A2 Weather Hazards and Climate Revision My Version

Weather and Climate and Associated Hazards

• Major Climate Controls: The structure of the atmosphere, the atmospheric heat budget, the general atmospheric circulation, planetary surface winds, latitude, oceanic circulation and altitude•A Cool Temperate Western Maritime Climate: The climate of the British Isles: Temperature, Precipitation and wind, air masses, the origin and nature of depressions, weather changes associated with the passage of a depression, the origin and nature of anticyclones, associated weather in summer and winter, storm events, their occurrence, impact and responses, one case study•Tropical Monsoon Climate: India: temperature, precipitation and wind, the role of the sub-tropical anticyclones and the inter tropical convergence zone, tropical revolving storms, their occurrence, management and responses• Climate on a local scale: Urban climates: the urban heat island, precipitation, air quality and winds, changes associated with urban environments•Anthropogenic climate change/global warming: Climate change over the last 20,000 years, possible causes and effects of global warming on global scale, on chosen tropical region and on the British Isles, Responses to global warming: international, national and local

Major Climate Controls

Composition of the Atmosphere.Gas Percentag

eImportance Other functions

Nitrogen 78.09% Passive Needed for plant growth

Oxygen 20.95% Passive Produced by photosynthesis (reduced by deforestation)

Water vapour 0.20-4.30% Source of cloud formation Essential for life on Earth

Carbon dioxide 0.03% Absorbs long wave radiation

Used in photosynthesis

Ozone 0.00006% Absorbs UV radiation Damaged by CFC’s

Inert gases (Argon) 0.93

Helium, neon, krypton

Trace

Non- gaseous (dust) Trace Reflects incoming radiation Volcanic dust

Pollutants (SO2, No) Trace Causes acid rain From industry, power stations and car toxins

The atmosphere is very delicate, any slight changes, especially in methane and CO2 can result in global warming. Generally in the lower atmosphere, where most of the water vapour is help, the atmosphere is constant.

Troposphere:- closest to the Earth's surface, up to 10-15 km- contains 75% of the atmosphere's mass,- wider at the equator than at the poles. - temperature and pressure drops with altitudedue to adiabatic cooling.

Layers of the Atmosphere

Stratosphere:- extends from about 15 to 50 km above the Earth's surface,- lower portion of the stratosphere - near constant temperature with height but in the upper

portion the temperature increases with altitude because of absorption of sunlight by ozone.

Mesosphere:- 50 to 80 km above the Earth's surface,- cold layer where the temperature generally decreases with increasing altitude. The

atmosphere is very thin but is still thick enough to slow down meteors hurtling into the atmosphere and burn where they burn up.

Thermosphere

- extends from 80 km above the Earth's surface to outer space. The temperature is hot and may be as high as thousands of degrees because the small amount of oxygen is heated up by solar radiation.

Factors that affect climate

Atmospheric Heat Budget

Lateral transfers of energy

• Winds = 80 %• Ocean currents = 20 %:-Warm = North Atlantic DriftCold = Humboldt

Vertical transfers of energyEarth’s surface absorbs incoming solar radiation –

insolation.Earth’s surface ( a solid) conducts heat energy to the

surface air – conduction.Surface air gains heat energy, air particles move around

faster, take up more space, become less dense than the surroundings so rise up via convection – eg to produce convectional thunderstorms over cities.

As air rises it cools, its relative humidity rises until at the dew point it condenses to release latent heat – heat released in the state change from gas to liquid.

Precipitation… the conversion & transfer of moisture in the atmosphere to the land and sea. It includes three types of rain:•Convectional•Stratiform•Orographicas well as snow, frost, hail and dew.Convectional RainConvection occurs when the Earth's surface within a conditionally unstable, or moist atmosphere, becomes heated more than its surroundings and leads to a significant upward motion. Common on the Equator and over UK cities in summer heatwaves.Frontal Stratiform rainfall is caused by frontal systems surrounding extratropical cyclones or lows form when warm and often sub-tropical air meets cooler polar air. Stratiform precipitation falls out of nimbostratus clouds. When masses of air with different density (moisture and temperature characteristics) meet, warmer air overrides colder air, causing precipitation. Changes in fronts results in change of precipitation. Warmer fronts lead to extended periods of light drizzle whereas cold fronts experience short burst of more intense rainfall.OrographicOrographic or relief rainfall is caused when masses of air pushed by wind are forced up the side of elevated land formations, such as large mountains. The lift of the air up the side of the mountain results in adiabatic cooling, and ultimately condensation and precipitation. In Hawaii, Mount Waiʻaleʻale

Precipitation: snow• Causes include:-Polar continental air masses – sucked in from an

anticyclone - moving across from Siberia, becoming unstable (since surface air is warmed so wants to rise) in the lowest layer above the North Sea – air mass hits cold east coast of England giving rapid condensation and heavy snow.

Warmer temperatures over the Poles causes greater snowfall especially between -10 to +4 ºC

General Circulation Model

• 3 cells per hemisphere.• Hadley Cell – from the Equator to sub-tropical

high pressure zone.• Ferrel Cell – from the sub-tropical high

pressure zone to the mid-latitude temperate zone.

• Polar Cell – from the temperate zone to the poles.

3 Cell Circulation Model

Hadley Cell• ..is the most clearly defined cell of air flow due to the Coriolis Effect having only a minimal

effect.• Overhead sun heats the earth’s surface with concentrated solar energy.• The surface absorbs this energy and conducts the heat to the lowest layer of the atmosphere.• Surface air warms up, the molecules move around quicker and take up more space – they

become less dense and rise via convection.• Low pressure now at the equator so winds blow from the sub-tropical high pressure regions –

Trade Winds.• Trade winds are from the NE in the Northern Hemisphere and SE in the Southern Hemisphere

– due to the Coriolis Effect.• The Coriolis Effect is the imaginary force of the earth’s rotation; it causes winds to deviate to

their right in the Northern hemisphere and to their left in the Southern hemisphere.• Air rises at the equator until it hits the tropopause – bouyed as it is by convection - and then

drifts polewards.• At the sub-tropical high pressure latitudes, air sinks from the tropopause because:-• - it is now much colder and denser.• - the Coriolis Effect has slowed the wind’s path to the Poles.• - towards the Poles the troposphere gets narrower and shorter and so the winds are

squeezed into a declining area which increases their density, further increasing the rate of subsidence.

• Trade Winds blow from sub-tropical highs to the Equatorial low along a pressure-gradient force.

Inter-tropical-convergence zone..

• .. The band of cloud which follows the overhead sun as it drifts across from 23º S in December to 23º N in June.

• ..it is discontinuous around the planet and moves forwards across land at a faster rate than over the oceans (higher specific heat capacity).

