Topic 1: Climate change

GCSE geography edexcel

Weather definition

The day to day changes in the state of atmosphere e.g precipitation, temperature, wind speed and direction

Climate definition

Average weather measured over a period of 30+ years

Why does temperature vary with latitude? (in areas closer to the poles)

In areas closer to the poles, incoming solar radiation has a 'thicker' atmosphere to pass through and the sun is at a lower angle in the sky so the incoming radiation is spread over a large area of the the Earth's surface. This means that temperatures are low

Why does temperature vary with latitude? (in areas near the Equator)

In areas near the Equator, incoming solar radiation has 'thinner' atmosphere to pass through and the sun is at a higher angle/ the sun is shining directly towards this area so the incoming solar radiation is concentrated at the Earth's surface. This means that temperatures are high

Hadley cell?

The warm air at the equator rises into the upper atmosphere then moves away and as it cools, it descends at the tropics

Polar cell?

Cold air at the poles descends, then moves away towards the mid latitudes

Ferrel cell?

Cold air from the Poles meet warm air from the tropics in the mid latitudes

Atmospheric pressure definition

The 'weight' of the air and the force this exerts on the ground

Air and the distribution of pressure

The warmth of the Earth's surface heats the air above it, increasing the amount of energy in the air. This causes the air to rise. Rising air exerts less pressure on the ground and so an area of low pressure is formed below it. As the air continues to rise away from the Earth's surface, the heating effect from the warm ground is reduced and the air begins to cool. Cooler air has less energy and so it begins to sink back towards the Earth. The 'weight' of the sinking air exerts more pressure on the ground and an area of high pressure is formed.

Generally precipitation is _ at the Equator, _ at the tropics, is _ in the mid latitudes and is _ near the poles

Generally precipitation is high at the Equator (rainforest), low at the tropics (desert), high in the mid latitudes (Manchester) and low near the poles

Low pressure belt

1) Warmed air is unstable and rises

2) As the air rises, it cools and cannot hold as much water vapour

3) This results in condensation, cloud formation and precipitation

High pressure belt

1) cooled air descends

2) This results in dry stable conditiins

Surface ocean currents are driven by...

Surface ocean currents are driven by the movement of wind across the top of the water

Deep ocean currents are driven by ...

Deep ocean currents are driven by water sinking and rising because of the temperature change

A warm ocean current than the UK is affected by?

The UK is affected by a warm ocean current from the Gulf of Mexico, called the Mid Atlantic drift

Quaternary Period?

2.6 million years ago to present

Pleistocene

Last ice age (glacial) period, 2,600,000 to 11,700 years ago

Holocene

Current interglacial period, 11,700 years ago to present

Warm periods are called

interglacials

Cold periods are called

Glacials

Evidence for natural climate change

- Tree rings (Thick - Wetter/ warmer, Thin - drier/colder, Scars from forest fire)

- Historical sources (Personal diaries, paintings, religious records)

- Ice cores (drilled into snow to extract ice core samples, bubbles allow us to measure CO2 levels in the atmosphere, each layer allows us to see previous Earth's climate)

- Modern times (photographic evidence of glacial retreat)

What are the natural causes of climate change?

- volcanic activity

- Variations in solar output

- Orbital changes (Milankovitch cycles)

- Asteroid collisions

How does volcanic activity cause climate change?

Big volcanic eruptions releases ash and sulphur dioxide gas into the atmosphere creating a blanket around the air. The blanket of ash and gas will stop sunlight reaching the Earths's surface as sunlight is reflected off the gas and ash back into space which cools the planet and lowers the average temp

Example of how volcanic activity causes climate change

In 1991, Mount Pinatubo in the Philippines erupted releasing 17 million tonnes of sulphur dioxide. This reduced global sunlight by 10% cooling the planet by 0.5 °C for about a year.

How does variations in solar output cause climate change?

Dark spots tell us that the sun is more active than usual. Lots of spots mean more solar energy being fired out from the sun towards the Earth which results in an increase in temperature

Example of how variations in solar output causes climate change

Cooler periods (e.g Little Ice Age) and warmer periods (.g Medieval warm period) may have been cause by changes in sunspot activity

How do orbital changes cause climate change?

It is changes in the way the Earth orbits the sun (circular or ellipse/ Earth's axis tilts - upright or on its side/ axis wobbles) This alters the amount of sunlight the Earth receives and also affects where sunlight falls on the Earth's surface. On timescales of thousands of yrs, these changes could be enough to start an ice age, or end one (Milankovitch cycles)

Example of orbital changes

- takes 100,000 yrs for the Earth,s orbit to change from being more circular to an ellipse and back again

- takes 41,000 yrs for Earth's axis to tilt, straighten up and back again

- takes 26,000 yrs for Earth's axis to wobble, straighten up and wobble again

How do asteroid collisions cause climate change?

