Environmental Studies - The Physical Environment

The Atmosphere - Compostion, Climate Change, CFCs & UV


Compostition of the Atmosphere

NITROGEN = 78% --- often used for quick freezing in liquid form

OXYGEN = 21% --- used in combustion

CARBON DIOXIDE = 0.038% --- used in fire extinguishers and fizzy drinks

RARE GASES (eg Crypton, Helium, Argon) = 1%

WATER VAPOUR = variable --- used for steam electricity

OZONE = 0.000007% --- used to purify water

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Respiration & Photosynthesis


oxygen + glucose -------> carbon dioxide + water + energy

> Plants always respire


carbon dioxide + water -----chlorophyll&light-----> glucose + oxygen

> Plants only photosynthesise in daylight

> Within a 24 hour periodm CO2 levels would be higher at night, when photosynthesis isn't take place, and therefore would be lower during the day when it does take place.

> CO2 levels fluctuate on an annual basis, because levels are higher when it is the Northern Hemisphere's winter, as there is less photosynthesis. It then falls when it is the Northern Hemisphere's summer as there is more photosynthesis.

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The Atmosphere

is a turbulent gaseous envelope that surrounds the planet and consists of several layers, the most significant for life being the stratosphere. These are also the layers that are affected by human activities.

The Troposphere

> Lowest layer, 10 miles high

> Where weather occurs

> Temp. decreases with altitude

> Cold & windy at the top

> Most gases are found here

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The Atmosphere ctnd

The Stratosphere

> Stable, aircraft can go here and avoid turbulence

> 30 miles high

> Air is 1000x thinner that at sea level

> Where most ozone is found - it absorbs UV

> Temp. rises with altitude

> Few clouds/vapour - very dry

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The Atmosphere ctnd

The Mesosphere

> Starts at 30 miles high

> Little known about it

> Temp. drops

> Pressure drops

> Where meteors burn up

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The Atmosphere ctnd

The Thermosphere

> 500 miles high

> Temp. influenced by sun

> Very little there

> Space shuttles orbit here

> Xrays are absorbed

> Southern/Northern lights

The Exosphere

> Very thin - nothing there

> Atoms + molecules escape here

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The Importance of the Atmosphere as a Life Support

Living organisms require:

> Oxygen - for aerobic respiration to produce energy (ATP)

> Carbon Dioxide - for photosynthesis

> Nitrogen - found in all proteins and DNA. Animals get it from eating, which gets it from soil as nitrates

> Water Vapour - some organisms have permeable skin. Also, a general need in rainfall patterns in the water cycle.

> Presence of Ozone - absorbs UV which would otherwise damage cells

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Solar Radiation + the Atmosphere

The sun generates its energy by nuclear fusion:

> The intense heat and pressure inside the sun cause two hydrogen nuclei to join and form a helium.

> This radiation generates massive amounts of energy and this is emitted from the sun as electromagnetic raditation.

The characteristics of radiation:

> At outer limits of atmosphere - mainly visible light and UV light

> As it passes through the atmosphere, UV light is absorbed by ozone layer, some visible light scattered, reflected or absorbed by clouds

> Some visible light is absorbed or reflected by particulate matter and clouds

> When it reaches the Earth's surface, remaining visible light is reflected or absorbed, to then be radiated as infrared radiation.

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Global Climate Change

The Earth's climate is generally defined at the average weather over a long period of time.

Paleoclimates - looking at past records allows scientists to predict future climates and how it may changes.

> Ice cores, tree rings, pollen, fossils and temperature records can all be used to study past climates.

> Information about temperatures, precipitation and chemicals of past climates can be obtained in these ways.

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The Greenhouse Effect

is important to life on Earth, because it keeps the Earth's temperature in a liveable/tolerable range at all times.

The Natural Greenhouse Effect: Sunlight passes through the atmosphere, warming the Earth. In turn, the Earth radiates this energy back towards space. As it passes through the atmosphere, greenhouse gases absorb part of the energy, while the remainder escapes into space. This means that some of the sun's energy becomes trapped - thus making the lower part of the atmosphere, and the Earth, warmer.

An increase in certain gases may result in heat being retained for longer and therefore global climate change. These gases include - carbon dioxide, methane, CFCs, oxides of Nitrogen and low level ozone.

It is therefore the ENHANCED GREENHOUSE EFFECT that is the problem.

