Greenhouse gases emissions: is the world in danger?
Background
The greenhouse gases are the gases in the atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and ozone (O3), also indirect greenhouse gases such as SO2 and CO. It is important to know that without greenhouse gases, the average temperature of Earth's surface would be about −18 °C rather than the present average of 15 °C.
Human activities since the beginning of the Industrial Revolution (taken as the year 1750) have produced a 40% increase in the atmospheric concentration of carbon dioxide, from 280 ppm in 1750 to 400 ppm in 2015 it means that the atmospheric concentrations of carbon dioxide are currently 120 ppm higher than pre-industrial levels. This increase has typically occurred from the combustion of carbon-based fuels, principally coal, oil and natural gas in the range of 82% for electricity and heat and 18% come from deforestation. It has been estimated that if greenhouse gases emissions continue at the present rate, Earth's surface temperature could pass a threshold of 2°C global warming, which the United Nations' IPCC designated as the upper limit for "dangerous" global warming, by 2036.
CO2 the greatest threat
Although CO2 is a weaker greenhouse gas than methane; but it has a longer lifetime (The atmospheric lifetime of CO2 is estimated of the order of 30–95 years, while CH4 has an atmospheric lifetime of 12 ± 3 years. So that increase in the concentration of carbon dioxide in the atmosphere is so significant. In fact, the direct contribution to the greenhouse effect, of CO2 is about 9–26% while for CH4 is about 4–9%. The sources of the most atmospheric concentration of CH4 are termites, each termite produces, on average, about half a microgram of methane per day, a seemingly insignificant amount. However, when this is multiplied up by the world population of termites, global methane emission from this source is estimated to be about 150 million tons of methane a year. Oil and natural gas wells and gas pipelines leakage also are sources of atmospheric methane.
Other viewpoints
Although the public has been led to believe that increased carbon dioxide from human activities is causing a greenhouse effect that is heating the planet, but also the public is facing to the other opinions. It is said that the overwhelming majority (97%) of carbon dioxide in the earth's atmosphere comes from nature, not from man. Volcanoes, swamps, rice paddies, fallen leaves, and even insects and bacteria produce carbon dioxide, as well as methane. According to the journal Science (Nov. 5, 1982), termites alone emit ten times more carbon dioxide than all the factories and automobiles in the world. It is said that during the Ordovician Period, the carbon dioxide level was 12 times what it is today, and the earth was in an Ice Age, and during the time of the dinosaurs, the carbon dioxide levels were 300–500% greater than today.
For energy development, especially for provision of electricity, the world needs numerous energy sources, and at this period the best energy sources and technologies are as follows:
• Hydroelectric
• Ocean Energy
• Wind
• Nuclear
• Biomass
• Solar thermal
• Geothermal
• Oil derivatives
• Coal
• natural gas
Conclusion
Considering the fossil fuel, natural gas is often described as the cleanest fossil fuel. It produces about 29% and 44% less carbon dioxide per joule delivered than oil and coal respectively. However, in absolute terms, it comprises a substantial percentage of human carbon emissions, and this contribution is projected to grow. According to the IPCC Fourth Assessment Report, in 2004, natural gas produced about 5.3 billion tons a year of CO2 emissions, while coal and oil produced 10.6 and 10.2 billion tons respectively. Therefore it seems if demand for natural gas would be increasing in comparison with coal and oil the CO2 emission will be declined. Also will be new ideas and technology to fix and solve the problem of greenhouse gases level in the atmosphere. In this case, the role of the other non-fossil energy sources in energy development is so important and vital.
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