Yea…I would have definitely chosen the Heartland meeting. No brainer.
This was fascinating though, and I was suprised to learn that there is still water vapor there. I was curious as to what kind of climate implications there might have been (or that extended to the present day) from the global resurfacing of the planet?
[Response: It's just in traces, but it's there. And it's still escaping from the planet. An exciting question is the extent to which the Venusian mantle is still hydrated. Are we seeing the last gasp of water vapor, or is there still a bit coming out through episodic volcanism? The catastrophic resurfacing theories do various things to climate depending on the composition of outgassing -- water vapor vs SO2. With a lot of SO2 you can cool things down by making clouds, which gradually dissipate and give warming. At the end of the cloud cycle you get really hot surface temperatures, maybe 100C warmer than at present. If there's a lot of H2O outgassing as well, then you can get an additional pulse of heat through the added H2O greenhouse effect. This, by the way, shows the importance of the "thinning and cooling" effect we highlighted in the "Saturated Gassy Argument" post on Angstrom vs. Arrhenius: no matter how optically thick a planet's atmosphere becomes, you can always make it hotter by adding more greenhouse gas, because the "new" greenhouse effect is added near the top of the atmosphere where thing are thin and cold and the existing opacity is weak. --raypierre]
Is it possible, now, to get a more accurate idea of relative contribution, to greenhouse effect, of atmospheric venusian constituants?
Is an important contribution of H2O, HDO,… , confirmed?
[Response: The state of the art work on this would be Bullock and Grinspoon, which is also nicely summarized in Grinspoon's popular book on Venus. There are some questions around the margins involving the vertical distribution of water vapor, and the radiative modelling of water vapor at high temperatures and pressures. And further, the whole point of the PFS thermal infrared instrument was to help resolve some issues about the CO2 continuum and the modelling of the effect of the clouds on infrared. So, there's still work to be done, but nobody expects really big surprises --still sometimes surprises come sometimes from trying to close the last few percent gap in understanding. The hotter issues involve things like the sulfur cycle and the nature of the UV absorber. -raypierre]
Note that the original idea to search the Vegetation Red Edge in the Earthshine started with our group
at Paris Observatory in 1998, leading to the first observation in 2001.
Published in Astronomy and Astrophyics. 392, 231, 2002.
Actually, V. Arcichovsky had the same idea in 1912. But at that time the photographic plates were not sensitive enough in the infrared.
“But no worries — the instruments that did work provide a great wealth of new material to think about.”
I was under the impression that “no worries” was a uniquely Australian expression.
[Response: It's crept into my vocabulary through hanging around Australians and advising an Australian postdoc; to say nothing of my work in New Zealand, where the phrase seems to be creeping in. Just wait -- eventually you'll hear me saying things like "Too right!" --raypierre]
You wrote about the disagreement between David Grinspoon and Sue Smrekar. Fine, but then you sidestepped into trying to convince your readers that they in fact were in some kind of consensus. About what exactly was the consensus about, if the disagreement was real?
[Response: I'm happy to amplify on that statement. Science builds from areas of consensus into areas of disagreement, gradually conquering the unknown territory. Thus, although David and Sue disagree on the extent to which the surface features on Venus can be interpreted as evidence for catastrophic resurfacing, there are various underpinnings they agree on: things like the principle of radiation balance, the dominance of CO2 as a greenhouse gas in the atmosphere, the radiative physics that is used to determine the albedo vs. greenhouse effects of the clouds, the way this physics affects the surface temperature (which in turn can affect surface morphology), the role of mantle convection in transporting heat, the necessity of resupply of sulfur to the cloud deck, and many other things. I could add in the basic fact of the high temperature of the surface of Venus, which in 1955 was certainly not a matter of consensus, but is absolutely settled now, as is the explanation in terms of the joint effects of CO2, clouds and the traces of water vapor. The consensus I am referring to is not just a matter of things having been settled by observations, since there is a substantial modelling component involved in making sense of the observations. --raypierre]
One quibble. “Consensus of this sort exists for Venus as well as for Earth, and nobody makes a fuss about it.” I think this should read “Consensus of this sort exists for Venus as well as for Earth, and nobody of any note makes a fuss about it.”
Venus is so cool!!!!! Metaphorically speaking, that is. I still haven’t succeeded in modeling its atmosphere adequately, but I’m going to keep trying.
Some random Venus facts:
Surface pressure 9,210,000 pascals according to Seiff et al.’s 1986 Venus standard atmosphere; surface temperature 735.3 K. About as hot as a self-cleaning oven, they tell me.
Air 96.5% carbon dioxide, 3.5% nitrogen, 150 ppmv SO2, 30 ppmv or so H2O. But note that that’s 30 ppmv of an atmosphere much more massive than Earth’s. Venus’s trace water vapor is actually comparable in mass to that of Earth’s atmospheric water vapor (about half, as I recall).
Semimajor axis 0.72333 AUs, bolometric Bond albedo 0.750 according to NASA, which gives the Venus climate system a solar constant of 2,611 watts per square meter, an absorbed flux of 163 watts per square meter, and an equilibrium temperature of 232 K — colder than Earth’s equilibrium temperature!
Mass about 0.815 Earth masses, volumetric mean radius 6051.8 km.
But there’s plenty still to be learned about Venus, and there probably always will be, at least until the sun engulfs it several billion years from now.
Raypierre, Thank you, thank you, thank you. This was a great summary and obviously a lot of work. Those of us who have day jobs that only let us follow such developments as spectators rely on this type of trip report to keep us up to date.
Speaking of “day jobs,” I’d be interested in the degradation of the filter–was it perchance due to radiation darkening? Do you know who I could contact to get more info?
Again, thanks for providing this summary, and I hope that the laymen who read it will note the flavor of how science is really done that shines through the reporting.
Comment by David B. Benson — 17 Mar 2008 @ 11:19 AM
Thank You for the report. Not quite as good as being there, I’m sure, but I feel like I got a real sense of the excitement and the interrelatedness of all this science we have studied and find uses for.
Is it possible/plausible that there might have been life on Venus before it went into runaway warming — I can now use “runaway” without scientific consternation. :)
Of course, the slow rotation may have made life very difficult, so I image if there were some life, it would not have evolved much.
[Response: Actually the slow rotation wouldn't be all that much of a problem, as long as there is an ocean to even out the dayside/nightside contrast. One of the hottest topics in Venus studies these days is the nature of the pre-runaway climate, and there are indeed speculations that life could have arising there only to be snuffed out in the runaway. --raypierre]
Raypierre, thanks for presenting this interesting science. Let me test my understanding: the small amount of water vapor on Venus has relatively more effect than on Earth because its infrared spectrum is expanded due to the great pressure of the atmosphere?
I have a problem understanding this phrase:
A key feature of the atmosphere of Venus is the sulfuric acid cloud deck. These clouds account for the high reflectivity of Venus, but because they also reflect infrared back to the surface (unlike water clouds, which absorb and emit), they have a warming effect as well, and constitute the second most important factor in the greenhouse effect of Venus after carbon dioxide. Radiation model calculations demonstrate that the clouds have a pronounced net cooling effect on the planet, when both factors are taken into account.
I take it that sulfuric acid, unlike sulfur dioxide, is not a greenhouse gas, so it acts like a reflector. Then how can the clouds be a factor in the greenhouse effect? And when you talk about the clouds having a net cooling effect, is the other “factor” the reflection of incoming sunlight?
[Response: By the way, there is also SO2 on Venus, and its greenhouse effect comes in behind water vapor. Indeed, the pressure broadening helps water vapor become important, but it's also significant because in the upper part of the atmosphere the CO2 absorption is pretty weak in the continuum regions, and water vapor can help plug the gap. It's a minor, but significant player. Regarding the cloud greenhouse effect, the concentrated sulfuric acid droplets are relatively less good infrared absorbers/emitters than Earth's water clouds. However, they can still reflect infrared back to the surface, and inhibit cooling to space that way. Water clouds don't have a scattering greenhouse effect of this sort because water is such a good absorber the infrared gets absorbed and there's not much left to scatter back toward the surface. Sulfuic acid comes in all concentrations, and as it gets more and more dilute with water, the sulfuric acid clouds would start to act more and more like water clouds. Even at Venus concentrations there's actually some absorption as well as reflection, but unlike on Earth, the scattering greenhouse effect needs to be incorporated in radiation models. It's rather similar to the stuff I was proposing regarding the scattering greenhouse effect of CO2 clouds on Early Mars or a Snowball Earth. And yes, the "other factor" I was talking about was good old-fashioned reflection of incoming sunlight, which is a cooling influence. --raypierre]
Ray, does collision-induced absorption matter much on Venus, like the H2-N2 and N2-N2 collisional continuum that happens on Titan? I would think it is signifiant, being some 90 bars, but I never here much about that on Venus…just the CO2 and sulfuric acid.
[Response: Collision-induced absorption is very much at play for CO2 on Venus, in the spectral regions between where CO2 has optically active transitions. The continuum coefficients in use largely go back to experiments done by Pollack decades ago, and it would seem prudent to re-do some of those measurements using modern spectroscopic methods. There are some people involved with Venus Express that are going to do more lab experiments relating to the continuum in the near-IR, which is important for some of the cloud retrievals and window channel observations people are doing, but the thermal infrared continua are pretty tricky to measure, and they don't seem to be on anybody's to-do list right now. It will be very interesting to see what happens to the water vapor foreign continuum at high CO2 pressures and high temperatures. --raypierre]
“Is this article an attempt to demonstrate that what applies on earth also applies on Venus and hence climate science has got AGW right?”
Physics is physics, and you can drop a banana on either planet and it will fall…but no, I don’t think that is what Dr. Pierrehumbert had in mind. More like to share some interesting new science/discoveries that others would enjoy. But comparative planetology has its role too; if you insist that there is nothing to astrophysics and climatology aside from pushing AGW, then I would suggest that the lessons from Venus assist in the predictive and explanatory power of a CO2-enriched atmosphere, and what might happen as we continue to add CO2 on Earth (not a runaway, but warming).
If anyone thinks that runaway global warming is not a real threat to Earth then they are unaware that many feedback mechanisms are at play to set Earth on a logarithmic warming trend, quite similar to the effect seen on Venus.
[Response: Gee, what happened to the frog in a pot talk? I was looking forward to that. Actually, the fossil hydrogen thing sounds quite interesting (Heartland's monkeying with your title notwithstanding). I hope you'll post the write-up somewhere so we don't have to buy the whole Heartland book just to hear what you have to say about coal-to-hydrogen. --raypierre]
Although positive feedbacks certainly exist in the climate system (e.g. the responses from water vapor, ice-albedo) the “runaway” scenario is one I would not worry about for some billions of years when the sun goes into a red giant phase, ends up engulfing Mercury, etc. Something that might happen first is if plate tectonics stops from lack of mantle convection and CO2 is no longer able to be sufficiently outgassed and we end up in another snowball state.
The reason a runaway occurs (but will not on Earth anytime soon) is that there is a limit at which the planet can lose radiation to space, which depends on certain things like the mass of the atmosphere. See this image from Atmospheric Dynamics – Chapter 2 (Energy balance) – Aarnout van Delden; http://chriscolose.files.wordpress.com/2008/03/co2limit.jpg
From the lower curve, you can see that a high CO2, and saturated atmosphere is very sensitive and T^4 no longer applies. If the Kombayashi-Ingersoll limit is exceeded by incoming solar radiation then eventually the oceans will evaporate and the water will separate into its hydrogen and oxygen parts and escape the atmosphere, and with no more oceans you lose your big carbon sinks. The Earth and Venus have roughly the same amount of CO2, but on Earth it is all locked up in rocks and in the oceans and biosphere, with just enough in the atmosphere to make it livable. Can you get that on Earth? As it turns out, the incoming solar radiation would need to be much higher, with much, much more CO2 (and saturated with water vapor) for this to happen in the here and now.
I’m curious – could there be some similarity between Venusian superotation and Earth’s QBO (the later having a phase that could be considered superotation, occuring near the equator where the coriolis effect is weaker, and being driven by wind-shear dependent damping of vertically propogating Rossby-gravity and Kelvin waves)?
