Photo from Water Supplies Department)( 相片來源：水務署 Photo from Water Supplies Department)
極端少雨的年數極端少雨的年數 Extremely dry yearsExtremely dry years
極端多雨的年數極端多雨的年數 Extremely wet yearsExtremely wet years
期間Period
1885 - 2000 2 2
21st century 4 10
( 相片來源：水務署 Photo from Water Supplies Department) ( 相片來源：渠務署 Photo from Drainage Services Department)
Notes : Extremely dry years - annual rainfall less than 1282 mm; extremely wet years - annual rainfall more than 3187 mm 極端少雨的年數 - 年雨量低於 1282 毫米 ; 極端多雨的年數 - 年雨量高於 3187 毫米
( 相片來源：渠務署 Photo from Drainage Services Department)
Personally per capita 100 litres/day
Daily food consumption 2000-5000 litres
1 kg bolt of cloth >10 000 litres
1 kg of beef 15 000 litres
1 kg of vegetable 2000 litres
Water usage
(source : The Economist, 11 April 2009)
What about the melting glaciers in the Himalayas?
Mean annual mass balance [Note] of reference glaciers from 1980 to 2008
with positive values in blue and negative values in red..(Source : World Glacier Monitoring Service : Preliminary
glacier mass balance data 2007/2008
http://www.geo.unizh.ch/wgms/mbb/sum08.html)
Source : World Glacier Monitoring Service : Preliminary glacier mass balancedata 2007/2008 http://www.geo.unizh.ch/wgms/mbb/sum08.html)
Flooding of the coastal areas becomes easier
under tropical cyclone situations
Sea level rise, plus storm surge
waves caused by typhoon rise in sea level
coast coast
Magnitude of extreme sea levels at Victoria Harbour based on past data, a projected rise of 0.59 m and of 1.4 m.
Extreme sea-levels at Victoria Harbour
Return period (year)
Extreme sea-level (mCD) based on
past data
Extreme sea-level (mCD) after a mean of sea-level rise of 0.59 m
Extreme sea-level (mCD) after a mean of 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.
(courtesy of TVB)
Flooding in Tai O after Typhoon Hagupit (September 2008)
