Global warming and climate change – the causes

Temperatures are rising

Starter: What is ‘climate change’? What three words do you think of when someone says ‘climate change’? In pairs write these words down on a post-it- note and stick it onto the board.

Key words Global Warming: the worldwide warming of the atmosphere. Global Climate Change: The changes in global patterns of rainfall and temperature, sea level, habitats and the incidences of droughts, floods and storms, resulting from changes in the Earth’s atmosphere, believed to be mainly caused by the enhanced greenhouse effect.

What has happened to our climate over time? Stick the graph of the world’s temperature since 8,000BC into your book – what does it show? Using the graph answer the following questions: 1.In the past 10,000 years, when was the world’s temperature at its highest? (1 mark) 2.Describe the climate change in the past 10,000 years. Use data in your answer. (4 marks)

Self Assessment 1. 4,000BC 2. Point marked – allow a maximum of three if no data is used. -The lowest temperature was 10,000 years ago (1) when it was 5 degree Celsius lower than now (1) -After the last ice age the temperature rose rapidly (1) for 1,200 years (1) -The climate has fluctuated (gone up and down) (1) -There have been warm and cold periods (1) -The temperature since the last ice age has increased by 6 degree Celsius (1) -In the past 100 years the temperature has begun to rise steadily (1)

How do we know the climate has changed? Ice Cores Fossil / Pollen Analysis Dendrochronology Historical Analysis We’ve only been able to use technology (thermometers) to measure temperature since 1861 so how do we know the climate has changed?

What are Milankovitch Cycles?

What are the natural causes of climate change? The causes of long-term climate change can be external (from space), or internal, from the ocean, land and atmosphere -Solar Output -Orbital Geometry -Volcanic Activity -Surface Reflection

Human (anthropogenic) causes of global warming and climate change Deforestation Use of fossil fuels Air pollution Agricultural change CFCs There are other human causes as well – however these are the ones you are required to study for your exam

The Earth’s Atmosphere Sun’s energy heats up the Earth’s surface (insolation or solar radiation) Some of this heat is reflected (or ‘bounces’) off the Earth back into space (infrared emission) The natural greenhouse effect

The Earth’s Atmosphere Greenhouse gases limit the amount of heat energy that can ‘bounce’ back up into space Greenhouse gases – Any gas that absorbs infra-red radiation in the atmosphere, e.g. carbon dioxide (or monoxide), nitrous oxide, methane, chloro-fluro carbons (CFCs) etc.

The Earth’s Atmosphere The sun continues to heat the Earth but a lot of the heat energy cannot ‘escape’ out into space – it becomes trapped due to the greenhouse gases that have built up. The Earth begins to warm up like a greenhouse The enhanced greenhouse effect

What trends can you see? Percentage of Carbon dioxide in the atmosphere Global average temperature (5 year average) The trend shows that….

Use your knowledge and page 15 of the atlas to annotate your diagram, to describe different types of greenhouse gases as well as what causes them

Exam Question: Explain why higher levels of greenhouse gases cause a rise in global temperatures (4 marks). 10 minutes Level 10-1 marks Identify at least one major greenhouse gas and add something about how they have increased in recent years. Level 22 marks Explain how the rise of greenhouse gases traps more solar radiation causing temperatures to rise. Level 33-4 marks Explains that the solar radiation is trapped by greenhouse gases as it is radiated back from the ground surface, heating the atmosphere from below. Also that rising temperatures increase temperatures further e.g from changes in the surface reflection.

The future? What do you think will happen to greenhouse gas emissions in the future? Think about population growth and economic development. 5 minutes

Human (anthropogenic) causes of global warming and climate change Deforestation Use of fossil fuels Air pollution Agricultural change CFCs There are other human causes as well – however these are the ones you are required to study for your exam

How does human activity affect global warming and climate change? Human activity How does it affect global warming and climate change? Deforestation Use of fossil fuels Air pollution Agricultural change Chloro-fluro carbons (CFCs) Name: