Global Warming

[Tomeck]

Mercury has almost no atmosphere at all. Venus has an atmospheric pressure equal to almost 1000 meters deep in the ocean. If its atmospheric makeup (O2/N2/CO2/etc) was equal to Earth's, do you think the temperature would be similar, despite how thick the atmosphere is?

If both planets had equal amounts of atmosphere and one was purely CO2 and the other was O2/N2 you could do a fair comparison. What you're saying is like comparing a Ferrari and a Yugo and saying the Ferrari is faster because it's red.

Yes, Mercury don't have an atmosphere. CO2 is small concentration in the atmosphere, but CO2 is an important component of atmosphere.

From Wikipedia (Greenhouse effect - Wikipedia, the free encyclopedia):

The molecules/atoms that constitute the bulk of the atmosphere: oxygen (O2), nitrogen (N2) and argon; do not interact with infrared radiation significantly. While the oxygen and nitrogen molecules can vibrate, because of their symmetry these vibrations do not create any transient charge separation. Without such a transient dipole moment, they can neither absorb nor emit infrared radiation. In the Earth’s atmosphere, the dominant infrared absorbing gases are water vapor, carbon dioxide, and ozone (O3). The same molecules are also the dominant infrared emitting molecules. CO2 and O3 have "floppy" vibration motions whose quantum states can be excited by collisions at energies encountered in the atmosphere. For example, carbon dioxide is a linear molecule, but it has an important vibrational mode in which the molecule bends with the carbon in the middle moving one way and the oxygens on the ends moving the other way, creating some charge separation, a dipole moment, thus carbon dioxide molecules can absorb IR radiation. Collisions will immediately transfer this energy to heating the surrounding gas. On the other hand, other CO2 molecules will be vibrationally excited by collisions. Roughly 5% of CO2 molecules are vibrationally excited at room temperature and it is this 5% that radiates. A substantial part of the greenhouse effect due to carbon dioxide exists because this vibration is easily excited by infrared radiation. CO2 has two other vibrational modes. The symmetric stretch does not radiate, and the asymmetric stretch is at too high a frequency to be effectively excited by atmospheric temperature collisions, although it does contribute to absorption of IR radiation. The vibrational modes of water are at too high energies to effectively radiate, but do absorb higher frequency IR radiation. Water vapor has a bent shape. It has a permanent dipole moment (the O atom end is electron rich, and the H atoms electron poor) which means that IR light can be emitted and absorbed during rotational transitions, and these transitions can also be produced by collisional energy transfer. Clouds are also very important infrared absorbers. Therefore, water has multiple effects on infrared radiation, through its vapor phase and through its condensed phases. Other absorbers of significance include methane, nitrous oxide and the chlorofluorocarbons.

 

[Eris Lucan7*]

Uranos is my favor at all,his carateristic geologie is for me of all

planet in the solarsytem 10 time more intresnting then Mars he have more

minerals Helium and Nitrogen as any else reachabel Planet,All Venus sonde the

the ESA or the Nasa had trey to land on Venus had faild mean there is massiv

Teta radioactivity or he the Venus is have no constant ground(Liquid gas or

magma)sontime constant then it went broken and liquid again.I think there is a

mix off all off this.....

E.L.7*

 

[Tassie_Rohan]

Given that the data appear to suggest that the ice sheets which previously covered the planet periodically throughout its known history were rather substantial, extending nearly to the equator in some instances and of significant thicknesses, what melted them?

Mankind's influence had yet to manifest itself.

It would appear that throughout the planet's history periods of intense cooling have been followed, cyclically, by periods of intense warming.

Allowing for even significant climatic degradation recently caused - to some extent - by mankind's deplorable abuse of natural resources, could it not also be that a cyclical period of warming may also naturally be occurring?

Yep - the world has been a lot colder, and a lot warmer, than current temperatures. Even during the current post-ice age epoch (the Holocene) we have had warmer periods and oscillations in temperatures. However, as Dr Bill points out, these cycles occurred over periods of 100's of years or 1000's of years. What we see at the moment is a sharp peak over the last hundred years.

Data for the Holocene (last 10,000 years)- note the cylic changes (thick black line). Many sudden drops correlate with major volcanic eruptions. Significantly - the arrow '2004' points the level we are currently at (see insert) - the recent changes are too rapid to show on a graph on this timescale:

Data for the last 2000 years:

As you can see the temperature changes we are currently experiencing appear to be occuring far more rapidly then previous 'natural changes'.



As for the global ice cover- google 'snowball earth' and you will get a ton of reading material. One important thing to keep in mind is that this extensive ice age occurred in the Precambrian, when the earth and atmosphere were very different from today. The atmosphere had very little oxygen and a lot more CO2 and methane, for a while most continents where down near the south pole, and the only life was simple single cell organisms in the oceans. The actual extent of the Precambrian glaciations is a contentious issue in geology. Most models that explain how it thawed invoke the build up of methane/CO2 from volcanic eruptions and/or movements of assorted continents, over the time scales of 1000's to millions of years depending on who you listen to.

Cheers,
Rohan.

 

[Doc Intrepid]

Thanks Tassie, appreciate the primer.

As Hank49 suggests, I suppose we'd better next discuss mitigation of consequences.

I don't think that modern societies have an "off"-switch.

