Evidence for Negative Water Feedback

Abstract: Positive linear climate feedback for combined water effects is shown to be incompatible with the Faint Sun Paradox. In particular, feedback values of ~2.0 W/m2K-1 favored by current GCM models lead to non physical results at solar radiation levels present one billion years ago. A simple model is described whereby Earth like planets with large liquid water surfaces can self-regulate temperature for small changes in incident solar radiation. The model assumes that reflective cloud cover increases while normalized greenhouse effects decrease as the sun brightens. Net water feedback of the model is strongly negative.  Direct evidence for negative water feedback is found in CRUTEM4 station data by comparing temperature anomalies for arid regions (deserts and polar regions) with those for humid regions (mainly saturated tropics). All 5600 weather stations were classified according to the Köppen-Geiger climatology [9]. Two separate temperature anomaly series from 1900 to 2011 were calculated for each region. A clear difference in temperature response is observed. Assuming the difference is due to atmospheric water content, a water feedback value of -1.5 +/- 0.8 W/m2K-1 can be derived.

I.            INTRODUCTION

The Faint Sun Paradox was first proposed by Carl Sagan [1] who pointed out that the geological evidence that liquid oceans existed on Earth 4 billion years ago appears incompatible with a solar output 30% dimmer than today. The sun is a main sequence star whose output is known to increase slowly with age. The total change in solar radiation over this long period turns out to be huge ~ 87 W/m2.   It has been argued that an enhanced greenhouse effect due to very high CO2 and/or CH4 concentrations could resolve this paradox [2]. However, recent geological evidence does not support CO2 as being responsible but instead the authors propose a greater ocean surface leading lower albedo as a likely solution [3]. Others have suggested that high cirrus clouds effectively warmed the Earth [4]. Although the atmosphere must have been very different before photosynthesis began, the presence of large liquid oceans still implies that clouds and water vapor played a similar role in the Earth’s energy balance then, as they do today.

II.            MODELS

All current IPCC models adopt net positive feedbacks for water vapor and clouds [6]. A doubling of CO2 increases TOA radiative forcing by ~3.6 W/m2 causing a baseline surface temperature rise of about 1°C to restore global energy balance through increased outgoing Infrared [5]. GCM models predict larger temperature rises ranging from 2-5°C due to these positive feedbacks. What do positive feedbacks imply for the Faint Sun Paradox? For a change in forcing DS, a feedback strength F, and G0 as the baseline response, the temperature rise DT is given by

DT = (DS +F.DT)G0

Black body radiation from the Earth’s surface is the primary negative feedback to any temperature rise DT.

DT  =DS/(1/ G0 -F)                         1/ G0 = 4σT3 = 3.75 W/m2K-1    T=288K

GCM model feedbacks F range from +1.6 to 2.5 with an average positive feedback of ~ 2.0 W/m2K-1  [6].

The sun has brightened 30% over the last 4 billion years and current average incident solar radiation is ~342 watts/m2. Assuming a slow linear increase of solar radiation with time yields a net forcing increase of 0.02 W/m2 every 1 million years. The temperature response to this forcing has been calculated for feedback values   F=-2, 0, +2. This can be integrated backwards 4 billion years from current temperatures. The results are shown in Figure 1.

Figure 1: Past temperatures extrapolating backwards from today (T=288ºK) assuming different linear feedback values.

It is apparent that a simple linear positive feedback of +2 leads to unphysical results. The basic problem is that if the temperature falls sufficiently so that 4σT3= F then a singularity occurs ~1.5 billion years ago.  Instead a negative feedback value of -2 W/m2K-1  is more compatible both with current temperatures and with the Faint Sun Paradox..

The evidence is that global surface temperatures have changed rather little over the Earth’s history.  It therefore seems likely that feedbacks were negative during the early lifetime of the Earth to avoid run away surface heating as the sun brightened.  The continuous ~70% surface coverage of water on Earth has apparently stabilized global temperatures. A simple model of how this could work is described next, in analogy with Daisy World proposed by James Lovelock to justify Gaia theory [7].

III.            WATER WORLD

Water world is a hypothetical planet 100% covered in water with an atmosphere similar to that on Earth but with no other greenhouse gas except water vapor. The climate is driven only by the thermodynamics of water evaporation and solar forcing. In all other respects conditions on Water World are exactly the same as on Earth except there are no seasons.  Can such a water covered planet self regulate its temperature as the sun’s output gradually increases? When the planet’s sun is 4 billion years younger its output is 33% less  ~ 274 W/m2. Solar radiation slowly increases over the following 4 billion years to 342 W/m2.

