The 5 major greenhouse gases are carbon dioxide, methane, nitrous oxide, CFC-12, and CFC-11. 

Greenhouse Gases
Greenhouse gases in the atmosphere are similar to the glass covering a greenhouse. That is, they allow short
wavelength solar radiation to pass through the atmosphere to reach the earth's surface, but absorb the longer wavelength heat that is radiated back into the atmosphere from the earth. The concentration of greenhouse gases in the atmosphere thus has an effect on the average temperature at the surface of the earth. If the atmospheric concentration of greenhouse gases decreases over time, then more heat will escape through the atmosphere, and the average temperature at the earth's surface will go down. If the greenhouse gas concentration in the atmosphere increases, however, less heat will escape to outer space and the average temperature at the earth's surface will increase.

• Carbon Dioxide
• Sources of Carbon dioxide (CO₂)
  

  • Combustion of any organic fuel (wood, natural gas, fuel oil, coal, etc.)

  •  decomposition and decay of dead plant and animal matter. 

  
  

  

  Some of the carbon dioxide from the atmosphere is taken up by plants through photosynthesis; some is absorbed by the ocean waters, and some is absorbed in soil. Currently however, we're putting carbon dioxide into the atmosphere faster than it is coming out. Based on measurements that were initiated in the latter half of the 20th century, carbon dioxide levels in the atmosphere have increased from about 270 ppm before the beginning of the industrial revolution in the mid-1700s to about 380 ppm today. As shown, carbon dioxide in the atmosphere is responsible for 55% of the greenhouse effect.

• Methane

  Methane (CH₄) is the main component of natural gas, which is widely used as a fuel. The methane that we're concerned about in the atmosphere, however, doesn't come from burning natural gas (which puts carbon dioxide into the atmosphere, but not methane). The primary source of methane in the atmosphere is anaerobic decomposition of organic matter, for which methane is one of the end products. Some of the anaerobic processes (meaning in the absence of oxygen) that produce methane are in sanitary landfills, from concentrated waste organic matter (like livestock manure), from bogs and swamps, and  from termites. Methane is produced in anaerobic digesters in wastewater treatment plants, but in most cases it is either captured for use or burned in a flare.
   Methane is approximately 25 times as effective as carbon dioxide in retaining heat in the atmosphere.

• Nitrous Oxide

  Nitrous Oxide (N₂O) is probably most widely known through its use as laughing gas, a mild anesthetic. The sources for its presence in the atmosphere are a variety of agricultural and industrial sources. Nitrous oxide is part of the natural nitrogen cycle as well; it is an intermediate in the denitrification of nitrate to nitrogen gas. A significant characteristic of nitrous oxide as a greenhouse gas is its longevity, with an average persistence in the atmosphere of 120 years. Nitrous oxide is approximately 300 times as effective as carbon dioxide in retaining heat in the atmosphere.

• CFC-12 and CFC-11

  CFC-11 (CCl₃F) and CFC-12 (CCl₂F₂) are the two chlorofluorocarbons (CFCs) that have the greatest greenhouse effect. CFCs do not occur naturally. They were first created in 1928, and saw significant use as cleaning solvents, aerosol propellants, and refrigerants. Based on the effect of CFCs in destroying stratospheric ozone, a very successful global effort has essentially halted their production, so that atmospheric levels are now remaining constant or decreasing. Atmospheric concentrations increased from zero before 1928 to current levels of about 240 ppt for CFC-11 and about 530 ppt for CFC-12. At parts per trillion, the concentrations of these two CFCs are less than atmospheric carbon dioxide concentrations by a factor of 10⁶. They still have some greenhouse gas effect, because they are 5,000 to 10,000 times as effective as carbon dioxide in retaining heat in the atmosphere.
  

Microbe responsible for methane from landfills identified

Microbe responsible for methane from landfills identified

Nuclear Energy

Pros and cons of nuclear power

As a result of the current discussion how further global warming could be prevented or at least mitigated, the revival of nuclear power seems to be in everybody's - or at least in many politician's - mind. It it interesting to see that in many suggestions to mitigate global warming, the focus is put on the advantages of nuclear power generation, its disadvantages are rarely mentioned.
Hopefully, the following summary of arguments for and against nuclear power can fill this gap:

Advantages of nuclear power generation:

• Nuclear power generation does emit relatively low amounts of carbon dioxide (CO₂). The emissions of green house gases and therefore the contribution of nuclear power plants to global warming is therefore relatively little.

• This technology is readily available, it does not have to be developed first.

• It is possible to generate a high amount of electrical energy in one single plant.

Disadvantages of nuclear power generation:

• The problem of radioactive waste is still an unsolved one. The waste from nuclear energy is extremely dangerous and it has to be carefully looked after for several thousand years (10'000 years according to United States Environmental Protection Agency standards).

• High risks: Despite a generally high security standard, accidents can still happen. It is technically impossible to build a plant with 100% security. A small probability of failure will always last. The consequences of an accident would be absolutely devastating both for human being as for the nature (see here , here or here ). The more nuclear power plants (and nuclear waste storage shelters) are built, the higher is the probability of a disastrous failure somewhere in the world.

• Nuclear power plants as well as nuclear waste could be preferred targets for terrorist attacks. No atomic energy plant in the world could withstand an attack similar to 9/11 in New York. Such a terrorist act would have catastrophic effects for the whole world.

• During the operation of nuclear power plants, radioactive waste is produced, which in turn can be used for the production of nuclear weapons. In addition, the same know-how used to design nuclear power plants can to a certain extent be used to build nuclear weapons (nuclear proliferation).

• The energy source for nuclear energy is Uranium. Uranium is a scarce resource, its supply is estimated to last only for the next 30 to 60 years depending on the actual demand.

• The time frame needed for formalities, planning and building of a new nuclear power generation plant is in the range of 20 to 30 years in the western democracies. In other words: It is an illusion to build new nuclear power plants in a short time.

Sustainability: Is nuclear energy sustainable?

For several reasons, nuclear power is neither «green» nor sustainable:

• Both the nuclear waste as well as retired nuclear plants are a life-threatening legacy for hundreds of future generations. It flagrantly contradicts with the thoughts of sustainability if future generations have to deal with dangerous waste generated from preceding generations. See also here .

• Uranium, the source of energy for nuclear power, is available on earth only in limited quantities. Uranium is being «consumed» (i.e. converted) during the operation of the nuclear power plant so it won't be available any more for future generations. This again contradicts the principle of sustainability.

Is nuclear power renewable energy?

Nuclear energy uses Uranium as fuel, which is a scarce resource. The supply of Uranium is expected to last only for the next 30 to 60 years (depending on the actual demand). Therefore nuclear energy is not a renewable energy.

Conclusion

From the above mentioned pros and cons of nuclear power plants, it should be evident that nuclear energy cannot be a solution to any problem. Even worse: it is the source of many further problems.

We must not any longer shut our eyes to the consequences of our being on earth. Besides moral, ethical and spiritual reasons, at least for the pure will to survive we should consequently strive for a sustainable living and realize it in our personal life. It's time for change!