Ferrel Cell• Forms between the northerly edge of the Hadley Cell (over the hot

deserts/high pressure belts) and the southerly edge of the Polar Cell/low pressure belt)

• Receives south-westerly winds from the sub-tropical high pressure belt (eg the Azores) and cold north-easterlies from the Poles.

• Warmer air rises over colder air, anticlockwise in the Northern Hemisphere to form a depression then cools, condenses and creates frontal rain.

• Boundary between the Ferrel and Polar Cells is a classic low pressure belt and leads to some of the highest average wind speeds on the planet.

• The wind directions vary according to the location of the centres of high and low pressure.

Jet Stream and Rossby Waves• Rossby Waves occur at the boundary between the

Polar and Ferrel Cells; they are upper-atmospheric winds which help to distribute heat energy across the planet.

• Descending limb sees wind converge at upper altitude, subside to form anticyclones (high pressure). The remaining upper atmospheric air – perhaps fuelled by stronger solar radiation levels – ‘shoots’ off at 200 mph north eastwards causing a suction effect on the surface which causes surface air to converge and rise anticlockwise to create a low pressure area.

Polar Cell• Air sinks at the Poles as it gets squeezed into

the ever narrowing troposphere.• Thin levels of solar radiation cools the air so it

sinks to form a high pressure zone.• This air drifts over ice towards the low

pressure belt in temperate latitudes.

Oceanic circulation

The Climate of the British Isles

CTWM Climate Characteristics• Boundary between the Ferrel and Polar Cells is a classic low pressure belt

and leads to some of the highest average wind speeds on the planet.• The wind directions vary according to the location of the centres of high

and low pressure.• Pressure-gradient force is roughly cancelled out by the Coriolis Force to

produce geostrophic winds which blow roughly parallel to the isobars (lines of equal pressure).

• Low annual temperature range for the latitude because of the moderating influence of the seas; seas/oceans have higher specific heat capacities so winters are mild and summers cool compared with continental climates.

• Precipitation falls in all 12 months due to frontal rain; some convectional rainfall over urban areas in summer; relief rainfall to the North and West of the UK – up to 3,000mm in Seathwaite, Lake District, down to 770mm in Maidstone, Kent.

• Western side warmed up by the North Atlantic Drift/warm ocean current; Cornwall mean January temp = 7º C, whereas Kent = 4º C.

• Southern Britain warmer than Northern due to latitude; Kent mean July temp = 17º C whereas Northern Scotland = 14º C.

Basic Climate Characteristics: Precipitation, Temperature and Wind

• Temperature

• Precipitation• Wind

The Characteristics of CTWM climates

• One of the most striking features in unpredictability, changeability on a day-to-day basis, mostly because of the dominance of low pressure weather systems

• Summer: m

Air Masses in the Cool Temperate Western Maritime Climate- ie the British type climate. Air masses are large amounts of air with broadly the

same temperature and humidity characteristics which are gained from their source region.

- The UK experiences 5 main types:-- Polar Continental: very cold, source region Siberia; heavy snowfall in Eastern

England, sub-zero temperatures; winter only. Brought in with an anticyclone to the North and a depression to the South. Severe hazard level to transport; loss of business from ‘snow days’; higher death rate among the elderly.

- Tropical Continental: very hot, source region Sahara; strong sunshine, local sea and land breezes, convectional thunderstorms especially over cities; anticyclone to the N/NE and depressions to the SSW; winter only. Hazard rating high: sun burn, dehydration, death rates higher for the elderly; photochemical smogs in cities.

- Arctic Maritime: cold, snow in Scotland; snow flurries in SE; straight from the Arctic, anticyclone to the West, depression to the East. Hazard level medium to high.

- Polar Maritime: cool, windy, wet; source region Iceland and the North Atlantic; anticyclone to the SW, depression to the NE; common. Hazard level high if coupled with the Jet Stream, otherwise low to medium.

- Tropical Maritime: mild, windy, less wet; source the Azores; anticyclone to the SE, depression to the NW; hazard level low unless coupled with the jet stream eg Great Gale 1987.

Air Masses Affecting The British IslesPolar MaritimeA very common air mass over BritainGives cool conditions throughout the yearIt warms slightly as it crosses the AtlanticIt is unstable in its lower partsGives heavy showers across highlandsCumuliform cloudsGood visibility strong winds and hails after the passing of a cold front

Tropical maritimeCommon air mass with the passing of a warm frontWinter: wet and mild weather, stratoclouds to give hill and coastal fog , poor visibilitySummer: it is warm but not hotLower air is stable but forced to rise it may become unstable to give showersWinds: moderate to fresh

Impacts of CTWM Climates on Human Activity• Opportunities • Constraints

• Intense low pressure systems cross the British Isles, 100 depressions per year. These systems can bring gale-force winds and heavy rainfall

• If rainfall is above what is normally expected, soils may become saturated – increased runoff – more water reaching rivers - may lead to severe flooding e.g. River Severn 1998 – Shrewsbury 400 residential and commercial properties damaged

• Anticyclonic weather conditions may lead to drought – summer 2003 – severe drought across W Europe, temperature maximums in Paris, emergency measures to restrict water use, Heatwaves may lead to more elderly people dying due to poor hypothalamic response, Sun strokes and burns, threat of skin cancer, Dehydration

• Urban areas, particularly those with high levels of car exhaust emissions, may develop photochemical fog and ground level ozone which are prevented from dispersing by subsidence associated with anticyclones: asthma attacks, bronchitis, watery eyes, headaches

• Winter: thick freezing fog, black ice cause disruption on the roads, flight cancelled in airports

The nature and origin of depressions

• When two masses of air meet, they do not mix readily as they have different temperatures and densities.

• The junction between two air masses is called a front and recent studies have shown that this is a zone rather than a simple, linear clear division.

• A warm front occurs when warm, less dense air is forced to override colder, denser air.• A cold front occurs when cold, dense air undercuts a body of warm air.• Warm air rises in a spiral movement cools and forms clouds. Upon reaching its dew point it

condensates, releases latent heat and leads to precipitation. Both the warm and the clod front are associated with precipitation.

• The most notable front is the Polar Front where Tm –Tropical maritime- warm, moist and less dense air meets Pm – Polar maritime- dry, cold air and give birth to depressions or temperate cyclones which predominantly affect the British Isles

• Depressions as with all winds act to counteract the spatial variation of incoming solar radiation across the planet – they help stop the Equator getting warmer and the Poles getting colder.

• There are three stages in the development of a depression: the embryo or formation stage, the stage of a mature depression and the occlusion or decay stage.

