Which human activities cause climate change and why?
|1. Living things absorb carbon dioxide (also called CO2) from the atmosphere.||2. The living things die and and begin to decay.||3. Sometimes the remains of the living things sink into the ground and become compressed.||4. After millions of years the plant and animal remains become coal or oil. These fossil fuels are mined or pumped out of the ground.||5. When the fuels are used the carbon dioxide (CO2) returns to the atmosphere . But it takes much longer to make fossil fuel than to use it!|
In 2004 emissions totalled 49 gigatonnes of carbon dioxide or equivalent (Gt CO2-eq). That's 49 thousand million tonnes being pumped into the atmosphere every 365 days.
Human induced climate change is caused primarily by the burning of fossil fuels and by deforestation, both of which increase the atmospheric concentration of greenhouse gases in the atmosphere. The main greenhouse gas is carbon dioxide (CO2); other greenhouse gases include methane (CH4 ) and nitrous oxide (N2O). For an explanation of the greenhouse effect, click here.
Breakdown of UK emissions
A breakdown of UK emissions
- Between 1980 and 2005 the number of cars in the UK increased by 78% to 27.5 million. The average four person family owns two or three cars.
- Aviation emissions account for at least 9% of UK greenhouse effect.
- More than 30% of the trips made by cars in Europe are for less than 3km and 50% for less than 5km.
- Emissions from homes are responsible for an estimated 27% of the UK's total carbon emissions.
- A report by the Energy Saving Trust predicts that by 2010 the UK could waste up to £11 billion annually and emit around 43 million tonnes of carbon dioxide through wasted energy, such as leaving lights on and appliances on standby.
- Although gains in energy efficiency have been made by many individual appliances, the resulting energy savings have been more than offset by the increasing numbers of appliances. Between 1972 and 2002 electricity consumed by household domestic appliances doubled from 44TWh to 89TWh and is forecast to rise a further 12% by 2010.
- Standby power consumption accounts for 2.25% of electricity production.
Deforestation - why does this produce greenhouse gas emissions?
Cutting down forests accounts for 20% of global emissions.
- Mature forests store enormous quantities of carbon, both in the trees and vegetation itself and within the soil in the form of decaying plant matter.
- When trees are cut down or burnt, the stored carbon is released into the atmosphere.
- We are destroying forests at an alarming rate: global forest cover is currently around 3952 million hectare (30% of the world's land area). Between 2000 and 2005 the net loss of forest was 7.3 million hectares per annum, with the largest losses in South America, Africa and Southeast Asia. Deforestation is such a problem that Indonesia and Brazil are now the third and fourth largest emitters of carbon dioxide on the planet.
Aviation - why does aviation do so much damage?
- In 2002 global aviation amounted to 480 megatonnes of CO2, accounting for around 2% of total CO2 emissions. However the overall climate impact of aviation is estimated to be two to four times greater than this: as well as emitting CO2 aircraft emit nitrogen oxides which are particularly effective in forming the greenhouse gas ozone when emitted at cruising altitudes. Aircraft also trigger the formation of condensation trails which are suspected of enhancing the formation of cirrus clouds, which add to the global warming effect.
- In 2005 agriculture accounted for an estimated emission of 5.1 to 6.1 GtCO2-eq. CH4 contributed 3.3 GtCO2-eq and N2O 2.8 GtCO2-eq.
- The absolute area of global arable land is around 1400 million hectares, an overall increase of 8% since the 1960s. A further 500 million hectares are expected to be converted to agriculture by 2020, mostly in Latin America and Sub-Saharan Africa.
- Food demand is a dominant land-use driver, and population and economic growth are the most significant food demand drivers. Total world food consumption is expected to increase by over 50% by 2030. Per person meat consumption is also expected to increase, in the order of 25% by 2030, with corresponding increases in overall food and livestock feed demands. Additional cropland is expected to be required to support these projected increases in demand.
Which countries are driving greenhouse gas emissions?
- The industrialized world (UNFCCC Annex I countries) represents 20% of the global population, produces 57% of global GDP, and accounts for 46% of global GHG emissions.
- In the US and Canada on average each person emits 26 tonnes of CO2-eq per year. In the UK the average is 14 tonnes per person. This compares to 3 or 4 tonnes per head in the developing world. Imagine what would happen if the developing world adopted the Western lifestyle.