Русский New site

Advanced search

[ New messages · Forum rules · Members ]
Page 2 of 2«12
Forum » SpaceEngine » Science and Astronomy Discussions » CO2 on Venus, Earth, and Mars (For those who've studied Astronomy and Earth/Space Sciences.)
CO2 on Venus, Earth, and Mars
midtskogenDate: Sunday, 08.09.2013, 17:46 | Message # 16
Star Engineer
Group: Users
Norway
Messages: 1668
Status: Offline
Quote (HarbingerDawn)
In that case, yes. When they built their town there, it was a safe location because the sea ice protected their land from erosion.

The Bering sea has always been seasonally open (in the Holocene, at least) exposing the island for many months a year. What's currently happening is that the protection is there for a shorter time every year, so the erosion likely happens faster. At most we can say that the warming speeds up the inevitable, but ultimately it's speculation due to the chaotic nature of weather. We do not know what storms would have hit the area if the seasons were "normal". Freak warm weather could in theory (not necessarily there but in similar places) also move the place away from the shore due to silting. They've place a town in a relatively unpredictable place.

The inhabitants of Kivalina might have a case against the government, though, who relocated them to the current place a hundred years ago.

I think people easily forget that coastlines (river mouths and barrier islands in particular) aren't static. They may change a lot over a few centuries, and it's only within a lifetime that they might appear relatively static. So people forget. That town and ports have to move is nothing new. Sometimes it affects big cities as well with big economic consequences. A couple of notable examples are Ostia, once the port of Rome, now kilometres away from the beachline. And Dunwich, in mediaeval times a capital and international port rivalling London in size, but it was eventually lost to the sea.

Quote (Enki)
I doubt undeveloped nations are even conscious of this issue.

Oh, they are. It could be their opportunity for payback from the rich world. The rich world feels guilty.





NIL DIFFICILE VOLENTI
 
HarbingerDawnDate: Sunday, 08.09.2013, 18:01 | Message # 17
Cosmic Curator
Group: Administrators
United States
Messages: 8713
Status: Offline
Quote (midtskogen)
The Bering sea has always been seasonally open (in the Holocene, at least) exposing the island for many months a year. What's currently happening is that the protection is there for a shorter time every year, so the erosion likely happens faster.

Yeas I know. I was under the impression though that the ice had previously provided protection during the times with the most severe storms, and now it doesn't, hence the dramatically accelerated erosion. I might be mistaken.

Quote (midtskogen)
The rich world feels guilty.

They do a good job of pretending otherwise rolleyes





All forum users, please read this!
My SE mods and addons
Phenom II X6 1090T 3.2 GHz, 16 GB DDR3 RAM, GTX 970 3584 MB VRAM
 
midtskogenDate: Sunday, 08.09.2013, 18:56 | Message # 18
Star Engineer
Group: Users
Norway
Messages: 1668
Status: Offline
Quote (HarbingerDawn)
I was under the impression though that the ice had previously provided protection during the times with the most severe storms, and now it doesn't, hence the dramatically accelerated erosion. I might be mistaken.

I wont pretend having detailed local knowledge of this place, but it should be evident from the pictures that this isn't exactly ancient surface. It may well be possible that the most severe storms generally happen during winter when ice previously dampened the waves. But it also takes some pretending to think that a pile of sand is perfectly safe just because it's less windy during the time of year when the sea is open anyway. Also, if your home is about to vanish into the sea, it's in your interest to find something to blame.

The arctic is a great place to witness landscape changes happen in a few decades. Tundra, lack of vegetation, ice and much larger amplitude of climatic variation speed up the process. I've found maps only a couple of decades old obviously wrong in the field. I've even circumnavigated a peninsula (it has not yet been renamed). smile





NIL DIFFICILE VOLENTI
 
WatsisnameDate: Sunday, 08.09.2013, 19:53 | Message # 19
Galaxy Architect
Group: Global Moderators
United States
Messages: 2610
Status: Offline
Enki, So far you've presented exactly zero good reasons for your taking issue with standard global warming theory, but instead a very large number of misunderstandings. It's fine, and good, to apply skepticism to topics in science, but if you are going to do so then you should probably first have a reasonably good understanding of the science in question.