Formation (Embryo)A depression begins as a small wave on the Polar FrontThe wave is not a simple, linear division but rather a zoneWarmer, less dense air is forced to rise in a spiral movementBecause air is moving upwards there is less air at the surface and this creates the low pressure zoneDepressions usually move in a north-easterly direction due to the influence of the upper westerlies (i.e. The Polar Front jet stream which creates a suction effect on the surface causing air to converge on the surface, rise up and diverge in the upper-atmosphere)

Warm front, marking the advance of warmer air

Cold front, marking the advance of colder air

north easterly path under the influence of the jet stream

Mature DepressionIt is characterised by an increase in amplitude of the initial wavePressure continues to fall as more warm air from the warm sector is forced to rise Pressure falls and the pressure gradient steepens, anticlockwise winds increase in strengthDue to the Coriolis effect, the winds come from the south westAs warm air rises at both fronts it will cool to its dew point, release latent heat, form clouds and cause precipitationWarm front: 150-200 km band of precipitation, low and thick cloud cover, nimbostratus cloudsCold Front: 50 km band of precipitation, heavy showers, cumulonimbus clouds

Occlusion (Decay)Occlusion occurs when the cold front, travelling quicker, has caught up with the warm frontOcclusion begins in the centre of low pressure and moves outwardsAs all air has been uplifted there is no further decline in pressureInblowing winds begin to infill the depressionWind strength decreasesIn time the low pressure zone is eradicatedStill wet, windy weather

Weather Changes Associated with the Passage of Depressions

Weather Behind the cold front

Passing of the cold front (50 km)

Warm sector (200 km)

Passing of the warm front (150-200 km)

Depression approaching (600 km)

Pressure Rise more slowly Sudden rise steady Fall ceases Steady fall

Wind direction NW SW to NW SW SSE to SW SSE

Wind speed Slowly decrease very strong decrease strong Slowly increase

Temperature cold Sudden decrease mild Sudden increase cool

Humidity Rapid fall High during precipitation high High during precipitation

Slow rise

Cloud cover Decreasing in succession

Very thick and towering cumulonimbus

Low or may clear Low and thick nimbostratus

High and thin

Precipitation Heavy showers Short showers of heavy rain

Drizzle or none at all

Continuous, steady, quite heavy

none

Anticyclones: high pressure..Causes: convergence in the upper atmosphere causes divergence

on the surface - descending limb of Rossby Wave.• Air is sinking/subsiding and, • diverging on the surface,• Moving out clockwise in the Northern Hemisphere• Creating gentle winds and clear skies because as air subsides

it warms up on approaching the earth’s surface (radiator effect), relative humidity declines and cloud cover evaporates.

• In summer anticyclones give heatwaves and bring in a tropical continental air mass eg August 2003, hottest ever UK temp = 38.2ºC; also Summer 1976 – sets up land and sea breezes

The Origin and Nature of Anticyclones

• An anticyclone is the name given to a large mass of air subsiding to give high pressure conditions at the Earth’s surface

• The source of the air is the upper atmosphere: upon rising, the air cools down, becomes denser than it surroundings and begins to subside

• As it approaches the surface, it warms up and its capacity to hold the moisture it has retained increases

• As a result, there is less condensation and reduced cloud cover and precipitation• Winds tend to be weak due to a gentle pressure gradient force. Winds that do

blow do so outwards, clockwise from the centre of high pressure (in the northern hemisphere)

• Anticyclones can have large diameters of several hundred kilometres (i.e. 3000 km)• Their passage is much slower than that of depression• They tend to give stable conditions over several days but which differ according to

the season in which the anticyclone occurs

Summer anticyclones• Due to reduced cloud cover, the Earth’s surface receives maximum insolation – hot,

sunny days with daytime temperature over 25 degrees C• Significant radiation loss at night could leads to temperature inversion and the

formation of mist and dew at night, although these rapidly clear the following morning

• Coastal areas may experience advection fog and land and sea breezes (different specific heat capacities of land and sea)

• Sea breeze – day time hot land/low pressure/cooler sea (higher specific heat capacity)/higher pressure; local winds blow from high pressure (sea) onshore to low pressure (land).

• Land breeze – night time, land cooler (high) than sea (low); local pg force, winds blow offshore.

• If the source of the air is in North Africa (Tc), heatwave conditions may result• Anticyclones give heatwaves and bring in a tropical continental air mass eg August

2003, hottest ever UK temp = 38.2ºC; also Summer 1976 – sets up land and sea breezes.

• HP areas deflect LP depressions to the North, reducing the likelihood of wet weather in the summer - Drought if persistent eg from a blocking anticyclone (produced from a ‘cut-off’ in the Rossby Waves).

• Elderly suffer due to poor hypothalamic response to the heat death rates rise eg NW Europe 2003, death toll est.30,000.

• Cause photochemical smogs, eg London July 1994, vehicle exhaust fumes + sunlight = low level ozone.

Impacts of Summer anticyclones

Heatwaves may lead to more elderly people dying due to poor hypothalamic responseAugust 2003 an estimated 40,000 deathsSun strokes and burns, threat of skin cancerDehydrationVehicle exhaust emissions react with sunlight to cause low level ozone and photochemical smog which may cause asthma attacks, bronchitis, watery eyes, headachesMore people take time off work- may halt businesses to a stopCars overheatTraffic congestion on roads to roads to the coast Drought due to reduced precipitationThreat of forest firesLow levels of oxygen in rivers, may affect biodiversity

Winter anticyclones• Bring in cold Polar Continent air mass, source region – Siberia.• Causes heavy snowfall as unstable air over the North Sea sucks up

relatively warm moisture.• Rapid loss of terrestrial radiation in clear skies at night so cold surface air

sinks to lower ground causing frost hollows (lowest valley basin) and radiation fog.

• Radiation fog caused from coldest air sinking to become colder, so relative humidity rises sharply causing condensation of water vapour in the atmosphere.

• Cold katabatic winds blow down valley in mountainous areas.• Coldest UK temp ever = -27º C at Braemar, a frost hollow village located

close to the Cairngorms, Scotland.• Black ice on roads as water vapour freezes straight to ice.• egs Winter of 1962/63, a blocking anticyclone brought over a cold Polar

Continental air mass which caused large parts of the UK to be frozen from Boxing Day to April; also Winter 2009/10, coldest since 1979/80.

• Snow cover causes severe disruption and loss of school days, closure of businesses, reduction in spending, transport chaos, traffic accidents, flight cancellations, surges in domestic energy consumption, increased death rates among the elderly – sometimes morgues in S.England overflow!