[Response: There is a pretty close connection, in that both phenomena involve transport of angular momentum by wave-mean-flow interactions. The QBO theory is closer to the older theory of Venus superrotation, which involved thermal tides (basically wavenumber 1 gravity waves). That theory is not completely dead, but the favored theory seems to be that of Gierasch, which involves both a Hadley cell to put angular momentum up there and upgradient angular momentum transport by barotropic instability eddies to accelerate the equatorial flow. Once somebody gets around to analyzing the eddies in the French Venus GCM and comparing them with the cloud patterns from VEX, it will be nailed. --raypierre]
It might help to understand the relative importance of different gasses by (visually) comparing emission spectra of Venus and Earth. (I know pressure and composition of the whole gas mixture affect gas spectra, and also, temperature, both by doppler broadenning and by shifting the relative importance of different wavelengths.) Could differences in vertical variation of mixing ratio be important? – water vapor in Earth’s atmosphere declines ‘precipitously’ with height, afterall :); it would be an interesting to compare concentrations at the levels of significant radiation to space (at the relavent wavelengths). It might also be interesting to graph the temperature profile of the two planets’ atmospheres using pressure as the vertical coordinate. How high up are the 1 and 2 bar levels on Venus? Where is the Venusian Tropopause (in pressure; I can see it’s around 90 km from the graph)?
[Response: I like to plot things vs. pressure myself. I have a plot in my climate book (Chapter 2) from Magellan and Pioneer data. The tropopause is between 500mb and 100mb, judging by where the sounding starts to be more stable than the CO2 adiabat. So, Venus, is just about an "all troposphere" planet, judging by mass. If PFS worked I'd be able to show you nice spectra comparing Venus to Earth. There's a PFS on Mars Express, and some people are working on convincing the team to point that at both Earth and Venus, which would be cool. There are good spectra from older probes, which you can find in the Venus Book, but I haven't been able to get my hands on digital versions of those. --raypierre]
At the risk of packing too much into one comment, someone once tried to argue to me, with regards to volcanic outgassing of CO2 as a way to end a snowball state, that the CO2 dissociates in the upper atmosphere; I pointed out that C is too heavy to escape much (I vaguely recall coming up with a rough guesstimate of some trillions of years for thermal escape to draw down CO2 concentration by 1 ppm), and so would just diffuse downward to where greater pressure favors synthesis reactions (well maybe I didn’t go into the diffusion part but oh well…). Reading about the O escape from Venus got me to rethinking that. But even with chemical energy liberation, and also magnetic fields accelerating ions (for Earth, not Venus), my understanding is that O escape (and so I would expect C escape) from Earth is negligible compared to H escape. Is the daytime upper thermosphere on Venus much hotter than Earth’s (being closer to the sun and above the clouds)?
[Response: The stoichiometric O escape is measured directly. It was something of a surprise to me. Basically, even for Hydrogen, nonthermal escape processes rule. Jeans escape is certainly too slow for anything heavier, but the kick you get from chemical energy, at levels so high there are no further collisions after dissociation, is very important. Then, there's the whole subject of hydrodynamic escape, likely to have been important on Early Venus and Earth. I'm still trying to get a straight answer from the Venus folks as to how important the lack of a magnetic field is to the escape rate. It certainly makes the interaction with the solar wind very different. --raypierre]
Ray, do you see any prospect of terraforming Venus?
Has anyone done the math for a sunshade between Venus and Sol, for example?
It’d be foolish to lose any chance of prospecting for any traces of past life there, if there’s hope of finding such; would resurfacing, if it did happen, have occurred after the planet overheated from whatever friendlier conditions it may have had?
I miss the swamps of Venus from the old stories.
[Response: I was about to say that there' little chance that records of past conditions on Venus have survived, but then I remembered the remarkable tale of how some aspects of Hadean Earth climate can be inferred from zircons. It would take a sample return mission and a lot of digging around, but I wouldn't discount the ingenuity of the folks who keep thinking of more and more clever proxies. As for terraforming, water is the key. A sunshade wouldn't do you much good unless you had some way of binding up the CO2 atmosphere into carbonate rocks, and that means water. Perhaps some of the thinking about engineered geochemical sequestration reactions that has been done for sequestraton problems on Earth could be recycled into Venus? Nobody's thought much about that. If there's any water vapor still outgassing it's a pretty small amount, so in addition to a sunshade, you'd need to smash in enough comets to make an ocean. Or maybe divert a nice icy moon like Europa (but please do an environmental impact statement first!). Regarding sunshades, I have a theory that a rather modest increase in solar absorption in the Venus cloud layer could actually cause the whole deep atmosphere to become isothermal and condense into a CO2 ocean. Needs work before it's ready for prime time, though. --raypierre]
18 re I suspect they didn’t want the frog to upstage the Rush Limbaugh impersonator who warmed up the crowd at the opening event.
I’ll send along the fossil hydrogen screed- the basic idea is that since the volatile hydrocarbon fraction in coal varies by a factor of ~8 from deposit to deposit, and carbon content for the same energy density varies by ~ 30 %, the CO2 emissions of existing plants could be significantly mitigated by policies favoring mines with higher hydrogen contents.
Re the response to #22: an entire LPSC session is being devoted to two meteorites from an as-yet undetermined, “differentiated planetary body,” which I guess is likely to be Venus or Mercury. Any discussion of this at the conference?
The record of past conditions on Venus may have survived in the form of meteorites here on Earth or on the Moon.
Grinspoon once had a theory that microbial life might survive in the venusian cloud deck and could be the source of mysterious large particles identified by the Pioneer probes. Sounds like this idea didn’t come up though.
Excellent article. Thanks for the report and all the comment replies. I learned a lot on the first read and will do a second.
Whenever this layman looks up and gets aggravated at all the airliners carbonizing his atmosphere it’s good to know that some of the people on those planes are traveling to expand our knowledge of the Earth and its neighbors. Keep up the good work,
there are obviously other things going on between the planets. If you removed the greenhouse effect on both Venus and Earth, Venus would actually be colder (even being closer to the sun) because of its thick cloud cover that allows only ~17 W/m2 of solar radiation to get to the surface on average. You also need to figure in pressure broadening which makes the greenhouse gases more effective because it spreads the absorption over a broader range of wavelengths/frequencies. If you shift one planet over in the other direction you have Mars which is pure CO2 but only ~ 7-10 millibars of total atmospheric pressure, and CO2 is relatively short-lived there because it condenses out because it is so cold. You also have no oceans. On Earth, the thermal capacity of the oceans is very, very large. In fact, if you heated the world’s oceans by just 0.1 C and then took all that heat you did that with and threw it in the atmosphere, the atmosphere would warm by some 100 degrees C. If we had no oceans, then we’d be a bit more sensitive to external perturbations– Venus’ thick atmosphere makes up for some of that.
I also don’t know, but looking from Ray’s lapse rate figure, I would imagine the greenhouse effect is stronger on that basis (stronger lapse rate= stronger greenhouse effect).
Once you get outside a certain CO2 range (not really one relevant to us today), but you will start to lose the logarithmic range. I would imagine Venus follows a different relationship, but I highly doubt it resembles forcing = 5.35 ln(Cf/Ci), also in part because the primary CO2 absorption is not at 667 cm-1 but at something like 2500 cm-1.
A lot of what I said is speculation, but it is at least quite obvious it would not be so easy get a climate sensitivity from Venus and apply it to Earth.
[Response: For Earthlike gravity you lose the logarithmic dependence of radiative forcing on CO2 somewhere around 20% CO2 in a 1 bar background atmosphere. The radiative forcing starts to get steeper after that. This is discussed in Chapter 4 of my Climate Book. Further, once you get past one bar of CO2, the pressure broadening stsrts to make CO2 much more effective as a greenhouse gas. It's the flip side of Mars: Mars has much more CO2 per unit surface area than Earth, but the CO2 there winds up having about the same greenhouse effect because it's at much lower pressure than on Earth -- 7 mb vs 1000 mb. --raypierre]
John, I imagine being ~40 million km nearer the sun has an effect on the baseline temperature, so it would be less than 30C per doubling.
[Response: That affects the runaway greenhouse, but is not the issue for the present state of Venus. The highly reflective clouds more than offset the effects of closer proximity to the Sun -- and that continues to be true even if you take into account the greenhouse effect of the clouds. On top of that, on Venus you don't get much help from water vapor (only a little). The real answer is that CO2 becomes a much better greenhouse gas at high pressures. --raypierre]
Raypierre, I tried to post this yesterday but it didn’t get through for some reason. Regarding absorption/scattering by cloud particles, in the Fraunhofer regime droplets scatter twice as much light as they intercept (in the Mie regime it can be as much as 4x), so even for complete absorption the absorption/scattering ratio is ~1.
[Response: Yes, but for strongly absorbing particles a great deal of that scattering is in the forward direction, and then when you figure in that a lot of that scattered light will be absorbed by the next few cloud particles encountered you don't get much backscatter from strongly absorbing clouds like water clouds. On the other hand, for weakly absorbing clouds, the infrared is actually backscattered somewhat better than visible and UV if the droplets are around 10 microns, since they are then well matched to the wavelength of the light and hence you get a bigger cross-section than in the geometric optic limit. On Venus there seem to be a lot of large sulfuric acid droplets, whereas sulfate aerosols take the form of very small particles on Earth. I have a lot to learn about the microphysics that governs drop size, but the larger sizes on Venus presumably are due to a greater supply of SO2. --raypierre]
I was a bit surprised to see the tropopause of Venus being deeper into the atmosphere than Earth’s, as I would expect the troposphere to eat it’s way upward with an increase in the greenhouse effect, but then I reminded myself that it’s absorbed solar radiation is lower (and also, different gas properties, and different gravity, so even with the same composition, the pressure wouldn’t translate to optical depth quite the same way. Also there is the lack of a stratosphere or mesosphere. Although not all of these points would explain a deeper tropopause…)
I am interested in learning more about wave/eddy-mean flow interaction, and also how climate change would affect that. It occurs to me that in additiong to changing mean conditions, the increased longwave opacity should have some effect directly on thermal damping of thermal perturbations (I figure that the middle of thick perturbations would last longer but very thin ones would dissipate more readily, although the argument for that comes from increased opacity at a single wavelength and so the necessarty definition of thin/thick is wavelength depedent, so the total effect would be hard to figure out without computer modeling), and while it might be more subtle than other effects, I’m curious how this could affect vertically propogating Kelvin/Rossby-gravity/planetary waves and the way extratropical synoptic-scale eddies affect the stratosphere and how that might feed back to those eddies. While more subtle than sea level rise, I’m in general curious about how internal variability on different timescales interact and how that would affect or be affected by climate change, and that includes questions about would extratropical storms and anticyclones be larger or smaller horizontally, more or less strong (and where and when (seasonal dependence of storm track positions and changes in them), and how fast would they move (and where), how long would they last, how would their cloud patterns change, etc. (And how might that affect severe thunderstorm occurance, MCCs, etc.) Also, I wonder how much regional climate change could be caused by changes in the thermal and topographic forcing of the quasi-stationary planetary waves. Could you recommend any books on those subjects? Thank you. (I had read that teleconnection patterns resulting from low-frequency SST variability are most sensivite to tropical SST anomalies because of the higher mean temperature of the water … well without going into why here, I could imagine that this would be one mechanism by which global warming would increase low-frequency variability. Could new modes of internal variability emerge? Could others vanish or lock into one phase?)
[Response: Viewed in terms of mass (equivalently pressure) the tropopause isn't deeper in than Earth. If you put the tropopause at 1 bar, that makes the troposphere close to 99% of the atmosphere by mass. On Earth the tropical tropopause is around 100mb, which puts the troposphere at 90% of the atmosphere by mass -- and considerably less in the extratropics. What makes the Venus tropopause high? There are two ways to get a high tropopause: low lapse rate or large optical thickness. On Earth it's the lapse rate that makes the tropical tropopause relatively high. On Venus, the dry CO2 adiabat is relatively steep, and instead it's the huge optical thickness of the atmosphere that pushes up the tropopause. It's not obvious a priori how the tropopause behaves as a function of optical thickness, but the mathematics is not too hard to work out. --raypierre]
I’m not sure I see your point. The atmospheric pressure on the surface of Venus is 92 times that of Earth at sea level. C02 represents 96.5% of the Venusian atmosphere – that’s 965000 ppm compared to 380 ppm on Earth. Even allowing that Venus is a little smaller than Earth there must be around 200,000 times as much CO2 in the Venusian atmosphere. Unless my “back of the envelope” calculations are way out…
[Response: But the point was that 200,000 is only 18 doublings, so if you use a logarithmic law you don't appear to get enough greenhouse effect to account for the temperature of Venus. The answer to that is that in fact the log law only holds up to about 0.2 bars of CO2, and after that the effect starts to get stronger -- even more so once you get enough surface pressure that the self-broadening takes off. --raypierre]
Hank, fie, I was planning to make just such a comment :-)
Yes, Venus was a nicer place with tropical rain forests.