Quote (Enki)

In Chemistry class I stumped my teacher when I asked her about the CFCs and the equation that showed perpetual never-ending decay. A mono-atomic oxygen appeared out of nowhere in the equation, which was required to make it perpetual. She had no explanation. And yes, I am even challenging CFCs, which are supposed to be worse than CO2.


The free oxygen atom is produced by the disruption of ozone (O3) in the atmosphere, as well as the photo-dissociation of molecular oxygen by the sun's UV rays.

No offense, but your school doesn't sound like it was a very good one based on what you've been telling us so far...





 
fmilluminatusDate: Sunday, 08.12.2013, 06:14 | Message # 20
Observer
Group: Newbies
United States
Messages: 5
Status: Offline
Quote Enki ()
You hear all the time, impending death by global warming because we're producing to much CO2 emissions.


Quote HarbingerDawn ()
Fact: carbon dioxide is a greenhouse gas, it's a simple matter of physics.


We aren't headed for an impending death by global warming. That's because while CO2 is a greenhouse gas, it's a very weak one. Further, CO2's effectiveness as a greenhouse gas decreases logarithmically as CO2 concentrations rise. [Each time CO2 levels double, an additional 3.7w/m^2 of sunlight is absorbed by our atmosphere - which translates to about a 2.1C increase in average global temperature.] If our atmosphere was 100% CO2, it would only raise global temperature by about 23C. In order to raise global temperature by 12C, CO2 levels would have to increase so much that we would all suffocate. In order to raise global temperatures by 2.1C, we would have to increase our CO2 output by 20X our current levels.

There's no global warming crisis. At our current rate, we simply aren't raising CO2 levels enough to make a difference. Further, the paleo-climate record shows that global CO2 levels have been as high as 10x what they currently are, and life thrived.

Finally, regarding Venus - 'greenhouse Venus' is a myth and a fantasy. Venus isn't lead-boiling hot because of the 'greenhouse effect'. It's lead-boiling hot because of it's thick atmosphere. A principle called 'adiabatic lapse rate' describes how this works. Basically an atmosphere gets hotter as it get's thicker and cooler as it thins. [This also explains why Mars is so cold.] The 'greenhouse effect' only accounts for <60C of the planet's extreme temperature.

I was actually curious about this recently and wrote an article on my blog that explains the temperature of Venus in a little more detail. Venus, further thoughts


Edited by fmilluminatus - Sunday, 08.12.2013, 06:37
 
HarbingerDawnDate: Sunday, 08.12.2013, 07:47 | Message # 21
Cosmic Curator
Group: Administrators
United States
Messages: 8713
Status: Offline
Quote fmilluminatus ()
We aren't headed for an impending death by global warming.

Who said we were?

Quote fmilluminatus ()
Finally, regarding Venus - 'greenhouse Venus' is a myth and a fantasy. Venus isn't lead-boiling hot because of the 'greenhouse effect'. It's lead-boiling hot because of it's thick atmosphere.

Yes, its thick atmosphere of gases that absorb and re-emit infrared rays. If it had an atmosphere of pure nitrogen or such, it would not be nearly so hot.

Quote fmilluminatus ()
the paleo-climate record shows that global CO2 levels have been as high as 10x what they currently are, and life thrived

Yes, because the Sun was much dimmer back then, and even so Earth was still extremely hot during the more recent CO2-rich periods (there were times when the climate on Antarctica was nearly tropical if I'm not mistaken).





All forum users, please read this!
My SE mods and addons
Phenom II X6 1090T 3.2 GHz, 16 GB DDR3 RAM, GTX 970 3584 MB VRAM
 
WatsisnameDate: Sunday, 08.12.2013, 09:52 | Message # 22
Galaxy Architect
Group: Global Moderators
United States
Messages: 2610
Status: Offline
Hi fmilluminatus, thanks for your post. I think you've mixed things that are correct and things that are incorrect or based on misunderstandings, so I'd like to try to clarify some things for you.

You are correct that on a per molecule basis, CO2 is not as strong as other greenhouse gases, because there is already much of it in the atmosphere, so the relevant spectral lines are already partially saturated (and yes, it follows a log scale). Even so, CO2 is and has been the most important greenhouse gas through much of Earth history. Indeed, one cannot make sense of much of past climate changes without understanding the role of CO2.