Figure 2: Schematic of Water World

The model has 2 basic assumptions.  At low solar forcing epochs it is assumed that cloud cover is zero and evaporation mostly increases greenhouse warming. Further evaporation increases low convection clouds, reducing the planet’s albedo. The global average temperature at any time is then a balance between these two effects. Ad hoc simple dependencies for both low clouds and net greenhouse effects on incident solar energy are assumed. Defining x= S0/342 as the normalized solar radiation flux.

1. Low Cloud Cover (CC) is assumed to be linearly dependent on solar radiation: CC = 0.4x. The albedo for low clouds is taken as 0.5 so the planet albedo varies as 0.1+0.2x. For x=1 albedo equals that on Earth today ~ 0.3.

2. The normalized greenhouse effect g is assumed to depend inversely on x. The assumption is that g= 0.3/x giving a value of 0.3 on Earth today. 4 billion years ago g works out to be 0.45.

Defining SU as the surface outgoing IR, energy balance gives:

(0.9-0.2x) S0 = SU(1.0-0.3/x),

SU = (342(0.9-0.2x)x)/(1-0.3/x) and assuming T (x) = Tnow4(SU(x)/SUnow)

This is easy to calculate and the results are shown in Figure 3.

Figure 3:  Water World model compared to a constant normalized greenhouse and albedo fixed at today’s values.

Average temperatures change by just 5 degrees over 4 billion years. The presence of liquid water 4 billion years ago effectively rules out constant values for g and albedo in this model. Others have argued that a greatly enhanced CO2 greenhouse effect is responsible for warming in the early history of the Earth, however the geological evidence doesn’t support it [3]. This simple model also predicts a low climate sensitivity of 0.2°C from a doubling of CO2. Is there any evidence for large negative feedbacks in recent climatology data?


Water vapor feedback in recent climate data have been investigated by studying differences between regions with very low atmospheric water vapor (Deserts and Polar) and those regions with very large water vapor content (Tropical Wet regions).  The latest CRUTEM4 data [8] consisting of 5500 individual station data covering global land areas has been studied. Each station was classified by indexing its geographic location against the Köppen-Geiger climate classification [9].

“ARID” stations are defined as those with precipitation values ‘W’ or with climate ‘E’ in [9]. These are situated either in deserts or in polar areas having the lowest atmospheric water column on Earth [10]. “WET” stations are defined as those within fully humid Tropical areas – Climate ‘A’ and precipitation ‘f’ in [9].  These are situated in tropical rain forests or year-round humid climates having the highest atmospheric water column on Earth [10]. Global anomalies have been calculated for both stations ARID and WET stations independently using the same algorithm as used for CRUTEM4. The results are shown in Figure 4.

Figure 4: Temperature anomalies for ARID(DRY) stations in red and WET stations in blue. The smooth curves are FFT smoothed curves. The black dashed curve is an FFT smooth to the full CRUTEM4 global temperature anomalies.

There is a clear trend in the data that ARID stations warm faster and cool faster than WET stations. They respond stronger to changes in external forcing. The WET humid stations respond less than both the ARID stations and the global average.

Climate change is complex and global so it is reasonable to assume that both anthropogenic and natural forcing are reflected in the temperature anomaly data. For a given forcing DS the consequent change in temperature anomaly is gDT where g is a gain factor. The period between 1900 and 2005 is used to measure the temperature rise for each region DT1 and DT2 as given in Table 1. DS is assumed to be global in extent.

Table 1 : Temperature changes for ARID and WET regions and their ratio.  Errors on DT are derived from differences between the FFT smooth and a linear fit.

Period DT1(DRY) DT2(WET) DT1/DT2
1900-2005 1.1 +/-0.1 ºK 0.8+/- 0.1 ºK 1.4 +/- 0.2

Heat inertia effects due to nearby oceans may cause tropical climates to react slower than desert regions, but not over such long periods. If positive feedbacks from increased water evaporation lead to enhance warming then this should be apparent in the tropics, and this is not observed. In fact the opposite is the case implying a negative feedback. Under the assumption that net water feedback F is present only for the WET stations (taking F=0 for ARID stations) then F can be measured from the data:

DT1/DT2 = 1 – G0F  ,    where DT1 = G0DS   and DT2 = G0 (DS+FDT2)

For G0-1  = 3.75W/m2K   gives Water Feedback  F =  – 1.5 +/- 0.8 W/m2K-1 

This is compatible with the value needed to resolve the Faint Sun Paradox. As has been pointed out by Lindzen [11] and others, much of the Earth’s heat is transported bodily through evaporation and convection to the upper atmosphere where IR opacity is low and can then escape to space. Therefore water feedback effects depend mostly on the water vapor content of the upper atmosphere.  Increased evaporation, convection and consequent rain out could then result in lower humidity in the upper atmosphere. This is a possible mechanism for negative feedbacks in the tropics.  Such effects would be largely absent in ARID areas, which have no local sources of evaporation.

