Human Causes

The Greenhouse Effect

Some gases in the Earth’s atmosphere stop heat radiating into space from the Earth. This is called the greenhouse effect and the gases involved are called greenhouse gases. 
Radiation from the Sun passes through the Earth’s atmosphere.
The Earth absorbs radiation with short wavelengths and so warms up. Heat is radiated from the Earth as longer wavelength infrared radiation.
Some of this infrared radiation is absorbed by greenhouse gases in the atmosphere.
The atmosphere warms up.

The Enhanced Greenhouse Effect

Human activities are causing the release of large amounts of Greenhouse gases, particularly carbon dioxide. 
As the percentage of carbon dioxide in the atmosphere has increased, so in general has the Earth’s mean temperature.

The Greenhouse Effect

Global Warming

Human Cause - Greenhouse Gases

Carbon Dioxide (CO₂)

Methane (CH₄)

Nitrous Oxides (N₂O)

Chlorofluorocarbons (CFC’s)

Hydrofluorocarbons (HFC’s)

Sulphur hexafluoride (SF₆)

There are 6 main Greenhouses gases, but the most important ones are the first three.
The amount of these gases have all been increasing in our atmosphere due to human factors.

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Carbon Dioxide (CO₂)

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Burning fossil fuels, for example coal, oil and natural gas release Carbon Dioxide into the atmosphere. These has been used increasingly to generate electricity in power stations and to heat homes.

Deforestation, especially in the Amazon Rainforest, has resulted in more carbon dioxide being released when trees are burnt.

With fewer trees there is less photosynthesis so less CO² is captured by vegetation. 

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Methane (CH₄)

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21 times as effective in trapping heat than CO2.

Methane is produced when organic material is broken down anaerobically, without oxygen. This can happen in the following ways:

In landfill sites as waste / vegetation decomposes.
In padi fields when the rice plants are left to rot after they have been harvested.
In the stomachs of cows as they digest grass and then released as they belch and fart.
When permafrost melts the methane trapped in the ground for thousands of years can continue to biodegrade and is able to escape into the atmosphere. 

Nitrous Oxides (N₂O)

310 times more effective in trapping heat than Carbon Dioxide. 

The largest source is agriculture and the majority of agricultural emissions result from nitrogen fertilisers of agricultural soils (87 percent of the agriculture total). When too much nitrogen feritsier is put on the farmland it can react with the rain and atmosphere and turn into nitrous oxide.

Nitrous Oxide is also released from vehicles especially diesel cars / lorries.

F-Gases

SF6 - 23,500 time more potent than CO2 at trapping heat. It also lasts in the atmosphere for approx. 1000 years.

It is a cheap and non-flammable, SF6 is a colourless, odourless, synthetic gas. It makes a hugely effective insulating material for medium and high-voltage electrical installations.
It is widely used across the industry, from large power stations to wind turbines to electrical sub-stations in towns and cities. It prevents electrical accidents and fires.

SF6

Human Causes of Greenhouse Gases

Growth of the global population but mostly an increase in wealth means more people need food especially an increase in meat production. Growing demand for heating and electrical supply as well as cars and transport have also increased these gases.

Video: Human causes of climate change

Global Climate Change 2

Diagram Q2: Global air temperatures 1850—2011

Explain the human activities which have contributed to the changes in global air temperatures.
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Global Effects

Sea level rises caused by an expansion of the sea as it becomes warmer, and also by the melting of glaciers and ice caps in Greenland and Antarctica. When ice melts in the Arctic Sea it does not effect the sea level as the ice displaces the same volume of water it releases but when ice on Greenland melts it turns to water and flows into the Atlantic rising the sea levels.

Climate change: Why are sea levels rising? - CBBC Newsround

Low–lying coastal areas, e.g. Bangladesh affected with large-scale displacement of people and loss of land for farming and destruction of property