Quote
If our atmosphere was 100% CO2, it would only raise global temperature by about 23C.

Only if you consider the direct warming by CO2... the result fails rapidly once you allow for carbon cycle feedbacks and tipping points. A more accurate statement would be that if Earth's atmosphere was 1atm of 100% CO2, we really don't know what would happen, because many of these tipping points are poorly quantified. Carbon cycle feedbacks are important even when considering only a doubling of CO2, as discussed widely in the scientific literature. They are the reason why a doubling of CO2 raises global temperature by ~3C (with error bars, of course), instead of just ~1C as you might expect purely from radiative forcing arguments.

Quote
In order to raise global temperatures by 2.1C, we would have to increase our CO2 output by 20X our current levels.

Did you mean to say 21C? 2.1C is an outcome that we are already nearly committed to. surprised

Quote
There's no global warming crisis. At our current rate, we simply aren't raising CO2 levels enough to make a difference.

Yes we are, and this difference is already observed and quantified. We'd actually be in a period of long term gradual cooling if not for human activity, and we have undone thousands of years of that cooling. The warming response expected under moderate to high emissions scenarios brings Earth back to temperatures that haven't been seen in millions of years, with much of that change happening during this century.

Quote
Further, the paleo-climate record shows that global CO2 levels have been as high as 10x what they currently are, and life thrived.


Certainly. smile The problem though is that human civilization has developed under a particular and relatively stable climate state, upon which much of our infrastructure, agriculture, and water supply depends on. Because we are changing the climate so rapidly, this poses very serious challenges for us.
The effect of AGW on ecosystems is complex, and some benefit while others suffer. Amazonia in particular is projected to experience significant species loss under high emissions scenarios.

Quote
Finally, regarding Venus - 'greenhouse Venus' is a myth and a fantasy. [etc]


You are correct in the sense that the thickness of the atmosphere (high pressure) is important, but your association with lapse rates is wrong. What were your sources for this information? Have you studied atmospheric physics or are you repeating stuff you've read somewhere?

The lapse rate only describes how the temperature changes with altitude. It says nothing about what the temperature at any location actually is. For that, you have to do radiative flux analysis. And for Venus, the greenhouse effect is crucial to describing that flux balance. The lower Venusian atmosphere receives much of the incoming solar flux (cloud/haze layers absorb and reflect much light, so visible light mostly does not reach the ground itself). The atmosphere has high opacity to the outgoing longwave radiation, so a great deal of heat is trapped at low levels. This is the greenhouse effect. As per above, the high partial pressure of CO2 on Venus makes a very strong greenhouse effect.

The greenhouse effect also describes why the upper atmosphere is actually colder than what you would predict purely by composition and lapse rate arguments, and I have posted about this topic in other threads. The greenhouse effect heats the lower atmosphere and cools the upper atmosphere. The same phenomenon is observed on the Earth as well, with enhanced stratospheric cooling due to global warming. Counter-intuitive, but true. You just have to consider radiative flux balance.

If you are interested in more information, you may find detailed analyses of planetary atmospheres and their thermal structures in various scientific journals. I can help you find them if you like.

Quote HarbingerDawn ()
(there were times when the climate on Antarctica was nearly tropical if I'm not mistaken).


You are not mistaken. smile During the PETM there was probably no or very little ice anywhere on the planet.





 
fmilluminatusDate: Monday, 09.12.2013, 03:05 | Message # 23
Observer
Group: Newbies
United States
Messages: 5
Status: Offline
Quote Watsisname ()
Hi fmilluminatus, thanks for your post. I think you've mixed things that are correct and things that are incorrect or based on misunderstandings, so I'd like to try to clarify some things for you.

You are correct that on a per molecule basis, CO2 is not as strong as other greenhouse gases, because there is already much of it in the atmosphere, so the relevant spectral lines are already partially saturated (and yes, it follows a log scale). Even so, CO2 is and has been the most important greenhouse gas through much of Earth history. Indeed, one cannot make sense of much of past climate changes without understanding the role of CO2.


Right.

Quote Watsisname ()
Only if you consider the direct warming by CO2... the result fails rapidly once you allow for carbon cycle feedbacks and tipping points.


