Nature Features
Carbon dioxide and the greenhouse effect
Apr 6, 2007, 7:30 GMT
Hamburg - The so-called greenhouse effect of the earth's atmosphere is vital: a layer of air enveloping the planet lets about 70 per cent of incoming sun rays pass through, but retains a large part of the heat reflected by the Earth's surface.
This effect makes sure that the planet always has a comfortable median temperature of 15 degrees Celsius. Without the greenhouse effect we would be freezing at minus 18 degrees.
The greenhouse effect is caused by certain trace gases in the atmosphere that let short-wave radiation such as sunlight pass through easily, but hold back long-wave heat radiation.
Carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O, known as laughing gas) are among the main greenhouse gases after steam.
Since the beginning of industrialization, these gases, especially CO2, have been entering the atmosphere in large amounts through the burning of fossil fuels like coal, oil and gas.
Agriculture is another source of greenhouse gases.
With more intensive farming practices, deforestation, increasing numbers of cars on our roads, rising industrial production in developed countries and the industrialization of developing nations, the situation is getting worse by the day.
As humans produce more greenhouse gases, the atmosphere absorbs more heat, causing global warming and changing the Earth's climate.
Some visible effects of global warming are melting glaciers, rising sea levels, and worsening weather conditions such as heat waves and stronger storms.
CO2, methane and nitrous oxide make up nearly 90 per cent of man- made greenhouse gases, says the United Nations World Meteorological Organization (WMO). With the emission of those gases, humans increase the natural greenhouse effect.
Compared to measurements taken around 1750 - before industrialization - figures at the end of 2005 had increased as follows: carbon dioxide up 35.4 per cent, nitrous oxide up 18.2 per cent and methane up 154.7 per cent.
The average CO2 concentration in 2005 was 379.1 ppm (parts per million of air). The average for methane was 1.78 ppm, for nitrous oxide 0.32 ppm. At the beginning of industrialization, the CO2 concentration stood at 280 ppm. (internet: www.wmo.int)
© 2007 dpa - Deutsche Presse-AgenturCOMMENT
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Older Talkback
page: 1
Everything you say is true and has a bearing on Global Warming, but there is still very good reason to curb carbon emissions irrespective of whether other measures are being taken
Let us go back to basics - the Earth is a container of energy (=heat= temperature). It gains energy primarily from the sun [plus small amounts from geological activity and burning energy soucres i.e man made and natural combustion]. It loses energy by radiation of infra-red (heat) back into space. The difference between the input/output regulates the energy remaining in the container - either up or down
Over recent decades the sun has been increasing its energy and the input to Earth has been rising marginally faster than the output from Earth, so the retained energy has increased slightly (and thus the net temperature has risen)
To contain the rate of rise in net energy retained we need to either reduce the incoming energy or increase the outgoing energy, or both.
Reducing the incoming energy can happen to some extent by natural means - increased reflection from clouds and icecaps, volcanic dust and pollution particles in the air, etc - and possibly by man-made means such as increasing cloud cover by 'seeding', reflectors in space and other fairly long term ideas. We can also hope that eventually the sun will reach the point in its cycle where it begins to reduce output
Increasing the outgoing energy is very difficult - there will be some natural increase because a hotter body radiates more energy, dark surfaces (sea/land without ice) radiate more efficiently and so on - but currently the efficiency of the Earth losing energy is being curtailed by the so called 'greenhouse effect'. Consequently everything we can do to minimise this curtailment should be tackled.
A large constituent (25%) of the Greenhouse Effect is the amount of CO2 in the atmosphere, which is very good at absorbing the outgoing energy at certain wavelengths and not allowing it to pass into space. Water vapour is also a major constituent.
Water vapour may well increase as the temperature rises and more water is evaporated into the atmosphere, with an increase in the Greenhouse effect, but there is limited possibility for man's intervention in this area.
Co2 levels on the other hand, can be affected - maybe only by a small degree, but even so, any improvement will delay the rate at which Global Warming advances. Thus every restriction on CO2 emissions is a move in the right direction and will buy time for other measures to come into effect and/or mankind to adapt
Discussion about whether atmosphere or water or anything else is the major mover in the EFFECTS of Global Warming is not very relevant - the totality of the Earths retained energy is currently increasing and this results in a more volatile environment - wider weather variations, changed ocean currents, melting glaciers (and increasing glaciers in some places), etc etc. The effects are manifold and underline why it is so difficult for scientists to tie them all together into a robust forecast of effects.
