Global warming

The Earth receives energy from the Sun and absorbs it through its surface. The Earth’s surface radiates infrared energy that is absorbed by the greenhouse gases which, in turn, radiate energy both upward, into Space, and downward back to the Earth’s surface. The surface of the Earth is warmed by that part of the energy which is radiated back to its surface.

This mechanism makes life on Earth possible but if greenhouse gases are concentrated to the extent that less energy escapes to Space and more energy is radiated downward to the Earth, the surface of the Earth heats proportionately. The most abundant of all greenhouse gases is carbon dioxide and it is the concentration of this gas which is of greatest concern.

The surface temperature of the Earth

The world’s leading scientific body for the assessment of global warming is the Intergovernmental Panel on Climate Change (IPCC). Established by the United Nations and the World Meteorological Organisation, the IPCC reviews the most recent scientific, technical and socio-economic information contributed by scientists throughout the world, and issues regular reports. By contributing to, and endorsing, IPCC reports, governments acknowledge the authority of their scientific content.
According to the IPCC’s latest report, global surface temperature increased by almost 1o Centigrade in the 20th century and is forecast to increase by a further 1.1oC to 6.4oC during the 21st century. Increases of this higher magnitude will cause sea levels to rise, and the retreat of glaciers, permafrost and sea ice, with warming being the strongest in the Arctic. Other likely effects will be extreme weather conditions, species extinction and mass migration of people.

However, a more recent study in September 2009, prepared for the UK Department of Energy and Climate Change by scientists at the Meteorological Office, warns that a catastrophic 4oC rise in temperature could happen by 2060 without strong action on emissions.

The effect of human activities

There is almost universal recognition that there is an atmospheric concentration of greenhouse gases resulting in global warming, and there is general agreement that it is caused by human activities.
The IPCC has concluded that the concentration of greenhouse gases is primarily the result of fossil fuel burning and deforestation. The most abundant greenhouse gas is carbon dioxide (CO2). From the start of the Industrial Revolution in the mid 18th century until the present day, its concentration in the atmosphere has risen by 100 parts per million (ppm) to 380ppm – a 36% increase. The first 50ppm increase took place over about 223 years from 1750 to 1973; however, the second 50ppm increase took place over just 33 years from 1973 to 2006. The concentration of CO2 in the atmosphere is not just increasing – it is accelerating.

This has been borne out by a recent report from the UN Environment Programme which said that emissions since 2000 have risen faster than even the IPCC worst-case scenario.

CO2 concentration is at its highest level, according to ice core samples, than at any time in the last 800,000 years. There is also evidence to show that the last time CO2 concentration was at its current level was approximately 20 million years ago.

Road vehicles are responsible for a fifth of the UK’s CO2 emissions
Road transport is a major source of ‘man-made’ CO2 emissions. In the European Union, road transport is responsible for some 20% of all CO2 emissions, with passenger cars contributing about 12%. In Britain, 19% of the nation’s CO2 emissions come from road vehicles. On a global scale, the burning of transportation fuels account for 14% of annual greenhouse gas emissions. This is the third largest source (after power stations and industrial processes). If we take carbon dioxide emissions in isolation, transportation fuels represent almost 20% of the total (again, after power stations and industrial processes).