No, the numbers that I referenced account for the proposed CO2 forcing on water vapor [which is actually the most important greenhouse gas in our atmosphere]. If you consider CO2's effect alone [without taking water vapor into account] it's effect is much weaker.

Quote Watsisname ()
Did you mean to say 21C? 2.1C is an outcome that we are already nearly committed to.


No, I mean 2.1C. Many climatologists, specifically the ones pushing global warming alarmism, are bad at science / dishonest. They ignore the diminishing returns of CO2, the small role CO2 plays in climate, and fudge the numbers to make potential temperature increases look higher. We currently contribute 5% of total CO2 levels. In order for us to increase global temperature by 2.1C, we have to double current CO2 levels, which means contributing 20X more [over the short term, although we could probably achieve the same effect with a smaller contribution over a longer time, that level being dependent the absorption capacity of natural CO2 sinks].

Quote Watsisname ()
Yes we are, and this difference is already observed and quantified.


The science says no [well, technically 'we don't have enough evidence to claim it does']. CO2 doesn't account for the temperature change. I know that many global warming alarmists want CO2 to account for the temperature change [and carry that bias into their work], but that simply means their work in unreliable. Water vapor can account for current warming trends, but there isn't good evidence for CO2 'forcing', it's basically conjecture [the correlation between the two is too weak] - which doesn't stop global warming alarmists from spouting it as fact. Further, there isn't even very good data showing that the current warming trends are actually warming trends. The time is too short and the record is too spotty.

Quote Watsisname ()
Certainly. The problem though is that human civilization has developed under a particular and relatively stable climate state, upon which much of our infrastructure, agriculture, and water supply depends on. Because we are changing the climate so rapidly, this poses very serious challenges for us.
The effect of AGW on ecosystems is complex, and some benefit while others suffer. Amazonia in particular is projected to experience significant species loss under high emissions scenarios.


The affect of global warming [that it's anthropogenic hasn't been demonstrated by evidence] is complex. That's the point. We don't have any understanding of how it will affect climate. Climate is a chaotic system, we can't predict it reliably in the very short term - we certainly can't predict it reliability decades or centuries in advance. The hysteria just isn't justified.

Quote Watsisname ()
You are correct in the sense that the thickness of the atmosphere (high pressure) is important, but your association with lapse rates is wrong. What were your sources for this information? Have you studied atmospheric physics or are you repeating stuff you've read somewhere?


I've studied atmospheric physics to some shallow extent. I'm looking into writing a journal review on this theory.

Quote Watsisname ()
The lapse rate only describes how the temperature changes with altitude. It says nothing about what the temperature at any location actually is. For that, you have to do radiative flux analysis. And for Venus, the greenhouse effect is crucial to describing that flux balance. The lower Venusian atmosphere receives much of the incoming solar flux (cloud/haze layers absorb and reflect much light, so visible light mostly does not reach the ground itself). The atmosphere has high opacity to the outgoing longwave radiation, so a great deal of heat is trapped at low levels. This is the greenhouse effect. As per above, the high partial pressure of CO2 on Venus makes a very strong greenhouse effect.


No. The short answer is, Venus's albedo is too high to absorb the necessary levels of radiation for the greenhouse effect to account for the temperature. I understand your point, but what I've read and worked on so far seems to show that Venusian atmosphere simply isn't absorbing enough radiation. Perhaps my numbers are too low ... we'll see.

Quote Watsisname ()
The greenhouse effect also describes why the upper atmosphere is actually colder than what you would predict purely by composition and lapse rate arguments, and I have posted about this topic in other threads.


Well, the upper atmosphere of Venus is actually much warmer than what my model predicts [it should be -260C at 100km], but it's really not supposed to work above the troposphere anyways. Regardless, it definitely tells the opposite story.

Quote Watsisname ()
The greenhouse effect heats the lower atmosphere and cools the upper atmosphere. The same phenomenon is observed on the Earth as well, with enhanced stratospheric cooling due to global warming. Counter-intuitive, but true. You just have to consider radiative flux balance.

If you are interested in more information, you may find detailed analyses of planetary atmospheres and their thermal structures in various scientific journals. I can help you find them if you like.


