Since pre-industrial times, the atmospheric concentration of greenhouse gases has grown significantly. Carbon dioxide concentration has increased by about 31%, methane concentration by about 150%, and nitrous oxide concentration by about 16% (Watson et al 2001). The present level of carbon dioxide concentration (around 375 parts per million) is the highest for 420,000 years, and probably the highest for the past 20 million years.
Central to any study of climate change is the development of an emissions inventory that identifi es and quanti- fies a country’s primary anthropogenic sources and sinks of greenhouse gas. The IPCC has prepared guidelines for compiling national inventories. The major greenhouse gases are included within six sectors: Energy; Industrial Processes; Solvent and Other Product Use; Agriculture; Land Use Change and Forestry; and Waste.
Emissions are not usually monitored directly, but are generally estimated using models. Some emissions can be calculated with only limited accuracy. Emissions from energy and industrial processes are the most reliable (using energy consumption statistics and industrial point sources). Some agricultural emissions, such as methane and nitrous oxide carry major uncertainties because they are generated through biological processes that can be quite variable.
Contributing to emissions
Historically the developed countries of the world have emitted most of the anthropogenic greenhouse gases. The U.S. emits most in total, and is one of the countries with highest emissions per capita. China is the second largest emitter, but has very low emissions per capita. Over the last 20 years, industrial development has led to a rapid rise in the volume of emissions from Asia, but on a per capita basis, emissions in this region are still at the bottom of the global scale.
The people of the Arctic have numerous words for ice, but in the future perhaps they won’t need so many. Results of an Arctic Climate Impact Assessment (ACIA) demonstrate the reality of global warming in the polar region. The Inuits believe there is sufficient evidence to demonstrate that the failure to take remedial action to stop global warming by reducing emissions constitutes a violation of their human rights – specifi cally the rights to life, health, culture, means of subsistence, and property (Watt-Cloutier 2004).
Emissions from air traffic represent 3.5% of the global CO2 emissions. Aircraft causes about 3.5% of global warming from all human activities according to a special report from IPCC (Penner et al 1999). Because the enormous increase in travels done by aircraft, the same report predicts that greenhouse gas emissions from aircraft will continue to rise and could contribute up to 15% of global warming from all human activities within 50 years. Still emissions from international air traffic are not controlled by the Kyoto Protocol.