Factors Affecting Our Climate

• Global Warming

• Acid Rain

• Ozone Effects

Global Warming

Scenario : Gradual increase in temperature

Reasons : • Uncontrolled

combustion of fossil fuels since Industrial Revolution

• Greenhouse gases (major: CO2)released continuously

• mainly the anthropogenic source

• Emission rate of CO2 > photosynthetic rate• Accumulation of Carbon dioxide in

atmosphere

Other greenhouse gases:• CFCs introduced as refrigerant, solvent and aerosol propellant• Ozone formed naturally in Stratosphere• Nitrous Oxide a by-product of nylon production released by fertilizer used in Agriculture

• Methane

produced in coal mining

natural gas production

• Water vapour

• Other hydrocarbons

Climatic Effects

• Atmospheric temperature increases steadily since the start of Industrial Revolution

• Unbalance of heat received and emitted on the Earth

• May increase the frequency and the strength of El Nino

• Doubling of CO2 concentration will raise the global surface temperature by 1.5-5.5 degree Celsius

• Annual emission of CO2 is 29 gigatons

Acid Rain

• NO2 and SO2 contributes the most to the decrease in pH of rain water from normal pH 5.6

• Source of NO2

• NO2 and SO2 ‘s source:

Emitted from fossil-fuels-fire power plants

Industrial boilers

Metal smelters

Automobiles

Causes

• SO2 dissolves in rain water to form H2SO3

• SO2 reacts with atmospheric oxygen to form SO3, and then dissolve in rain water to form H2SO4.

• NO reacts with oxygen to form NO2 which dissolves to form nitric acid.

• Acid rain damages plants by destroying their leaves

• It poisons soil which is in turns made unfavourable for the plant’s growth.

• It dissolves useful nutrients so that they are easily washed away

• Therefore, It destroys forest

Climatic Effects

• Forest number decreases

• World’s photosynthetic rate decreases

• Difference between photosynthetic rate and the emission rate of CO2 increases

• More CO2 accumulate in the atmosphere

• Give rise to Global Warming indirectly

• Effects of acid rain on forest first found in West Germany in 1982

• 8% of forest was damaged

• In 1983, 34% was damaged

• In 1986, 54% (the peak) was damaged

Percentage of Forest damaged in Europe

Ozone

• O + O2 <> O3 ( in the presence of sunlight)

• Absorb large amount of harmful Ultra Violet light

• Protect the Earth

Ground level Ozone

In unpolluted atmosphere• Natural process : NO + O3 > NO2 + O2

In polluted atmosphere

• NO + hydrocarbons > NO2 + other

products

• Originally, ozone concentration at ground level can be balanced by removing it by NO

• Hydrocarbons provide an alternative pathway for the NO to form NO2

• More ozone remains unconsumed

• Ozone concentration is elevated

Climatic Effects

• Ozone is the second major greenhouse gases

• Ozone concentration increases

• Contributes to Global warming

Ozone in Stratosphere

Why is there Ozone loss?

• Cold temperature and polar winter lead to formation of Polar Stratospheric clouds

• Heterogeneous reactions convert chlorine and bromine into more active forms

• Once sunlight reaches, chlorine is converted into radicals which initiates the catalytic ozone destruction cycle

Climatic Effects

• Ozone depletion alters the wind patterns and water current in the ocean

• Ozone depletion may increase the frequency and the strength of El Nino

• Cooling effect in the two poles

Potential Disastrous Consequences

• Global Warming -- Effects on vegetation -- Rising sea level -- Food supplies & agriculture -- Weather -- Epidemics and rapid growth of harmful insects

Effects On Vegetation

• Grain crops and trees may ‘’migrate’’ from hotter zone to cooler zone

• Some species or grassland may dry out in hotter zone

• These 2 factors lead to the soil in hotter zone unprotected (soil fertility decreases)

• Soil erosion occurs and more serious condition ----desertification may happen

Rising sea level

• Rise in temperature leads to melting of polar ice-caps

• Thermal expansion of seawater mass• Submerge many coastal wetland• Floods may occur• Terrestrial and aquatic ecosystem is severely

disrupted • Collapse of the Ross Ice Shelf in Antarctica • Loss of huge and densely populated coastal

areas

Food supplies & Agriculture

• Increased temperature brings about change in water cycle

• Rainfall pattern shifts and frequency of droughts and floods increases

• Higher temperature favours pests population

• Soil fertility decreases in hotter zone• Thus, decrease of crop yields leads to

decrease in food supplies

Epidemics

• Warmer climate favours growth of microorganisms which some may cause diseases

• Metabolic rate/ enzymatic rate increases

• Population increases

• diseases mushroom

Weather

• Ocean currents is altered

• Changes the distribution of rainfall

• Regions’ climate changes

• Storms, typhoon, hurricanes may become more violent

• Incitement of El Nino

Potential Disastrous Consequences

• Ozone effects

-- leads to global warming problems

-- alter water current and wind pattern

-- incitement of El Nino

• Acid Rain

--destruction of forests leads to

Global warming problems

El Nino

In Non-El Nino condition• Trade winds blow towards the west

across the tropical Pacific • These winds pile up warm surface

water in the west Pacific • Higher temperature in west• Lower temperature in east due to

an upwelling of cold water from deeper levels

• Cold water is nutrients rich

• Give diverse marine ecosystems and major fisheries

In El Nino Conditions

• the trade winds relax in the central and western Pacific

• Lead to a depression of the thermocline in the eastern Pacific, and an elevation of the thermocline in the west

• Warm water moves to eastern Pacific suppressing the cold water going up to cool the surface

• The supply of nutrients of East Pacific is cut off or reduced

• Rise in surface temperature in east Pacific

• Drops in surface temperature in west pacific

• More rainfall in east Pacific

• Less rainfall in west Pacific

Potential Consequences

• Flooding in Peru or some coastal areas along the east pacific

• Droughts or even forest fires may happen in Indonesia and Australia

• Less nutrients supply, thus less commercial fisheries

• Large change of the global atmospheric circulation