> Or maybe divert a nice icy moon like Europa
Hmmm. Energetically a Kuiper belt object/objects would be more attractive. (More like the comets idea.) Or if Europa as a whole is too big, use electromagnetic “mass drivers” on its surface to send a stream of ice cubes to Venus…
How much water would be needed? It would be a catalyst, right? But, wouldn’t it disappear into the rock as crystal water — at room temperature, unlike at present temperatures?
[Response: That's a very good question about how much water would disappear into hydrating minerals. Part of that would depend on whether you started up plate tectonics, but there are minerology questions that need to be resolved. Various people are working up experiments to look into this. Even for the Earth, estimates of how much water in the mantle vary considerably, from about a third of an ocean to one or two oceans. --raypierre]
When would the atmosphere on Venus have been more conducive to life. How many millions of years back? And what triggering the runaway warming?
[Response: Around 3-4 billion years ago, the Sun was fainter and Venus was just a bit above the margin for a runaway greenhouse under clear sky condition. Cloud effects are an uncertainty, but one estimate suggests that clouds could have inhibited a runaway, leading to a situation where it gets very hot (maybe even 370-400K), but you still have a liquid ocean and only a slowish leakage of water to space. The planet would eventually dry out (maybe taking 100 million years to do so), allowing CO2 to accumulate in the atmosphere until Venus was hot like at present. Or, as the Sun gets brighter, you could pass a runaway threshold even in the presence of clouds and lose the ocean more quickly. Cloud effects on a runaway are rather speculative at present, and I think it will take an Early Venus GCM to provide the dynamical context to take the next step in improving estimates of cloud -- and water vapor subsaturation -- effects. --raypierre]
Ref 34 from Bill Bua. May I suggest that both references are correct, and are different interpretations of the same data. It is true that in the latter part of the 20th century world temperatures rose significantly, and temperatures are still higher than they were 30 years ago. It is also true that in recent years, this rise seems to have at least stopped. World temperatures, I would suggest, have either gone through a shallow maximum, and are now declining, or are going through a point of inflexion. Looking at the GISTEMP data for January and February 2008, it is arguable that all five sets of world temperature anomalies are in agreement with this interpretation. Such a point of inflexion was forecast by Smith et al in Science, August 10 2007, pp 796 to 799, with their Decadal Model. However, I would point out that their forecast for 2008 is 0.4 C, and the average for January and February 2008 is 0.13 C, according to the HAD/CRU data set. Which interpretation of what is happening to world temperatures is correct, is not, IMHO, clear; it may be what anyone likes to believe. I would suggest that we need quite a few more months of data to know whether we have have seen a maximum, or are seeing a point of inflexion.
Lynn V #35: billions rather than millions of years. And it’s even possible that it never happened, i.e., that Venus has always been, well, uncomfortably warm.
The mechanism would be, from what I’ve read, first reaching temperatures where large parts of the ocean go up in vapour, and the water vapour feedback exceeds 100% until the ocean is gone. After that, with rock weathering gone, CO2 would build up due to volcanism, gradually driving the CO2 out of the carbonate crustal and mantle rock into the atmosphere.
Quote: “On Venus there seem to be a lot of large sulfuric acid droplets, whereas sulfate aerosols take the form of very small particles on Earth.”
It has been proposed to inject SO2 or H2S into the stratosphere as a “last resort” to directly counter global warming. I believe the idea is that these chemicals will react in the atmosphere to produce sulphuric acid droplets to scatter sunlight back into space. But you argue that larger droplets are better at back scattering. Is that true, weight for weight, since if you double the size of droplets, you can only have an eighth the number for a given weight? Is there any way one could increase the size of particles, if that produced a higher albedo for given weight?
[Response: The larger particles are only better at backscattering infrared. If you somehow managed to make large droplets by injecting SO2 on Earth that would be bad news, since you could get a similar effect. It's unlikely, though. Until particles get much smaller than a wavelength, the scattering goes roughly like the cross section area. Hence, for a given mass, you get more scattering by divvying up the mass into small particles. Once the particle size gets smaller than a wavelength, though, the scattering efficiency goes way down. The sulfate sunshield proposed by some desperate individuals for Earth works by reflecting sunlight, hence you want particles with a size of around a micron. --raypierre]
Has there ever been an experiment in which we have replicated the atmosphere of Venus in say a greenhouse, and then watched its temperature rise to at least half of that on Venus 400 degrees say? It seems that would be a perfect and easily done experiment tp prove our assumptions. Does anyone have a link to a study showing such a study?
I was told several were attempted but no dramatic increase observed.
Fascinating stuff. Now about the earth’s runaway greenhouse. I had been under the impression that only another .5-1 billion years of solar evolution (3-6% brightening) would set it off. I get the impression that some here might think that is way too early. Perhaps the shorter time period is for enough warming to be catastrophic for life as we know it, but not yet the true runaway greenhouse?
The terraforming of Venus is science fiction, but if a sun shade was put at Sun-Venus lagrange point to freeze out the CO2 at the poles, you would be left with an N2 atmosphere.
Getting water to the planet to make those shallow seas of SF would require a hell of a lot of ice, but the energy could be less than you’d think if you play a clever game of billiards, using the outer planets gravity to smack little comets into larger kuiper belt objects, thus changing their orbits to get that slingshot planetary flyby to Venus.
According to James Lovelock by 2100 most of the equatorial regions of the earth will resemble ‘mars’ not venus? As an observer..I am seeing many many environmental effects around the world relating to ‘climate change’ but not necessarily ‘greenhouse effect’. The climate is definately more variable and extreme that in decades past..case in point..the world is getting divided between those countries suffering from drought and those suffering from frequent flooding. I’m not sure referring to venus when arguing about greenhouse conditions is that appropriate..coz that is venus’s stable state, it has never had a fragile and complex atmosphere like ours. A pathogenic condition is noticable only when it deviates from the mean, in venus’s case a dense swirling gas blanket is the mean and probaly has been for a billion years or more.
Been reading more on Lovelock, and his pedigree as a scientist is unquestionable.. a real scientist’s scientist!..the only critisim that keeps popping up is his underestimation of CFCs as a pathogenic gas for humans..it isn’t, but it sure as hell was for mother earth! The one thing that is very apparent to him is that we are now well into a positive feedback world and with the world still obsessed with boosting economies and a population likely to peak at 9bil (if we get there??), there is little chance of reversing the +ve path we’re on. In anyone’s opinion..what are the 3 most important things the world has to do collectively..NOW.. to cut the 30bil tonnes of CO2/yr not just by 1/2..not by 3/4 but totally elimiante it. This forum is not about politics although scientific/political/social solutions are the only way I can see us capturing this genie.
Comment by Lawrence Coleman — 20 Mar 2008 @ 3:51 AM
When might we expect thirsty (they need our water!) Venusian climate scientists, plus guns natch, to arrive here and disprove for ever the theory of AGW?
[Response: Ah, that would explain a lot of mysteries! No doubt the same NASA scientists and media experts who so effectively faked the Moon Landings have turned their attention to simulating returns from the supposed Venus missions; one of their early brilliant accomplishments was way back in the 60's when they put up a stealth satellite to simulate anomalous microwave emissions from Venus. Obviously, Arrhenius was right all along about Venus being a steamy paradise, and it's all a cover to buy time for preparations for the Venusian invasion. --raypierre]
We talk of climate sensitivity and we gauge that 550 ppmv of CO2e probably means 3C of mean global temperature rise but what about systems response to that rise ? The Arctic sea ice, Greenland and West Antarctic Ice sheets and global glaciers are all responding to warming so surely the problem for humanity is not climate sensitivity per se but the response of earths systems to that warming. The intertia presumed/assumed in these large scale ice based systems is not as great as forecast and hence we are see possible rapid non linear responses to 0.8C of warming with 0.6C in the pipeline and another 0.5C (James Hansens words) from the current fossil fuel infrastructure making 1.9C in total almost to be guaranteed. if system response to 0.8C is troubling and ahead of RC/IPCC projections then what happens when it is a whole degree warmer please?
Re #40 Andrew Worth: Getting the CO2 to freeze out on the poles would be a bit of a problem as most of it would first become liquid, forming a CO2 ocean.
One possible technique would be to arrest Venus’ rotation, which is very slow already, to make it always face the same side to the sun. Doable with a suitably designed impact, requiring “little” (by terraforming standards) energy. Then, the permanently dark side could become a “CO2 graveyard” under a kilometres thick near-hemispherical CO2 ice sheet, while the sunny side could enjoy Earth-like climate. Even with a range of climate zones… wonder how thick the atmosphere could be while preserving the needed temperature gradient. No free water vapour though, that’s for sure. A bit of a limitation.
What a wonderful demonstration that, beyond wages of hype being less sin than sci fi, planetology is where you find it:
If an atmosphere exerting a pressure of a tonne per square centimeter is frozen into a pair of polar hockey pucks > 100 kilometers high, the crust is not going to like it.
Squashed into the Venereal mantle by a kilobar of dry ice, the oppressed polar crust will sink and crinkle into a bull’s eye horst and graben, looking for all the world like …Egads has this guy explained the Martian polar terrane ??
THE VENUSIAN CHRONICLES
A lunar expedition discovers remains of an earlier space expedition…way too much earlier (gulp) to be from Earth. There are writings, and as top linguists back on earth try to decipher them, people panic. What if the spacelings made it to Earth and are among us?
Linguists find out they were from Venus over a billion years ago. The Venus science then gets corrected and cleared up (from the Venusians’ advanced scientific and natural history writings that are slowly deciphered). It was the Venusians who had triggered the runaway warming, millions of years earlier than would have happened naturally. They knew they were in a fragile climate balance, but had dithered and gone on with their proligate party life. In their venus-engineering-gone-wrong they had even slowed down the rotation of Venus.
But a small colony of Venusians were able to escape, planning to settle on earth. Then their spaceship had problems, and they were forced to land on the moon, where they perished, despite their desperate attempts to venus-form it. Or did they all perish? There was a space pod mentioned in their chronicles, and their hope that perhaps some would make it to earth. But no trace of the pod can be found….
I like the idea of using the Kuiper belt ice to arrest the planets rotation, would 50 million cubic kilometres coming in at 70 km/sec (guesstimate) relative to the planet be enough to do that?
Freezing it all out over a smaller area at one point rather than two makes more sense, but surely we can keep the area of this dry icecap down to less than 60 million square kilometres?
OK, here is a crazy idea. Please tell me why it wouldn’t work (I am a layman). Would it be possible to geo-engineer a plant that does photosynthesis and could survive in that temperature? Some type of GMO cactus perhaps? Then send an unmanned ship to Venus to plant said cactus. The plant would then start converting all that CO2 into O2, and reproducing. At some point, then you could test the theory of whether the atmosphere would cool as the CO2 concentration (965,000 ppm) came down. I guess one problem, other than getting there, would be if the plant could survive 116 days without sunlight.
[Response: Water is going to be a problem. If it weren't for the lack of water and the high acidity in the clouds, I'd say the place to start is not at the surface, but with some kind of cloud-deck airborne cyanobacteria. It's colder there. You'd want something that would make a very refractory form of organic carbon, and which would clump together and reach the surface. As things cool further it would work its way down. However, even apart from the water (which is needed for oxygenic photosynthesis to work), you have a problem with this scheme since you wind up with as many moles of O2 as you started with CO2, and that's pretty deadly at the resulting surface pressures (exercise to the reader: compute the resulting surface pressure). That's why it would be better to convert the CO2 into carbonate instead (at the surface this would happen by reaction with silicate rocks). No matter what, at some point you're going to need to bring in a lot of water. An advantage of the cloud deck idea is that you wouldn't need to bring in enough water to make an ocean, just enough to give you water clouds at the cloud level. Getting airborne cyanobacteria to precipitate carbonate shells using what's available in the clouds is going to be tricky, though. All this is just science fiction, of course, but it's still stimulating to think about. --raypierre]
Re #48 Lynn: I remember somewhere reading a story like that…
A perhaps more realistic idea: if Venus was indeed habitable for the first couple billion years, we must expect micro-organisms to have developed there just like on Earth. But due to the greater input of Solar energy, we should expect all life cycles, and thus evolution, to have moved forward faster than on Earth.