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Greenhouse Gases

Carbon Dioxide (is 60% of them)

Anthropogenic sources: combustion of fossil fuels, deforestation

Prevention: carbon sequestration, reduce use of fossil fuels, increase combustion efficiency


Anthropogenic sources: landfill sites, paddy fields, livestock

Prevention: reduce livestock production, reduce landfill

Oxides of Nitrogen

Anthropogenic sources: vehicle exhausts, power stations

Prevention: different vehicle engines

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Greenhouse Gases ctnd


Anthropogenic sources: aerosol propellants/solvents, fire extinguishers, refridgerators

Prevention: banned in aerosols/fridges - Kyotol Protocol

Tropospheric Ozone

Anthropogenic sources: by break down of NO2 and then reacted with oxygen

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Consequences of Global Climate Change

Sea Level Changes

.> Increased temperatures cases water to expand

> Can also cause land ice to melt, flow into the sea and increase the volume of the sea

This leads to...

> Low lying areas around coast line will flood and change the shape of the coastlines

> Small islands are put at risk of disappearing

> Possible intrusion of saltwater into freshwater - this can drastically change and damage freshwater habitats

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Consequences of Global Climate Change ctnd

Changes in Climate

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

> Wind patterns - change in velocity, frequency and direction

> Precipitation - higher temps increase evapouration rates. The water vapour will be transported by winds and result in precipitation when the air cools sufficiently. Changed wind patterns may result in areas getting more or less rain too.

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Consequences of Global Climate Change ctnd

Ocean Current Changes

El Nino - Occurs in the Pacific Ocean about every 4-10 yrs. The Western coasts of Peru, Equador experience unusually warm waters which cause climatic disruptions. Trade winds subside as do ocean currents. Warmer water does not 'collect' on the East Side of Pacific. On the West, it remains warmer. Colder nutrient rich water does not surface on the West.

Effects: The warmer seas on the West disrupts marine life; heavy rainfall in South America due to increased evapouration; droughts in South East Asia/Australia.

Climatic change effects El Nino because it increases the event, makes it stronger and could possibly prevent it reverting back to normal.

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Consequences of Global Climate Change ctnd

The Gulf Stream - one of the strongest ocean currents in the world. Driven by surface wind patterns and differences in water density. Surface water in North Atlantic is cooled by winds from the Arctic. It becomes more salty and dense, and sinks to the ocean floor. Cold water moves towards the equator and gradually gets warmer. To replace the cold equator bound water, the gulf stream moves warm water from the Gulf of Mexoco north into the Atlantic.

The Gulf Stream brings warmth to the UK and North West Europe - its the reason why the UK has mild winters - but, the average annual temps of Northwest Europe is 9C above average for our latitude.

> An increase in global temps and precipitation may add more fresh water to the North Atlantic, similar to the end of the last Ice Age.

> As Gulf stream becomes weaker, it becomes less stable and may eventually shut down completely.

> Reduced Gulf = harsher winters.

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Ecological Impacts of Climate Change

eg - growth rates, wetland sizes, drought areas, desertification, hibernation patterns, flowering times, migration, nesting, changes in ranges of tolerance, more invasive species, more disease, more pests etc.

Changes in Timing

> Earlier laying dates of common birds and spawning dates of amphibians

> Earlier arrival/later departure of migratory birds

> Earlier appearences of butterflies

> Earlier leafing/flowering dates

> Later leaf-fall in autumn

> Earlier appearences of mushrooms/toadstalls in autumn

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Ecological Impacts of Climate Change

Changes in Distribution of Species

> Northern areas becoming more habitable/warmer

> New species colonising in England, eg little egret

> Other non- native species finding it easier to survive in UK

Examples in the UK

> Dormouse - affects length of its hibernation, disrupts how many young are born

> Swallow - overwintering at home and ealier nesting dates

> Bluebells - earlier flowering

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Climate Change Predictions

> All countries in Central England Region are predicted to become warmer on average, drier in summer and wetter in winter

> Frequency and severity of storm events likely to increase

> Number of snow cover/frost days decrease

> Number of extremely hot days likely to increase and new maximum summer temp records likely

UKCIP low emission models predicts that by 2080s in CER - Average daily temperature 2-3C higher, summer precipitation reduced by 15-30%, winter precipitation increased by 0-15%.

UKCIP high emission models predicts that by 2080s in CER - Average daily temperature 4-5C higher, summer precipitation reduced by 45-60%, winter precipiation increased by 15-30%.

