Transcript Climate change - Department of Applied Physics

The Hong Kong Polytechnic University
Department of Applied Physics
GE Subject : Climate and Our Environment
Global and Local Climate Change
22 Sept 2008
Content
• Climate and Weather
• Greenhouse Effect & Global Warming
• Global Climate Change
• Hong Kong Connection & Urbanization Effect
• Future Projections
• Potential Impacts of Climate Change
• What can we do ?
What is Climate ? What is Weather ?
"Climate is what you expect; weather is what you get.“
by Robert A. Heinlein
• Weather is the day-to-day state of the atmosphere
• Climate describes the long-term character of all weather
variations -- the ‘expected’ weather
• Climate ≈ average of weather
Greenhouse Effect & Global Warming
Greenhouse Gases & Global Warming
Air composition
Nitrogen
78%
Oxygen
21%
Noble gas
Carbon
dioxide
carbon dioxide 0.038%
Air consists of nitrogen (N2), oxygen (O2), carbon dioxide (CO2),
noble gases (argon (Ar), helium (He) etc) and variable amount
of water vapour (H2O)
Condition for no greenhouse gas in the atmosphere
visible
sun
Heating = Heat Dissipation
Surface temperature ≈ -18 oC
earth
infra-red
Greenhouse Effect
sun
visible
infra-red
Average Temperature about 15℃
partly absorbed
Heat-trapping
greenhouse gases
act like a blanket
and keep the surface
and the lower
atmosphere warmer
than it would be
without them.
re-emitted
infra-red
earth
greenhouse
gases
Condition for greenhouse gases in the atmosphere; greenhouse gases include carbon dioxide
(CO2), nitrous oxide (N2O), methane (CH4), chlorofluorocarbons (CFCs) , ozone (O3) and
water vapour (H2O)
Human activities produce greenhouse gases (GHG)
Burning of fossil fuels and long term deforestation have been increasing the
concentration of GHG in the atmosphere, thickening the greenhouse blanket
energy production, industry:carbon dioxide(CO2)
husbandry: methane(CH4)
waste landfill: nitrous oxide(N2O)
freezer, aerosol spray:
chlorofluorocarbons(CFCs)
vehicle exhaust : ozone(O3)
nitrous oxide (ppb)
methane (ppb)
carbon dioxide (ppm)
Rising trends of greenhouse gases
time (before 2005)
time (before 2005)
time (before 2005)
(Source: Intergovernmental Panel on Climate Change)
Since 1750, the concentrations of global atmospheric carbon
dioxide, methane and nitrous oxide have risen sharply due to
human activities
Climate Change
Natural factors
• Solar activity,
• Volcanic gases
• Dust in the atmosphere
• Distribution of heat in the ocean
Anthropogenic (human-causes)
factors
• Greenhouse gas emission
• Land use changes / Deforestation
Global Warming
• Warming Of The Climate System Is Unequivocal
• Most of the observed increase in global average temperatures
since the mid-20th century is very likely due to the observed
increase in anthropogenic greenhouse gas concentrations
(IPCC)
Global Climate Change
The Consequence of Global Warming
Enhance greenhouse effect
Rising temperature
Thermal expansion of sea
water & melting of snow on
land
Sea level rise
Enhance the water cycle
Regional differences in
precipitation
Change in atmospheric
circulation and chemical
composition
Increase in occurrence
of extreme weather and
climate events
The world has been warming !
Global mean temperature has been rising at a rate of 0.13 degree per decade
in the past 50 years. This rising trend is double that of the trend in the past
100 years
Eleven (1998, 2005, 2003, 2002, 2004, 2006, 2001,
1997, 1995, 1999, 2000) of the last twelve years rank
among the 12 warmest years on record. The warmest
year being 1998.
(Source: Intergovernmental Panel on Climate Change)
Annual mean temperature trend in 1979-2005
Temperature has been rising in almost all regions, larger rises are
observed in high-latitude than low-latitude areas, and in land areas than
oceans
degree/decade
(white crosses represent trends are statistically significant at 5% level, areas in grey represent not having enough
data for computation of reliable trends)
(Source: Intergovernmental Panel on Climate Change)
Sea level rise
Global mean sea level has been rising at 1.8 mm per year in 1961-2003.
The rate of sea level rise is higher at 3.1 mm per year in 1993-2003.
blue：tidal gauge data
red：satellite data
(Source: Intergovernmental Panel on Climate Change)
Water cycle
Global warming will enhance the water cycle, causing the mean global precipitation to
increase. Precipitation here includes rain and snow.
sun
cloud
condensation
precipitation
evaporation
transpiration
evaporation
runoff
land
sea
Regional differences in land precipitation
The diagram shows the precipitation trends (1900 – 2005) at various regions.
