SHIFT IN TEMPERATURE

GHG emissions have been rising since industrialization in the 1900s, due to increased burning of fossil fuels. Further significant increases in GHG levels are expected, particularly as developing countries become more industrialized. Based on present trends, the IEA World Energy Outlook predicts a 53 percent increase in global primary energy demand by 2030, with 70 percent of that coming from developing countries. The EU has defined dangerous climate change as an increase in 2 degrees Celsius of average global temperatures. Since 1900, global temperatures have risen by 0.7 degrees Celsius and are continuing to rise at an estimated rate of 0.2 degrees per decade. If left unchecked, this implies global warming of at least 1.4 degrees Celsius. Future emissions of greenhouse gases will raise temperatures by 1.4 to 5.8 degrees Celsius during this century.

FACTORS RESPONSIBLE FOR THE SHIFT IN TEMPERATURE

Certain gases in the atmosphere block heat from escaping. Gases that contribute to the greenhouse effect (shift in temperature) include:

• Water vapor. The most abundant greenhouse gas, but importantly, it acts as a feedback to the climate. Water vapor increases as the Earth’s atmosphere warms, but so does the possibility of clouds and precipitation, making these some of the most important feedback mechanisms to the greenhouse effect.

• Carbon dioxide (CO₂). A minor but very important component of the atmosphere, carbon dioxide is released through natural processes such as respiration and volcano eruptions and through human activities such as deforestation, land use changes, and burning fossil fuels. Humans have increased atmospheric CO₂ concentration by a third since the Industrial Revolution began. This is the most important long-lived “forcing” of climate change.

• Methane. A hydrocarbon gas produced both through natural sources and human activities, including the decomposition of wastes in landfills, agriculture, and especially rice cultivation, as well as ruminant digestion and manure management associated with domestic livestock. On a molecule-for-molecule basis, methane is a far more active greenhouse gas than carbon dioxide, but also one which is much less abundant in the atmosphere.

• Nitrous oxide. A powerful greenhouse gas produced by soil cultivation practices, especially the use of commercial and organic fertilizers, fossil fuel combustion, nitric acid production, and biomass burning.

• Chlorofluorocarbons (CFCs). Synthetic compounds of entirely of industrial origin used in a number of applications, but now largely regulated in production and release to the atmosphere by international agreement for their ability to contribute to destruction of the ozone layer. They are also greenhouse gases On Earth, human activities are changing the natural greenhouse. Over the last century the burning of fossil fuels like coal and oil has increased the concentration of atmospheric carbon dioxide (CO₂). This happens because the coal or oil burning process combines carbon with oxygen in the air to make CO₂. To a lesser extent, the clearing of land for agriculture, industry, and other human activities have increased concentrations of greenhouse gases

Variation in CO2 during the past 400000 years