It has been argued that micro-organisms, or their spores, could be transported from planet to planet inside rock fragments thrown off-planet by impacts. In the early years of the Solar System there were a lot more large impacts than today.
So, did life on Earth originate on Venus? And was it at irregular intervals replaced by new batches of immigrants?
Shades of Arrhenius’ panspermia. Surely a crazy idea… or is it?
[[It is also true that in recent years, this rise seems to have at least stopped. World temperatures, I would suggest, have either gone through a shallow maximum, and are now declining, or are going through a point of inflexion.]]
This is completely wrong. Temperatures are still rising. Take either the GISTEMP or the HADCRU temperature series for 1995-2007 and they are both significantly upward.
[[ Looking at the GISTEMP data for January and February 2008, it is arguable that all five sets of world temperature anomalies are in agreement with this interpretation.]]
Two months of data is not enough to decide anything at all.
Re response to 31 – okay; I think I may need some clarification. On Earth, of course, increasing the greenhouse effect leads to a warming of the surface and troposphere but a cooling of the upper atmosphere —
(because it is more opaque, so radiates more effectively to space, while at the same time is recieving a greater proportion of upward radiation from the cooler upper troposphere and less from the surface – all that being wavelength and cloud-cover dependent, of course, where at some wavelengths in clear low humidity skies, all of the atmosphere becomes more visible from space at the expense of the surface only, whereas at other wavelengths only the upper atmosphere becomes more visible from space at the expense of all below it, and then the ozone layer adds an interesting twist),
which when combined (warming below, cooling above), suggest a rising tropopause, adding mass to the troposphere at the expense of the stratosphere (PS I also wonder how that would affect tropospheree-statosphere dynamic interactions, such as with synoptic-scale systems or planetary waves, or the QBO).
The assumption I had, then, was that, overall, provided a large share of absorbtion of solar radiation occurs below the tropopause (is that not the case on Venus, then?), the troposphere must be significantly visible from space in the longwave band. Otherwise, a significant net LW flux must go from the troposphere to a cooler part of the upper atmosphere (it would have to be the lower part of the upper atmosphere) and then to space. Is that how it is happenning on Venus? On a related note, I noticed a distinct bend (around 60 km) in the lapse rate in the graph above between a higher positive lapse rate below and a lower but still positive lapse rate above. Is that the tropopause, as opposed to the temperature minimum around 90 km?
PS about my dynamics questions earlier – I realize there are papers I could look at but I’m not actually a climate scientist (yet) and at this time I don’t have easy access to most of the journals, and I was just hoping there might be some resources where I could find a concentration of information on those subjects.
(One additional question I could add to the last part of my last comment (31)(My apologies for going so far along this tangent) – while not the same for all latitudes, longitudes, and seasons (or perhaps phases of low-frequency internal variability modes), there is an expected tendency for overall reduced pole-to-equator thermal gradient in the lower troposphere (for the Northern Hemisphere, anyway) but an increase in the upper troposphere – I haven’t seen much explanation as to how these two effects might together shape changes in weather patterns (I would imagine that at some places and times (summer in particular), one of the two occurs but not the other, which would have interesting effects). What would the combined effect of different changes in thermal gradients at different levels be on the occurence and life-cycle of synoptic-scale systems and their associated phenomena? On mesoscale systems? Severe thunderstorms and tornados?)
In comment #42,Lawrence C. says:”I’m not sure referring to venus when arguing about greenhouse conditions is that appropriate….”
Lawrence,Venus has an atmosphere that consists of a mass of over 96 percent carbon dioxide, (http://en.wikipedia.org/wiki/Venus) and its surface is hot enough to melt lead! There’s got to be a lesson for us, in there someplace!
“The sulfate sunshield proposed by some desperate individuals for Earth works by reflecting sunlight, hence you want particles with a size of around a micron”
And re #44:
“The Arctic sea ice, Greenland and West Antarctic Ice sheets and global glaciers are all responding to warming so surely the problem for humanity is not climate sensitivity per se but the response of earths systems to that warming.”
Concerning the latter (#44 quote), the Arctic sea ice is responding to the current temperature, and, through the albedo effect, is amplifying that temperature, independent of greenhouse gases. The only way to stop that amplification is to counter it with an albedo cooling. No amount of emissions reduction will stop the Arctic sea ice from receding further, and the sea ice could disappear by September 2009.
Concerning the former (#39 response quote), it seems logical to consider the sulphate sunshield as perhaps the only method to quickly produce the albedo cooling necessary to stop the Arctic sea ice from disappearing in the next few years, however desperate and environmentally naff this method might seem at first sight. We have to balance the risks. The danger from rising temperatures in the polar region, with release of methane from tundra and destabilisation of the Greenland ice sheet, is much greater than the danger that somehow the sulphate sunshield will backfire (as in the biofuel fiasco).
BTW, a problem from albedo cooling is that people might see it as an excuse to continue polluting the atmosphere with greenhouse gases. We have to keep the pressure up on emissions reduction.
The Earth’s magnetic field is attributed to a dynamo effect of circulating electric current, but it is not constant in direction. Rock specimens of different age in similar locations have different directions of permanent magnetization. Evidence for 171 magnetic field reversals during the past 71 million years has been reported.
Although the details of the dynamo effect are not known in detail, the rotation of the Earth plays a part in generating the currents which are presumed to be the source of the magnetic field. Mariner 2 found that Venus does not have such a magnetic field although its core iron content must be similar to that of the Earth. Venus’s rotation period of 243 Earth days is just too slow to produce the dynamo effect.
Right now the Earth’s magnetic field is weakening. Since the climatologists claim they know everything important about the weather, can anybody tell me what a reversal of the magnetic poles will do to global temperature? Migratory birds?
John Nissen wrote: “it seems logical to consider the sulphate sunshield as perhaps the only method to quickly produce the albedo cooling necessary to stop the Arctic sea ice from disappearing in the next few years”. Were it not for the fact that stratospheric aerosol may very well lead to high latitude winter warming, thus counteracting what you want to achieve. I absolutely agree with your last statement (BTW).
Ref 53. I have done the analysis you suggest, Barton, but over a 30 year period, since satellite data became available in 1979, not just since 1995. As I have pointed out many times, if you force the data into a linear fit, as Tamino does, then the resulting graph shows a straight line with positive slope. Temperatures in 2008 are higher than they were in 1980. However, if you use non-linear least squares regressiion analysis, the graphs show what is either a maximum or a point of inflexion. I suggest you get something like CurveExpert 1.3 and do the analysis for yourself. Of course two months of data dont prove anything. But if they show that a trend is continuing, then they may well be significant. The issue is that 4 sets of data show the maximum/point of inflexion idea. GISTEMP did not. The fact that the GISTEMP January and February 2008 data show a large drop in temperature, MAY indicate that the GISTEMP data set is going to produce the same trend as the other 4 dada sets.
Re #59 [joel] “can anybody tell me what a reversal of the magnetic poles will do to global temperature? Migratory birds?”
Don’t know about temperature, but I’ll have a shot at the birds. Some birds appear to use a magnetic sense during migration (Thord Fransson, Sven Jakobsson, Patrik Johansson, Cecilia Kullberg, Johan Lind and Adrian Vallin (2001) “Bird migration Magnetic cues trigger extensive refuelling”, Nature 414:35), but innate “star maps” are probably more important, and birds who have migrated before will also use learned landmarks. So my guess is a reversal would lead to a lot more birds making errors (often fatal, occasionally leading them to previously unused but useable areas), but to few if any extinctions. Since the field reverses on average every few 100,000 years, migratory species have evidently got through reversals before.
Re Consumer #51: for the surface of Venus it sounds rather hopeless, but higher up there could actually be a level where some kind of green plants could function. Surrounded by a lot of hi-tech that is, like aerial floating habitats :-)
Joel, Actually, we understand the geodynamo pretty well. I recommend looking at some of the work by Gary Glatzmaier. The way reversals happen is that the orderly flow of the outer-core liquid iron breaks down, and more energy flows out of the dipole moment and into the higher multipoles. What this will do under normal conditions is increase the flux of GCR that make it into the atmosphere–especially in the tropics. If anything, this will likely have a slight cooling effect by increasing cloud nucleation sites. However, the effect is likely to be minor, as the GCR flux is only 6 particles per square cm per second. Keep in mind that this period persists for thousands of years, so if there were a really big effect, it would likely be evident in the geologic record.
A somewhat larger effect would happen during a solar flare. Normally solar particle fluxes are too low-energy to penetrate the geomagnetic field. However, these events last a few days at most.
Some migratory birds will be hurting, no doubt, but this happens every few hundred thousand years, so I wouldn’t expect catastrophe. Cancer and birth defect rates will go up.
Eventually, the flow in the core begins to stabilize in the new configuration. Once this happens the solid inner core acts as an inductor and strengthens the field and the new equilibrium persists for hundreds of thousands of years.
This is entirely irrelevant to the current climate of course.
re:57 Lawrence B, has anyone done the arithmatic to project the CO2 concentration and temperature of the earth when most of the carbon sources have been transformed into CO2 due to a runaway greenhouse effect…ei: when all the carbon locked up in the tundra has rotted, when the vegetation has died either from extreme heat/fire or flooding and when all fauna inc humans and all corals/placknton/krill/vertabrates/invertabrates have died. Presumably no more CO2 could enter the atmosphere or the oceans and a greenhouse equilibrium will be in affect for 1-2 million years. Most of the earth’s oxygen reserves and methane would have escaped into space. Nitrogen still would be quite high due to intense lightning activity, but can anyone project what the likely final temperature would be of the earth?? Just academic curiousity.
Comment by Lawrence Coleman — 21 Mar 2008 @ 7:58 AM
re: joel, we seem to be on the same bandwidth about the significance of venus, but I’ve been hearing about pole reversals my whole life, if it’s true what you say about the magnetic field weakening could it have anything to do with the artic ice cap disappearing?, since the earth’s magnetic field is a dipole with longitudinal orientation. Could ice or lack of – play a part in it’s weakening? I can’t see how it can but who knows! Ok guys!…WHO knows???
Comment by Lawrence Coleman — 21 Mar 2008 @ 8:30 AM
#59 & “Venus is so different from the Earth. Anybody who claims we can understand the DETAILS of Earth climate from a study of Venus sounds odd to me”
Which makes physics and climate science all that stronger — if they are able to explain both earth and venus.
re:59 Joel..are pole reversals cyclical – sinosoidal in nature or are they triggered by some random event?. I believe planetary alignments can cause the rotational speed of the earth to fluctuate slightly especially if they involve the giant planets.
Comment by Lawrence Coleman — 21 Mar 2008 @ 10:02 AM
Pete Best, thanks for the glowing reference of Jim Hansen. Just read some of his latest reports and trying to get my head around the many graphs he uses. One graph in particular puzzled me and was of CO2, CH4 and Temp since 400000BC. Up to 240000years back there was a regular upward spike in CO2/CH4/Temp uccuring every 100000 years but before that from 400K yrs – 250K yrs these dramatic spikes occur every 75K years. Question..what is causing these spikes? What hit me is that ACC is many times more deadly now because the increase in CO2 and CH4 is amplifying (on the back of) a regular spike which began 20K years ago. The last spike ocurring 140K years ago where the temp shot up by 5C. My apologoies for being ignorant but what natural phenomenon is causing these regular blips?
Comment by Lawrence Coleman — 21 Mar 2008 @ 11:08 AM
Lawrence C, I posted this in a previous topic, it’ll help you understand what’s happened in the past:
Re 67 – from what I’ve read (not quite as much as Ray Ladbury, apparently), magnetic reversals are not part of a sinusoidal cycle but are episodic events. I would assume the butterfly effect exists in this system (but on much longer time scales than the weather – it is obviously quite predictable out for two weeks, at least), so small perturbations from planetary alignments, as well as other things, could be factors, but from what I’ve read, It’s my impression that external perturbations are not necessary for reversals to occur.