Precipitation curves with white background are having rising trends and those with
yellow background falling trends.
(Source: Intergovernmental Panel on Climate Change)
Weather and climate extremes
Global warming leads to increase in occurrence of heat wave, drought and flooding
events, and possibly the increase in tropical cyclone intensity of the Atlantic.
Heat wave
Tropical cyclone
Drought
?????
(Source: US National Oceanic Atmospheric Administration)
Flooding
Hong Kong Connection & Urbanization Effect
Climate of Hong Kong
Hong Kong's climate is sub-tropical, tending towards temperate for nearly half the year.
HOT & WET in Summer
COOL & DRY in Winter
Monthly Mean Rainfall and Mean Temperature in Hong Kong from 1971
to 2000
600
35
Monthly Mean Rainfall
Monthly MeanTemperature
30
Mean Rainfall (mm)
25
400
20
300
15
200
10
100
5
0
0
JAN
FEB MAR APR MAY JUN
JUL
Month
AUG SEP OCT NOV DEC
Mean Temperature (deg C)
500
Mean Number of Tropical Cyclones affecting Hong Kong
(Standby Signal No. 1 or above) and
Mean Number of Thunderstorm Days in Hong Kong from 1961 to1990
3
8
No. of Tropical Cyclones
No. of Thunderstorm Days
No. of Tropical Cyclones
6
2
5
1.5
4
3
1
2
0.5
1
0
0
Jan Feb Mar Apr May Jun
Jul Aug Sep Oct Nov Dec
Month
No. of Thunderstorm Days
7
2.5
Climate Change in Hong Kong : Observations
Climate change in HK = Global Warming + Local Urbanization Effect
Rise in mean air temperature (global warming and urban heat island)
Increase in rainfall
Rise in sea level
Decrease in wind speeds (urban sheltering)
Rise in the frequency of reduced visibility
Increase in cloud amount
Reduce the amount of solar radiation
Urbanization Effect on Local Climate
• Due to urban development, change in land use, increase in
population, human activities, etc.
• A main characteristic is the significant difference in the temperature
between urban and rural (the countryside) areas. Average temperature
in the urban area is higher than that of the rural area.
• Large difference in diurnal variation :
Daytime --- Urban temperature < Rural temperature
Nightime --- Urban temperature > Rural temperature
• Buildings and other concrete surfaces in the urban areas retain the heat
produced by incoming solar radiation during the day and release the heat in the
form of long-wave radiation during the night. High-rise buildings also inhibit the
transfer of long-wave radiation to the atmosphere. This results in a slower fall of
temperatures at night and a higher minimum temperature than when buildings
were absent.
從市區到郊區香港晚間氣溫的變化圖(氣溫為上午5時，2007年平均值)。
Change in mean nighttime temperature from urban to rural areas in Hong Kong
(Average of 0500H temperature in 2007)
Mean hourly temperature difference between HKOHq and Ta Kwu Ling
(1989-2007 average)
HKOHq > TKL (red area)
HKOHq < TKL (blue area)
Annual mean temperature recorded at the Hong Kong Observatory Headquarters
(1885-2007)
There was an average rise of 1.2°C per 100 years from 1885 to 2007.
the global average surface temperature rose by 0.6℃ (IPCC)
Annual mean temperature recorded at the Hong Kong Observatory Headquarters
(1947-2007)
The warming at the Hong Kong Observatory Headquarters has become significantly
faster in the period 1989 to 2007, at a rate of 0.34°C per decade.
Comparison of recent trends in annual mean temperature in Hong Kong
(1989-2007)
HKO Headquarters is a station in the urban area of Kowloon
Ta Kwu Ling is a rural station in the northern part of the New Territories
(Data period:
Global: 1989-2005, HKO Headquarters and Ta Kwu Ling : 1989-2007)
Annual number of hot nights (minimum temperature >=28 deg C)
from 1947 to 2007
Annual Number of Hot Nights (Daily Minimum Temperature >=28oC)
in Hong Kong from 1947-2007
40
Number of HOT Nights
+3.9 days/decade
30
20
10
0
2007
2004
2001
1998
1995
1992
1989
1986
1983
1980
1977
1974
1971
1968
1965
1962
1959
1956
1953
1950
1947
Year
Annual number of Cold Days (minimum temperature =< 12 deg C)
from 1947 to 2007
Annual Number of Cold Days (Daily Minimum Temperature <= 12oC)
in Hong Kong from 1947-2007
50
Number of Cold Days
40
-2.9 days/decade
30
20
10
0
2007
2004
2001
1998
1995
1992
1989
1986
1983
1980
1977
1974
1971
1968
1965
1962
1959
1956
1953
1950
1947
Year
Annual Mean Number of Very Cold Days (Minimum Temperature =< 7oC) in a Decade
(No data in 1880-1884 ; 1937-1946 ; 2008-2009)
Annual Mean Number of Very Cold Days (Minimum Temperature =< 7oC) in a Decade
(No data in 1880-1884 ; 1937-1946 ; 2008-2009)
Mean Number of Days
4
3
2
1
2000-2010
1990-1999
1980-1989
1970-1979
1960-1969
Decade
1950-1959
1940-1949
1930-1939
1920-1929
1910-1919
1900-1909
1890-1899
1880-1989
0
Annual rainfall at the Hong Kong Observatory Headquarters
(1947-2007)
The annual total rainfall at the Hong Kong Observatory Headquarters has been
risen at a rate of 46mm/decade, though not statistically significant at 5% level.