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Climate Change Impacts on Important Habitats


+ Positive - none.

- Negative -

>Drier summers could lead to higher severity/more fires which damages many habitats

> Prolonged droughts may dry out valley mires affecting bog plant communities and invertabrates eg rare dragonflies

> Possible impact on compositon/pattern of UK's heathland habitats

> Change in distributions of certain heathers

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Climate Change Impacts on Important Habitats

Native Broadleaf Woodlands

+ Positive -

> Re-emergence of woodland species eg small leaved lime

> Broken branches/snapped trees resulting from more frequent storms beneficial to diversity of nesting sites

- Negative -

> Warmer/wetter winters may lead to serious root damage

> Hatching blue **** may not coincide with the peak of caterpiller numbers

> Summer migrant birds arriving late so at a disadvantage for nesting sites

> Some mammals are benefitting from the warmer winters BUT this could be the reason for recent woodland bird declines.

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Climate Change Impacts on Important Habitats


+ Positive -

> May become a 'method' of flood management

- Negative -

> Warmer water holds less oxygen, so may affect the organisms living in it

> Saltwater intrusion is harmful to the existing habitat

> Hotter/drier summers could hasten drying and succession

> Maintaining water levels would become more difficult, causing problems for stock management

> Spring flooding may kill newly hatched wader chicks

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Feed Back Mechanims

Positive Feedback Mechanism

When an environmental change causes other changes which increase the rate or amount of the initial change, it therefore increases the effect.

eg, the increased rate of decomposition, melting permafrsot and methane from marine sediments

Negative Feedback Mechanism

When an environmental change causes other changes which decrease the rate or amount of the initial change, it therefore decreases the effect.

eg, increase in cloud cover and increasing rate of photosynthesis

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Control of Global Climate Change

The Kyoto Protocol

> Set up to cut greenhouse gas emissions worldwide

> Those signed up include - UK, Japan, Russia, other EU countries

> USA & Australia have not signed up, mostly because they feel it would damage their economy

> Every country has different targets for reduction of emission, depending on their current emissions

> Emissions trading - allows countries to buy & sell their agreed allowance of greenhouse gases. Countries can also gain credits for activities which boost the environments capacity to absorb carbon

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Control of Global Climate Change

Stratagies to COPE with Climate Change

> Alternative crops that can grow in different conditions, + crops with different properties

> Build on higher areas, or houses with stilts

> Different architecture of buildings, with stronger infastructure. Storm resistant, with stronger bases

> Build on more porous areas so water can drain through the ground quicker

> More trees also prevents flooding as they take in water so that it does not just rest on the ground

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UV Radiation

Ultraviolet light is electromagnetic raditation with a wavelength shorter than that of visible light, but longer that x rays.

UV A ---- wavelength = 320nm-400nm ---- not absorbed by ozone ---- ageing effects

UV B ---- wavelength = 280nm-320nm ---- mostly absorbed by ozone ---- can cause cancer and damages DNA cells, causes release of free radicals which destroy proteins etc, supresses the immune system and can form cataracts

UV C ---- wavelength = <280nm ---- completely absorbed by ozone ---- no effect on body due to complete absorbtion

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The Problems with CFCs

In early years, CFCs were so useful because....

> Non-toxic

> Easily compressable

> Low boiling point

> Odourless

> Non-flammable

> Chemically stable

> Freezing points low enough not to freeze in a fridge - acts as a coolant

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The Problems with CFCs ctnd

CFCs were used as....

> Refridgerants

> In air-conditioning units

> As propellants in aerosol cans

> As blowing agents for expanded plastics such as polystyrene

> As solvents in dry cleaning and degreasing

As a result of the development of CFCs, refridgerators became more effiecient, cheaper and widely available.

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The Problem with CFCs ctnd

In 1985, a hole in the ozone layer was found above Antarctica.

This was very much to do with the effects of CFCs.

The Montreal Protocol

Safeguarded the ozone layer - it was extremely successful and the ozone layer is well on the road to recovery. It has prevented millions of deaths from skin cancer, and saves billions of dollars in health services related to skin cancer etc.

However, the problem with CFCs is that they are very stable and stay in the atmosphere for a very long time which means recovery will be slow. Scientists predict that the ozone hole will start to recover by 2010 but complete recovery is not expected until around 2070.

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<3 thank you 

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