Teachers Notes

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The atmosphere

changes with altitude

more ozone naturally occurs in the stratosphere where UV reacts with oxygen

Temperature declines in the troposphere due to heating from IR from the ground, but increases in the stratosphere due to UV from the sun

Atmospheric pressure declines with altitude.

the importance of the atmosphere as a life-support system, a source of oxygen, carbon dioxide, nitrogen and water vapour for the hydrological cycle.

The ozone provides layer of protection from UV light

monatomic, diatomic and triatomic oxygen form a dispersed layer in the stratosphere. They absorb the UV light which creates a dynamic equilibrium of chemical reactions that form and destroy the ozone. Prevents most UV from reaching the earth surface.

solar radiation and the atmosphere

nuclear fusion occurs in the sun. The nuclei of hydrogen atoms join at high temperatures causing the release of energy.

The characteristics of radiation:

at outer limits of the atmosphere: main visible light and UV light

as it passes through atmosphere: UV light is absorbed by the ozone layer, some visible light is scattered, absorbed or reflected by clouds and particulate matter

some visible light is absorbed or reflected by clouds and particulate matter

when it reaches the earths surface: visible light reflected or absorbed, to be radiated as IR

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Global Climate Change

The Greenhouse effect

natural phenomenon in controlling the energy and heat balance of the atmosphere and Earth's surface.

IR radiation is emitted by the Earth surface and partly absorbed by gases in the atmosphere. The atmosphere becomes warmer until the surplus of heat energy is radiated into space.

Enhanced Greenhouse Effect and global climate change

the role of gases in the atmosphere is to maintain the heat balance and global climate change of earth. Increase in some gases causes heat to be retained longer ~global climate change

gases which may contribute to global climate change :

carbon dioxide,methane, CFCs, Oxides of nitrogen and tropospheric ozone.

Major anthropogenic sources of these gases:

Carbon dioxide

combustion of fossil fuels, deforestation

Methane

livestock, padi fields, landfill sites (due to anaerobic bacteria), produced by forming of fossil fuels and released ventilation of coalmines, leaks from natural gas fills and oil pipelines

oxides of nitrogen

reaction of oxygen and nitrogen at high temperatures in vehicle engines and power stations

CFCs

aerosols, fire extinguishers, refrigerants, solvents, expanded foam plastics

Tropospheric ozone

Produced during the photochemical breakdown of NO2 and the subsequent reaction the oxygen

Gas Approximate relative effect per molecule

Carbon dioxide 1

Methane 30

Tropospheric ozone 2000

Nitrous oxide 160

CFCs 25 000

likely consequences of global climate change

sea level rise:

increased temperature cause water to expand

increased temperature cause land ice to melt , flow into the sea and increase the volume of the sea

Climate in change,

Most climate systems are driven by energy from the sun. Retention of more energy in the atmosphere my change these systems :

wind patterns - changes in velocity, frequency and direct

precipitation - higher temperatures increase evaporation rates which will increase precipitation rates. Water vapour will be transported by wind and result in precipitation when the air cools sufficiently. Changes in wind patterns may result in areas getting more or less rain.

Ocean current changes

El nino changes in the Peruvian current may become more frequent. Increased amounts of cold freshwater from melting glaciers may cause the gulf stream to slow and have less of a warming effect on North West Europe.

ecological changes

Temperature increase may cause growth rates of plants to increase

precipitation changes may cause wetlands to enlarge or shrink

oak trees have deeper roots than beech trees and can survive droughts better

Dormouse hibernation maybe disturbed by warmer winters and cause them to use stored fat and give them less chance of survival

Timing of ecological events; flowering, nesting and migration may change. Survival of interdependent species may be reduced e.g; if pollinating insects aren't present when flowers are produced

Consequential changes in species distribution and extinction of species that cannot colonise suitable new habitats

Difficulties of predicting global climate change

Some processes fluctuate naturally or have multiple causes

limited historical records of climate data

many positive and negative feedback mechanisms

different processes may combine to reduce or increase effects

changes may be slow

changes may be different according to the area

incomplete understanding of how climate and related processes work

Feedback mechanisms

could increase or decrease the rate of global climate change

positive feedback mechanisms

When an environmental change causes other changes that increase the rate or amount of the initial change and therefore increase it's effect

Examples of raise in temperature:

increase rates of decomposition cause cause more carbon dioxide to be released

reduced areas of ice and snow reduces albedo of land and sea so less sunlight is reflected and solar heating is increased

methane released from methane hydrate in marine sediments

melting of permafrost releases methane trapped in the the ice

These either increase temperature directly or increase the concentration of gases which then cause further temperature rise

Negative feedback mechanisms

when an environmental change causes a change that decreases the rate or amount of the initial change, and therefore reduces it's effect and helps re-establish the original equilibrium.

examples caused by higher temperatures;

increased rates of photosynthesis, which stores more carbon dioxide in the biomass

increased low-level cloud may increase albedo and reflect away sunlight which will reduce solar heating.

Ozone Depletion