It's probably too late at this stage of development even if they did.

I suspect, however, that a more intelligent analysis of causation will find ever more increasing complexity, as opposed to a single 'cause'=>'effect' dyad. The more complex the issues we're facing, the more complex any effective response would need to be.

 

[Eris Lucan7*]

*Yokotomo*

 

[hd2o.tv]

This is a sorry argument. Dinosaurs were killed by global cooling, is that what we'd prefer? Instantly freezing isn't too hip, just ask those giants who were a bit tougher skinned than we are. Yes the earth is warming... but it has gone up and down for billions of years. Remember; the ice age was really several ice ages with temperature changes up and down and ice building up and retreating several times. That's science. Mr. Gore claims CO levels cause temperature change and we humans are to blame, but if you look at his own data... and read it correctly, it's the other way around. Temp. gains PRECEDE rises in CO levels. One of several non-truths in his "THEORY".
Human impact. Yes! We live, so therefore we consume. You have to have nerve to complain about human impact and sit before a computer. And don't run that motor to pump air into your dive tank, and don't take a boat out there, and don't drive to the dock. Walk in with a hollow reed and no mask.
Go ahead and drive a hybrid, if you think that's helping you're naive and being led by the nose by enterprising business. One volcano eruption puts out more CO than you could in several lifetimes, remember Mt Saint Helen??? How about the Kuwait oil rigs that burned for three years?
The earth is a living moving planet. You can't change that and souldn't want to. Neither could the dinosaurs stop it from cooling, rapidly. Not even with there totally hipster "zero carbon footprint".
Note that it's only liberals who are on a witch-hunt for anyone who disagrees. Death threats are no way to treat our scientists nor is it the way to advance science. Unless you think the universe revolves around the earth. Same witch-hunt happened to those early thinkers. Sad really to be so closed to discussion and resort to name calling in leu of facts.
Regards,

 

[drbill]

Here we go again.

 

[Tassie_Rohan]

Oh God - where do I start? Why do I bother?

Dinosaurs were killed by global cooling, is that what we'd prefer? Instantly freezing isn't too hip,

Why do non-scientist get fixated on 'dinosaurs' in these arguments? The consensus is that the Cretaceous-Tertiary extinctions were triggered by a massive meteorite impact off the coast of Mexico, with follow up extreme climatic changes: these killed off a lot of species (including dinosaurs), but the climatic changes were short lived: we don't see an increase in glaciations at this time.

Yes the earth is warming... but it has gone up and down for billions of years. Remember; the ice age was really several ice ages with temperature changes up and down and ice building up and retreating several times. That's science.

Correct - do please read the last few pages of this thread to see how the changes occur - and the lengthy time scales involved.

Mr. Gore claims CO levels cause temperature change and we humans are to blame, but if you look at his own data... and read it correctly, it's the other way around. One of several non-truths in his "THEORY".

Why do nonscientists get fixated on 'Al Gore' in these arguments. Mate - Al Gore did not 'invent' global warming. He is just publicising the large body of work on the subject.

Temp. gains PRECEDE rises in CO levels.

Heres some excellent data for the last 500,000 years. It reflects several ice ages. Looks like a pretty close relationship, and on a more detailed scale temperature seems to lag slightly behind CO2 (the world is a big place and takes a while to warm up). Note the huge spike in CO2 at the very end - the last 150 years.

Now - if you think that graph shows a relationship between temperature and CO2 concentrations - then heres some food for thought:

One volcano eruption puts out more CO than you could in several lifetimes, remember Mt Saint Helen???

Correct- a volcano puts out more CO2 into the atmosphere in one day than a single person in a life time. Volcanic dust can cause short term cooling after a large eruption, however individual volcanic eruptions make no difference to the global CO2 level - as seen in the graph above (there were big climate-cooling eruptions just prior to 1600 and around 1820).

How about the Kuwait oil rigs that burned for three years?

Exactly! That oil was going to be burnt anyway (inside engines), and keep in mind that it was a tiny amount of oil compared to the total amount the world uses every year.

Note that it's only liberals who are on a witch-hunt for anyone who disagrees. Death threats are no way to treat our scientists nor is it the way to advance science. Unless you think the universe revolves around the earth. Same witch-hunt happened to those early thinkers.

Wrong - I am one of those scientists mate: and like the majority of scientists I am concerned about global warming. We were worried about it even before Al Gore or liberals took up the issue.

Sad really to be so closed to discussion and resort to name calling in leu of facts.

So - where are your facts? I see a rant about 'liberals', 'dinosaurs' and 'Al Gore' but no evidence.

Cheers,
Rohan.

 

[Kim]

Sad really to be so closed to discussion and resort to name calling in leu of facts.

There was actually a rather good discussion going on until your post IMO. It seems to me that YOU are the one who has restarted the name calling, "liberals", "Gore", generally painting many as "nose led" and so forth. It also seems that your "facts" are somewhat suspect.

 

[Warthaug]

By the way, current models are unable to correctly show what temperature the Earth would be at with no GW gasses present.

Given that the earth has never had no greenhouse gasses, then we cannot actually say what that value is.

And your assertion is wrong, at least at the level of what we know of the earths emission vs absorption. About 18C worth of our surface temperature is due to greenhouse gasses, a factor taken into account by most modern models.

Bryan