Annual mean sea level at North Point/Quarry Bay (1954-2007)
The mean sea level in the Victoria Harbour has risen 0.13 m from 1954 to
2007, at an average rate of 2.4 mm per year
Annual average of 12-hourly 10-minute mean wind speed
of King’s Park and Waglan Island (1968-2007)
8
Waglan Island
no significant trend
7
Mean wind speed (m/s)
6
5
4
King's Park
-0.24 m/s per decade
King's Park
-0.60 m/s per decade
3
2
Relocation of anemometer
within King's Park
1
1968
1973
1978
1983
1988
1993
1998
2003
Year
Growing of tall buildings increases the roughness of the surface
underlying the atmosphere and exerts a drag on the low-level winds
Annual total number of hours with visibility at the Hong Kong
Observatory Headquarters below 8 km from 1968 to 2007
(relative humidity below 95 % and not counting rain, mist or fog)
Caused by suspended particulates of one
kind or another thrown up by human
activities in the city
Annual mean cloud amount recorded at the
Hong Kong Observatory Headquarters (1961-2007)
Urbanization causes the increase in the concentration of condensation nuclei in
the air (a factor favourable to the formation of cloud)
Annual mean daily total global solar radiation at King's Park (1964-2007)
the annual mean daily global solar radiation has decreased at a rate of 0.84 MJm-2 per
decade from 1964-2007.
Long term trend in annual total evaporation, 1961-2005
Attributed to greatly decreased prevailing wind speed and reduced amount
of solar radiation reaching the ground
Climate Change in Hong Kong :
Future Projections in the 21st century
Temperature : Downscaling based on IPCC’s Fourth Assessment Report (AR4)
Rainfall : Downscaling based on IPCC’s Third Assessment Report, being
updated using AR4
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.
Schematic diagram showing the downscaling technique
for future temperature in Hong Kong
Annual mean temperature anomaly (oC)
Past and projected annual mean
temperature anomaly for Hong Kong
+6.8 oC high-end
+4.8 oC
middle-of
the-road
+3.0 oC low-end
Observation
Projection
Decade
(Projection of Global Mean is about +1.8 to 4 oC, IPCC)
Past and projected number of cold days in winter
Number of cold days in winter
Observation
Projection
1980-1999 average : 14 days
middle-of
the-road
high-end
Decade
low-end
Temperature Projections for Hong Kong
Temperatures
• The average temperature will continue to increase (Middle condition:4.8ºC,
low-end:3.0ºC, high-end:6.8ºC)
• More very hot days and hot nights in summer
• Less cold days in winter
Parameter
Projections for 2090-2099 based on AR4
Middle-of-theLow-end
High-end
road
Average for
1980-1999
Average temperature (oC)
26.1
27.9
29.9
23.1
Annual number of
hot nights (nights)
30
41
54
15
Annual number of
very hot days (days)
12
15
19
7
The decade with
“no cold days”
2040-2049
2030-2039
2020-2029
Past and projected change in annual rainfall for Hong Kong
Lowest rainfall in the
past 120 years or so:
901 mm in 1963
(相片來源：水務署 Photo from Water Supplies Department)
Highest rainfall in the
past 120 years or so:
3343 mm in 1997
(相片來源：渠務署 Photo from Drainage Services Department)
Expected number of occurrences of even Expected number of occurrences of even
lower annual rainfall in the 21st century: higher annual rainfall in the 21st century:
3 times
6 times
A Quick Summary of Climate Change in Hong Kong
In the Past
The average temperature has increased by 1.2 degrees in the past century
The mean sea level has risen by 0.12 metre in the past 50 years, at an average
rate of 2.3 millimetres per year; and
The annual total rainfall has been risen at a rate of 46mm/decade, though not
statistically significant at 5% level.
