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Environment and greener living
Causes of climate change
There is very strong evidence that people are changing the climate with actions which create emissions of greenhouse gases like carbon dioxide and methane. In the UK, 40 per cent of these emissions are caused by individuals, mostly from energy used in the home, driving and air travel.
Natural causes or human activity?
Human activity is the main cause of the changes seen in climate
The world's climate varies naturally as a result of:
- the way the ocean and the atmosphere interact
- changes in the earth's orbit
- changes in energy received from the sun and volcanic eruptions
However, there is now strong evidence and almost universal agreement that significant global warming can’t be explained just by natural variations. The changes seen over recent years, and those predicted for the next 80 years, are thought to be mainly as a result of human behaviour.
The Intergovernmental Panel on Climate Change (IPCC) is a scientific body set up by the UN to look at climate change. It says that human activity is the main cause of the changes seen in climate.
The greenhouse effect
The earth is surrounded by a layer of gases which act like the glass walls of a greenhouse. These gases let the sun’s rays enter, but stop much of the heat from escaping. This is a natural process, and it’s these ‘greenhouse gases’ (mainly carbon dioxide and water vapour) that keep the planet warm enough to sustain life.
However, as humans cause more greenhouse gases to be released into the atmosphere, the greenhouse effect becomes stronger. More heat is trapped and the earth's climate begins to change unnaturally.
Since the Industrial Revolution, which began in the 18th century, the amount of carbon dioxide (CO2) in the atmosphere has increased by 35 per cent. In fact, the concentration of CO2 is now higher than at any point in the past 650,000 years.
Why greenhouse gases have increased
Deforestation produces 18 per cent of global CO2
Human activity is changing the amount of greenhouse gases in the atmosphere in three important ways:
1. Forests are being cut down
Trees absorb carbon dioxide so, with fewer trees, more carbon dioxide builds up in the atmosphere. Also, the agriculture and industry that replaces the forests can often be a source of emissions. The Intergovernmental Panel on Climate Change (IPCC) estimates that deforestation produces 5.9 billion tonnes of CO2 per year or 18 per cent of global CO2.
2. Fossil fuels are being burned
Burning fossil fuels like coal, oil and gas - to generate heat or to power transport for example - releases greenhouse gases. In 2005, burning fossil fuels emitted about 27 billion tonnes of carbon dioxide.
3. The world’s population is growing
A growing population is leading to an increased demand for food, livestock and energy, which is in turn leading to increased emissions.
The main contributors to climate change in the UK
In the UK, around:
- 4 per cent of emissions come from industrial processes
- 7 per cent are from agriculture – for example methane emissions from livestock and manure, and nitrous oxide emissions from chemical fertilisers
- 21 per cent are from transport
- 65 per cent come from the use of fuel to generate energy (excluding transport)
About 40 per cent of emissions in the UK are the result of decisions taken directly by individuals. The biggest sources of emissions for most people are likely to be:
- energy use in the home (the main use is heating)
- driving
- air travel
Other things in people's homes contribute to climate change indirectly. Everything, from furniture to computers, from clothes to carpets, uses energy when it is produced and transported – and this causes emissions to be released.
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