Global Warming and Greenhouse effect

[ccyy1993]

What is Global Warming and greenhouse effect?

[Clanad]

A theory in dispute with many scientists is that human activity in the form of coal burning power plants, automobiles and other forms of fossil fuel consumption, over a long period of time have added significant amounts of carbon dioxide to the atmosphere.  This, in turn, traps more heat and causes the earth to warm causing harm to the environment. The theory is disputed by scientists that believe any warming trend is the result of natural cycles...

[gen2]

It is not just carbon dioxide that causes this effect. Although methane is released in smaller quantities, its effect is 10 times that of CO2.

[gen2]

Maybe ccyy1993 wants a clarification of the terms in his question, rather than know the causes, some of which (like Clanad said) are disputed.

Global warming is simply an increase in the average global temperature from whatever cause.  In the geological past, there have been several periods of both global warming and global cooling (eg ice ages).  These were caused by natural events.  Two things are in dispute in relation to this:
(a) Is global warming taking place at the present time? and
(b) Is human activity contributing to this effect?

The greenhouse effect is one factor that can raise the temperature of the lower atmosphere.  In a greenhouse, the glass allows energy in the form of light to enter easily.  The light is absorbed by surfaces that convert the light into heat - the darker the surface, the greater the conversion.  This heat is then prevented from escaping by the glass and the greenhouse gets hotter.  Carbon dioxide and methane in the global atmosphere have the same effect as the greenhouse glass and so it is galled the greenhouse effect.

Over recent decades there has been a measurable increase in the amount of CO2 in the air and so there has been an increase in the greenhouse effect which could contribute to global warming.

As I stated above, there are many factors involved in the possible current global warming episode, some of which tend to increase global temperature and some which decrease it.

Personally, I think the heating is greater than the cooling and so we are in an episode of global warming.

[3Styler]

the greenhouse effect is what makes all life possible on this planet as the effect causes short wave radiation emmitted by the sun to be trapped as long wave radiation by gases in our atmosphere such as CO2 and Sulphur dioxide and many others, and this trapping of heat keeps the temperature of the earth at a level that can support life. 

Global warming is the theory that the more heat is being trapped and so the temperature of the planet is increased.

The believed reasons for this is that humans are increasing the volume of greenhouse gases and also that deforestation causes less CO2 to be taken up.  I think it has been proved with concrete evidence that global warming is occuring but the debate is that it is not possible to tell whether it is because of human activites because it may be down to stella sources or the sun simply giving off more heat etc and so is difficult to prove.

[ccyy1993]

What has CO2 got to do with Methane?

[gen2]

ccyy1993, CO2 has nothing to do with methane.  As 3styler says, the greenhouse effect is produced by many gases.  CO2 is the one we read most about in the press but others, though released in smaller quantities into the atmosphere, are more efficient at trapping the long wave radiation.  Methane is one such gas and is 10 times as efficient at trapping heat as CO2.

There are many sources of methane:
  Rotting vegetation e.g. marsh gas
  Herds of ruminant herbivores e.g. cattle
  Schoolboys feasting on baked beans
  Escapes of natural gas, either from leaky pipes
      or directly from geological faults
There are also large stores of methane in cool ocean sediments in the form of methane hydrate.  If the oceans warm at depth, then this could become unstable and release the methane to the atmosphere thus adding further to global warming.

[jake-the-peg]

I don't know many scientists (apart from those being paid by petro-chemical or concrete corporations) who dispute that the climate is changing and the green house effect is simple fact - look at venus (further from the sun than mercury but hotter)

I think what is in dispute is whether human activity is having a significant impact on the greenhouse effect.

I can't remember who said it but personally I'd go along with the view that at a time of climate change the last thing you want to do is conduct a large unregulated expreiment on the atmosphere