How Climate has Changed in the Past
Weather = short term, day to day changes in the temperature. Climate = the average weather conditions over 30 years
Climate has changed in the distant geological past. We have always had temperature fluctuations from +3C changing to -9C
- Interglacials = warm periods. Glacials = cold periods, ice ages, ice sheets 400-300m thick extended across the northern hemisphere
- These long term changes in climate in the distant past can be explained by orbital theory
How we know climate was different in the distant past
- Fossils of animals and plants that no longer live in the UK e.g. woolly mammoth lived when climates where much colder
- Landforms left by glaciers e.g. U-shaped valleys are found in the Lake District these were formed by glaciers during the last Ice Age when it was much colder
- Samples from ice sheets in Antarctica made up of layers of ice, one for each year. Air bubbles are trapped in the ice sheets. Climatologists study CO2 levels to reconstruct past climates
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How do we know climate has changed in the more recent years (last 2000 years)
- Old photos, paintings e.g. Picture of Thames frozen over
- Diaries or Novels e.g. Dickens' Christmas Carol
- Recorded dates of blossom and migration of birds
Theories to explain why climate has changed in the past (Natural Events)
- ERUPTION THEORY- very large and explosive volcanic eruptions change the earth's climate. Ash and gas spread around the stratosphere and reduce sunlight reaching the earth's surface- this cools the earth. E.g. Mt Pinatubo, 1991, Philippines- reduced global sunlight by 10% and cooled the earth by 0.5 degrees for a year.
- SUNSPOT THEORY- black areas on the sun's surface. Sometimes there are more then they disappear. More spots means greater activity and more solar energy being sent towards the earth- this warms the earth. Fewer spots means less solar energy reaches the earth
Past Climate Change
- ORBITAL THEORY/ MILANKOVITCH CYCLES- changes the way the earth orbits the sun from circular to elliptical alters the amount of sunlight the earth receives. The earth's axis also moves and wobbles about affecting how much sunlight is received
- ASTEROID THEORY- If asteroids hit the earth, dust and debris can block the sun and therefore reduce temperatures.
The Medieval warm period could have been caused by: more sunspot activity
The colder period of the Little Ice Age may have been caused by: less sunspot activity or more volcanic eruptions
Modern Scientists argue the modern period of warming since the 50s is caused by the enhanced greenhouse effect. However some people argue we could be moving into a period of natural warming as we have evidence on interglacials in the distant past.
Impacts of the Little Ice Age
The Little Ice Age was a period of unusually cool conditions between 1300 and 1850 A.D.
Impacts on Farming
- Drop in agricultural output- the cool wetter summers meant that wheat and oats did not ripen and harvests failed. Farms on marginal, less productive land (e.g. mountains in the UK) were abandoned
- Many Farmers could not produce enough food and this resulted in greater poverty
- However farmers did adapt by changing their crops from wheat to potatoes which could ripen in the cooler, wetter conditions. They also adapted by moving from marginal land as it was no longer productive
Impacts on Ecosystems in the Little Ice Age
- Increased sea ice in northern latitudes which meant food chains were affected and this had an impact on food for higher trophic levels e.g. seals
- Some animals e.g. deer experienced rapid population decline as there was less tundra food as plant growth slowed down due to colder temperatures.
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Impacts on People
- Smaller crop yields due to colder temperatures led to grain price increases and this had the greatest impact on the poor. In 1315 there was a great famine caused by crop failure due to the climate
- Cool, wet summers led to outbreaks of diseases e.g. St Anthony's Fire which is a skin disease. There was a rapid spread of disease like bubonic plague
- A positive factor: Herring moved southwards from Norway as the sea had become cooler around the UK. This increased the herring fishing industry.
Geological Climate Events- Ecosystem Change e.g. Megafauna extinction
Ecosystems- where plants and animals interact with eachother and their environment (climate, soil, relief) in order to survive
Impacts of Climate Change on Ecosystems in the pas
- Climates started to warm up after the end of the last Ice Age 10 000 years ago. Plants and animals became vulnerable to climate change. Many scientists believe it was due to climate change affecting humans and habitat
- Warming climates reduced the habitat of the woolly mammoth which ate tundra grasses and mosses only found in cold environments. This mean they had less food and could have become extinct from starvation and disease
- Humans moved north into these warmer areas as they became more suitable to live in. They hunted some of the megafauna e.g. woolly mammoth and giant deer meaning there was less prey for carnivores like the Sabre-Tooth Tiger
The Enhanced Greenhouse Effect
Greenhouse gases trap heat from leaving the atmosphere and re-radiate the heat back down to earth. The greater the concentration of greenhouse gases, the more heat is trapped and the warmer earth becomes.
We need the natural greenhouse- it makes the planet 16 degrees warmer. Without it, the world would be too cold for us to survive.
