What is a greenhouse gas?
They are called greenhouse gases as they produce the same warming effect on our planet that greenhouses have when growing plants. Greenhouses work by trapping heat – the glass panels of the greenhouse let in light but stop heat escaping. This causes the greenhouse to heat up and keeps the plants warm enough to live in the winter.
Greenhouse gases in the atmosphere behave similarly to the glass panes in a greenhouse. Sunlight enters the Earth’s atmosphere, passing through the greenhouse gases. Some of the sunlight’s energy that reaches the Earth’s surface is absorbed by the land, water, and the biosphere. Once absorbed, some of this energy is sent back into the atmosphere as infra-red radiation. Some of this radiation passes back into space, but much of it remains trapped in the atmosphere by the greenhouse gases, and causes our world to heat up.
What is the greenhouse effect?
The greenhouse effect is the rise in temperature that the Earth experiences because of the presence of greenhouse gases (e.g. water vapour, carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4)) in the atmosphere that trap energy from the sun. Without these gases, Earth’s average surface temperature would drop from around 14°C to about minus18°C.
Where do greenhouse gases come from?
Greenhouse gases are naturally present in the atmosphere. Carbon dioxide (CO2) and water vapour are the most common greenhouse gases and these help keep our planet liveable and at a temperature for life to flourish on Earth. However, as we pump more greenhouse gases, particularly carbon dioxide, into the atmosphere, the greenhouse effect becomes stronger. More heat is trapped, and the Earth’s climate begins to change unnaturally.
CO2 is emitted in a number of ways. It is emitted naturally through the carbon cycle and through human activities like the burning of fossil fuels.
The whole natural carbon cycle. Showing the six main global reservoirs of carbon. The boxed numbers are the sizes of the reservoirs in 1012 kg
Natural sources of CO2 occur within the carbon cycle where trillions of tonnes (that is 1012) of atmospheric CO2 are removed from the atmosphere by oceans and growing plants, also known as ‘sinks’, and are emitted back into the atmosphere annually through natural processes also known as ‘sources’. When in balance, the total carbon dioxide emissions and removals from the entire carbon cycle are roughly equal.
Since the start of the industrial revolution, the amount of 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.
Sources of greenhouse gases in the UK:
- 4% of emissions come from industry
- 7% are from agriculture – for example methane emissions from livestock, manure and chemical fertilisers
- 21% are from transport
- 65% comes from the burning of fuel to generate energy (excluding transport)
About 40% 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:
- the energy you use in your home (the main use is heating)
- air travel
Other things in people’s homes contribute to climate change indirectly. Everything, from furniture to computers, from clothes to carpets – these all use energy to be produced and transported, and this in turn causes emissions to be released.
What are the differences between greenhouse gases and air pollutants?
The main differences between greenhouse gases and air pollutants are how they affect our health and the environment.
- Air pollutants like sulphur dioxide and ozone have direct effects on our health when we breathe them in;
- Greenhouse gases have always been present in the atmosphere at levels that do not affect our health, but as humans produce more and more, they increase the natural greenhouse effect;
- The main problems caused by air pollution occur close to the ground, such as soiling of buildings and producing health effects, but greenhouse gases affect the whole of the atmosphere.
What is my carbon footprint?
A ‘carbon footprint’ is the total set of greenhouse gas emissions caused directly and indirectly by an individual, organization, event or product. The term ‘carbon footprint’ is very commonly heard nowadays, but the correct scientific term for what we are talking about is Carbon Dioxide or C02. Carbon footprint is a shorthand way of talking about CO2 footprint / emissions. You can calculate your CO2 footprint here