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The runaway greenhouse effect on Venus

What the science says...

Venus very likely underwent a runaway or ‘moist’ greenhouse phase earlier in its history, and today is kept hot by a dense CO2 atmosphere.

Climate Myth...

Venus doesn't have a runaway greenhouse effect

Venus is not hot because of a runaway greenhouse.

In keeping with my recent theme of discussing planetary climate, I am revisiting a claim last year made by Steven Goddard at WUWT (here and here, and echoed by him again recently) that “the [runaway greenhouse] theory is beyond absurd,” and that it is pressure, not the greenhouse effect that keeps Venus hot.  My focus in this post is not on his alternative theory (discussed here), but to discuss Venus and the runaway greenhouse in general, as a matter of interest and as an educational opportunity.  In keeping my skepticism fair, I’d also like to address claims (sometimes thrown out by Jim Hansen in passing by) that burning all the coal, tars, and oil could conceivably initiate a runaway on Earth.

It is worth noting that the term runaway greenhouse refers to a specific process when discussed by planetary scientists, and simply having a very hot, high-CO2 atmosphere is not it.  It is best thought of as a process that may have happened in Venus’ past (or a large number of exo-planets being discovered close enough to their host star) rather than a circumstance it is currently in.

A Tutorial of Present-Day Venus

Venus’ orbit is approximately 70% closer to the sun, which means it receives about 1/0.72 ~ 2 times more solar insolation at the top of the atmosphere than Earth.  Venus also has a very high albedo which ends up over-compensating for the distance to the sun, so the absorbed solar energy by Venus is less than that for Earth.  The high albedo can be attributed to a host of gaseous sulfur species, along with what water there is, which provide fodder for several globally encircling sulfuric acid (H2SO4) cloud decks.  SO2 and H2O are the gaseous precursor of the clouds particles; the lower clouds are formed by condensation of H2SO4 vapor, with SO2 created by photochemistry in the upper clouds. Venus’ atmosphere also has a pressure of ~92 bars, nearly equivalent to what you’d feel swimming under a kilometer of ocean.  The dense atmosphere could keep the albedo well above Earth’s even without clouds due to the high Rayleigh scattering (the effect of clouds on Venus and how they could change in time is discussed in Bullock and Grinspoon, 2001). Less than 10% of the incident solar radiation reaches the surface.

Observations of the vapor content in the Venusian atmosphere show an extremely high heavy to light isotopic ratio (D/H) and is best interpreted as a preferential light hydrogen escape to space, while deuterium escapes less rapidly.  A lower limit of at least 100 times its current water content in the past can be inferred (e.g. Selsis et al. 2007 and references therein).

The greenhouse effect on Venus is primarily caused by CO2, although water vapor and SO2 are extremely important as well.  This makes Venus very opaque throughout the spectrum (figure 1a), and since most of the radiation that makes its way out to space comes from only the very topmost parts of the atmosphere, it can look as cold as Mars from IR imagery. In reality, Venus is even hotter than the dayside of Mercury, at an uncomfortable 735 K (or ~860 F). Like Earth, Venusian clouds also generate a greenhouse effect, although they are not as good infrared absorbers/emitters as water clouds.  However, the concentrated sulfuric acid droplets can scatter infrared back to the surface, generating an alternative form of the greenhouse effect that way.  In the dense Venusian CO2 atmosphere, pressure broadening from collisions and the presence of a large number of absorption features unimportant on modern Earth can come into play (figure 1b), which means quick and dirty attempts by Goddard to extrapolate the logarithmic dependence between CO2 and radiative forcing make little sense.  The typical Myhre et al (1998) equation which suggests every doubling of CO2 reduces the outgoing flux at the tropopause by ~4 W/m2, although even for CO2 concentration typical of post-snowball Earth states this can be substantially enhanced.  Figure 1b also shows that CO2 is not saturated, as some skeptics have claimed.

 

 Figure 1: a) Radiant spectra for the terrestrial planets.  Courtesy of David Grisp (Jet Propulsion Laboratory/CIT), from lecture "Understanding the Remote-Sensing Signatures of Life in Disk-averaged Planetary Spectra: 2" b) Absorption properties for CO2. The horizontal lines represent the absorption coefficient above which the atmosphere is strongly absorbing.  The green (orange) rectangle shows that portion of the spectrum where the atmosphere is optically thick for 300 (1200) ppm.  From Pierrehumbert (2011)

 How to get a Runaway?