I've probably already read what you would suggest - but if you have anything you think I should read, send me a link, I'll read it if I haven't already. smile

Added (09.12.2013, 06:05)
---------------------------------------------
Quote HarbingerDawn ()
Yes, its thick atmosphere of gases that absorb and re-emit infrared rays. If it had an atmosphere of pure nitrogen or such, it would not be nearly so hot.


Yes, it would. This is because CO2 and N2 have almost the same molar heat capacity, and adiabatic lapse rate is the primary mechanism that drives the heat, not the greenhouse effect. In fact, if we factor out greenhouse effect completely [which we couldn't, because it does have a small effect], a pure N2 atmosphere would be hotter than a pure CO2 atmosphere.

Quote HarbingerDawn ()
Yes, because the Sun was much dimmer back then, and even so Earth was still extremely hot during the more recent CO2-rich periods (there were times when the climate on Antarctica was nearly tropical if I'm not mistaken).


Nope. The highest CO2 concentrations in the atmosphere since the great oxygenation event was about 500 million years ago, and the sun was only, at most, 3-4% dimmer than it is today. The levels were around 4000-6000 ppm, about 10-15x what they are today.

Quote HarbingerDawn ()
(there were times when the climate on Antarctica was nearly tropical if I'm not mistaken)


You're not mistaken. However, those times don't line up that well with times when CO2 levels were high. The last time the antarctic was a rainforest was during the Eocene period [about 34-56 mya] - CO2 levels only about a little less than double now. Periods before the Eocene had higher atmospheric CO2 levels while being colder than now. The point is, based on past climate estimates, there isn't a strong link between CO2 levels and temperature.


Edited by fmilluminatus - Monday, 09.12.2013, 03:26
 
WatsisnameDate: Monday, 09.12.2013, 07:26 | Message # 24
Galaxy Architect
Group: Global Moderators
United States
Messages: 2610
Status: Offline
You replied to the first section with 'Right', and then proceed with the rest of your post with arguments otherwise... so which is it?

Did you watch the AGU presentation that I linked to? If not then please do, it's really excellent.

Quote
No, I mean 2.1C.


Then you are wrong.

Quote
The science says no [well, technically 'we don't have enough evidence to claim it does']. CO2 doesn't account for the temperature change.


A literature review of various journals in climate science will reveal that the reality is the opposite of what you claim it is.

Quote
No. The short answer is, Venus's albedo is too high to absorb the necessary levels of radiation for the greenhouse effect to account for the temperature. I understand your point, but what I've read and worked on so far seems to show that Venusian atmosphere simply isn't absorbing enough radiation. Perhaps my numbers are too low ... we'll see.


If your model is showing that Venus is not absorbing enough radiation to be consistent with its observed atmospheric temperature profile, then your model is wrong. I would recommend that you review some of the literature.

Quote
The upper atmosphere of Venus is actually much warmer than what my model predicts [it should be -260C at 100km], but it's really not supposed to work above the troposphere anyways. Regardless, it definitely tells the opposite story.


All you've demonstrated then is that your model is wrong. How does your model work? You said it is not supposed to work above the troposphere. Why not?

The fact that the greenhouse effect causes a warming in the lower atmosphere and a cooling of the upper atmosphere is a simple result of radiative physics, and it should be a natural result in your model if you did it correctly.

Quote
Yes, it would. This is because CO2 and N2 have almost the same molar heat capacity, and adiabatic lapse rate is the primary mechanism that drives the heat, not the greenhouse effect. In fact, if we factor out greenhouse effect completely [which we couldn't, because it does have a small effect], a pure N2 atmosphere would be hotter than a pure CO2 atmosphere.


N2, unlike CO2, does not have a dipole moment and thus is not important for radiation transfer through the atmosphere. If Venus had a pure N2 atmosphere then you wouldn't need to use radiative transfer in your model. Since it is mostly CO2, you do. And as I told you earlier, the lapse rate only describes how the temperature changes with altitude. It does not tell you what the temperature actually is.

HarbingerDawn was completely correct. If Venus had a pure N2 atmosphere, or an atmosphere made up of any kind of optically transparent mixture of gases without dipole moments, then its surface temperature would not be nearly as hot. You could estimate it easily by calculating the equilibrium temperature of a blackbody with the same albedo, ignoring the atmosphere altogether. (It would actually be colder than this calculation would suggest, because of the clouds, convection, and zonal winds.)