As I recall, in terms of current atmospheric carbon content (mostly in CO2), about the same amount exists in living organisms, about twice that amount exists in soil. About 7 times that amount is in fossil fuels (mostly coal) – not counting methane hydrates/clathrates, which is more uncertain but one estimate I’ve seen woule put the carbon content of methane hydrates/clathrates at twice fossil fuels, or about 13 times the atmospheric content. I think roughly 50 atmospheres’ worth of carbon content is in the ocean (somebody double check that, though; this is a pop-quiz for me).
There’s also some organic carbon in rocks that is too distributed among other materials to be used as fossil fuels; I don’t know that amount. There’s tons and tons and tons and tons (way more than in the ocean) in carbonate minerals in the crust. Of course there’s some in the mantle and core, too.
Obviously a lot of these carbon reservoirs would not be immediately available just in response to climate change, … etc.
Lawrence C, re previous cycles, the first link under Science on right side of the page will get you the best summary. Google also leads to the same spirce:
Past Climate Cycles: Ice Age Speculations
The Discovery of Global Warming Spencer Weart …. By the 1940s, some climate textbooks were teaching that Milankovitch’s theory gave a plausible solution … http://www.aip.org/history/climate/cycles.htm
65: There is almost no connection between the current weakening dipole weakening, and arctic sea ice loss. The dipole field is only decreasing by a few percent per century. Reversals are a kind of chaotic process, if the dipole strength disappears it is about equally likely (IIRC) to come back with the original polarity as it is to reverse. The chaotic period could last for thousands of years before the dipole field gets strong enough to gain dominance. I don’t know the details about the statistics of periods between reversals, but would bet they are pretty random. I’m sure someone has looked at the distribution of reversal intervals to determine if it is anomalous (departs from expected for completely random). The geological record shows that the frequency of reversals has varied dramatically with time, so such statistical studies might not be very useful.
Re #68, I personally thought that we came out of the latest glacial around 15K years ago and fully out of its effects some 10K years ago. Hence what are known as Milankovitch cycles are responsible for most of the 100K, 41K, 21K year cycles due to earths orbit, tilt and angle of incidence to the Sun.
[[has anyone done the arithmatic to project the CO2 concentration and temperature of the earth when most of the carbon sources have been transformed into CO2 due to a runaway greenhouse effect…ei: when all the carbon locked up in the tundra has rotted, when the vegetation has died either from extreme heat/fire or flooding and when all fauna inc humans and all corals/placknton/krill/vertabrates/invertabrates have died. Presumably no more CO2 could enter the atmosphere or the oceans and a greenhouse equilibrium will be in affect for 1-2 million years. ]]
You’re confusing putting all the fossil fuel and biosphere carbon into the air with a runaway greenhouse effect. The former would raise the temperature of the Earth several degrees and could cause a very large mass extinction. But the latter would release the carbonates in the rocks, boil the ocean, and transform the Earth into an uninhabitable furnace-hot desert like Venus. Life can recover from the first, but not from the second.
re:69 Hank Roberts..Ok! assuming in the P/E era a sporadic outgassing from the mantle in the form of a surge in numbers of volcanic eruptions and/or subsequent earthquakes caused the PE theral maximum..can we also assume a similar mechanism for the sudden jump ocurring or initiated around 330K years ago where the temp jumped over the period of 20K years to +6C hotter?; then again 250K yrs ago where Temp+5C/CO2/CH4 jumped simultaneously and then again at around 135K yrs ago(temp+5C). We are not talking here of 55Mil yrs ago..but in the time frame of humanity from 400K yrs to the present, ocurring on average every 85-95K yrs. It’s difficult to see on the graphs which rose first…if it was mantle outgassing then CO2/CH4 would have led the charge but with +temp causing all the other CO2/CH4 sinks to be released into the atmosphere. Still the question still to be answered is why do these sudden outgassings if that’s what they are (if that’s what initiate these spikes) occur with such regularity? It looks almost like the cardiogram of gaia herself..haha!
Comment by Lawrence Coleman — 22 Mar 2008 @ 8:33 AM
The application of Venus to the argument of the CO2 effect on current Earth warming lies in the fact that even though less radiation is received by Venus from the Sun, than from Earth(Venus has an albedo value of about 75%)and that Venus has no water vapor in its atmosphere.
Therefore the CO2 is responsible for explaining the greenhouse effect on Venus and serves as a counter argument to those who say that the rising amount of CO2 in our own atmosphere isn’t contributing to climate change here on Earth, because of solar variability and increasing water vapor( which is an effect rather than a cause). If CO2 caused Venus to become very hot, then increased levels of CO2 here have to be warming our own planet.
Comment by Lawrence Brown — 22 Mar 2008 @ 10:48 AM
“There is a narrow window region in the vicinity of 1 micron wavelength, which allows the surface to be observed in the infrared”
Actually CO2 doesn’t start absorbing infrared until you get to about 2 microns. Two points here;
a) hardly a “narrow window”
b) not much in the way of band-broadening here even at about 90 bar CO2!
Re 76 – those most recent variations are mainly not due to volcanism or other geological emissions (there have been big eruptions that have left there mark – Toba around 75,000 years ago, for example, but the entirety of the last ice age was not caused by that event – PS singular volcanic eruptions tend to have a cooling effect – especially tropical eruptions – via aerosols. A long enough period of greater volcanic activity can have a warming effect because aerosols come out of the atmosphere relatively fast, whereas CO2 emissions linger (not forever, but long-enough) and accumulate. CO2 can also be emitted from geological sources without actual eruptions. Over very long periods of time geological CO2 sinks tend to balance geological CO2 emissions, and there is a long-term negative feedback that can maintain this balance – the process is too slow to prevent ‘short term’ variations, where ‘short term’ in this context extends out to at least 100,000 years, and I’m not sure just where the ‘cutoff’ is.)
The series of ice age – interglacial transitions over the last few million years (I think roughly 3 million, right?) is associated with more ‘rapid’ (geologically speaking) redistribution of carbon among the atmosphere, ocean, biomass and soil, and variations in the rate of burial of organic carbon (such as produced by phytoplankton), and also, I’m more vague on this point but dissolution of carbonate minerals on the sea floor may be involved. However it works (it isn’t fully understood but it is understood to happen), this change in the carbon cycle is a positive feedback that amplifies the changes between ice ages and interglacials via the affect on the greenhouse effect. What actually starts the changes is likely to be the Milankovich cycles, which don’t so much affect total solar radiation reaching the Earth but have a large effect on it’s spatial and temporal distribution, such that changes can occur which are more or less favorable to the formation or destruction of glaciers and ice sheets, which have an albedo effect on global climate. However, the way the climate responds to Milankovich cycles has varied – obviously the climate state has to be cold enough for any particular phase of Milankovich cycles to initiate an ice sheet, and a generally colder or warmer state would alter the response. Past history could also have an effect – in the first few in a series of ice ages, ice sheets may form on top of loose material on the land surface, which may allow the ice to flow more easily; as this material is scoured away, later ice sheets may form on bedrock, and be less able to flow, thus they may build up to greater thickness. The greater elevation of the ice surface makes it colder and this affects how easily the ice sheet may be warmed up to the point of it’s destruction. The elevation of the ice surface is not just the original land surface plus the ice thickness – it is less, because the crust sinks underneath the ice’s weight. There is or may be some threshold level to end an ice age that is not reaced in every cycle, depending on where the threshold is, which may vary (such as due to how easily ice sheets flow). There is also the idea that the Earth’s climate has a natural frequency on this time scale that the Milankovich cycles stimulate. There is a general phenomenon called stochastic resonance…
Obviously the arrangements of the continents and the oceans (and their currents) have an important effect, as well as geologic outgassing rates and chemical weathering and organic carbon burial rates, in whether or not the Earth is primed to experience any ice ages, and in the nature of those ice ages.
Chemical weathering and organic carbon burial put carbon from geolical emission back into geological reservoirs. Chemical weathering can act as a negative feedback over very long time periods (as mentioned earlier) – a warmer climate, and also, I would assume, higher atmospheric CO2 levels, tend to increase the chemical weathering rate, so if the geologic outgassing rate rises, CO2, and as a result, temperature, tend to rise, until the chemical weathering rate responds to balance geologic outgassing, leaving the CO2 and temperature, not as before, but at new steady (over the long-term) levels. Chemical weathering can also act to lower CO2 over hundreds of millions to billions of years in response to gradual solar brightenning. However, chemical weathering is also affected by the arrangements of the continents and oceans, and topography – mountainous areas in the humid tropics are generally quite favorable for chemical weathering (rapid mechanical weathering by glaciers and liquid water occuring on the steep slopes can produce large surface areas of sediment for chemical weathering to act on – chemical weathering is not favored in the cold of the glacier, but ultimately glacial debris can be carried down the mountain to warmer levels) (unless they lack certain minerals that are important in the process – I’m not sure how variable on the large scale the mineral content could be – it might not be much of a factor). Organic carbon burial on land is more favorable in flat lowlying areas with humid climates. Then there is organic carbon burial at sea …
A continent near a polar region may make ice ages more likely, but a continent that is too large may experience too large a seasonal temperature variation, so that the summer heat prevents ice sheet formation; also, less moisture may reach the interior of a large continent.
Comment by Lawrence Coleman — 23 Mar 2008 @ 1:53 AM
re: 74 P.B… from that graph you can clearly see how CO2 practically mirrors Temp. 350K years ago a CO2 upsurge lead temp and CH4..but from then on it’s quite ambiguous in that the upsurges appear simulataneous. Take the ’0′ on the x axis as being the 1900AD mark as what I see is that temp has peaked and may be falling but CO2 & CH4 are still at max levels and rising sharply..interesting??
Comment by Lawrence Coleman — 23 Mar 2008 @ 2:14 AM
BTW: HAPPY EASTER!!! to ALL the contributers at RC. Keep all your own levels of CH4 and H2SO4 to reasonable levels wont you after inevitable overconsumption of easter eggs..haha!
Comment by Lawrence Coleman — 23 Mar 2008 @ 9:23 AM
Re #81, hmmm, I believe that this is a resolution problem. Getting ice core data on decadal and century time scales. However the forcings can be worked out from this data and hence via pg 11 in the presentation (thats why it is there) which gives legitimacy to the data and findings on forcings and hence current warming levels.
The entire presentation is linked to a video available over at youtube or video.google.com. In it he explains it all and shows that models are helpful but limited but there exists a real world of data that explains the present forcings.
He reckons that 2C is essentially unavoidable (mainly due to existing ff infrastructure guaranteeing another 0.5C on top of the 0.6C in the oceans and the 0.8C we have had already in the 20th century).
He knows asserts that we must think and act deeply to avoid >2C rises. Truely grave.
I should amend my previous post, since scientists now believe that Venus does contain trace amounts of water vapor as Raypierre states in the lead article. However, the argument still holds that if CO2 is the major contributor to greenhouse warming on Venus, then raising our own levels of CO2 and other greenhouse gases has to be a contributing factor in causing Earth to warm.
RE: Wayne @ 88,
Perhaps you meant to say “not that Venus _isn’t_ very interesting”?
Anyway, I certainly think Venus is very interesting, but I’m interested in solar activity, too, what with all the talk in some circles about correlations between sunspot numbers and Earth surface/atmosphere temperature. I looked at http://www.solarcycle24.com/ and couldn’t immediately tell from their mention whether these recent sunspots are of the cycle 24 polarity or the cycle 23 polarity. Does anyone here know whether these latest spots belong to 23 or 24?
I don’t have time to read it yet, nor is climate science my true expertise, but it sounds like the author, Ferenc Miskolczi, has rederived radiative transfer equations for a FINITE atmosphere (rather than infinite, as is done by Milne 1922) and the result is much less warming from CO2 absorption and a tendency for radiative balance not to wander much. This sounds counter to what I know about radiative processes, and I was hoping one of you would comment on this in a future blog entry, if it warrants it.