Weather fluctuations are easy to quote - the US is currently having very cold conditions in some areas which should enjoying Spring sunshine. Here in England, last year at this time there was frost on the ground, today the temperature in London will be 25C. These are not proof that any particular predictions are correct but they do show that the weather is becoming increasingly unusual. Equally there are probably pieces of evidence related to changes in sea conditions.
But it doesn't matter what is happening in either atmosphere or water or land - these are all related and the interdependency is difficlut to analyse. What does matter is that the overall container is getting warmer and we need to minimise this rate of change - CO2 can be marginally influenced and we should attempt to do so - every little measure could help in the long term
RE: 'A large constituent (25%) of the Greenhouse Effect is the amount of CO2 in the atmosphere, which is very good at absorbing the outgoing energy at certain wavelengths and not allowing it to pass into space. Water vapour is also a major constituent.'
Horsefeathers and self-delusion. There is seventy-five times as much water vapor in the atmosphere as there is carbon dioxide and water vapor is one whole hell of a lot better at absorbing energy in the EM spectrum. I an't buyin' the GHG argument. It makes no sense whatsoever and it is being espoused out of political sentiment rather than hard-headed scientific thought.
Also, I think, no one likes to think about the sun being something less than a steady energy source. But let's face the facts. The sun lacks engineering controls of any kind. It is essentially a great big collection of hydrogen jammed into too small a space to remain peaceful. Aren't we lucky! We would not be here if the sun did not exist, but this does not grant us sound reason to assume that the sun is as reliable as the central air units in our homes.
The sun brightens and dims owing to the conditions internal to the sun. We have absolutely no control whatsoever of those conditions. The sun may well become bright enough long enough to kill us all, or it may well become dim enough for long enough that we freeze to death.
The good news, though, is that we could, if it became necessary, deal with high solar output problem if it continues for very long. What we might do about the sun staying too dim for us for too long is much more difficult problem to solve.
Sorry, but you do not appear to grasp some of the fundamental facts:
It is true that there is far more water vapour in the atmosphere than CO2, but the relative Infra Red absorptions as percentages of the greenhouse effect are - Water Vapour 36-70%, CO2 9-26%, O3 (Ozone) 3-7%. Furthermore, taken together water vapour and CO2 combine to produce an even greater percentage. (These figures are ranges because of different conditions and locations on the Earth, but are backed by countless experiments). {See Wikipedia or many similar sources}
Thus CO2 does provide a major effect, even though the CO2 is at an extremely small concentration compared to water vapour
The atmospheric effect IS large in terms of heat retention. Of the long wave radiation (heat) from the surface of the Earth - whether water or land - 90% is reflected back by the greenhouse effect to further warm the surface, which again radiates, which is again 90% reflected and so on as a feedback system. Consequently the atmosphere does have a major influence on the RATE at which energy moves from the surface.
All these interactions are, however, taken into account in the explanation I gave for overall warming. At any point in time after energy has been incoming, and all the interflows between land/sea/atmosphere currents, winds, greenhouse effect and whatever have taken place, some energy will be outgoing. At that point in time, there will be a small imbalance between the incoming and outgoing radiation and (as currently there is more incoming) this will result in a small increase in the Earth's overall energy and thus temperature.
At another point in time as short or as long later as you wish, after all the energy has come in, bounced around between atmosphere, water or so on, and another lot has been outgoing, there will another imbalance and a new addition to the Earth's total energy (temperature).
And you can continue picking points in time with the same result as often as you wish - each time there will be a balance after all the ebbing and flowing of energy and (currently) the earth will gain a bit more. It doesn't matter how much you postulate differences between heat held in water, air, land or anything else, it is the net result after all these movements which adds to the heat content of the Earth as a whole - irrespective of which medium holds greater or lesser amounts
Clearly on a day to day basis this addition to the Earth's energy cannot be precisely measured, but taken over longer periods it is measurable as a temperature and is the warming effect that has taken place over the past decades.
Your point about the sun brightening or dimming is precisely what I was covering in my earlier note. The process of incoming radiation being larger than outgoing will continue until the sun lessens or a way of blocking the radiation is found and/or until the amount of outgoing radiation from earth can be increased.