The Enhanced Greenhouse Effect
The extra greenhouse gases produced by humans by burning fossil fuels in power stations for transport, industry, and homes which means more heat is trapped and re-radiated back to the earth, warming it even more
Global Warming: the warming of the Earth's temperatures caused by the Enhanced Greenhouse Effect (humans have polluted the atmosphere so the greenhouse effect is working at a stronger rate)
Global temperature rise leads to climate change. This leads to rising sea levels due to thermal expansion. Glaciers and ice sheets on land melt so the volume of sea water increases
Evidence for Global Warming Today
- 19 out of 20 warmest years on record have occurred since 1980
- Sea ice in the Arctic is shrinking
- 90% of global glaciers are melting and shrinking
- Sea levels have rise e.g. in the Maldives
How human activity increases the amount of greenhouse gases released
- Increased use of transport. Petrol is a fossil fuel that releases CO2
- Thermal power stations generate electricity through the burning of fossil fuels which releases CO2 and nitrous oxides into the atmosphere
- Deforestation has removed trees which previously absorbed CO2 through photo synthesis so there is more CO2 in the atmosphere
- Increasing populations have led to more paddy rice being grown. Microbes in the water emit methane. More cattle are raised for meat and they emit methane
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- Burning fossil fuels in thermal power stations
- Increased use of nitrogen fertilisers to grow more food
CFCs- these are man made chemicals found in fridges, air conditioners, aerosols etc are extremely effective greenhouse gases
How have greenhouse gas levels changed over time?
- Rates of methane have also doubled since the 1800s due to the rapidly growing global population demanding an increasing amount of cows for meat and rice to eat
- Increased affluence has led to more cars being used so more CO2 is generated
- As countries develop and people become more affluent, demand for electricity increases e.g. in China most electricity is produced by burning coal which creates CO2 and nitrous oxides
- Industrial processes and demand for coolants has increased for CFCs although production is banned in most countries
Countries that produce the most Greenhouse Gases
As countries become more industrialised, the people become consumers of energy and goods as well as producers of air pollution through burning fossil fuels. This increases atmospheric concentrations of greenhouse gases.
Most greenhouse gases are produced in the developed world - e.g. The EU, USA and Japan. The average person uses 20-25 tonnes of carbon a year
In the developing world, the average production of carbon is 1 tonne
The world's current level of CO2 is increasing 200x faster than at anytime in the past 1 million years.
China is now the world's largest producer of carbon (but not per person). This is due to its large increasing population of 1.4 bn as well as increasing demand for fossil fuels for manufacturing industry and increasing affluence of China's population. They demand more consumer goods and electricity which require fossil fuels to manufacture and transport goods. The output of carbon has increased enormously
Climate and Sea levels in the future
Scientists don't know exactly how global warming might affect our planet but predictions include:
- Temperatures to rise between 1.1 and 6.4 degrees Celsius by 2100
- Sea levels to rise between 30cm and 1m by 2100
- Floods, drought and heatwaves would become more common
- Storms and hurricanes would become stronger
Predicting Future Global Warming is hard because we don't know:
- What the future population size will be. Populations may increase beyond the 9 million predicted by the UN or they might not increase as fast e.g. people may decide to have fewer kids
- We may continue to use fossil fuels at the same or an increasing rate. The more we use the more we are contributing to the enhanced greenhouse effect. Or people may change to more sustainable sources of energy e.g. solar and wind. In the future we may develop more sustainable energy sources that cost less than oil like tidal wave or cost effective hydrogen cells.
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- We don't know how lifestyles may change in the future e.g. more people may begin to recycle or use public transport and buying locally produced goods, reducing the demand for goods and transport which produce greenhouse gases.
How climate change might effect people and environment in the developing world Egypt's People
- Rising sea levels and more frequent storms are already eroding the Nile Delta by up to 5m per year which is a low lying area.
- A rise on 1m could flood a quarter of the Delta forcing 10% of Egypt's population from their homes in the Delta- they will be environmental refugees with over 7million people having to find a new place to live
- Egypt's food supply could be threatened. Nearly half of Egypt's crops including wheat, bananas and rice are grown in the Delta. GDP could be reduced by 77%
- Areas not under water could also be affected with salination from the Mediterranean contaminating the fresh ground water from the River Nile used for irrigation and domestic uses further threatening food supplies and export crops possibly leading to famine
Desertification and Salination
- Warmer temperatures means less water is available for irrigation so plants will die. There would be no roots to bind the soil resulting in wind erosion and desertification. This could cause the spreading of the Sahara desert onto areas of farmland
- Salination of the soil due to sea level rise will result in plants dying with a knock on impact on higher trophic levels and biodiversity overall
- 86% of the Nile's water starts its journey in Ethiopia. Uganda, Sudan and Ethiopia are all building HEP dams which could reduce the amount of water reaching Egypt which could lead to conflict and war
Egypt has a debt of $30 billion. It may not be able to adapt to the impacts of climate change because it can't afford the expensive hard engineering e.g. building sea walls to reduce the impact of sea level rise. Also building new dams to store water for irrigation is also expensive
Egypt also relies on agriculture for its GDP. If temperatures increase, crops may need more water as evaporation rates increase. This water may not be available
Developed World Affected by Global Warming: The UK
- Summer drought and water shortages, especially in Southern England. More reservoirs need to be built which will increase the cost of water for individuals, farmers and industry
- As temperatures get higher more evaporation occurs and there is less water for crops. More money will have to be spent on irrigating crops so increasing food prices.
- Extinction of some plant and animals as it gets warmer. E.g. tundra plants may disappear from the highlands of Scotland and this is a food source for birds like the Ptarmigan so they could become extinct.
- Puffin numbers have declined and could decrease further as the eat fish and fish eat plankton. As the seas warm there is less plankton and therefore less food for fish to eat, affecting higher trophic levels.
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- Cheaper household energy bills as the cost of winter heating may fall as winter could become warmer.
- If it becomes warmer in the UK, growing seasons may become warmer and longer so new crops can be grown e.g. vineyards for wine and other Mediterranean crops. Some farmers in Devon have introduced olives and hope to grow them commercially.
- There may be a northward shift in vegetation increasing deciduous forests. This could increase habitats for some birds and animals increasing biodiversity.