[Response: This paper is more nonsense of a piece with the unpublished MS by Gerlich and Tseuschner, though with the difference that this one is published in an obscure Hungarian weather journal rather than not being published at all. The main use of this paper is as an exercise in "spot the errors" for a grad student in radiative transfer. We could comment on it, but on the whole it's more worthwhile to spend time commenting on things that have passed review in the more major journals and don't have such obvious flaws (even if they nonetheless have flaws). --raypierre]
Bill, It appears to me that there’s less here than meets the eye. It really reads more like a script for CSI, where the characters don’t really understand what they’re saying. If I felt like wading through 40 pages of mumbo jumbo, I’d probably find the kitchen sink in there, too, but certainly he had everything but.
The denialosphere has adopted this guy as a cause celebre, but buggered if I can find anything he ever did of not previously. Certainly no climate expertise. When will people realize that climate science is a mature science? You aren’t going to see the whole thing overturned with the publication of a single paper.
Any chance you can give us a hint as to (some of) the fundamental errors in the Miskolczi paper? My radiative transfer was in stellar atmospheres (35 years ago) with limited application to the planetary case. Start me off and I can probably work through the rest. And, I promise not to share with your graduate students. Thanks.
[Response: I'd start with his assumption (g) which I have never seen applied to the Earth's atmosphere before and the logic in section 3.1 - there he equates E_u (the upward LW from the atmosphere, a flux) with the total internal energy of atmosphere. That would appear to be an fundamental error in units (or description). The erroneous conclusion in section 3.3 that the greenhouse effect does not depend on optical depth presumably arises from this (i.e. the total mass of the atmosphere determines the gravitational PE (assuming hydrostacy), which sets the internal energy (via assumption 'g') and therefore the outward LW). None of this makes any sense, but I haven't worked through his algebra in any detail (so it's possible I've read this wrong). If you (or someone else) wants to do so, we'll post it up. - gavin]
#89 Kevin, You right, Venus is very interesting. Those sunspots darkened a lot as well.
As of late a lot of Climate events are on going right now, like Wilkins Ice shelf disintegration, also Arctic Ocean start of melt season along with interesting Polar clear air . There is a need for an open thread as mentionned, so many things to discuss.
Sorry to be off-topic, but I don’t know how else to suggest a topic for a future post. (Is there an appropriate way?)
There is much excitement in the blogs over Spencer et al, GRL 2007, which contains some observations that are at least consistent with Lindzen’s left-for-dead Iris hypothesis.
Sadly, Spencer’s cautious tone was superceded by some Ms. Marohasy, who has proclaimed that the water vapor feedback has been refuted. The blogs are trumpeting her quote.
So, if anybody has any interest, is it time for a post about the current understanding of high and low altitude clouds?
[Response: We've been aware for quite a while that Spencer's article deserves a comment. As you note, the spin being put on these results in the blogosphere is quite different from the more cautious interpretation given in the paper itself, but there's no question this is something worth discussing, particularly as the paper doesn't actually breathe any new life into the IRIS idea -- that interpretation confuses cloud changed caused by dynamics with a temperature-related feedback. Papers in respectable journals deserve comment, and I hope we get to it eventually. --raypierre]
I want to make a rebuttal to the relevant recent comments by Jennifer Marohasy claiming that recent temperature flattening sheds doubt on CO2-based AGW. I don’t recall the source but I got this quote (checks with my memory anyway) from a thread at Washington Monthly:
“Actually, no. The head of the IPCC has actually acknowledged it. He talks about the apparent plateau in temperatures so far this century. So he recognizes that in this century, over the past eight years, temperatures have plateaued … This is not what you’d expect, as I said, because if carbon dioxide is driving temperature then you’d expect that, given carbon dioxide levels have been continuing to increase, temperatures should be going up … So (it’s) very unexpected, not something that’s being discussed. It should be being discussed, though, because it’s very significant.”
No, false reasoning. With fluctuations imposed upon a trend it is perfectly expected to have flat periods (that would have been downturns if no upward trend!) Good lord, just plot e.g. y = ax + RND(x) for cryin’ out loud! Do it, and look at the graph! Well, that theoretical point was wrong, but it is possible that the weather effects will cancel AGW as she later claims. But what if they don’t? Our asses are grass.
Jim Galasyn, One should always assume the form suggested by physics. However, even if we have no physical reason for assuming a simple model, it should be favored as an underfit model is more likely to give a good fit than an overfit model. As an extreme example, a quadratic fit to 3 points will always give at least as good as a linear fit–but it will be devoid of any information. Information theory provides a very elegant way of looking at this using Hirotsugu Akaike’s Information Criterion (AIC).
Akaike set out to find an unbiased estimator for the information lost as one uses models both more complicated and less complicated than the true model and found a very elegant result–proportional to the difference between the number of parameters in the model used minus the logarithm of the likelihood (which measures how well the theory fits the data probabilistically).
In effect, this means that as we increase the number of parameters, the fit to data has to improve exponentially in the number of parameters!
This is no ad hoc penalty term for model complexity, but rather a fundamental result of information theory.
I’ve been using this quite a bit lately as I look at fitting data with models of differing complexity. Wikipedia has a reasonable write-up of the subject:
How long before increased CO2 results in a runaway greenhouse on Earth like has happened on Venus.
I’m afraid if we don’t do something about increased CO2 soon, we will end up with something close to Venus, although I don’t think that temperatures will be so high that even lead can be melted but something close.
As a kid I read a science fiction book in which astronauts visited Venus. When they dropped below the cloud deck they discovered that is was a hot tropical world of jungles populated by dinosaurs. I prefer thinking of it that way.
May I make a request for a future post … could someone do a summary article that tabulates all the various oceanic climate phenomenon such as El Nino/La Nina, the Indian Ocean Dipole etc., their effects on climate patterns, how well we understand them, and how important they are to the estimation of global warming by climate models.
Here in southern Australia we just got hammered by a ridiculously record breaking set of extreme temperatures. This caps off a period in which we learnt a hard lesson about the fact that El Nino does not necessarily bring rain to southern Australia like we all thought/hoped. Turns out that it brings rain to coastal New South Wales and Queensland, and that a phenomenon called the Indian Ocean Dipole is more important down south and in the interior. Indian Ocean temperatures are high now, so southerners have been sweating and gazing forlornly at dead gardens and dry rivers.
There are promises afoot that scientists have begun to work out how the Indian Ocean Dipole works, and that it will soon be incorporated into climate models. How important is it to existing models that this and other features are not yet included adequately? It would be interesting to see a table listing all of these phenomenon, their effects and the state of the science with regards to each.
[[How long before increased CO2 results in a runaway greenhouse on Earth like has happened on Venus.]]
About a billion years.
[Response: And even then, it won't be rising CO2 that triggers a runaway, but the continued long-term secular increase of solar luminosity. --raypierre]
[[I’m afraid if we don’t do something about increased CO2 soon, we will end up with something close to Venus]]
Don’t worry about it. Not going to happen.
[Response: Actually, if you want to worry about something runaway-like you should worry about what clouds might do on the destabilizing end of the possible spectrum of cloud effects. Clouds have a net cooling effect on Earth's climate at present. If you take away this net cooling effect, then the Earth gets a lot closer to the runaway greenhouse threshold for a saturated atmosphere (though the undersaturation of the atmosphere still helps to preserve a margin of safety). I don't actually think there's much risk of cloud cooling disappearing completely, or going into a runaway, but still this line of thought shows you how much potential clouds have for making things a lot worse than the mid-range IPCC scenarios. --raypierre]
> 88, 89, sunspots
See the discussion over at
Solar Cycle 24.com /Forums/ Solar Cycle 24/ Solar Activity/ New Sunspot
See posting by marconis 03/24/2008 — restates the FAQ explaining why
“These are more likely to be cycle 23 spots.”
Re 99, 101 – I wonder, though – what if plants (perhaps with our super-wise distant descendents’ help) evolved to incorporate titanium dioxide, producing nanoparticles of it in leaves, as a pigment for photosynthesis (realizing that may be hard to do giving the stability of titanium minerals – right? Maybe the plant produces special enzymes in the roots…). With enough UV driven photosynthesis, the plants could over time abandom chlorophyll, and then we’d have bright white vegetation. (of course, then the continents would be much colder than the oceans, so the monsoons wouldn’t work, I’d think… – but where the monsoons fail, the plants migh die and get covered by darker sand, and then the rains might come again?). Of course, in order for that to work, there’d have to be a selective advantage of the white plants over the green plants. A whole field of white plants might do well by staying cool (especially if surrounded by darker plants that can help bring the rains of thermally direct convection), but a single white plant wouldn’t have any obvious advantage – unless … well, that’s probably too off-topic.
Now, I’m not saying that I’d want to live in that world, or leave that world for my great grandkids or their great great grandkids or their … – but for SO long in the future, who knows? Maybe just easier to put out the space mirror ($4 trillion? but they’d have millions of years to build it. It wouldn’t have to be a single piece – many small mirrors with solar powered steering mechanisms could be mass-produced. They might even be colored to reduce the solar IR while letting in more visible. They could be retasked to push asteroids off of collision courses when necessary)… Maybe just easier to lay out the white tarps and floating white pumice (made from real rock!) rafts.
Re 104 – actually, at least some plants are reflective in the solar IR – Sudan grass comes to mind. As the sun gets brighter – well I know it will eventually expand and become a red giant, but before then, is it already very slowly reddenning and expandind or is it turning more blue or just staying put at it’s current color? That would matter for how best to design plants – reddenning might leave some opportunity to use the IR albedo. If the red and/or blue fluxes are increasing, some color-selective reflection could limit absorption to narrower wavelength bands where photosynthesis is most efficient, leaving the overall appearence a lighter shade of green.
RE #99, Lowell, while this current bout of GHGs & GW will not go into permanent runaway conditions, it could go into what I call limited runaway (from human control), or hysteresis. That is, the warming caused by human emissions could lead to nature emitting more GHGs (e.g., from frozen methane in permafrost and ocean hydrates) and reduced albedo (whiteness of snow & ice), leading to further warming, leading to further conditions that increase warming, and so on until it gets pretty hot — hot enough perhaps to release other monsters, like hydrogen sulfide from anoxic oceans that could kill off a lot of life in the sea and on land. You can read Mark Lynas’s SIX DEGREES to get a better idea of what’s possible in the geological short run (over the next 100,000 years or so).
OTOH, even if we drastically reduce GHGs and avoid tipping into a situation that will eventually take us up to 6 degrees and serious long-drawn out catastrophe, there are lots of bad things in the pipes right now, which may lead to many people dying and many species going extinct. Disease spread, severe water shortages (due to drought and glacial & snow pack cycle diminishing around the world), crop reductions (due to pests, heat, flood, drought), severe storms, floods, even floods amid droughts. Consideration of even half the damages of this best-case scenario should have been enough to make every person on planet earth start reducing their GHGs way back in 1990. Sad commentary on “humanity.”
Spencer’s presentation of both his 2007 GRL paper and a precis of its forthcoming sequel was about the only fundamental science on offer at the NYC affair, and I look forward to seeing your take on it, and that of others , as Roy has done interesting work in the past, and now has a bona fide modeler on his team.
To all you ‘not going to happen’ folks, this post is about Venus. Venus is there for all of you to see. Venus seems to easily refute, in the most glaring manner possible, all of this ‘not going to happen’ rhetoric.
Not only can it happen in the long term it’s a done deal.
Comment by Thomas Lee Elifritz — 28 Mar 2008 @ 11:15 AM
Re Thomas Lee Elifritz @ 111: Venus is Venus, Earth is Earth. Taking into account all of the differences between the two at this point in time, it’s not going to happen on any time scale meaningful to humans.
# 100, & “As a kid I read a science fiction book in which astronauts visited Venus. When they dropped below the cloud deck they discovered that is was a hot tropical world of jungles populated by dinosaurs. I prefer thinking of it that way.”
I agree with you, Craig; that’s the way I’d like to think of it. And your comments made me think about the real, unspoken point of this topic on Venus, a planet so inhospitable to life that it’s rather poignant. The important lesson from this post is that we have a beautiful, wonderful, life-sustaining planet (in contrast with Venus and other planets). We should cherish it and take care of it.
Re 111: To all you ‘not going to happen’ folks, this post is about Venus. Venus is there for all of you to see. Venus seems to easily refute, in the most glaring manner possible, all of this ‘not going to happen’ rhetoric.