• Winter anticyclones also give clear, cloudless skies• Yet, there is little incoming radiation sue to the low angle of the sun in the

sky• At night, the little amount of heat gained during the day is lost into space as

terrestrial, long-wave radiation• The absence of clouds allows low temperatures causing fog and frost to

develop• These may take a long time to disperse in the mornings due to reduced

sunshine• Polar continental (Pc) air is cold, dry and stable as it moves across the cold

European landmass (dragged by clockwise winds of the HP system)• Upon reaching the North Sea, lower layers acquire some warmth and

moisture• This turns into snowfall when the air reaches the relatively colder east

coasts of the British Isles (e.g. January 2010)• Winter anticyclones deflect warm depressions to the north leading to dry,

freezing conditions

Impacts of Winter AnticyclonesElderly die due to poor hypothalamic response- sometimes mortuaries overflow i.e. in Eastbourne, refrigerated lorries held surplus corpses in hospital car parksPower surges as energy consumption roarsTreacherous driving conditions: Radiation fog, black iceSnowmelt (after anticyclone passes) leads to flash floodsSpring crops suffer from frost damageDisruption to schools and businesses, winter of 2009-2010Frost biteSports fixtures are cancelled as are flightsTransport chaosReduction in spending

Radiation fog in a valley due to temperature inversion

Other Impacts of HP Systems

• 1998, Bush fires in Indonesia• 1984-85, Ethiopian famine as a result of

drought, estimated 5 million deaths

Depressions v TRSsSimilarities: both low pressure systems, air rising anticlockwise in

the N. Hemisphere, both accompanied by wind and rain. Both capable of winds in excess of 75 mph. Both capable of storm surges: N Sea Storm Surge 1953, Cyclone Nargis 2008.

Differences: formation – TRSs over warm tropical seas, Deps over cool North Atlantic and can form over land; scale TRSs up to 500km across, deps half that size; TRSs have a central eye with clear skies and subsiding air; TRSs tropical Deps temperate; TRSs capable of 200+mph winds – far stronger. Deps = frontal rain, TRSs = convectional rain to start with. TRSs require a lack of wind sheer so central eye not torn apart, not a requirement of deps. TRSs decay over land always, Deps not necessarily so. Deps far more common for their latitude.

Depression Tropical Revolving Storm

1987 Great Gale: a British Isles storm.• Famously NOT predicted by the Met Office.• Sustained winds over 100 mph and up to 120 mph.• Strong jet stream intensified causing rapid suction of air over the English

Channel.• Hit Southern England over night, in the early hours.• Sharp swing in wind direction brought warm winds up to 15ºC – unusual

for an October night – which rose sharply to create a barometric low pressure value of 958 mb.

• 15 million trees blown down and £1.4 billion damage to property.• 19 killed, mainly night time drivers struck by falling trees.• Unusually low amount of rainfall, only 4mm/hr over Oxfordshire. (More

died (48) in the Burns Day Storm of 1990 because that happened during the day)

• Over 3,000 miles of telephone lines down, severe transport disruption, ferry ran aground.

• Quick recovery since happened over the weekend, many trees cleared off the roads and railways by emergency services over the weekend.

• Ecologists criticised the clear up of fallen trees – destroyed potentially rich ecosystems.

Case Study: The Great Gale

Case Study: The Great Gale

The Tropical Monsoon Climate

Tropical Monsoon Climate• Characteristics: Distinct Wet and Dry seasons. Dependent on the overhead sun which moves between 23½º N

and 23 ½º S and the shadowing ITCZ. Hottest months are April and May before the south-west

monsoon arrives when rain clouds block the sun and daily maximum temperatures decline to a more comfortable 27ºC rather than 40+ºC.

Coolest months are january and february during the north-east monsoon.

Basic Climatic Characteristics:

• Temperature• Monthly mean temperatures above 18

degrees Celsius in every month of the year• Driest month• Precipitation• Wind

West coasts of India and Burma, Bangladesh, Indonesia, equatorial Asia

NE Australia, Papua New Guinea, Brazil, Madagascar

Wind

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Tropical Monsoon Climate: eg India• Monsoon = season• 2 monsoons: - SW Monsoon- Sun migrates to 23½ºN and heats Indian sub-continent; land heats up quickly since

low specific heat capacity; land hotter than sea; air rises on land = low pressure, air sinks over sea = high pressure – pressure gradient force set up; Inter-Tropical Convergence Zone (ITCZ follows overhead sun to intensify precipitation – moves in a series of ‘pulses’ from the southern tip northwards. Winds blow from cool sea to hot land giving world’s largest sea breezes. Gives 80% of annual rainfall – from June to October.

NE Monsoon- Sun migrates to 23½º S, ITCZ drifts with it, less concentrated solar energy; India

cools down; sea warmer than land as has higher specific heat capacity; sea low pressure, land high pressure (now part of the sub-tropical high pressure belt), winds blow from land to sea along pressure gradient force = land breezes to form the dry, NE Monsoon.

Notice SW and NE Monsoons are deviated to their right due to the Coriolis Effect.Tropical Revolving Storms can effect the region during the SW Monsoon.

Drought during the N-E Monsoon• In tropical monsoon climates, the coolest and driest months of the year are

from December to February• From March, temperatures increase and the drought continues• Sometimes, the SW Monsoon, expected to bring heavy rainfall upon which the

agriculture of India is based, fails, only brings light, local rainfall• This tends to coincide with a El Nino Oscillation but this may not always be the

case• Temperatures of the Indian Ocean are 3 degrees warmer and fail to set up a

strong enough pressure gradient force• Results for food crops are disastrous• The famine of 1943 – an estimated number of deaths between 4 and 5 million• India, August 2009, almost half of India’s districts were affected by drought

after the monsoon brought 29% less precipitation than usual• Driest June for 83 years• This affected approx. 700 million, in a country where 70% of individuals are

dependent on farming incomes and also led to 20 suicides among farmers

The Role of Sub-tropical anticyclones and the ITCZ• Formed on the edge of the Hadley and Ferrel Cells.• Air sinks due to narrowing troposphere, loss of heat energy and being slowed down by the deviation from

thecoriolis effect.• Dry stable conditions eg NE Monsoon in India, can lead to drought if the dry season extends long into June.• Sub-tropical high pressure belts drift towards the Equator in winter (eg dry NE Monsoon in India) and rise

towards temperate latitudes in summer (eg dry Mediterranean climate in Spain.• Subsidence is weaker on the western sides so tropical storms can ‘spawn’ into tropical revolving storms via

strong convection.

Causes

• Warm sea temperatures (>26C), to a depth of 50m. Sustained heat over wide area, which in turn provides heat source to create large mass of unstable air.

• Air rising with a relative humidity of at least 60 % - to ensure quick condensation on rising; releases latent heat which further fuels convection.

• The storm system needs to move further than 5 º N/S of the Equator in order for the Coriolis Effect to cause the storm to rotate/spin.

• Wind shear (speed and direction) must be similar from the surface to 5km high so the central eye can develop.

• Occur in autumn when sea temps are at their highest built up over summer and start up on the western sides of sub-tropical high pressure systems, where subsidence is weaker.