In short, you cannot make sense of Venus' atmospheric temperature profile if you don't consider radiative transfer. The greenhouse effect is a result of radiative transfer.

Quote
Nope. The highest CO2 concentrations in the atmosphere since the great oxygenation event was about 500 million years ago, and the sun was only, at most, 3-4% dimmer than it is today. The levels were around 4000-6000 ppm, about 10-15x what they are today.


I think Harbinger was referring to the Faint Young Sun paradox.

Quote
Periods before the Eocene had higher atmospheric CO2 levels while being colder than now.

Which ones? Be specific.

Quote
The point is, based on past climate estimates, there isn't a strong link between CO2 levels and temperature.


High CO2 with low temperature does not invalidate the greenhouse effect, it means there is more going on that you didn't account for, e.g. insolation, albedo, atmospheric circulation, partial pressure of other atmospheric gases, etc. The role of CO2 on planetary temperature is just physics and this has been known for over a hundred years.

Quote
I've studied atmospheric physics to some shallow extent. I'm looking into writing a journal review on this theory.


That's great, I wish you the best of luck. Lone wolf researchers are seldom correct, but when they are they tend to become famous. smile I hope you are able to successfully show that the established knowledge in climate and planetary sciences is wrong.





 
midtskogenDate: Monday, 09.12.2013, 09:00 | Message # 25
Star Engineer
Group: Users
Norway
Messages: 1668
Status: Offline
CO2 keeping Whatisname up late again. I admire your efforts. smile

Quote Watsisname ()
A more accurate statement would be that if Earth's atmosphere was 1atm of 100% CO2, we really don't know what would happen, because many of these tipping points are poorly quantified.

If the premise is really 1 atm 100% CO2, not a single molecule of anything else, wouldn't that rule out much of the otherwise possible feedback making the situation much simpler? It would not be particularly relevant to the real world, though.





NIL DIFFICILE VOLENTI


Edited by midtskogen - Monday, 09.12.2013, 09:02
 
WatsisnameDate: Monday, 09.12.2013, 12:54 | Message # 26
Galaxy Architect
Group: Global Moderators
United States
Messages: 2610
Status: Offline
Quote midtskogen ()
CO2 keeping Whatisname up late again. I admire your efforts.


It’s no bother. smile I’m I night owl anyway, and atmospheric physics is a topic I have studied at a graduate level. I am pretty comfortable talking about it.

Quote midtskogen ()
wouldn't that rule out much of the otherwise possible feedback making the situation much simpler?


Not at all, rather quite the opposite.

A feedback effect, in this context, is where a change in CO2 concentration (or to be more precise, partial pressure) causes a change in temperature via mechanisms other than directly by radiative forcing. There are many of these, and they can depend non-linearly on temperature and CO2. They can also lead to tipping points, such as the ice-albedo feedback during Snowball Earth episodes, or terrestrial carbon sinks becoming sources under various global warming thresholds.

Our knowledge of feedbacks and tipping points grows fuzzy very rapidly with greater departure from present conditions, as we have fewer data to guide our understanding. If the atmosphere suddenly became pure CO2 the situation would be incredibly complex and unpredictable. I can pretty much guarantee there would be effects that nobody has even thought of yet.





 
desertsoldier22Date: Monday, 17.03.2014, 08:22 | Message # 27
Astronaut
Group: Users
United States
Messages: 51
Status: Offline
We have a big thread about climate change in the OT section

Edited by desertsoldier22 - Monday, 17.03.2014, 08:49
 
midtskogenDate: Monday, 17.03.2014, 08:54 | Message # 28
Star Engineer
Group: Users
Norway
Messages: 1668
Status: Offline
There already is a separate global warming thread, or for such views perhaps the conspiracy theory thread.

50 more years of observation alone will not be sufficient to know for sure, but that and 50 years of scientific advance might get us close. During the next 50 years the AMO will be falling for most of the time and we should not be surprised by a long "hiatus". 50 more years will give satellite observations on the multidecadal oscillations which we do not yet have.





NIL DIFFICILE VOLENTI
 
Forum » SpaceEngine » Science and Astronomy Discussions » CO2 on Venus, Earth, and Mars (For those who've studied Astronomy and Earth/Space Sciences.)
Page 2 of 2«12
Search: