VI Geography - Weather, Climate and Ecosystems

Evidence for Climate Change

• Sea-floor sediments - Indicate previous ocean temperatures

• Ice Cores - CO2 Levels have fluctuated - Indicate previous gaseous composition of the atmoshphere

• Lake Sediments - Pollen grains indicating the vegetation types from the past

• Tree rings - the width of the annules vary depending on the temperature

• Fossils - Indicates the plants and animals that were able to survive in the conditions

• Glacial and Inter-Glacial periods - we have not entered one

Human Causes for Climate Change

• Fossil Fuels - releases CO2 from the lithosphere into the atmosphere

• Agriculture - cattle farming releasing methane

• Deforestation - releasing CO2 from the biosphere into the atmosphere

Natural Causes for Climate Change

• Solar output - measured using sunspots

• Orbital changes - the ellipse of the earth’s orbit changes, so does the angle of the axis and it wobbles

• Volcanic activity - emit clouds of dust and gas that reflect the short waves from the sun back out of the atmosphere, cooling the planet

Global Circulation System (tri-cellular model)

Low Pressure Hazards and Formation

Tropical storms (Hurricane):

• A strong upward movement of air draws water vapour up from the warm ocean surface

• This evaporated air cools as it rises and condenses to form towering thunderstorm clouds

• As the air condenses it releases heat which powers the storm and draws up more and more water from the ocean

• Several small thunderstorms join to form a giant spinning storm

• As the storm is carried across the ocean by the prevailing winds it continues to gather strength

• The storm now develops an eye at its centre where air descends rapidly

• On reaching land the storm’s energy supply is cut off and friction with the land slows it down

High Pressure Hazards and Causes

Droughts and Heat Waves:

• Weather

• Global Warming

• El Nino

• Overpopulation

• Overcultivation

• Overextraction

• Deforestation

Distribution of: Low Pressure Storms

• Found over warm oceans (27 degrees +) - the tropics

• Form 5-15 degrees north and south of the equator as there is not enough ‘spin’ at the equator

• The intense heat in tropical climates makes the air unstable causing air to rise rapidly

Distribution of: High Pressure Systems

Higher risk in:

• LICs

• Places with overpopulation

• Places with hotter climates

Change overtime of: Low Pressure Systems

Form in the summer and autumn when sea temperatures are at their highest

Increased due to climate change

Change overtime of: High Pressure Systems

Increase in drought in the last 100 years due to climate change

Low Pressure System Case Study

What: Hurricane Matthew

Where: Caribbean, SE Coast of USA

When: October 2016

Consequences: Homelessness, Displacement, Separation of families, Death, Flooding, Destruction of property, Contaminated water (LICs),

Responses: Evacuation, Money donation from other countries and NGOs, Donation of resources from this places (LICs)

High Pressure System Case Study

What: California’s Drought and Wildfires

Where: California

When: 2012-2015

Causes: Jet stream that usually brings precipitation to California was too high up

Consequences: Lower precipitation → dry soils → wildfires, fires engulfed many homes, housed pipe bans, property damage, loss of crops, vegetation dies

Responses: Mass Evacuation

Factors that create Weather Variation in the UK

• Latitude

• Altitude (+ relief rainfall)

• Ocean Currents - North Atlantic Drift (warm)

• Continentality - land heats up and cools down quickly whereas water does so slowly

• Air Masses

Distribution of Biomes (Tropical Rainforests, Tundra and Savanna)

Tropical Rainforests: Grow in a band around the equator where the equatorial climate is hot and wet.