The Earths atmosphere protects us from the impacts of comets and meteorites by vaporising most of the material before reaching the Earth's surface. An impact from a body this size would've released huge quantities of vaporised material into the atmosphere blocking out the sun and causing an initial "impact winter" and a potential drop of temperatures of 5-6 °C. After, there would've been a temperature rise caused by large amounts of CO2 released by a spread of global forest fires

Example of how asteroid collisions cause climate change

This theory has been considered to account for the extinction of dinosaurs 65 million years ago

things that release CO2

- cars

- deforestation

- power stations

- draining peat bogs

(89% of all greenhouse gas emissions)

Things that release methane

- cows

- rice fields

- landfill sites

(7% of all greenhouse gas emissions)

Greenhouse effect

The natural trapping of sun's energy in the atmosphere due to the presence of greenhouse gases

Enhanced greenhouse effect

The increase greenhouse effect resulting from human action and leading to global warming

How do carbon dioxide and methane contribute to the enhanced greenhouse effect?

1) incoming short wave solar radiation

2) short wave radiation passes through the atmosphere and greenhouse gas layer

3) short wave radiations is reflected off the surface and becomes long wave radiation

4) some long wave radiations passes back into space

5) some long wave radiation is reflected of greenhouse gases back to Earth, heating the Earth up

Evidence for how human activity is causing climate change

- Surface air temperature change

- Upper ocean temperature change

- Sea level change

- Arctic sea ice change

- Mountain glacier change

- Changes in extreme weather events

How surface air temperature change shows how human activity is causing climate change?

- global surface air temps are rising e.g in 2015 the av global temp was 1°C above the average global temperature in 1850-1900

How upper ocean temperature change shows how human activity is causing climate change?

- the oceans warmed by 0.11°C per decade between 1970-2010

How sea level change shows how human activity is causing climate change?

- From 1880 to 2000 the sea level has gradually increased by approx 20cm

- small islands such as the Solomons are vulnerable.

How Arctic sea ice change shows how human activity is causing climate change?

- Arctic sea ice covers 13% less of the sea each decade

- Arctic sea ice is shrinking towards the North Pole

- sea ice off the coat of northern Russia and Alaska have disappeared

How mountain glacier change shows how human activity is causing climate change?

- Almost all areas of glaciers worldwide are thinning

- most significant glacier change is around New Zealand by approx 2 metres per year since 1970

How changes in extreme weather events show how human activity is causing climate change?

- Weather related disasters increased globally

- Asian typhoons becoming more intense across china, Japan, Korea and Philippines (intensified by 50% in past 40 years)

Positive consequences of climate change on people in the UK

- Domestic tourism is likely to grow particularly in coastal resorts such as Blackpool and Bournemouth due to increase in temperature

- In winter, heating costs and road gritting costs could fall

Negative consequences of climate change on people in the UK

- Rising sea levels and more extreme storms which will likely increase river flooding and threaten more homes (and increase from 0.3 million to between 0.6 and 1.2 million homes by 2080)

- flooding damage costs are likely to increase from around £1billion per yr to between £2 billion and £12 billion by 2080

- In the summer, drought and water shortages are likely to become more common especially in the south (27-59 million people affected by 2050)

Possible consequence of climate change on people in Egypt

Up to 20% less rainfall in parts of Egypt, Sudan etc meaning extreme drought and water shortages which results in less water for irrigation as well as less land for agriculture. They then need to invest in new water projects increasing the likelihood that Egypt fails to develop economically and socially

Possible consequences of climate change in the Maldives

Almost all of the Maldives' inhabitants are likely to be affected by rising sea levels as the Maldives is projected to experience sea level rise of approx 50cm by around 2100. As a result many inhabitants may be forced to move to other countries as environmental refugees and tourism with over 600,000 visitors annually is likely to be hard hit

Possible consequences of climate change in Nepal

A likely reduction in precipitation in the dry season will cause water shortages and irrigation problems for agriculture. Overall crop yield could decrease by 30% by the end of the century. A likely increase in precipitation in the monsoon season will result in increase river flooding and landslides in the mountainous areas which may lead to migration to lead to failure of development

IPCC

Intergovernmental Panel on Climate Change

They reported in 2014 that scientists were ore than 95% certain that global warming is mostly being caused by human (anthropogenic) activities

Why future climate change is hard to predict?

- Population growth: the UN's prediction of population growth varies massively from between 6 billion to 16 billion by 2100 as population growth is difficult to predict due to changing role in women and laws etc. If population growth is limited or decreased, climate change is likely to not increase as much as if population growth increases.

- Future energy use and production: Many countries are adopting alternative energy uses such as wind in the UK and technology is becoming more advanced such as electric cars. The scale is hard to predict. However if fossil fuels are still constantly being used and production increases then climate change will become drastic as these all contribute to CO2 emissions

Human factors which contribute to climate change

- Future population change: An increase in population results in an increase in climate change as more people require more greenhouse gases emitters for e.g increase demand for meat which contributes to methane emissions (cows), increase in cars which then increases CO2 emissions

- Future economic growth: industrialisation means increase in factories which contributes to the emission of greenhouse gases, continued growth in china and India mean more emissions due to burning of fossil fuels

- Future energy supply: Renewable energy results in decrease in CO2 emissions as less burning of fossil fuels, fossil fuel discoveries ( fracking, Arctic oil) results in increase in Co2 emissions