There is one important distinction to make is between hurricanes and hurricane force winds. Hurricanes are tropical revolving storms. When they reach the UK, they have lost most of their characteristics by moving over the colder Atlantic. Hurricane force winds, as we had in the 1987 storm, are purely and simply winds reaching at least force 12 on the Beaufort scale. They do not necessarily have anything to do with tropical storms.

Characteristics…• Slowing Moving systems of extreme low pressure. .. sustained winds of at least

74 miles per hour. • They travel westwards on unpredictable courses • On landfall they move towards the nearest pole, transferring surplus energy

from the tropics along with vertical displacement• Away from their ocean heat source they rapidly loose power and become

storms before they become depressions.• The entire hurricane/cyclone/typhoon system can last a fortnight from birth to

death.• Cover large areas, a category 5 storm can have sustained wind speeds of 200

mph (Hurricane Andrew, 1992) and have a diameter of 500km.• They all have a central eye with a downdraft of sir surrounded by an eye wall

which has the fastest winds – violently rotating upwards and anticlockwise.• Towering thunderclouds gradually thinning away from the centre with a distinct

‘tail’. Winds weaken away from the eye wall.• As the eye passes over, winds drop away, often tempting people outside. The

eye is typically about 10 miles wide. Soon the eye wall approaches and winds rise to their fastest in the oposite direction.

Tropical Revolving Storms• Are systems of intensive low pressure by which heat is transferred away from the Equator• Hurricanes are the tropical cyclones of the Atlantic• They form of the West coast of Africa and travel in a chaotic manner, north westwards across the

Atlantic• They form after the ITCZ has moved to its northerly extent enabling the convergence of the warm

trade winds and westerlies at low levels, closer to the Equator

Why are hurricanes destructive?• High speed winds: wind speeds are over 160km/h and

in some extreme cases may reach up to 300km/h, they can cause structural damage to high rise buildings in MEDCs and wipe out entire villages in LEDCs, cause damage to communication and electricity lines, wind blown debris can also be particularly dangerous

• Storm surges: may reach 4 ft with a Cat 1 hurricane and 18+ ft with a cat 5, can cause flooding of low lying areas especially if it coincides with naturally high tides, responsible for 90% hurricane related deaths, large amounts of salt are deposited inland in bays and estuaries

• Flooding: may occur as a result of the storm surge or due to intense precipitation

• Landslides: occur after the complete saturation with water of porous soils

• Salt Spraying: may damage vegetation due to the accumulation of salt on leaves, economic and food problems if the country relies on one crop

Storm surge: a large dome of water, 50-100 miles long that sweeps across the coastline near where the hurricane makes landfall and which is pushed inland by the force of the winds swirling around the storm

Mediating Factors of Hurricane Impacts

• Altitude of the land: low lying areas are most vulnerable to flooding and storm surges, e.g. Most of the US Atlantic and Gulf coast lies only 10 ft above sea level

• State of the tides: storm surges cause increased damage if they coincide with naturally high tides

• Warning, prediction and communication: e.g. National Hurricane Centre, Florida, US

• Building height and structure: poorly constructed, unreinforced buildings suffer more damage, and so do high rise buildings because wind speed increases with height, less frictional drag from the earth’s surface

• Management strategies and funds: if available may help minimise secondary impacts and help reconstruction efforts

• Insurance: lessens the burden of loss and covers the costs of repairs

Management Strategies

Central eye

Hurricane Katrina August 28th, 2005Economic• Cost 150 billion dollars• Fallouts of oil supply, food export, tourism

Environmental• Contaminated water supply• Pollution of groundwater reserves• Samples of floodwater contained high amounts of E. coli bacteria, medical waste sewage, oil, toxic lead, hexavalent chromium and arsenic along with particulate matter• Industrial wastes, oil spills, household sewage, toxic chemicals

Social• 1800 people lost their lives• Hundreds of people were left without homes, jobs and social security• Lack of food, water and sanitary hygiene. • Survivors suffered from emotional and psychological stress

Hurricane Katrina - evaluation of the strategies

• Storm predicted and an evacuation ordered, low take up in the black community.

• Hurricane passes with only slight structural damage to buildings eg roof panels from a Sports Stadium. New Orleans breathes a sigh of relief.

• Torrential rain over the Mississippi catchment area and a storm surge combined to overtop the 16m artificial levees.

• Almost 2,000 killed. Bush Administration criticised for a delayed response; anarchy, looting, contaminated water, decomposing bodies.

Cyclone Nargis, May 2008Category: 4 / Location: Burma, Bangladesh, India, Sri Lanka)Highest winds: 105 mph (165 km/h), Lowest pressure: 962 mbar

Impacts on the ...Environment: heavy rainfall led to flooding and landslides across ten districts in the country

Economic: 600,000 hectares of agricultural land were damaged and 60% of farming implements were lost / 42% of Burma‘s food stocks destroyed / most businesses and markets were closed; Damage: US$ 10.1 billion (2009).

Social: Burma‘s worst ever natural disaster: 1.5 million people effected, 138,000 people dead or missing / 450,000 homes were destroyed and around 350,000 were damaged / 95% of buildings in the Irrawaddy Delta area were destroyed / 75% of hospitals were destroyed or damaged.

Political: Relief efforts were slowed for political reasons as Burma‘s military rulers initially resisted aid.Political background:•The aftermath of the storm was characterised by a lack of information and an apparent state of confusion for most of the aid and rescue organisations

•since 1962 the country has been ruled by a military junta•poor human rights record and limited contact with many countries in the outside world

•physical difficulties of moving around - roads were flooded or washed away

USA TRS Management Strategies• Satellite Images tracking the storm – images taken every 30 minutes and

transmitted down to Coral Gables Hurricane Centre.• Computer models predict the track and changes in hurricane intensity

from data from previous storm events.• Predictive strategies ensure that the landfall prediction is within 50 miles

24 hours in advance• Reconnaisance planes have flown into the eye of the storms, eg Hurricane

Gilbert, 1988, to record humidity and wind speeds.• Evacuation ordered by the Authorities with a 48 hour warning. • Hard engineering schemes to prevent damage from coastal erosion (such

as sea walls, breakwaters), coastal and river flooding (levees).• FEMA sent in to distribute Aid including fresh water, food, blankets,

medicines as well as helicopters to rescue the stranded.

Other TRSs to know about..• East Pakistan (today Bangladesh)1970 – killed 500,000; totally

unprepared.• Hurricane Catarina, 2004, Brazil – 1st South Atlantic hurricane;

supports global warming as seas get warmer.• Cyclone 2B Bangladesh May 1991 – 140,000 killed; only 4

helicopters to distribute water to the vulnerable coastal population.

• Hurricane Andrew, Florida, 1992 – winds speeds gusting > 200 mph.

• Galveston Texas, 1900 – 6,000 killed; totally unprepared for the 5m storm surge.