To get a true runaway greenhouse, you need a conspiracy of solar radiation and the availability of some greenhouse gas in equilibrium with a surface reservoir (whose concentration increases with temperature by the Clausius-Clapeyron relation).  For Earth, or Venus in a runaway greenhouse phase, the condensable substance of interest is water— although one can generalize to other atmospheric agents as well.

The familiar water vapor feedback can be illustrated in Figure 2, whereby an increase in surface temperature increases the water vapor content, which in turn results in increased atmospheric opacity and greenhouse effect.  In a plot of outgoing radiation vs. temperature, this would result in less sensitive change in outgoing flux for a given temperature change (i.e., the outgoing radiation is more linear than one would expect from the σT4 blackbody-relation). 

 

Figure 2: Graph of the OLR vs. T for different values of the CO2 content and relative humidity.  For a fixed RH, the specific humidity increases with temperature. The horizontal lines are the absorbed shortwave radiation, which can be increased from 260-300 W m-2.  The water vapor feedback manifests itself as the temperature difference between b’-b and a’-a, since water vapor feedback linearizes the OLR curve.  Eventually the OLR asymptotes at the Komabayashi-Ingersoll limit.  Adopted from Pierrehumbert (2002)

 

One can imagine an extreme case in which the water vapor feedback becomes sufficiently effective, so that eventually the outgoing radiation is decoupled from surface temperature, and asymptotes into a horizontal line (sometimes called the “Komabayashi-Ingersoll” limit following the work of the authors in the 1960’s, although Nakajima et al (1992) expanded upon this limiting OLR in terms of tropospheric and stratospheric limitations).  In order to sustain the runaway, one requires a sufficient supply of absorbed solar radiation, as this prevents the system from reaching radiative equilibrium.  Once the absorbed radiation exceeds the limiting outgoing radiation, then a runaway greenhouse ensues and the radiation to space does not increase until the oceans are depleted, or perhaps the planet begins to get hot enough to radiate in near visible wavelengths.

 

Figure 3: Qualitative schematic of how the ocean reservoir is depleted in a runaway.  From Ch. 4 of R.T. Pierrehumbert’s Principles of Planetary Climate

 

On present-day Earth, a “cold trap” limits significant amounts of water vapor from reaching the high atmosphere, so its fate is ultimately to condense and precipitate out.  In a runaway scenario, this “cold trap” is broken and the atmosphere is moist even into the stratosphere.  This allows energetic UV radiation to break up H2O and allow for significant hydrogen loss to space, which explains the loss of water over time on Venus.  An intermediate case is the “moist greenhouse” (Kasting 1988) in which liquid water can remain on the surface, but the stratosphere is still wet so one can lose large quantities of water that way (note Venus may never actually encountered a true runaway, there is still debate over this).  Kasting (1988) explored the nature of the runaway /moist greenhouse, and later in 1993 applied this to understanding habitable zones around main-sequence stars.  He found that a planet with a vapor atmosphere can lose no more than ~310 W/m2, which corresponds to 140% of the modern solar constant (note the albedo of a dense H2O atmosphere is higher than the modern), or about 110% of the modern value for the moist greenhouse.

 

Earth and the Runaway: Past and Future

 

Because Earth is well under the absorbed solar radiation threshold for a runaway, water is in a regime where it condenses rather than accumulating indefinitely in the atmosphere.  The opposite is true for CO2, which builds up indefinitely unless checked by silicate weathering or ocean/biosphere removal processes.  In fact, a generalization to the runaway threshold thinking is when the solar radiation is so low, so that CO2 condenses out rather than building up in the atmosphere, as would be the case for very cold Mars-like planets.  Note the traditional runaway greenhouse threshold is largely independent of CO2 (figure 2 & 4; also see Kasting 1988), since the IR opacity is swamped by the water vapor effect.  This makes it very difficult to justify concerns over an anthropogenic-induced runaway.

 


 

Figure 4: The H2O–CO2 greenhouse. The plot shows the surface temperature as a function of radiated heat for different amounts of atmospheric CO2 (after Abe 1993). The albedo is the fraction of sunlight that is not absorbed (the appropriate albedo to use is the Bond albedo, which refers to all sunlight visible and invisible). Modern Earth has an albedo of 30%. Net insolations for Earth and Venus ca. 4.5 Ga (after the Sun reached the main sequence) are shown at 30% and 40% albedo. Earth entered the runaway greenhouse state only ephemerally after big impacts that generated big pulses of geothermal heat. For example, after the Moon-forming impact the atmosphere would have been in a runaway greenhouse state for ∼2 million years, during which the heat flow would have made up the difference between net insolation and the runaway greenhouse limit. A plausible trajectory takes Earth from ∼100 bars of CO2 and 40% albedo down to 0.1–1 bar and 30% albedo, at which point the oceans ice over and albedo jumps. Note that CO2 does not by itself cause a runaway. Also note that Venus would enter the runaway state when its albedo dropped below 35%.  Se e Zahnle et al 2007

 

This immunity to a runaway will not be the case in the long-term.  In about a billion years, the sun will brighten enough to push us into a state where hydrogen is lost much more rapidly, and a true runaway greenhouse occurs in several billion years from now, with the large caveat that clouds could increase the albedo and delay this process.

