Climate change

Climate change - any significant change in the Earth's climate over a long period 

The Earth is getting warmer.

• The Quaternary period (the whole of human history) is the most recent geological time period - from 2.6 million year ago to today. 
• In the period before the Quaternary, the Earth's climate was warmer and quite stable. Then things changed.
• During the Quaternary, global temperature has shifted between cold glacial periods that last for around 100,00 years and warmer interglacial periods that last around 100,000 years. 
• The last glacial period ended around 15,000 years ago. Since then, the climate has been warming.

Global warming - the sharp rise in global temperatures over the last century.

(Type of climate change)

SUMMARY -

During the Quaternary period, the climate repeatedly went from warm to cold and then back to warm again. Now, its getting rapidly warming.

Scientists can work out how the climate has changed over time using a range of methods:

1. Ice and Sediment Cores

• Ice sheets are made up of layers of ice - one layer is formed each year.
• Scientists drill into ice sheets to get long cores of ice.
• By analysing the gases trapped in the layers of ice, they can tell what the temperature was each year.
• The remains of organisms found in cores taken from ocean sediments can also be analysed. These can extend the temperature record back at least 5 million years.

2. Temperature records

• Since the 1850s the global temperatures have been measured accurately using thermometers. This gives a reliable short-term record of temperature change.
• Historical records can extend the record of climate change a bit further back.

3. Pollen analysis

• Pollen from plants can be preserved in sediment. 
• Scientists can identify and date the preserved pollen to show which species were living at the time.
• Scientists know the conditions plants live in now, so preserved pollen from similar plants show that climate conditions were similar.

4. Tree rings

• As a tree grows, it forms a new ring each year - the tree rings are thicker in warm, wet conditions.
• Scientists take cores and count the rings to find out the age of a tree.
• The thickness of each ring shows what the climate was like.
• Tree rings are a reliable source of evidence of climate change for the past 10,000 years.

1. Orbital changes 

• The way the Earth moves round the Sun changes. 
• These changes affects the amount of solar radiation (how much energy) the Earth receives. 
• If the Earth receives more energy, it gets warmer.

2. Volcanic activity

• Major volcanic eruptions eject large quanitities of material into the atmopshere.
• Some of these particles reflect the Sun's rays back out to space, so the Earth's surface cools.
• Volcanoes also release CO2 (a greenhouse gas) but not enough to cause global warming.
• Volcanic activity may cause short - term changes in climate. 

3. Solar output 

• The Sun's output of energy is not constant - it changes in short cycles of about 11 years and possibly also in longer cycles of several hundred years.
• Periods when solar output is reduced may cause the Earth's climate to become cooler in some areas.
• Most scientists think that changes in solar output don't have a major effect on global climate change.

Greenhouse effect - where greenhouse gases, such as CO2 and methane, absorb outgoing heat, so less is lost to space. It is essential for keeping the planet warm.

• Too much greenhouse gas in the atmosphere - too much energy is trapped and the planet warms up.
• Humans are increasing the concentration of greenhouse gases by:

1. Burning fossil fuels

• CO2 is released into the atmosphere when fossil fuels are burnt.

2. Farming 

• Livestock produces a lot of methane.
• Rice paddies contribute to global warming, because flooded fields emit methane.

3. Cement production

• Cement is made from limestone which contains carbon. 
• When cement is produced, lots of CO2 is released into the atmosphere.

4. Deforestation

• Plants remove CO2 from the atmosphere and convert it into organic matter using photosythesis.
• When trees and plants are chopped down, they stop taking in CO2.
• CO2 is released into the atmopsphere when treees are burnt as fuel/ to make way for agriculture.

Environmental effects 

• Warmer temperatures are causing glaciers to shrink and ice sheets to melt.
• Water stored on land as ice returns to the oceans - sea level rise.
• Sea ice is shrinking - loss of polar habitats.
• Rising sea levels means low lying coastal aras will be flooded.
• Coastal erosion will increase with sea level rise.
• Some coastal areas will be submerged - habitats will be lost.
• Species are declining. E.g, coral reefs.
• Precipitation patterns are changing - warming is affecting how much rain areas get.
• The distribution and quantity of some species could change and biodiversity could decrease.
• Some habitats are being damaged or destroyed due to climate change - species that are specially adapted to these areas may become extinct.

Effects on people

• In some places deaths due to heat have increased - but deaths due to cold have decreased.
• Some areas could become so hot and dry that they are difficult or impossible to inhabit. 
• Coastal areas could be lost to the sea - impossible to inhabit. Could lead to migration and overcrowding in other areas.
• Some areas are struggling to supply enough water for their residents due to problems with water availability caused by changing rainfall patterns. Can lead to political tensions, especially where rivers cross borders.
• Climate change is affecting farming. 

- Some crops have suffered.

- Some farmers in high-latitiude countries are finding that crops benefit from warmer conditions.

• Lower crop yields - could increase malnutrition, ill health and death from starvation, particularly in lower latitudes.
• Climate change means weather is becoming more extreme - more money needs to be spent on predicting extreme weather events, reducing their impacts and rebuilding after them.

There are strategies to aim to reduce the causes of climate change by reducing the concentration of greenhouse gases in the atmosphere. 

1. Carbon Capture 

• A new technology designed to reduce climate change by reducing emissions from fossil fuel burning power stations. 
• Involves capturing CO2 and transporting it to places where it can be stored safetly. E.g, underground.

2. Planting trees

• Increases the amount of carbon dioxide that is absorbed from the atmosphere through photosynthesis. 

3. Alternative Energy Production

• Replacing fossil fuels with nuclear power and renewable energy - reducing greenhouse gas emissions from power stations. E.g, wind farms, nuclear power plants.

4. International Agreements 

• Countries agree to monitor and cut greenhouse gases emissions by signing an international agreement - targets.

There are some ways that people are adapting to the effects of climate change.

1. Changing Agricultural Systems

• Changing rainfall patterns and higher temperatures will affect the productivity of existing systems.
• It may be necessary to plant new crop types that are more suitable to the new climate conditions.
• In some regions, biotechnology is being used to create new crop varieties which are more resistant to extreme weather events.

2. Managing water supply

• Dry areas are predicted to get drier, leading to water shortages.
• Water meters can be installed in people's home to discourage them from using a lot of water.
• Rainwater can be collected and waste water can be recycled to make more water available.

3. Coping with rising sea levels

• Physical defences - such as flood barriers - are being built.
• Better flood warning systems are being put in place.
• In areas that cannot afford expensive flood defences, people are building their homes on top of earth embankments and building raised flood shelters to use in emergencies.