Posted on July 31st, 2008
1. Carbon Dioxide (CO2)
“Since about the year 1750 according to analysis of ice core samples we have been tipping a balance that stood for 10,000 years, or since the last ice age. Without any CO2 in our atmosphere the planet would freeze. The concentration that has allowed life as we’ve known it to flourish is between 260 and 280 parts per million. We are now taking that number higher.”1 The global mean mixing ratio reached a new high of 391.19 ppm in January 2011, representing an increase of 2.74 ppm over the previous year. This ratio corresponds to 146.7% of the lower and 136.25% of the higher range pre-industrial level. The global growth rate varies significantly annually, and was 2.0 ppm/year on average for the 10-year period from 1998-2007. An El Niño event will amplify the yearly effect. A large enough volcanic event by increasing atmospheric dust and reducing sunlight reaching the Earths surface, will create negative values. Our atmospheric contains levels of CO2 that account for over 80% of global warming pollution. Today’s levels are higher than at any time in the past 420,000 years. It’s no insignificant fact that the 10 warmest years globally since 1856 have occurred in the last 15 years. Everything CO2 based, (coal, oil, gas) adds to the man made problem of global warming. Industrialized use of, (coal, oil, gas) in western countries contributes to 97% of their CO2 contributions. That’s about 800 tons a second or 25 billion tons a year.
2. Methane (CH4)
CH4 is the second most significant greenhouse gas; its level has increased since the beginning of the 19th century. The 2003-2004 global mean mixing ratio was 255% of the pre-industrial level. The 2002/2003 El Niño event and other events like it created spikes in yearly variations. There are large deposits of CH4 frozen in the ocean floor. Scientists estimate a rise in global ocean temperatures of four degrees will begin a release of the ocean bed CH4. Methane is explosive and as a greenhouse gas 26 times more potent than CO2. If you release enough of the frozen or trapped global CH4into the atmosphere a possible lightning strike over a city blanketed by a Methane concentration could be more devastating than a nuclear bomb. As the tundra in arctic regions thaws vast amounts of CH4 are being released. In tropical regions dam project reservoirs produce CH4. the hotter the year the more CH4 is produced. Capture strategies for further energy production are being studied. Dovetailing efforts into slowing the need for new usage strategies sounds like a better first step.
3. Nitrous Oxide (N2O)
A stratospheric regulator of ozone, this gas has 298 times more impact when considered over a 100-year period, than CO2. The direct human activity of agriculture, nitrogen fertilizers, and waste from animal husbandry, and industrial sources accounts for little more than 13%. Bacteria in the soil is responsible for most of the (N2O).Despite low concentration (N2O) follows carbon dioxide, methane, and water vapour as the fourth largest contributor to global warming and is one of the major gases. Control protocols are being formulated to curb greenhouse gas emissions under the Kyoto Protocol.
Halocarbons where found to be responsible for the depletion of the ozone level and where replaced under the Montreal Protocol with HCFCs.CFC-11 started decreasing around 1992. CFC-12 growth has almost stopped. CFC-113 growth stopped in the early 1990s and is decreasing slowly. CH3CCl3 Peaked around 1992 and is now decreasing. HCFCs (the industrial replacements of CFCs) are increasing at a rapid rate. We now know, Although HCFCs do not deplete the ozone layer they are a contributor to global warming.
5. Surface Ozone (O3)
Some of the O3 in the troposphere comes from the stratosphere; the rest is chemically produced in the troposphere through oxidation of CO or hydrocarbons in the presence of rich NOx. Seasonal and inter-annual global trends are hard to identify. Through radiating and chemical processes it absorbs UV radiation in the stratosphere, creates a temperature profile and with its absorbed energy circulates the atmosphere. Because it also absorbs IR radiation it is also a greenhouse gas.
6. Carbon Monoxide (CO)
It is not a greenhouse gas yet affects greenhouse gases by affecting hydroxyl radicals (OH). Mixing ratios have been increasing since the mid 19th Century. Seasonal cycles are driven by biomass burning, industrial emissions, world transportation fuel use, and seasonal changes in OH.
7. Nitrogen Monoxide (NO) and Nitrogen Dioxide (NO2)
Nitrogen oxides (NOx, i.e. NO and NO2) are not greenhouse gases; yet affect greenhouse gases by affecting OH. In the presence of NOx, CO and hydrocarbons are oxidized to produce ozone (O3), which affects the Earth’s radiating balance as a greenhouse gas and the oxidization capacity of the atmosphere by reproducing OH. NOx has large temporal and geographic variability, and it is difficult to identify a long-term trend.
8. Sulphur Dioxide (SO2)
Sulphur dioxide (SO2) is not a greenhouse gas but a precursor of atmospheric sulphate (H2SO4) aerosol. Produced by SO2 oxidation through photochemical gas-to-particle conversion we get sulphate aerosol. SO2 has also been a major source of acid rain throughout industrial times.
- Reginald Cottle: The Burden of Climate Responsibility ↩