• Hurricane Mitch, Honduras and Nicaragua, 1998 – 10,000 killed from mudslides; hurricane fed off both Pacific and Gulf of Mexico; category 5.

Urban climates

Climate on a local scale

What is an Urban Microclimate?

Urban areas’ effect on precipitation• Relative Humidity: levels are up to 6% lower - warmer air in cities due to urban heat island means air can hold more moisture • Evapotranspiration: limited – due to less vegetation and lack of exposed bodies of water in urban areas•Cloud cover: More frequent and thicker than rural areas – due to convection currents above urban areas in high concentration of cloud forming nucleii.•Precipitation: 5 to 15% greater in terms of the mean annual totals in the urban areas; 28 % higher 30 to 60 kilometres down wind of the cities; some cities show a total precipitation increase of up to 50% • Hailstorms: 400% greater incidence•Thunderstorms: 25% greater chance•Snow: More rapid snow melt due to higher temperature; the number of days with snow lying on the ground reduced by 15 days. •Fogs and mist: thicker and persist for longer especially under anticyclonic conditions (winds are too weak to blow the fog away); 100% more in winter and 25 % more fogs in summer

US cities:summer rainfall 9-27 % greater than in rural areas.10- 42% greater incidence of thunderstorms. 67-430% increase in the frequency of hailstorms

London:Moderate increase in precipitation in winter of up to 26% compared to rural areas Between 1951 and 1960 thunder was heard on 110 days in central London but only on 60 days on the Kent coast

The urban heat island effect• Condensation nuclei: Causes thunder storms and hail storms higher levels of

precipitation around the urban area are also common in areas downwind of the normal prevailing winds.

• Heat pollution: General heat from the dark composite materials of an urban area lowering the initial albedo and then slowly retransmitting the heat through the night. In the summer air conditioning units from offices and residents will cause larger amounts of heat pollution by releasing more heat into the atmosphere.

• Photochemical smog – low level ozone from sunlight fuelling a reaction of nitrogenous compounds with hydrocarbons in vehicle exhaust fumes to create alkyl nitrates and O3 compounds.

• General pollutants: although it is now generally speaking no longer a “pea soup” effect in the MEDW there are still sulphur compounds and simple smoke hydrocarbons in the atmosphere that add to the effect that photochemical smogs have on the population of an urban area.

• Forms spherical globe around the urbanised area of hot air and pollutants in a diffusion shell. Only in times of high wind is there a movement of this shell and movement of all the associated pollutants into the surrounding country side causing the higher levels of precipitation and storms.

Fogs and Smogs: under anticyclones• Fogs are caused by air cooling at the surface, eg radiation fog as cold air

sinks to the bottom of the valley and condenses.• Advection fog is fog caused by warm air passing offshore over a cold

ocean current eg Humboldt, Peru – so from horizontal cooling.• Smogs are fogs with air pollution – features of cities/urban heat islands. • Last deadly smog from coal fires was London December 1952 – 48 hours

visibility down to less than 50m; 4,000 deaths in a week. Prevented from happening again due to the Clean Air Act of 1956 which created smokeless zones in London.

• Modern day smogs in the MEDW are ‘photochemical smogs’ caused by the reaction of sunlight with vehicle exhaust fumes to give low level ozone and particulate matter – gives asthma attacks, headaches, watery eyes; London July 1994.

Form under anticyclonic conditions because air sinks/subsides, winds are gentle/non-existent so pollutants are trapped, especially in winter because of a temperature inversion (colder at surface than a few 100m up).

Air quality: Particulate pollution, photochemical smog and pollution reduction policies

• Air quality in urban environments is poorer than in the countryside• Urban areas can have up to 7x more dust particles in the local atmosphere• This is the result of the burning of fossil fuels in industrial activity and vehicular exhaust fumes• Particulate matter increases cloud cover and precipitation resulting in reduced sunshine• When combined with sunshine, it may generate photochemical smog and ground level ozone• These are secondary pollutants as they are the result of chemical processes• SO2 and NO2 contribute to acid rain formation• Urban areas: • 200x SO2 – sulphur dioxide from burning sulphur rich coal and oil

• 10x NO2 – nitrogen dioxide from high temp combustion, seen as brown haze dome or plume over cities

•10x hydrocarbons•2x CO2 – greenhouse gas, 0.03% in atmosphere, 30% increase since 1780• CO – carbon monoxide, colourless, odourless, poisonous gas resulting

from the partial combustion of natural gases, wood etc•PM – particulate matter, smoke and dust- PM10, 10μm in diameter, small

enough to enter nasal cavities, PM2.5, 2.5μm, reaches bronchial tubes, causes respiratory problems

•Most polluted urban areas: Delhi, Cairo, Calcutta, Mexico City, Tianjin (China)

SmogSmog

• Is a term used to describe the mixture between smoke and fog.

• It occurs when the smoke and sulphur dioxide (resulting from the burning of fossil fuels) mix with existing fog or cause a thickening of fog by adding more condensation nuclei to it.

• Smog usually originates from vehicular and industrial emissions

The London Smog of 1952• Occurred when an anticyclone was

stationary over Southern England for 5 days in early December

• High pressure system meant that there was no wind to disperse the pollution above London

• Temperature inversion trapped polluted air over the city

• Soothy, black coal smoke mixed with fog to produce smog which reduced the visibility of inhabitants ( residents could not see in front of them)

• Impacts of the smog included increased criminal activity, transportation delays and a complete shut down of the city

• It is estimated that 12,000 people died due to respiratory problems caused by the smog.

Photochemical SmogPhotochemical Smog

• Results from the chemical reaction of nitrous oxides and VOCs (Volatile Organic Compounds) in the presence of sunlight to produce air-borne particulate matter (PM 10 and 2.5) and ground level ozone (O3)

• It is most common above cities that have a sunny, dry and warm climate i.e. Los Angeles

London, April 2011• Causes: high holiday traffic releasing vehicle

exhaust emissions + high pressure system over SE England + ample sunshine + no characteristic April showers to clear atmosphere

• Impacts: temperatures (25-26 degrees C) 10 degrees C higher than monthly average + high levels of PM + cases of sun burns and strokes, exhaustion and dehydration

• Management: Department for the Environment issue a warning concerning smog alerts + advised people to take sensible precautions such as not to take exercise in the afternoon when O3 levels are the highest, to stay indoors, carry an inhaler if asthmatic, avoid taking short car journeys

• Evaluation: message not spread quickly and efficiently + smog alert only of the first day of the month when smog occurs+ Britain fined by the EU for not meeting air quality standards

Urban areas & wind frequency, patterns and velocity

• The surface area of cities is uneven due to the varying height of the buildings. Buildings in general exert a powerful frictional drag on air moving over and around them. This creates turbulence, giving rapid and abrupt changes in both wind direction and speed. Average wind speeds are lower in cities than in the surrounding areas and they are also lower in city centres than in suburbs. High rise buildings may slow down air movement but they also channel air into the .canyons between them.