Projections for the 21st century
Temperatures will continue to increase, the mean temperature in the decade 20902099 is expected to rise by 4.8 ℃. “long summer, no winter“.
Annual rainfall will increase at a rate of about 1% per decade, with more heavy
rain days and increase in the year-to-year variability in rainfall.
Potential Impacts of Climate Change
Possible Impacts :• Fresh Water Resources
• Ecosystems
• Food and forest products
• Coastal systems and low-lying areas
• Industry, settlement and society
• Health
Melting of ice caps and glaciers
Global warming leads to the melting of ice caps over polar land areas and the
glaciers on high mountains. The melted ice-water flows into the sea and
contributes to the sea level rise.
Muir Glacier, Alaska's Glacier Bay
August 13, 1941
August 31, 2004
(Image Credit: National Snow and Ice Data Center, W. O. Field, B. F. Molnia)
Between 1941 and 2004 the glacier retreated more than twelve kilometers and thinned by more than 800 meters.
Sea level rise causes flooding of coastal areas easier
waves caused by
typhoon
coa
st
rose in sea
level
coa
st
(Source: US National Oceanic Atmospheric Administration)
•
Flooding of the coastal areas becomes easier during typhoon
approaches or heavy rain
Sea level rise leads to the increase flooding risk in coastal areas
( Source : US Geological Survey)
Extreme weather threatens life and property
•
(Source: Geotechnical Engineering Office)
(Source: Apple Daily)
An Overview of Weather & Health
Direct
Thermal Stress
- cardiovascular and respiratory
morbidity and mortality
Indirect
Ecologically mediated
Weather
Vector-borne diseases
- malaria, dengue
Marine-borne diseases
- toxic algae, cholera
Food productivity
- malnutrition
Weather disasters
- deaths & injuries
- damage to health infrastructure
- increase risk of infectious diseases
- civil disorder/conflicts
With a death toll estimated to exceed 30 000,
the heat wave of 2003 is one of the ten
deadliest natural disasters in Europe for the last
100 years and the worst in the last 50 years.
Elderly people were most affected.
Source :
- Kovats S, Wolf T, Menne B. Heatwave of August 2003 in Europe: provisional estimates of the impact on mortality. Eurosurveillance Weekly. 11 March 2004;
8(11). http://www.eurosurveillance.org/ew/2004/040311.asp
- Environmental Alert Bulletin, United Nations Environment Programme
Risk of Thermal Stress
Public Health & Communicable Diseases
More mosquitoes, easier to transmit
dengue fever and malaria
More ticks, easier to transmit some
infectious diseases
Mosquitoe bites in a warm winter ?
Mosquitoes & ticks are expanding their territory ?
What can we do ?
The major cause of global warming is the excessive consumption of energy
and resources by human beings. As we are all contributors to global
warming, we should make effort to reduce global warming.
We could adopt a simple life style in our daily life to reduce global warming.
Save energy
• Use compact fluorescent bulbs and energy-efficient electrical appliances.
• Turn off electrical appliances and lighting when they are not in use.
• Use less air-conditioning. Set the temperature at 25.5°C.
• More use of renewable energy
(Source : Electrical and Mechanical Services Department)
On the road
• Drive less and use public transport. Consider walking or cycling.
• Drive smart, don’t rush into the traffic jam
• Buy fuel-efficient vehicles.
• Switch off idling vehicle engines.
Save Water
Don’t waste water. Take a shower instead of a bath.
Never brush your teeth under a running tap.
Only use your washing machine when you have a full load
and cut down the rinse cycle if possible.
Use less paper and plant more trees
• Disseminate information by electronic means where possible.
• Print both sides of the paper and minimize photocopying.
• Don't over wrap your gifts.
• Plant more trees to absorb carbon dioxide in the atmosphere.
Reducing waste and recycling
• Change the habit of excessive consumption and extravagant spending.
• Before purchasing a commodity, think whether it is needed. Use
recyclable products.
• Enhance waste separation and recovery for recycling.
Large amount of energy is used in producing commercial products and releasing
carbon dioxide
Encourage others to conserve energy and resources
Promote public awareness and understanding of climate change
The educational package on climate change
produced by the Observatory
Talks on Climate Change for Schools
In order to promote awareness and understanding of climate change to
students in Hong Kong, a team of professional meteorologists of the
Observatory has been delivering talks on climate change for primary and
secondary school children.
Website of Climate Change
http://www.weather.gov.hk/climate_change/climate_change_e.htm
THANK YOU