Not only can it happen in the long term it’s a done deal.
I thought the “worst case scenario”, in terms of runaway, was something closer to the Rain Planet (where they made the clone army) in Star Wars — the ice caps melt, the oceans rise, and then the diurnal temperature swings lead to a never ending collection of daily rain storms as the atmosphere is pumped full of water during the day and it all rains out (over the oceans …) at night when the temperatures drop.
Re # 106 Patrick:
I’m curious to know why you think Sudan grass reflects solar IR? Can you cite any references on that? It is my understanding that surface color (e.g., red) has no bearing on IR absorption – the only significant reflection of IR is by shiny metallic surfaces. But, I could be wrong on this.
Is it true that all the second order feedbacks (output from one process being a input for another) are amplification/positive ones and that no negative/dampening feedbacks exist at this level in the climate system. Humans would have to engineer them in order to mitigate climate change?
RE #117, & “Is it true that all the second order feedbacks (output from one process being a input for another) are amplification/positive ones and that no negative/dampening feedbacks exist at this level in the climate system. Humans would have to engineer them in order to mitigate climate change?”
That is the million dollar Q. My thinking is that even in a scenario with positive feedbacks dominating, there would still be some negative ones (which would make the temperature chart jagged rather than strictly increasing and straight or smooth).
However, we do know that earth has been in such positive feedback dominating scenarios in the past — 55 & 251 mya — though eventually the warming plateaued and came back down with positive cooling feedbacks…after annihilating a big chunk of life on earth.
So it’s possible we are in the beginnings of one now or could be so within this century or next. It’s not something we’d want to gamble with…though that’s what we’re doing.
I thought the “worst case scenario”, in terms of runaway, was something closer to the Rain Planet (where they made the clone army) in Star Wars — the ice caps melt, the oceans rise …
Ok, so far so good, and then what?
Ocean carbonates dissolve, methane clathrates are released, and then what?
Forests die, the Amazon withers, the biosphere collapses and then what?
Do the arithmetic, it ain’t pretty.
Comment by Thomas Lee Elifritz — 29 Mar 2008 @ 8:25 PM
Random hard rock responses to various venus stuff:
The high surface temperature and low partial pressure of H2O would make hydrating Venus rocks tricky. The CO2 would also complicate things, since alkali-earth hydrous minerals would then carbonate (unless too hot), releasing the water.
Also the calcite decomp temperature at 92bar CO2 is way higher than the current surface temp, so if that is where Venusian CO2 came from, it must have been much hotter in the past. calcite and anhydrite should be stable on the surface, but there is no evidence that they exist on Venus that I know of- presumably a result of slow kinetics due to no water.
Zircons require at least some igneous differentiation, for which there is little evidence on Venus’s surface. And if there has been resurfacing, then you would get that age.
Isn’t there something odd about Venus’s atmospheric Argon? An atmospheric sample return would be way easier than a surface one, and would let the noble gas guys do Kr, Ne, and Xe isotopes.
Re #118: That is the million dollar Q. My thinking is that even in a scenario with positive feedbacks dominating, there would still be some negative ones (which would make the temperature chart jagged rather than strictly increasing and straight or smooth).
We’ve never had run-away warming during any of the past large warm periods. The average global temperature has been between 12C and 22C for the past 600 million years or so — and I don’t have a handy graph going back any further. That tells me that there must be some negative feedback that happens near 22C that’s going to prevent any form of “Venus Effect”.
[[Pale Blue Dot or small(and growing) Black Hole? An article in yesterday’s NY Times by Dennis Overbye suggests that there’s a non zero chance that the new CERN Large Hadron Collider may make global warming( and everything else)moot.]]
I doubt they can make a black hole. But even if they could, it would be so small that it would evaporate by Hawking radiation before it did any damage. Colliders have to be superpowerful just to create tiny subatomic particles from collisions between other particles. They ain’t gonna make something big enough to swallow the Earth.
Lawrence Brown, This whole idea is crap. There is no way they are going to greate a black hole. They’ll be lucky if they even create any Higgs’ bosons (ther reason they built the thing). Black holes result from conditions in the core of supernovae. You won’t produce them terrestrially–ever. I do wish the Times reporters would either get the most tenuous clue about science or just leave it alone.
Re 116 – I saw it on a graph – albedo as a function of wavelength. Although looking at it again, I should qualify the information – it only goes from 400 nm out to 1000 nm (1 micron) – and only ~ 940 nm for some of the surfaces graphed, including Sudan Grass and Straw. On the same graph, the albedo of Alfalfa also rises sharply going into the infrared from visible, although not as much as Sudan Grass. Straw’s albedo increases gradually from blue to around 900 nm and levels off. Snow’s albedo declines going into the infrared but it is still relatively high at 1000 nm.
See p. 90, in Chapter 4 (The Energy Balance of the Surface), of “Global Physical Climatology” (Hartmann, – I think it was 1994).
Barton and Ray. Thanks for the reassurance. I realize that there’s a lot of weirdness in physics,like quantum tunneling, Shrodinger’s poor cat that’s neither in a live or dead state until somebody breaks down the wave function(looks in the box?) and Bell’s inequality, but having the LHC being able swallow the Earth or turn it into a shrunken lifeless dwarf called a “strangelet” appears to cross the line even the wild world of quantum physics. Good to know what some mainstream physicists think of this.
Lawrence Brown, These same two nutjobs filed a similar suit to block operations of the Relativistic Heavy Ion Collider at Brookhaven. The thing is that there are lots of different versions of string theory, and you can fine one or the other of them that will tell you just about anything. It’s just that there’s no reason to believe it.
Physicists have pretty much always had a macabre sense of humor about such things. The article mentioned that on the Manhattan Project, they’d looked at the possibility of igniting fusion in the water vapor in the air and turning the world to a mini-Sun. Fermi went around before Trinity and took bets on the odds of incinerating the State of New Mexico. When I was a grad student, the question was whether the vacuum was in fact stable or metastable (if there were greater than 22 flavors of quark, it was metastable, but as it turns out, there are 4).
Look, cosmic rays have energies up to 10^21 eV. Even transforming to the center of mass frame, a 10^21 eV proton colliding with a proton at rest has an energy ~1000 times as high as the CM energy of the LHC! Such events happen a few hundred times a year in Earth’s atmosphere. This one doesn’t even pass the straight-face test.
Comment by David B. Benson — 31 Mar 2008 @ 12:40 PM
RE #121 & “We’ve never had run-away warming during any of the past large warm periods.”
That’s true, we’ve never had permanent runaway warming as on Venus….or else we wouldn’t be here to talk about it.
However, from a lay perspective on the current situation, enquiring minds might want to know if we are causing the current warming, and is there a point in that human-caused warming at which nature takes over and continues the warming thru positive feedbacks up to some higher temp (as has happened in the past).
That may not be “runaway” from a non-human-centric, scientific perspective, but it would be a temporary (up to 200,000 years) runaway-from-human-control situation from an anthropocentric perspective, which some scientists have told me is better referred to as HYSTERESIS. But I think the term “runaway” is more informative and useful, as long as we’re clear we are not referring to a permanent situation as on Venus, but only a “runaway-from-human-control” situation (which, of course, would not apply to a prehuman era). And that situation, while not as dangerous as the Venus situation, could be dangerous for a large chunk of life on earth nevertheless.
On the recent post about air-capture, it looks like we still might have some ability to slow or halt this bout of global warming, even if we exceed the CO2 level tipping point for a short time. It seems no one knows exactly how much CO2 equivalent in the atmosphere will put us at a tipping point (into hysteresis), tho they do seem to have an idea that a 3C warming would likely do that.
This is to Ray Ladbury (Says: 25 March 2008 at 8:07 PM)
You are right, I am not an expert climatologist, I am just
a physicist. But climatologist sometimes has to learn
physics (meanwhile they can average temperature, ice cover
Nowaday they are asking money for supercomputers I do not
know why? It is quite sufficient to produce useless climate
change predictions on a 100 km spatial resolution…
They probably never heard of Von Neumann who pointed out long
time ago that climate prediction is a boundary condition
problem. If they do not put more physics into their GCM code
they will keep coming up with nonsense.
Where are you with your ‘finding a the kitchen
sink in there’…you were given plenty of time.
You know, there are two types of scientists. One is just
talking, the other can prove what he is saying…which one
you are? Well, NASA was not able to come up with any
computations or resuls against the theory in six years, so I
do not expect too much from you.
In case you have some definite results to discuss I shall
be happy to do so.
[Response: Thanks for stopping by. Please leave the insinuations at home next time. - gavin]
Ferenc Miskolczi (I presume), Climate science is not my day job. I do, however, know enough about it to realize 1)that the case for the current warming being caused by anthropogenic greenhouse gasses is not dependent in any way on GCM; 2)When a paramter is constrained by as many independent lines of evidence as CO2 forcing is, there’s not a lot of wiggle room.
And actually there are many types of scientists (You’ve no doubt heard the one: There are 10 types of engineers–those who understand binary and those who don’t). The type of scientist I seek to be is one who is an expert in his own field and has sufficient grasp of the rest of physics that I can follow it and understand it. I would not presume that such a level of understanding exceeds that of the experts in the field. That is why I come to this site to learn from the experts in climate science. You are welcome to do so as well.
…’We could comment on it, but on the whole it’s more worthwhile to
spend time commenting on things that have passed review in the more
major journals and don’t have such obvious flaws (even if they
nonetheless have flaws). –raypierre]’
If people are interested, my answer to such comments may be found at this link:
I came along to see the opinions of the experts about
My article is not about global warming.
Global warming should be a proven fact based on
measurements. If it is there, the question is what
might be cause. The co2 level is also rising, it is
another fact. But the way to the global average
surface temperature is not via the co2 concentration,
but via the total IR optical depth of the atmosphere
and, a sound theoretical relationship which
establishes the connection.
From about 1920 the only available theoretical
equation that related this two things is the Eddington
equation developed for the semi-infinite atmospheres
Applying this to the Earth’s atmosphere is wrong, since
for finite semi-transparent atmospheres the Eddington
equation is invalid. This means that when a GCM (after
correctly solving the local primitive equations with
resonable spatial and temporal resolution) they arrive
to the question of the global constraints. So far from
the Eddington solution they have the linear-in optical
depth relation which is incorrect.
My paper shows, that (independently of the Kirchhoff’s
law, virial theorem, cloudy energy balance equation etc.)
the global average thermal structure of the atmosphere
is a radiative equilibrium profile, with a global average
IR optical depth of 1.87. The relationship between the
surface temperature and outgoing IR radiation is not
linear in the IR optical depth, but contains the IR flux
According to this, the sensitivity of the surface temperature
for GHG forcing is much less…I would like to see the comments
of the experts on this.
If people dismiss a paper (like ‘raypierre’), because it is
in an ‘Obscured Hungarian Journal’, or because the consequences
of the results are against the IPCC report, it is bad enough,
and it is not in the interest of the improvement of our
understanding the planetary greenhouse effect.
[Response: I'm not dismissing the paper because it is in an obscure Hungarian journal. I mentioned that just to explain how a paper with so many elementary errors in it could pass peer review. The problem with the paper is that you understand neither Kirchoff's laws nor the Virial theorem -- nor even dimensional analysis, which would have caught your Virial error for you right away. Chris Colose, who is an undergraduate in the early stages of his study, in fact understands this all far better than you, as did the undergrads at Bowdoin. --raypierre]
link. You probably would like to explain the shown relationship
between the flux density terms to those who mistakenly attribute
it to the Kirchhoff law.
In case you manage to explain this figure or (Fig. 2 in the paper),
we may go on to discuss dimensional analaysis and virial
theorem. I am very much impressed with your students. My students
have no problem to read this paper and understand what it wants to
[Response: Your poor students. I won't spoil the surprise by stealing the thunder of the Bowdoin class. I'm going to give them the first shot at writing this up, even if it takes them a while since they have other class work to attend to as well. --raypierre]
The Senate minority is using work such as Miskolczi in attempting to dubunk the idea of a scientific consensus on man-made warming. Seems a ripe time to discuss use of science in the Senate as a number of carbon control measures are debated soon. I’d say the Bowdoin class should tesify!