• Winds are therefore affected by the size and shape of buildings. For a single building, air is displaced upwards and around the sides of the building and is also pushed downwards in the lee of the structure.

• On the windward side, the air will push against the wall on this side with relatively high pressures. As the air flows around the sides of the building it becomes separated from the walls and roof and sets up suction in these areas. On the windward side the overpressure, which increases with height, causes a descending flow which forms a vortex when it reaches the ground and sweeps around the windward corners.

• This vortex is considerably increased if there is a small building to windward. In the lee of the building there is a zone of lower pressure,

• causing vortices behind it.• If two separate buildings allow airflow between them, then the movement may be subject to the Venturi

effect in which the pressure within the gap causes the wind to pick up speed and reach high velocities.• Usually buildings are part of a group and the disturbance to the airflow depends upon the height of the

buildings and the spacing between them. If they are widely spaced, each building acts as an isolated block, but if they are closer, the wake of each building interferes with the airflow around the next structure and this produces a very complex pattern of airflow.

Pollution Reduction Policies• There are a number of ways in which governments and other organisations have tried to reduce

atmospheric pollution in cities.• Clean Air Acts: After the London pea-souper of 1952, the government decided legislation was needed to

prevent so much smoke entering the atmosphere. The act of 1956 introduced smoke-free zones into the UK.s urban areas and this policy slowly began to clean up the air. The 1956 act was reinforced by later legislation. In the 1990s, for example, very tough regulations were imposed on levels of airborne pollution, particularly on the level of PM10s in the atmosphere. Local councils in the UK are now required to monitor pollution in their areas and establish Air Quality Management Areas where levels are likely to be exceeded. Some have planted more vegetation to capture particulates on leaves.

• Vehicle control in inner urban areas: a number of cities have looked at ways of controlling pollution by trying to reduce the number of vehicles that come into central urban areas. In Athens, for example, the city declared an area of about 2.5 km² in the centre traffic free. Many British towns and cities have pedestrianised their CBDs. In London, attempts to control vehicle numbers have included introducing a congestion charge which means vehicle owners have to pay if they wish to drive into the centre. The Greater London Low Emission Zone is an extension of this. In Mexico City, the city council passed driving restriction legislation known as the Hoy no Circula (don’t drive today). This bans all vehicles from being driven in the city on one weekday per week, the vehicle’s registration number determining the day.

• More public transport: attempts have been made to persuade people to use public transport instead of cars. Such schemes have included Manchester.s development of a tram system (Metrolink), the development of bus-only lanes into city centres, the growth of park-and-ride schemes in many British cities and the encouragement of car-sharing schemes.

• Zoning of industry: industry has been placed downwind in cities if at all possible and planning legislation has forced companies to build higher factory chimneys to emit pollutants above the inversion layer.

• Vehicle emissions legislation: motor vehicle manufacturers have been made to develop more efficient fuel-burning engines and to introduce catalytic converters which remove some of the polluting gases from exhaust fumes. The switch to lead-free petrol has also reduced pollution.

Global Climate Change

Climate Change over the last 20,000 years

Climate Change over the last 20,000 years• 20,000 years ago the Earth was still plunged into an ice age, known as the

Devension Ice Age, temperatures were around 5 degrees Celsius• 15,000 years ago, exponential rise in temperature signalling the end of the ice age• Climate remained warm for approximately 1000 years• Temperature increase caused the melting of continental glaciers. These fed a

glacier lake in N America which broke through a moraine barrier and reached the N Atlantic Ocean. The large surge of fresh, warmer water caused the shutting down of the North Atlantic Drift which plunged Europe, and less so the Earth, into another ice stadial (11,500-10,500 years ago), temperatures 5 degrees lower in Western Europe

• This is known as the Loch Lochmond Re-advance or the Younger Dryas – name coming from a species of grass characteristic of tundra regions which was abundant over S England

• Over the last 10,000 years (Holocene), the Earth has had a relatively stable climate• There have been, however, small fluctuations such as the Medieval Warm Period

(1000 AD) and the Little Ice Age (1500-1850 with 1815 the last time the Thames froze – also known as the Maunders Minimum due to extremely low sun spot activity), these occurring in the last millennia

• Recent years, anthropogenic climate change can be observed

Changes to CO2 over the last 20,000 years

Reached approx 280 ppm upon the exit from the ice ageNot even in the past when climatic fluctuations were greater can an increase in CO2 as exponential as that observed nowadays be seenCurrently, at 392-3 ppm (Hawaii observatory – Mauna Loa)Tipping point – 450 ppm

Climate Change over the last 150 years.

Peaks in 1880, 1940 (higher than previous), nowadays

Troughs in 1910, 1960 (longer than the previous)

Temperatures now levelling off due to low sun spot activity

Overall, fluctuations in temperature no larger than 1 – 0.8 degrees Celsius

Climate Change since 1990• World’s 10 hottest years on record (going back

to 1860) have all come since 1990.• Hottest year on record is 1998 which

coincided with an extreme El Niňo event (reversal of the cold Humboldt Current which causes switches in pressure systems in the Equatorial pacific with a domino effect around the globe.

• UK hottest ever temperature = 38.2ºC, August 2003, Gravesend.

Cold Winter of 2009/10• Causes:-- Blocking anticyclone caused a Polar Continental Air Mass to

drag over from Siberia.- Fewer sun spots to maintain the protective magnetic shield

that blocks cosmic rays from entering the earth’s atmosphere.- Cosmic rays create cloud which reflects back some incoming

solar energy.- Sun has fewer sunspots than at any time since the 1920s.- Last winter was still a degree or 2 warmer than the coldest in

living memory – 1962/63.- Jet stream had moved south so no significant westerlies

arrived to bring warmer maritime winds.

Climate Change - the proxy evidence• Glacial and periglacial deposits- as ice sheets and glaciers retreat, they deposit all of the load that they have

transported on site. Wherever there are obvious surface deposits of ‘boulder clay’, ice must have been at work. These may provide evidence for a profoundly colder climate i.e. over Northern UK.

• Coloptera beetles in peat deposits –species tend to inhabit individual specific climatic belts with strict environmental conditions. Analysis of fluvial, lacustrine and terrestrial deposits could give an indicator of the location of former climatic belts

• Dendrochronology (tree-ring analysis)– based on the fact that with each year of a tree’s life one more ring is added: moist, warm years encourage rapid growth and a thickening of the trunk whereas cold, dry years show much smaller growth rates and the gaps between dark rings are smaller. Evidence from different species of trees can be cross-referenced and this can provide a reasonable idea about climate as far back as 10,000 years ago. However, they cannot provide a full picture of climate change as they are unable to indicate what the stressors that acted on the trees’ growth were e.g. A dry and cold year or a dry and warm year?