Interesting, some (e.g.. Zahnle et al 2007) have argued that Earth may have been in a transient runaway greenhouse phase within the first few million years, with geothermal heat and the heat flow from the moon-forming impact making up for the difference between the net solar insolation and the runaway greenhouse threshold, although this would last for only a brief period of time.  Because the runaway threshold also represents a maximum heat loss term, it means the planet would take many millions of years to cool off following such magma ocean & steam atmosphere events of the early Hadean, much slower than a no-atmosphere case (figure 5).

 

Figure 5: Radiative cooling rates from a steam atmosphere over a magma ocean. The radiated heat is equal to the sum of absorbed sunlight (net insolation) and geothermal heat flow. The plot shows the surface temperature as a function of radiated heat for different amounts of atmospheric H2O (adapted from Abe et al. 2000). The radiated heat is the sum of absorbed sunlight (net insolation) and geothermal heat flow. The different curves are labeled by the amount of H2O in the atmosphere (in bars). The runaway greenhouse threshold is indicated. This is the maximum rate that a steam atmosphere can radiate if condensed water is present. If at least 30 bars of water are present (a tenth of an ocean), the runaway greenhouse threshold applies even over a magma ocean. Note that the radiative cooling rate is always much smaller than the σT4 of a planet without an atmosphere

Conclusions

Venus likely underwent a runaway or “moist greenhouse” phase associated with rapid water loss and very high temperatures.  Once water is gone, silicate weathering reactions that draw down CO2 from the atmosphere are insignificant, and CO2 can then build up to very high values.  Today, a dense CO2 atmosphere keeps Venus extremely hot.

Last updated on 11 April 2011 by Chris Colose. View Archives

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Comments 226 to 250 out of 267:

  1. Michael Sweet  : "Since the base 2 log of 150,000 is 17.2, you must divide the forcing on Vensus (13870 W.m2 according to you) by 17.2, not 150,000. That yields an estimated forcing on Earth of 806 w/m2. It does not take into accoount the vastly different albeido's of Venus and Earth (Earth has a much lower albeido than Venus about 0.3 and 0.75)".

     

    But 806 W/m2 is not at all the value of the greenhouse effect of CO2 in the Earth's atmosphere (officially estimated at 26 W / m2 for 300 ppmv), so your calculation is not suitable ! In addition albedo does not intervene in the calculation of the greenhouse effect.

    Science seems to be unable to have a universal theory of the greenhouse effect that is capable of explaining the T ° of Venus and the Earth. . As long as this point is not resolved how can one claim to predict radiative forcing ?

    The amounts of CO2 (4.72.10 ^ 20 Kg of CO2 in the atmosphere of Venus, and 3.128.10 ^ 15 Kg for the Earth) were calculated taking into account the pressure and the temperature of each planet.

    I do not see anywhere calculations taking into account the actual amount of CO2, which is still surprising because it is still the number of CO2 molecule that play a role in the power of the greenhouse effect.

    Response:

    [DB] Sloganeering snipped.  You cannot simply ignore the rebuttals of your argument.  You have to use the math, physics and citations to credible sources to support your position.  That's how things work in science-based venues such as this.

    Failure to do so means you concede the points.

  2. JC,

    I am sorry, I do not have enough time to search the internet to find the correct calculation for you.  It is your responsibility to cite correct calculations to support your claims.  As I stated, the most likely error in my calculations is that your unsupported value for Venus is too high.

    I have shown that your calculation of the forcing from CO2 on Earth, using data from Venus, is incorrect.  Now you have provided the value of 26 W/m2 which seems reasonable to me.  You challange that value without providing any supporting data.  The value you originally calculated at comment 219 of 0.092 W/m2 is clearly completely incorrect.  My estimate of 322 W/m2 is closer to the value of 26 W/m2 you now propose, and I pointed out that my estimate had an error in it.  The albeido must be considered.  If the albeido was 100% the surface would be frozen no matter how much CO2 there was.

    If you do not know how to do the calculation you must withdraw your wild claims.  You have provided no citation of someone who knows how to do this calculation and you do not know how to do it.  You are making an argument from ignorance.  Scientists figured this out over 100 years ago.  Try to catch up.