Tundra: Found where Winters are cold and Summers are short (arctic areas)

Savanna: Found in regions that have a tropical semi-arid climate (above and below the equator)

Tropical Rainforests (Climate and Distinctive Features)

Climate: Hot and wet - humid

Distinctive Features: Hot climate and abundant rainfall allow for rapid plant growth and trees that can reach very high heights

Savannas (Climate and Distinctive Features)

Climate: Hot with wet and dry seasons

Distinctive Features: An open tree canopy (i.e., scattered trees) above a continuous tall grass understory

How humans impact the ecosystems of: Tropical Rainforests

Deforestation:

• Exposes soil to erosion

• Takes carbon dioxide out of the biosphere and then lithosphere contributing to global warming

• Creates ecological islands - separating groups of animals from others

• Nutrient cycles are broken

• The use of heavy machinery damages shrubs → derives insects of food → disrupts the food chain

How humans impact the ecosystems of: Savanna

Desertification:

• Slash and burn of trees → reduces evapotranspiration levels → reduces rainfall levels → reduces water for people who rely on rivers for water

• The removal of vegetation → leaf litter can no longer fall into the soil → the nutrient cycle is broken → shrubs no longer replace nutrients or help to maintain a healthy soil structure by adding organic material to the soil

• The destruction of the tree canopy → exposes the soil to rain splash erosion + during heavy rainfall the water flows over the surface of the ground in sheets, eroding all the organic material from the upper layers of the soil. On steeper slopes the power of the water picks up and carries soil particles and smaller rocks → it uses these to erode downwards into the soil in a process known as gulley erosion.

Sustainable Management of: Tropical Rainforests

• Wildlife corridors - planting strips of forest to connect the remaining fragments of forest together. Allows animals to move freely from one area of forest to another without coming into conflict with people.

• Buffer zones - encourages the local people to use the zone sustainably rather than just banning the usage of forests altogether - helps to make a living and educate people

Sustainable Management of: Savannas

Great Green Wall of Africa - involves planting a wall of native trees and shrubs across the width of Africa:

• Increase biodiversity

• Reduce soil erosion

• Reduce time women spend collecting firewood

• Grow medicinal plants

• Diversify plant incomes

• Improve soil fertility

• Increase fodder for livestock

• Provide shade for crops and increase their yield

• Increase capability of coping with climate change

How humans affect small scale ecosystems in the UK: Studland Bay Sand Dunes

BBQs - Burns vegetation

Dog waste - fertilises the soil so unwanted plants also grow

Walking - tramples vegetation and kills it

Can be managed by: Land-use zoning, dog waste bins

Weather

Day to day conditions/changes in the atmosphere

Climate

Weather over a long period of time (30 years)

Affect of: Latitude on Temperature

Temperature: Greater curvature = Greater area of land to heat up

Affect of: Altitude on Temperature and Rainfall

Temperature: Density decreases as altitude increases.

Rainfall: Air is forced to rise over areas of high altitude causing relief rainfall

Affect of: Ocean Currents on Temperature and Rainfall

Temperature: Warm and cold ocean currents bring different temperatures

Rainfall: Brings in different pressure systems

Anticyclones

• High pressure

• Air sinks in the lower atmosphere

• In the Summer: brings hot and sunny weather with light wind

• In the Winter: Anticyclones cause cold weather including fog and frost

Depressions

• Low Pressure

• When a warm front meets a cold front

• Air rising causes the formation of clouds, which brings rainfall. Depressions often move eastwards across the UK, bringing changeable weather as they travel.

• There are usually frontal systems associated with depressions. The diagram below shows the changing weather that the warm and cold fronts bring as they move towards the east.

Urban micro-climates

The buildings and traffic in a large city influence the local climate - creates temperatures that are warmer than in the surrounding rural area.

Factors of: Urban micro-climates

• Concrete, brick and tarmac all absorb heat from the Sun during the day. This heat is then radiated into the atmosphere during the evening and at night.

• Buildings that are badly insulated lose heat energy, especially through roofs and windows. Heat is also created by cars and factories, which is lost to the air from exhausts and chimneys.

• Tall buildings in a city affect local patterns of wind - act as a shelter so average wind speeds in cities are lower than in the surrounding countryside. However, rows of tall buildings can also funnel the wind into the canyon-like streets between them and cause high wind speeds. This may cause hazards for pedestrians and, in some extreme weather conditions, has led to the collapse of scaffolding.

• During the summer months, the extra heat due to the urban heat island causes air to rise over larger cities - this can lead to convectional rainstorms.

• Urban areas have 10 times the dust particles in the atmosphere than rural areas leading to higher amounts of rainfall - when water vapour condenses in the air to form water droplets it does so by attaching itself to a dust particle.