SecondarySchool Eng

Climate Change : 

Climate Change (Suitable for secondary school)

Slide2: 

carbon dioxide 0.038% Air composition Air consists of nitrogen (N2), oxygen (O2), carbon dioxide (CO2), noble gases (argon (Ar), helium (He) etc) and variable amount of water vapour (H2O) 78% 21%

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Heating and heat dissipation of the earth are in equilibrium visible infra-red earth sun Condition for no greenhouse gas in the atmosphere

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Greenhouse effect greenhouse gases Condition for greenhouse gases in the atmosphere; greenhouse gases include carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), chlorofluorcarbons (CFCs) , ozone (O3) and water vapour (H2O) partly absorbed re-emitted infra-red sun earth visible infra-red

Human activities produce greenhouse gases: 

Human activities produce greenhouse gases vehicle exhaust : ozone(O3) waste landfill: nitrous oxide(N2O) husbandry: methane(CH4) freezer, aerosol spray: chlorofluorcarbons(CFCs) energy production, industry:carbon dioxide(CO2)

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Rising trends of greenhouse gases carbon dioxide (ppm) methane (ppb) nitrous oxide (ppb) time (before 2005) time (before 2005) time (before 2005) Since 1750, the concentrations of global atmospheric carbon dioxide, methane and nitrous oxide have risen sharply due to human activities (Source: Intergovernmental Panel on Climate Change)

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Mean temperature of the earth’s surface 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 (Source: Intergovernmental Panel on Climate Change)

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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)

Annual mean temperatures of Hong Kong Observatory Headquarter at Tsim Sha Tsui (1947-2006): 

Annual mean temperatures of Hong Kong Observatory Headquarter at Tsim Sha Tsui (1947-2006) 1947-2006 0.17oC per decade 1989-2006 0.34oC per decade Year Temperature (oC) Trend of temperature rise was 0.17 degree per decade in post-war years, the trend increase sharply in recent ten years or so with the rate double that of the entire post-war period

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evaporation precipitation transpiration sun condensation evaporation runoff land sea cloud Water cycle

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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. Regional differences in land precipitation (Source: Intergovernmental Panel on Climate Change)

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Annual rainfall at Hong Kong Observatory Headquarters (1885 – 2006) Year Rainfall (mm) Rise of 1% per decade Lowest in 1963 (901 mm) Highest in 1997 (3343 mm)

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Rise in sea level - thermal expansion of sea water - melting of ice on land

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water expands when heated, water level rises as a result heating Expansion of water by heating Rise in global sea temperature leads to expansion of sea water and a rise in sea level water water

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Melting of ice caps and glaciers ( Source : US Geological Survey) 1928 2000 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.

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Sea level rise blue：tidal gauge data red：satellite data 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. (Source: Intergovernmental Panel on Climate Change)

Weather and climate extremes: 

Weather and climate extremes Drought Heat wave 水浸 Global warming leads to increase in occurrence of heat wave, drought and flooding events, and the increase in tropical cyclone intensity of the Atlantic. (Source: US National Oceanic Atmospheric Administration) Tropical cyclone Flooding

Number of heavy rain days recorded at Hong Kong Observatory Headquarters (1947-2006): 

Number of heavy rain days recorded at Hong Kong Observatory Headquarters (1947-2006) Rise in 0.47 days per decade Year Number of days Heavy rain day refers to a day with hourly rainfall greater than 30 mm

Number of cold days recorded at  Hong Kong Observatory Headquarters (1947-2006): 

Number of cold days recorded at Hong Kong Observatory Headquarters (1947-2006) Decrease in 2.6 days per decade Year Cold day refers to a day with daily minimum temperature of 12 degrees or below Number of days

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Storm surge High winds and low pressure near the centre of a tropical cyclone lead to the rise in sea level High winds pile up sea water against the coast Sucking up of sea level Sea level higher than normal Pressure is relatively low at the centre of tropical cyclone Pressure Normal sea level Sea level

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Flooding of the coastal areas becomes easier during typhoon approaches or heavy rain Sea level rise causes flooding of coastal areas easier waves caused by typhoon rose in sea level coast coast (Source: US National Oceanic Atmospheric Administration)

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(Source: Geotechnical Engineering Office) (Source: Apple Daily) Extreme weather threatens life and property

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Sea level rise leads to the increase in flooding risk in coastal areas ( Source : US Geological Survey)

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Change in temperature and rainfall affect the growth of plants Less food production in certain places

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Affect human health More ticks, easier to transmit some infectious diseases More mosquitoes, easier to transmit dengue fever and malaria

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Depending on the future greenhouse gases emission scenarios, temperature will most likely increase by 1.8 to 4.0 degrees and sea level rise by 0.18 to 0.59 metres. Global temperature and sea level at the end of the 21st century 1.8 to 4.0 degree 0.18 to 0.59 m Temperature Sea level

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Projection of cold days and very hot days in Hong Kong By the end of this century, the annual number of cold days in winter will decrease from the 1961-1990 mean of 21 days to less than a day By the end of this century, the annual number of very hot days in summer will increase from the 1961-1990 mean of 11 days to 24 days Number of cold days Number of very hot days Decade Decade

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(相片來源：水務署 Photo from Water Supplies Department) (相片來源：渠務署 Photo from Drainage Services Department)

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Ways to reduce atmospheric greenhouse effect (1) Reduce the burning of fossil fuels Save energy More use of renewable energy Solar power Wind power Use mass transport system whenever possible (Source : Electrical and Mechanical Services Department)

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Reduce waste Save paper Plant trees Prevent hill fires Ways to reduce atmospheric greenhouse effect (2) (Source: Agriculture, Fisheries and Conservation Department)

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Reduce expenditure Ways to reduce atmospheric greenhouse effect (3) Large amount of energy is used in producing commercial products and releasing carbon dioxide

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Reduce global warming with a simple life style !