    Where did you find this false information so I can read what the original person wrote?

  3. JC,

    Reading the OP I noticed this sentence:

    "In the dense Venusian CO2 atmosphere, pressure broadening from collisions and the presence of a large number of absorption features unimportant on modern Earth can come into play (figure 1b), which means quick and dirty attempts by Goddard to extrapolate the logarithmic dependence between CO2 and radiative forcing make little sense."

    This states that both our calculations cannnot be made because the atmosphere on Venus to too different from that of Earth for this simple extrapolation.  It apears that Goddard is the originator of this malarky.  Since the OP was written in 2011, it has been known since at least then that your source of information is incorrect.

    I suggest that you read more background information and come back when you have questions.  If you continue to read Goddard you will never understand what is happening.  Read more of the posts here at Skeptical Science and you will begin to understand the process of AGW.

  4. Once again, I note that JC does not dispute the fact that, unlike what his (her)previous claim suggested, global temperatures have not been stagnant since 2000.

  5. Philippe Chantreau : "Once again, I note that JC does not dispute the fact that, unlike what his (her)previous claim suggested, global temperatures have not been stagnant since 2000".

    Yet this is called hiatus in the last report of the giec !

  6. JC @230.

    "The giec" is usually known by its English acronym 'IPCC' and indeed the IPCC AR5 Technical Summary does include Box TS.3 'Climate Models and the Hiatus in Global Mean Surface Warming of the Past 15 Years.' This analysis dates to 2013 and thus predates Karl et al (2015) which rattled a number of 'artifacts' from the global surface temperature record and with it became an undeniable 'pause-buster' in the eyes of AGW-denying contrarians. And Box TS.3 will obviously not have been able to include in its analysis the last five years of global surface temperature (2014-18) which will soon become shown to comprise each of the warmest five years on record. Thus, if there were (as asserted by JC @222) some "stagnation of steam from 2000 to presently," it would not provide a "correlation" with global surface temperature which has been far from stagnant since 2000.

  7. On Mars :

    95.32 m3 of CO2 in 100 m3 of atmosphere.

    PV = nRT
    n = (685.4 Pa x 95.32 m3) / (8.314 x 210.15 ° K)
    n = 37.39 mol of CO2 in 100 m3 of atmosphere

    44 g of CO2 per 1 mol
    So 37.39 mol = 1645.16 g of CO2 in 100 m3 of atmosphere

    The density of Mars atmosphere = 1.9 Kg / 100 m3
    We have 1645.16 g of CO2 for 1.9 kg of atmosphere
    So 1645.16 / 1.9 = 865.87 g of CO2 per 1 kg of atmosphere

    The mass of the atmosphere of March = 25.10 ^ 15 Kg
    865.87 g of CO2 for 1 kg of atmosphere
    So 865.87 x 25.10 ^ 15 = 2.165.10 ^ 19 Kg of CO2 in the atmosphere of Mars.

    To summarize: The amount of CO2 (Kg) in the total atmosphere of each planet and its greenhouse effect (GHE) :

    Venus : 4.72.10 ^ 20 Kg  - GHE : 13870.15 W/m2 (+430°C)

    Earth : 3.128.10 ^ 15 Kg - GHE : 26 W/m2

    Mars : 2.165.10 ^ 19 Kg - GHE : 0 W/m2 !!!!!!!!!

    Where is the logic ?

     

  8. JC @232,

    You appear to be using misconceptions of the operation of GHG on other planets to argue that CO2 is not driving climate change. I think that makes you commenting off-topic.

    But to continue awhile here, there is no disagreement that Mars has a higher pressure of CO2 in its atmosphere (6.0mbar) than there is in Earth's atmosphere (0.6mbar) although you calculation is overly-complicated and wrong to suggest the atmospheric CO2 content on Mars is 2.165e19kg or 7,000-times greater than the value for Earth. The ratio will be less than the 10:1 ratio of CO2 pressures as Mars is a smaller planet. (NASA give the total weight of the Martian atmosphere as ~2.5e16kg suggesting a CO2 content of ~2.4e16kg, a ration of 7.7 to 1.0.)

    Also, the impact of GHGs on the Martian surface temperature is small but it is not zero as your "GHE : 0 W/m2 !!!!!!!!!" implies. How do you obtain the zero value?