• Fossil evidence: shows that bears once inhabited caves in the UK and that mammoths roamed on tundra plains now on the bottom of the North Sea

• Fossil landscapes: the glacier valleys of the Lake District and the granite at Dartmoor could not have been formed under present climatic conditions

• Paintings during the Little Ice Age by Breugel indicting frost fairs on the Thames and low temperatures during the peak of the ‘little ice age’. Good because dated and specific.

• Parish registers indicating individual storm events eg 1703 great storm which killed 8,000 including 1/3rd of the Merchant Navy and dairies e.g. of Samuel Pepys indicating cold, frost fairs. Nevertheless, their accuracy is questionable: 1703 – cattle blow in tops of trees and fish blown out of rivers

• Shift in vegetation belts as indicated by the pollen analysis of oxygen free peat bogs. These show which plants were dominant at any one time and enable the reconstruction of previous characteristic vegetation and climate

Climate Change: the scientific evidence.• Accurate readings of temperature and other weather

conditions taken since 1755 in Britain and daily weather reports have been kept since the 1870s

• Radiocarbon dating techniques help determine the age of plants and animals preserved in fossils especially over the last 20,000 years. Carbon is absorbed by these in the natural carbon cycle. Carbon 14 isotope decays radioactively with a half life of 5730 +/- 30 years. Carbon 12 isotope does not, however, decay. The abundance of C-14 can be compared with that of C-12 and accurate dating of organic matter can go back as far as 50,000 years. (Useful for dating coloptera beetles and other fossils)

• Isotope analysis of O 16 and O 18.In warmer conditions more of the lighter O-16 isotope evaporates out of the sea water leaving behind a higher ratio of O-18 in the water. There changes in ratios are monitored by sea life and evidence can be extrapolated from the analysis of sediments of radiolaria and foraminifera.

Ice Cores – scientific evidence for Climate Change

• Are extracted from ice sheets over Antarctica, the Arctic and Greenland• Analysed using a mass spectrometer• Layers, also known as ogives: dark indicative of summer due to the

accumulation of dust and grit/ white indicates snow accumulation during winter

• Air is trapped in snow and can provide details about the atmospheric composition: CO2, methane (CH4) and Beryllium 10.

• From the ice itself, the ratio of O 16 to O 18 may be recorded• Overall, at least 4 useful measurements + dust and snow fall accumulation• One of the key techniques of tracking ancient climates• May be extracted at different locations and suggest climate variations at a

smaller scale i.e. Loch Lomond re-advance impacted more N Europe – shutting down of the N Atlantic Drift – than Antarctica

Sun-spot Activity

Indirect Evidence• Beryllium levels are sun activity proxies. In the atmosphere thay

pinpoint the sun spot activity and may give an indicator of climate variations. With less sun spot activity, the electromagnetic shield which surrounds the Earth is weaker. This enables more cosmic rays to reach the atmosphere and create the 10 beryllium isotope from in reaction with the noble gas boron. Thus, levels of beryllium and sun spots are negatively correlated.

• Although sun spot numbers are available only from the last 4 centuries, beryllium falls on the Earth’s surface in snow and, using ice core analysis, may be traced further back

• Subsequently, data can be cross- dated and the influence of sun spot activity on the Earth’s climate can be determined for a longer period of time

Evidence for Climate Change

The Hockey-Stick Graph• An graph showing changes in temperature

over the last 1000 years put together by cross dating data from a variety of proxy indicators such as dendrochronology and ice-core readings

• It is indicative of the ‘Little Ice Age’ – 1500-1815 (last time the Thames froze)-1850

• Also shows a medieval warm period which preceded the ice age

• It is of importance as evidence for global warming as it shows temperatures increasing exponentially in the last 50 years, a growth unmatched by any other in the last 1000 years

The “Climate Gate” Scandal • Scandal just before the Copenhagen

summit on global warming in 12/2009• Reason: dendrochronology data over the

last 50 years veered away from other proxy indicators and data from sophisticated instruments so the data was removed

• Temperature readings were instead stitched onto the graph to fit consensus data

• Source: CRU- Climate Research Unit at the University of East Anglia

• Enquiry: UEA found not guilty of misleading the public

Climate change over the last 1,000 years – Hockey Stick Graph

An Ice Stadial Scenario- Anthropogenic Global Warming

National responses to global warming• Managing a retreat on low cost coastlines eg Abbott’s Hall

farm.• Encouraging afforestation programs eg St Albans NW London.• Change to wind technology – eg Kentish Wind Flats to reduce

consumption of fossil fuels.• Clean technology to filter out greenhouse gases from coal fire

power stations.• Allowing car owners to buy technology to convert used

vegetable oil to run diesel vehicles.• Rise in the Green Party – 2010 election first Green Party

candidate in the House of Commons.• Recycling depots set up to reduce waste and cut energy costs.• Investment in public transport and bicycle routes to reduce

petrol consumption.• Subsidies for home owners to invest in solar panels.

International responses to Global WarmingImportant summit meetings eg Kyoto 1997 where MEDCs agreed

to reduce carbon emissions by 5.2% of their 1990 totals by 2012.

Copenhagen Summit to focus on the issue and bring the LEDW into line.

Scientific stations set up to monitor climate change.Investment worldwide in new technologies.Conversion of rain forest into palm oil plantations to reduce fossil

fuel consumption from vehicles, eg Indonesia.Raising awareness around the globe with advances in

communications eg encouraging the rich to purchase TRFs to ensure protection.

Conservation of threatened ecosystems eg through National Parks and the World Wildlife Fund (WWF).

Local responses to Global WarmingThink global act local

• Setting up recycling depots• Afforestation programs – natural

ecosystems are the best cure for global warming consequences.

• Encouraging allotments/organic farming to reduce air miles of food transport.

• Draught excluders; double glazing; loft insulation; solar panels on homes.

• Car share schemes for commuters.

Likely impacts of warming on the Indian sub-continent

• Changes in the seasons of both SW Monsoon (later, hotter, drier) NE Monsoons (possibly wetter due to extra convection).

• Increased frequency of cyclones due to warmer seas. (Cyclone Nargis, 2008, strongest ever to hit Burma)

• Sea levels will rise (eustatic) and drown the Maldives.• Increased glacial lake outburst floods (GLOFS).• Decreased food security in the long term because of declining meltwater from

vanishing Himalayan glaciers.• Enhanced urban heat island effects as dark surfaces absorb more sunlight – greater

deaths from heat stroke.• Malaria found higher up the Himalayas.• More intense rainfall/flooding like Pakistan 2010.• Coral bleaching along the coastlines as warmer temperatures cause coral polyps to

evict their algal tenants and hence die of starvation.