Think of a car left in the sun on a hot day. As you know, unless the windows are open, the temperature inside the car soon rises to an unbearable temperature. In the case of the earth, certain natural and human-made gases – greenhouse gases (GHGs) – act like the windows of the car; the more of them that are released into the atmosphere, the more heat is trapped and the hotter the planet becomes.

Carbon dioxide and greenhouse gases

The major GHGs are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and chlorofluorocarbons (CFCs). The increasing atmospheric CO2 concentration is likely the most significant cause of global warming resulting increased climate variability (increased variance in weather patterns and incidence of extreme events) and climate change (long-terms change and shifts).

Human Activity and greenhouse gases

Much of the world’s economy is underpinned by carbon – the ‘fuel’ in fossil fuels. Coal, oil, and natural gas contribute energy to the majority of human activities in industrialised nations, and carbon dioxide (CO2) is a by-product of burning these fuels. Reducing CO2 emissions rapidly is difficult because to do so means major restructuring to the way that the industrial world operates. Other GHGs such as Chlorofluorocarbons (CFCs) also play a major role in industrial processes such as air conditioning.

Livestock and agriculture

Methane is the second most significant GHG and cause of climate change, and unit for unit is 21 times more damaging than CO2 (over a 100 years lifespan). A major source of methane comes from livestock and specifically cattle, which produce by digesting grass and exhale it through their breath.

Methane is also by-product of rice-growing, a considerable impact given that rice is a major staple food for a large part of the world’s population (366,921,000 metric tons of rice was consumed in 2007). Other GHG emissions resulting from agriculture include N2O which is released as a by-product of the application of fertilisers.

Land use change and deforestation

The major changes to the planet’s land cover since 1750, have resulted from deforestation in temperate regions where forests and woodlands have been cleared to make room for fields and pastures. More recently, deforestation has been rapidly taking place in tropical regions where economic development has come at the expense of conservation, and much of the world’s natural rainforests have given way to palm oil plantations, cattle pastures or the logging industry.

Deforestation accounts for 20% – 25% of global greenhouse gas emissions, making it the most significant source of emissions in developing countries. If these emissions are not reduced, they have the potential to undercut reductions in industrial and energy emissions. Deforestation also has significant negative impacts on soil quality, biodiversity, local livelihoods and indigenous communities. Despite the negatives impacts of deforestation, creating incentives to mitigate this source of emissions from developing countries has not been adequately addressed in either the UN Convention on Climate Change (UNFCCC) or the Kyoto Protocol.

Another major source of emission from land use change is through the degradation and harvesting of peat bogs. Peat is an accumulation of partially decayed vegetation matter. By volume there are about 4 trillion m³ of peat in the world covering a total of around 2% of global land mass. To date, about 7% of total peat lands have been exploited for fuel, agriculture and forestry. At 106 g CO2/MJ, the carbon dioxide emissions released through burning peat are higher than those of coal (at 94.6 g CO2/MJ) and natural gas (at 56.1).

Positive feedback or amplifiers

Factors that result from climate change and that can then amplify the causes of climate change are known as “positive feedbacks.” Some of the key positive feedbacks include thawing of permafrost (resulting in the release of previously trapped methane), forest loss due to drought (resulting in the release of carbon sequestrated in the wood) and the melting of the polar ice-caps (resulting in a reduced capacity to reflect solar energy from the earth’s surface).