  9. Ma Rodger : "NASA give the total weight of the Martian atmosphere as ~2.5e16kg suggesting a CO2 content of ~2.4e16kg, a ration of 7.7 to 1.0"

    2.5e16kg That's the value I use.
    But you made a miscalculation : 96% is the proportion in volume and not in mass. I want the real amount of CO2 (in kg or in mole) which explains my calculation :

    In 2.5e16kg of Martian atmosphere, there is 2.165.10 ^ 19 Kg of CO2 (or 7000 times more kg of CO2 than in the atmosphere of the Earth).

    The greenhouse effect of Mars is close to zero.

  10. JC @234,

    I think you demonstrate the problem we face with the discussion you bring here. How can a substance comprising 97.8% by weight of the Martian atmosphere weigh 2.165e19kg/2.5e16kg = 3800% of that atmosphere? To throw your own incredulity back in your face (and unlike yours, mine is well founded incredulity) "Where is the logic ?"

  11. I correct. I made a unit error at the end of my calculation. Thank you :

    The mass of the atmosphere of March = 25.10 ^ 15 Kg
    865.87 g of CO2 for 1 kg of atmosphere
    So 865.87 x 25.10 ^ 15 = 2.165.10 ^ 19 g of CO2 in the atmosphere of Mars = 2.165.10 ^ 16 kg

    To summarize: The amount of CO2 (Kg) in the total atmosphere of each planet and its greenhouse effect (GHE) :

    Venus : 4.72.10 ^ 20 Kg - GHE : 13870.15 W/m2 (+430°C)

    Earth : 3.128.10 ^ 15 Kg - GHE : 26 W/m2

    Mars : 2.165.10 ^ 16 kg - GHE : 0 W/m2 !!!!!!!!!

    But there is always more amount of CO2 in the matter atmosphere (x 6.9) than in the Earth.

  12. It would require a greenhouse effect theory that takes into account the exact amount of molecules and the available IR energy supported by these molecules.

  13. JC,

    But greenhouse theory does take into account the exact amount of molecules and the IR energy uspported by those molecules.

    On Mars there is a smaller greenhouse effect because the atmosphere is so thin.  Even so, Mars is about 10C higher in temperature from the greenhouse effect.  Because the atmosphere is so thin and there is no water vapor, the height in the atmsophere where the IR energy can escape is much lower than it is on Earth.  That makes the greenhouse effect less on Mars.

    Just because you do not understand the greenhouse effect that does not mean that scientists do not understand it.  Greenhouse models describe the temperature of Earth, Mars and Venus with great accuracy.  You have just not looked for the data.

    You have provided only your own error filled calculations to support your wild claims.  Why should I believe a person whyo cannot even keep track of obvious errors like saying the CO2 in the Mars atmosphere weighs more than the entire atmosphere?

  14. JC @236/237,

    I concur with michael sweet @238.

    Do note that the calculations required to determine GH-effects are complex. See for instance Postawko & Kuhn (1986) 'Effect of the greenhouse gases (CO 2 , H 2 O, SO 2 ) on Martian paleoclimate' which is a reasonably simple example of such analyses.

    Also note Fig2 in that paper which represents today's Mars and Fig3 which sows the effect of having a 1,000mbar CO2 atmosphere instead of today's 6mbar CO2 atmosphere. The result is a warming of some 30K requiring an additional GH-effect of some 80Wm^-2 (additional to today's GH-effect which is some 12Wm^-2), the increased CO2 requiring the atmospheric CO2 content to rise from 2e16kg to 361e16kg.

    Are you happy with these figures? If not we can perhaps try a different approach.

  15. JC @ 230:

    I don't see anything to add to MA Rodger's remarks, which also link to appropriate litterature. The pause-that-never-was is the only way to call this imaginary phenomenon. Who in their right mind would have expected a neutral/La Nina year to be warmer than a major El-Nino year after less than 20 years? That's the kind of warming we're seeing. and the answer is: scientists who study this stuff would have expected that, they even projected it in scientific papers.

    The same kind of people who published the studies that have been linked in this thread to try to point you in the right direction, the kind that really knows what they're talking about. Perhaps you should accept the fact that there is nore to this body of knowledge than your back of the enveloppe calculations.

    JC @ 237 "It would require a greenhouse effect theory that takes into account the exact amount of molecules and the available IR energy supported by these molecules."

    As with the water vapor thing, it's only your ignorance that makes you think it is not the case. If you had any interest in learning about what's out there before trying to make a point, you would have started here: http://modtran.spectral.com/

    And would have found this: http://web.gps.caltech.edu/~vijay/pdf/modrept.pdf

    And, since you were concerned about water vapor, you could also have looked at this: http://climatemodels.uchicago.edu/modtran/

    All of which are far more interesting than your "calculations." MODTRAN  models atmospheric IR radiation at all altitudes quite well, and has been validated against measurements in multiple studies. In case you hold ideological or tribal hang outs that prevent you from trusting the "other camp" sources, be aware than the US Air Force is a major developper of these models, has copyrighted the name and holds several patents on it. 