I then concluded that any restriction on CO2, however small, would be good as it would help contain the greenhouse effect and allow as much radiation as possible to be outgoing, even if this only bought very minor decrease in the RATE of increase in global warming
I am sorry if you haven't fully understood these points. However, if you are simply waving your arms about and sticking your head in the sand without sound logical explanations for your (to me unfounded) beliefs, then there is really no point in further discussion
Oh, I do understand your argument, Andrew. Here's what I am saying. I do not believe that carbon dioxide is nearly so efficacious at retaining heat as is claimed. From what I can see, carbon dioxide concentrations would need to be much higher, greater than toxic concentrations, before it would have any major effect on heat retention. Right now, it is the the sun, the oceans and water vapor that are in control of our overall temperature. I suspect the heat retained and absorbed the sea water is more important than anything the atmosphere does or doesn't do.
Now, does this mean that we can go right on doing what we have been doing for another three or four hundred years? I doubt it, but then we'll be worried about toxicity (the 8 hr exposure limit for CO2 is about one-half-of-one-percent), not the greenhouse effect.
The point I have been trying to make is that if we are going to worry about something so much that we find it necessary to coerce changes in people's lives, then we had best be doing it for sound reasons.
Here is what is happening. We are so focused on this false greenhouse effect that we are NOT spending money where we should be. We are NOT building desalinization plants. We are not improving our water delivery systems. We are STILL polluting our water supplies with toxins. The condition of our water resources and oceans thriving with life are what we should be worrying about, not carbon dioxide emissions.
If you are worried about carbon dioxide concentrations, then you should be deeply worried about what is happening to the oceans. The oceans are the only long-term carbon sink we have. All the terrestrial carbon sinks are transient and the carbon they sequester eventually makes its way back into the atmosphere.
We need to be investing our capital, valuta and political, on water. We should only be worried about toxins in the atmosphere right now, not carbon dioxide. Airborne toxins have a direct effect on human and animal health as well as fouling up our precious water.
Oh, something I neglected to mention. Limiting solar input is not such a horribly tough problem. We could solve that with millions shiny little balloons (little as balloons go) placed in orbit so that they reduce the sunlight coming in around the equator, say a thousand miles north and south of it.
We would only want to do that if the situation were becoming dire, ie, evidence that the sun were going to brighten and stay bright for a century or two.
I recommend going to www.aip.org/history/climate/co2.htm for a comprehensive review and unbiased summary
Okay, Andrew. I'll go have a look. I have read so much heavily biased crap that I am disgusted. If it does not appear to be biased to me, I'll come back here and say so.
If we are wrong and we are heading to a ice age we will need all the global warming we can get. 20 years of a warming trend is not science. If you review the academy of sciences data from the 1000's we are on average still cooling. Depends on what data you use, These computor models are worthless because you are entering data with 2 many varibles.
wat a stupid website
the earth has to end one day
why can't it end now...???
just like us humans are going to die so is the earth...!!!!!
so relax there's nothing we can do
it's in god's hands now
if we die we die
THE END
page: 1
NoharnessApr 13th, 2007 - 17:50:45
Carbon dioxide makes up about .04 percent of our atmosphere. Water vapor makes up about 3 percent. Water absorbs and emits a far greater range of electromagnetic energy than does CO2. More importantly water soaks up more energy per degree rise in temperature than any of the other gases, especially when it undergoes a phase change, which it does everywhere on Earth every day. It also EMITS a great deal of energy during phase change and that happens all over the world all of the time.
We haven't talked about all that water in the oceans, yet. Guess what, boys and girls, it's the water, not the air that regulates atmospheric temperatures.
The other factor too little discussed is the heat input from the sun. When the sun is brighter, we get warmer. When the sun is cooler, we cool off. It is no more complicated than your turning the burner up and down under your tea kettle.
It has been warm enough over the last thirty years to shrink the Martian polar caps. Guess what, Mars is twice as far out from the sun as we are. That means we are receiving four times as much energy from the sun as Mars receives.
Yeah, we have global warming. Yes, we SHOULD be doing something about it, but GHG emissions are not what we should be worried about. What we should be worried about is coastal flooding and prolonged droughts. Are we taking any steps to mitigate any of those disasters? No!
Instead, we are being told to stop driving our cars, using our lights and what-have-you, and all our problems will go away.
Let us assume, just to keep the Greens happy, that I am wrong about the greenhouse gases and that there really is something we can do to reduce energy absorption in the atmosphere. How long will it be before such a program can become effective? A hundred years, maybe? More? Meanwhile we are not going to do anything about the climatic changes to come?
That's brilliant! We have a problem. We know we have a problem and we can see it coming, but we aren't really going to do anything about it. Good night and good luck!
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