Prominent Hungarian Physicist Dr. Miklós Zágoni, a former global warming activist who recently reversed his views about man-made climate fears and is now a skeptic, presented scientific findings at the conference refuting rising CO2 fears. Zágoni’s scientific mentor Hungarian scientist, Dr. Ferenc Miskolczi, an atmospheric physicist, resigned from his post working with NASA because he was disgusted with the agency’s lack of scientific freedom. Miskolczi, who also presented his peer-reviewed findings at the conference, said he wanted to release his new research that showed “runaway greenhouse theories contradict energy balance equations,” but he claims NASA refused to allow him.
Comment by Jeffrey Chambers — 3 Jun 2008 @ 4:26 PM
I have been reading your paper, and I have the following questions:
a) Virial Theorem:
One of the essential new insights that you want to bring into the discussion is the application of the Virial Theorem. However, I find your actual discussion of it is very short and cryptic. In particular, you relate the upward flux from the atmosphere to the atmospheric kinetic energy, and the surface upward flux to the atmospheric potential energy. What does a flux have to do with a bulk energy? I would appreciate something more specific than what you have provided in Section 2(g) and Section 3.1.
c) Your Equation (7):
I don’t understand your argument for this equation. It seems to me that if it is a result of conservation of energy, it would be derivable from an examination of your Figure 1; but I can’t see any reasonable interpretation of (7) based on the fluxes and interfaces defined in Figure 1. Equations (1), (2) and (3) I can understand from that, but not (7).
d) Your Equation (8):
As a consequence of (7), you derive the relation S_u = (3/2) * OLR; which I believe is an important step in your derivation of a unique balancing condition. However, as a universal relationship, this seems highly suspicious. Let’s take the special case that the atmosphere is totally transparent to all radiation: this can be done by following a sequence of mathematical models parameterized by the IR-molecule interaction strength, finally reducing it to zero. Then, if we look at Figure 1, we would set all the arrows that terminate in/from the atmosphere to zero. When we do that, we find that OLR = S_u = F_0: the radiation comes in, is absorbed only by the ground, and is emitted only to space. So in that case,
S_u = (1) * OLR, not (3/2) * OLR.
So how did the firm factor of (3/2) disappear? Why doesn’t this general result apply in the trivial case? In the continuous reduction of an interaction parameter, at what point does the reasoning leading you to the (3/2) factor fail?
Your request to Dr. Miskolczi for evidence of Su = 3/2 OLR is produced like any good evidence.
Miskolczi is an experimental scientist first. If you read his previous paper using the data from the satellites he published a mountain of data and frequency by frequency, LBL, summations.
See his clear sky spectral decomposition paper of 2004, circa pages 200-225 especially 202 etc. Measured ratio of Su to OLR is about Su = 1.5 OLR.
He obtained the basis for his theoretical analysis and discussion, the old fashioned way… he went out, conducted an experiment, and measured it.
Unlike Milne,in the 1920s, he had access to the satellite data that give actual measures of OLR, and F.
You can use numerical methods to “solve” a differential equation with computational methods that were never conceivable to Milne.
Ask me sir, Is Mikolczi’s model of a finite atmosphere attached to a stable planetary surface, allowing for continuity equations driving temperatures convergence at the surface with a gravitationally bound, hence denser at the bottom fading to vacuum at the top, and thus allowing evaporation, rising columns of hot air, convection energy transport, and rain, a good model of Earth?
Or do you think that Milne’s stellar model of a infinite atmosphere created to model a star, with no surface, all gas or plasma, attached to only a mythical discontinuity at its gaseous center, more resembling of the real Earth? Milne’s infinite atmosphere model equipped with purposeful deviations, to trick the model into semi-computable simplifications? If so, tell me why?
How did Newton deduce an inverse square law? Why not an inverse cubic or inverse quartic law? Answer: He experimented, Measured and then analyzed to produce in inverse square relations that matched reality.
[Response: Newton's law turns out to work almost everywhere. The counter example given above shows that Miskolczi's observation doesn't. Therefore it is unlikely to be a universal truth or be of any help in determining climate sensitivity. That the relationship was said to be derived theoretically when in fact it is just an approximation to his data is particularly concerning. - gavin]
As Gavin pointed out, my question was about the explanation of what is presented as a theoretical derivation. A theoretical derivation does not draw its validity from measurements, but from reasoning: If it matches the measurements, that agreement gives support to the assumptions. But since, as I showed, that factor of (3/2) must instead be a factor of (1) in the trivial case, then if the reasoning is actually correct in the non-trivial case, there should be some disruption in either the reasoning or the assumptions as the interaction between molecules and radiation vanishes. Where’s the disruption?
A further point: In my original posting (#142), I originally had a point b). At my request, RealClimate staff edited this item out, because I came to doubt that point. After further study of the Virial Theorem, I have come to the following conclusion:
- The Virial Theorem (VT) does apply to the case at hand. But it doesn’t give the result that Miskolczi is claiming:
2*avg(KE) = avg(V), where V = mgz.
- Why? The equation above is true when the V in question is what is causing the gas to cohere (e.g., a cloud of gas, or a star). In particular, it applies to central, power-law, forces (e.g., gravity). But what is causing the atmosphere to stick around is binding between the individual molecules and the planet Earth. That would be a power-law force except for the fact that the bottom limit of the atmosphere is defined by the ground: the potential well becomes infinite for all distances less than the Earth’s radius. That’s no power law!
- The VT still applies, but the virial
(sum of r_i . F_i)
is no longer related in a transparent way to the potential energy due to the imposed external potential of the Earth’s gravity: It’s not equal to it.
- Instead, if you do the actual calculation of the virial over a region of limited size (so that the mass density can be taken to be constant), you find that you get a term which equates to 2*avg(KE), another term which equates to 3*pressure*volume, a term that corresponds to the pressure difference in the vertical dimension, and a term that corresponds to the downward pull on the volume of gas. It also turns out that the first two terms are independent of the origin of the coordinates, but the second two terms each depend on the origin. That leads to the conclusion that the first two terms together imply the perfect-gas law; and the second two terms together imply the equation of hydrostatic equilibrium. You do not get anything extra that corresponds to the average gravitational potential energy avg(mgz): the avg(KE) term is tied to the pressure*volume term. (I’m sorry this presentation of results is so brief, but it would take a lot of space to explain this well.)
- Indeed, as a separate exercise, you can take the model of an adiabatic atmosphere (http://farside.ph.utexas.edu/teaching/sm1/lectures/node56.html)
and explicitly integrate KE and PE = mgz from bottom to top. When you do that, you find that 2*avg(KE) = 3*avg(PE), which doesn’t look anything like the VT for either 1-dimensional or 3-dimensional gravity.
Finally, I have no opinion about Milne’s model applied to the atmosphere, as I haven’t studied it. I am just trying to understand what Miskolczi is doing. I believe I have identified some conceptual problems.
I’ve noticed this Real Climate site still talks about global warming as established scientific fact.
How did you all get past the inherent errors in satellite microwave sounding unit measurements? The methodology cannot be more accurate than +/- 1 degC (and is probably much less accurate), which means the intensive analysis of individual measurements can only produce a nice picture of satellite measurement instrument “noise”.
Meanwhile, surface measurements do not include the polar regions, and vastly over-sample land areas in relation to ocean areas. No matter how sophisticated is the model used with this type of data, systemic errors cannot produce better climate statistics than the satellite data. Indeed, individual weather monitoring stations have been shown to produce warming data for a reason which has nothing to do with atmospheric composition: they appear to be measuring the local increases in surface temperature near growing rural, suburban and metropolitan areas.
How are these systemic errors overcome in order to establish evidence for global warming — let alone a cause for such an hypothetical warming?
I’ve heard it said in a number of places that the earth’s mean temperature is actually decreasing — trending downward for the last 10 years. As far as I know, mankind is pumping more CO2 than ever into the atmosphere. Do you agree, or do you take issue with the claim of global cooling? Why is it misleading or why is it correct?
Each of these assertions have been addressed here at RC repeatedly. You would well advised to seek out the response(s) to them using the Start Here tab and the site search box before repeating them as you would then look much less foolish.
John, your questions are all answered on this site. You can either keep reading various threads, where much of this has come up repeatedly, or you can look at the FAQs and scientific links.
I will only tell you that the idea that “the earth’s mean temperature is actually decreasing — trending downward for the last 10 years” is a pure example of the “big lie” technique famously enunciated by Hitler’s PR guy, Goebbels, and I’m sorry that you have been mislead by those pushing it.
Every data set we have shows a warming trend. Here is a useful starting point for you to verify this for yourself:
If that is too much trouble, then I will reiterate here something I tell those who have a limited appetite for statistical analysis. Almost every year *since* 1998 (which I take to be “ten years ago” for practical purposes) has been warmer than almost every year before then. This fact alone should be enough to show you why the statement you repeat is at best highly misleading. Here is the actual ranking of top-ten warmest years (SR ’05 dataset, used by NCDC):
(Note that of the years since 1998, only ’99 and 2000 don’t make this top ten list. Also how close places two through six are–close to the confidence interval, if I remember right, meaning that these years are pretty close to being “tied.”)
John Olson, #146
“I’ve noticed this Real Climate site still talks about global warming as established scientific fact.”
Why is it you still talk about how Global Warming is false merely on one item which isn’t 100% proven accurate?
How come the items we DO know *must* be ignored because we don’t have measurements in all the places you want to see them made. Do you have anything that would explain how the places where measurements are taken would give the opposite picture of reality? No?
And I’ve heard in many places that Adam and Eve lived alongside the Allosaur (who was a vegetarian at the time).
And how come 40 years wasn’t enough to prove global warming yet less than 10 years is enough to prove it’s wrong?
John Olson, Where are you getting your information? The “oversampling” of land areas is irrelevant. What matters is that both land and ocean are sufficiently sampled. Indeed, the oversampling of land areas is a boon when it comes to dealing with local effects like urban heat island.
As to satellite errors, the absolute numbers are less important than trends, so this diminishes the importance of the errors. What is important is that when normalized to the same period, all temperature products give the same warming trend.
“I’ve heard it said in a number of places that the earth’s mean temperature is actually decreasing” – John Olson
Well of course, if you spend your time on denialist blogs, you will be told a lot of lies – what do you expect?
In addition to what others have noted, there is of course the continued melting of glaciers (most of which have receded for each of the past 18 years), the unprecedented summer melting of Arctic sea ice in 2007 and 2008, the continuing rise in ocean temperatures (that’s where most of the excess heat trapped by greenhouse gases goes), the shift of many species’ ranges polewards and/or upwards, and the earlier appearance of many spring phenomena.
May I say at the outset – that I think there may be a chance that amplification of the El Nino Southern Oscillation by the Pacific Decadal Oscillation may lead to 20 or 30 years of no warming. Given our state of understanding of these phenomenon – obviously quantification or even a definite maybe is out of the question. This is a year by year proposition. Will the current PDO cool mode hold out? Was the warm mode between 1977 and 1999, that contributed to warming through PDO amplfification of ENSO entirely natural, partly natural or driven by AGW? Relative imponderables for which we have no easy answer except to see which way events play out.
To get onto the subject of this post, Miskolczi, I have just had the unfortunate experience of suggesting in a skeptic forum that the short wave end of the spectrum (based on BBSO cloud work) might be a more fruitful avenue. Talk about a spirited defence.
The trouble is – the more I read – the more odd this paper seemed. I am happy to have read FM’s comments here – I was inclined before then to think it was a conspiracy to discredit skeptics. Really, I am only a skeptic because of the above imponderables. But I read Miskolczi. Thermal equilibrium that is not, internal kinetic energy that is not, atmospheric potential energy that is not, conservation of energy that is not. Radiation pressure that is bizarrely irrelevant and expressed as 1/3 of the surface upward energy flux. On what planet? Hydrostatic equilibrium on a real, blue spinning planet? I think not. Etc. Etc.
It is all claimed to be based on fundamental principles – but is in reality based on datapoints calculated from the TIGR database. What was it? Something Initial Guess something. Oh dear. The data is not properly presented or referenced – because it is all claimed to be based on fundamental principles – but if the principles don’t apply then it is based on proven and measured data that is more accurate than anyone else’s – but… so on and so forth.
I felt a bit like Alice in Wonderland at the Mad Hatters ball.