    "Reality is that which exists whether we believe in it or not."

     

    Response:

    [PS] "Quite well" would be more accurately stated as "with exquisite accuracy". As to accounting for all molecules, then please see Ramanathan and Coakley 1978 .  Arguments from personal incredulity dont cut it here, especially where the real science is confirmed by experimental evidence.

  16. I seek explanations figures on the 3 planets from a universal law of the greenhouse effect. For the moment I only read studies for each planet as if we could isolate the greenhouse effect of CO2 and unify its effects. However, CO2 must react well to energy wherever it is and heat accordingly.

    I am also a scientist (but not a climatologist or physicist) and the greenhouse effect does not seem clear to me at all, moreover no one can explain it simply. We are dealing with vague explanations.

    As for the hiatus, it is visible, as is the current drop in global T °. But that's not the subject of this discussion.

    As far as I am concerned, and in agreement with the studies of Leroy Ladurie, I realize that the current phase of warming follows the regularity of the last four thousand years.

    Image and video hosting by TinyPic

    Thank you for all the documents on the greenhouse effect, that's what I'm looking for. I would read them carefully. Thanks again.

    Response:

    [DB] Activated image link.  It works easiest to use the insert image tool instead of using html.

    "the current drop in global T °"

    There is no current change in the upward trend in global temperatures:

    "the current phase of warming follows the regularity of the last four thousand years"

    Multiple studies have shown the recent warming to be anomalous, regardless of the context of the time period involved, whether over the past 1,700 years, the past 10,000 years or even the past 22,000 years (below). 

    Thousands of posts on this site exist to edify the reader.  Of particular relevance to your statements made in this comment can be found here, here, here and here.

    A breakdown of skeptic arguments and the subsequent evaluation of them can be found here.

  17. JC @241,

    I appreciate you have a language barrier to leap with your contributions here. Yet you should appreciate that presenting a link to an illustration of unknown origin on a scientific web-site is not the done thing. Do we assume this diagram (pasted below) is somehow from historian Emmanuel Le Roy Ladurie? Is it just based on snow & ice or does it also involve the analysis of Grape Harvest Dates which ELR Ladurie has analysed for French regional harvests & more widely? (It is interesting that using Grape Harvest Dates as proxies for temperature has suffered correlation issues as "climate change has fundamentally altered the climatic drivers of early wine grape harvests in France", a bit like the famous "decline" problem faced by proxy tree ring reconstructions.)ERL Ladurie image

    Perhaps with the language barrier, your problems understanding why there is no simple relationship between levels of CO2 and the resulting GH-effects could stand further description of the workings of CO2.

    CO2 does not provide a planet with a full suit of winter clothes. On its own, CO2 provides only hat and gloves. And if you venture out into the "neiges hivemales" wearing only hat and gloves, you will likely freeze to death by morning. It doesn't matter how thick and woolly the hat and gloves are: you will freeze. Venus without its H2O & SO2 would be very-much colder than it actually is. Likewise Earth without its H2O, but on Earth it is the CO2 that raises temperatures to the point where H2O melts and evapourates into the atmosphere. No CO2, then no atmospheric H2O and the Earth freezes.

  18. There isn't and never was a hiatus. This has become a point because you attempted to make an argument about it, argument that was completely debunked right away because no part of it had any validity. "Visible" means nothing in the absence of real statistical analysis. Such analysis has been done and shows that there is no significant change in the long term trend. There is no current drop in temperature either. If you are trying to suggest that every year should be higher than the previous one in order to show a upward trend you are going to reveal that you are arguing in bad faith and should be ignored. What is happening now is similar to what happened after the massive El-Nino of 1998, when temperatures settled toward a baseline that was nowhere near where they were before the El-Nino, then continued increasing through natural variability.

    I am not climate scientist or physicist either but I can read. The greenhouse effect is not that difficult to understand at all on its principle:

    https://en.wikipedia.org/wiki/Greenhouse_effect

    As fas as I know, Ladurie is not a prominent voice in paleo climate circles. The weight of the evidence in that area suggests that we were in a long term cooling trend that was interrupted by the massive injection of radiatively active gasses in the atmosphere. There is plenty of info on that, do your homework yourself.

  19. Proper statistical analysis in the following paper:

    http://iopscience.iop.org/article/10.1088/1748-9326/6/4/044022/meta;jsessionid=DC09E8CC6988FE0F8B81759491CA3939.c5.iopscience.cld.iop.org

    That paper predates the multi year streak or record setting from 2014 on. The idea that there is a slow down in warming is unsupported by any data, even the satellite series that include a large stratospheric influence.

  20. I am French and I have very bad english. Concerning the hiatus, we do not have the same references, I understood that there are two groups that do not have the same reading of the data. Anyway the Giec says in chapter 9 page 769:
    "The observed global mean surface temperature (GMST) has been shown to increase in popularity over the past 15 years over the past 30 to 60 years (Section 2.4.3, Figure 2.20, Table 2.7, Figure 9.8, Box 9.2 Figure 1a, c). Depending on the observational
    data set, the GMST trend over 1998-2012 is estimated to be one-third to one-half of the trend over 1951-2012 (Section 2.4.3, Table 2.7; Box 9.2 Figure 1a, c). For example, in HadCRUT4 the trend is 0.04ºC per decade over 1998-2012, compared to 0.11ºC per
    decade over 1951-2012 ".

    As for the current catastrophism, I find it exaggerated.

    For the greenhouse effect, I understand the principle, the problem is to measure the impact of CO2 on temperature (and in particular the amount of CO2 released by humans). Georg Beck compiled data on the 19th century with high CO2 levels measured during the early ice age !

    Response:

    [DB] "Concerning the hiatus"

    Please understand that the "hiatus" was a discussion of the seeming slowdown in the rate of warming in a small portion of where the Earth stores energy, in its surface.  In reality, the vast majority of energy stored in the Earth system is found in the oceans.  The oceans continue to warm, unabated, unpaused and unhiatused (2017 was the warmest year on record for the ocean):

    Cheng and Zhu 2018

    And surface warming also continues unabated, as shown by NASA (132-month smooth applied to reduce the noise, allowing the underlying signal to be more readily shown):

    NASA Gistemp 132 month smooth

    "Georg Beck compiled data on the 19th century with high CO2 levels measured during the early ice age !"

    Beck's work has been amply shown to be in error, as has been pointed out to you (but which you have ignored).  Future references to such will be deleted unless you can furnish credible evidence to support your contentions.

    Atmospheric CO2 levels have been extensively studied and numerous converging lines of evidence show the recent rise in atmospheric concentrations of such to be anomalous over every timescale relevant to humans, whether the last 1,000 years, the last 10,000 years or even the last 800,000 years.

    Please stay on-topic.

  21. JC,

    Can you provide a citation for your claim that "Georg Beck compiled data on the 19th century".  What is your point?

    If you do not provide a citation to support your claims they have little meaning.

    Your claim about the GIEC has been addressed upthread.  To summarize: 

    1. 15 years is too short a time period to determine a trend.   
    2. The "hiatus" trend was never statistically significant.
    3. The data has been updated which increased the trend over the time period you specified.
    4. The four hottest years in the record are 2014, 2015, 2016 and 2017.  Adding these points to the data show that there was no "hiatus" in the trend.
    5. 2018 is currently the 4th hottest year in the record.  The most recent 5 years are the hottest 5 years in the record.
  22. http://www.realclimate.org/index.php/archives/2007/05/beck-to-the-future/

    Georg Beck is known to have publicized a graph with a discontinuity in the x axis and a change in time scale that was downright laughable, he was not a credible source at all. Beck's nonsense has been debunked multiple times, years ago.

     

    You need to choose your sources more carefully. It seems you're getting all your information from propagandists instead of looking in the litterature. You do not specifiy who the IPCC author you cite is and the date of the report. Cherry picking 1998 as a starting date is an obvious indication that one is trying to misrepresent the trend. 1998 saw a massive El-Nino and is obviously the worst possible choice for the start of any trend calculation, as would be a strong La-Nina year. Whenever I see a "trend" starting in 1998, I know that someone is trying to fool me and the alarm bells start ringing. The insistence by deniers to pick 1998 and their lack of mention of the corresponding El-Nino is the main reason why the so-called pause has no credibility. Start on any other year and the pause disappears. In the case of your citation, extend the period beyond 2012 to include 2017 and the trend is higher than ever. As was pointed above, there is no "current drop" in temperature. Attempting to argue with a pseudo trend that ended in 2012 does not help your case when there are 5 more years of data.

    Let's summarize your contribution: you started with attempting to correlate a supposedly stagnant level of water vapor in the stratosphere (which is, in fact, increasing) with supposedly stagnant temperatures, which all sources show to be increasing as of 2017, regardless of the start year (yes, even if you cherry pick 1998, it no longer works).  If you had even a superficial understanding of the seminal Iacono and Clough 1995 paper, you would have seen that water vapor (and other GH gasses) in the stratosphere contribute, in fact, to stratospheric cooling and have little influence on tropospheric temperatures.

    Nonetheless, this was part of a rather pitiful effort to try to invalidate the greenhouse effect altogether, with "calculations' that were worthless; as was quickly pointed to you, you were nowhere near close to understand what you were talking about and ignorant of a large body of scientific research and litterature that you later, indirectly, confessed to be over your head. Just to be clear as to the validity of the MODTRAN model: that's what they use to ensure that IR guided weapons go where they're supposed to go. It works.

    You did not have the decency to acknowledge any of these shortcomings in your argument, or the arrogance of the wide ranging pronouncements you made before the extent of your incompetence on the subject was revealed.

    Instead, you moved on to what you thought were new things, bringing in something you considered to be paleo data evidence. Once again, there is far more about this than you suspected and that was pointed to you but, once again, you could not acknowledge how weak your argument was.

    You are free to have whatever opinion you choose. Considering the level of ignorance and lack of understanding that you have shown in this thread post after post, it is obvious that your opinion is worthless and I am also free to point that out. Opinions do not have validity by virtue of their existence. Some people hold the opinion that the Earth is flat; their opinion has no value.

  23. To ignore certain data (Leroy Ladurie and Beck for example) is not science. Science must take into account all available data. Vostoc's data have also been criticized.

    Moreover, when science uses the deductive method, the initial hypothesis becomes an explanation only when the model works perfectly. This is not yet the case in climatology. Also the hypothesis remains a hypothesis.

    I am not trying to invalidate the greenhouse effect but to understand how 7000 times more CO2 in the atmosphere of Mars compared to the Earth can not even heat the planet by at least 26 W / m2. The answer given above to this question is remains very imprecise and implies that CO2 alone (without the water vapor gene) actually has a very low greenhouse effect.

    Response:

    [DB] "The answer given above to this question is remains very imprecise and implies that CO2 alone (without the water vapor gene) actually has a very low greenhouse effect"

    CO2 levels in the past were driven by known natural factors.  None of those factors are in play during the recent increase in atmospheric concentration of CO2.  The human forcing is now the largest forcing, dwarfing all natural forcings, including that from the sun itself.

    Radiative forcing

    Please remain on-topic to the nature of the OP of the post on which you place comments.  Thousands of posts exist on this venue, on every topic related to climate science you can think of.  Use the Search function present in the UL of every page or learn to use the Taxonomy listing of the site.

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter.

    Sloganeering snipped. 

  24. JC @248,
    You say that "CO2 alone has a very low GH-effect." And the only place where we find what is effectively "CO2 alone" is the 6mbar atmosphere of Mars which provides something like a 12Wm^-2 GH-effect. The usual-reported calculations put the 0.6mbar CO2 contribution to Earth's GH-effect as being 25%, perhaps 40Wm^-2, this the GH-effect if all other GHGs were taken from the atmosphere. But that CO2 would still sit within 800mbar of N2 and 200mbar of O2. You may have a problem with this situation. Science does not. (Consider, the Mercedes F1 W09 EQ Power+ has a 1.6litre engine yet can travel at speeds more than three-times that of a Mercedes OM 501 LA-541 which has a 12litre engine. To borrow your incredulity for a second time, "Where's the logic in that?")


    As for data being ignored, the publications of ELR Ladurie are not ignored, although the origin of the graphic you present up-thread @241 remains a complete mystery. The data examined by Beck (2007) or Beck (2008) is not ignored although it may be dismissed as irrelevant. What is ignored is the papers written by Beck because they are nonsense and unscientific. Beck agrees his analysis is ignored "The scientific community still ignore the above-cited critics," he says. But isn't that because Beck ignores all the real science, the stuff that shows he is spouting nonsense. He may feel that such a conclusion is "unjustified" but he does nothing to support his claim of injustice. Again he is unscientific!

  25. MA Rodger :

    « You say that "CO2 alone has a very low GH-effect." And the only place where we find what is effectively "CO2 alone" is the 6mbar atmosphere of Mars which provides something like a 12Wm^-2 GH-effect. The usual-reported calculations put the 0.6mbar CO2 contribution to Earth's GH-effect as being 25%, perhaps 40Wm^-2, this the GH-effect if all other GHGs were taken from the atmosphere. But that CO2 would still sit within 800mbar of N2 and 200mbar of O2.»

    I do not understand your explanation. Why would strong pressure prevent CO2 from having a greenhouse effect ?

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