V.            CONCLUSIONS

The Faint Sun Paradox effectively rules out constant positive climate feedbacks for water.  The evidence supports the hypothesis that the Earth’s oceans have stabilized temperatures for the last 4 billion years. It is proposed that the net effect of a surface with 70% water coverage self regulates Earth’s climate. A simple model that demonstrates how this could arise has been described. The model leads to average temperatures increasing by just 5 degrees over 4 billion years. This leads to predicted negative feedbacks from water of about -2 watts/m2/ºC. Direct evidence that the temperature response from arid and humid land regions on Earth are different has been identified in CRUTEM4 data. Assuming that these divergences are only due to atmospheric water vapor differences a measured negative feedback for water of 1.5+/-0.8 watts/m2/ºC. This agrees with that needed to explain the Faint Sun Paradox.


1. Sagan, C.; Mullen, G. (1972). “Earth and Mars: Evolution of Atmospheres and Surface Temperatures”. Science 177 (4043): 52–56. 1972

2. Pavlov, Alexander A.; Kasting, James F.; Brown, Lisa L.; Rages, Kathy A.; Freedman, Richard (May 2000). “Greenhouse warming by CH4 in the atmosphere of early Earth”. Journal of Geophysical Research 105

3. Hsien-Wang Ou, Possible Bounds on the Earth’s Surface Temperature, Journal of Climate, Vol 14, 2976, 2000.

4. Roberto Rondanelli and Richard Lindzen (2010) Can thin cirrus clouds in the tropics provide a solution to the faint young Sun paradox, Journal Geophys Research Vol 115, D02108

5.  Myhre et al,  New estimates of radiative forcing due to well mixed greenhouse gases, Geophysical Research Letters (1998)

6. S. Bony et al. How well do we understand and evaluate Climate Change Feedback Processes, Journal of Climate, Vol 19, P. 3445, 2006

7. Lovelock, J. E. (1983b), Daisy world—A cybernetic proof of the Gaia hypothesis, CoEvol. Q., Summer, 66 – 72

8. Jones, P.D., Lister, D.H., Osborn, T.J., Harpham, C., Salmon, M. and Morice, C. 2012:  Hemispheric and large-scale land-surface air temperature variations: An extensive revision and an update to 2012.  J. Geophys. Res. 117, D05127

9.  Rubel, F., and M. Kottek, 2010: Observed and projected climate shifts 1901-2100 depicted by world maps of the Köppen-Geiger climate classification. Meteorol. Z., 19, 135-141

10. H. Schrijver, A. M. S. Gloudemans, C. Frankenberg, and I. Aben, Water vapour total columns from SCIAMACHY spectra in the 2.36µm window, Atmos. Meas. Tech., 2, 561–571, 2009

11. Richard Lindzen, Some uncertainties with respect to water vapor’s role in climate sensitivity. Proceedings NASA workshop on the role of Water Vapor in Climate Processes, 1990.

Postscript: The above paper was submitted to Geophysics Research Letters on April 25th. The editor later rejected it on the grounds that “the work appears to represent an incremental advance in our understanding of a problem that has already received attention in the peer-reviewed literature, and extends its conclusions beyond what is supported by the research methods and results“. You are invited to decide for yourself whether that is true or not.

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41 Responses to Evidence for Negative Water Feedback

  1. Thank you for this stimulating paper. I hope you will resubmit it to other journals.

  2. Coincidentally, a paper was just published today on the inability to resolve the Faint Sun Paradox with conventional greenhouse gas assumptions:


  3. Clive Best says:

    All other explanations of the faint sun paradox seem to me contrived, relying on artificially exaggerated levels of CO2 or CHO4. Recent geological evidence now effectively rules this out. Only >70% liquid water cover in my opinion can explain stable Earth’s temperature over eons.

  4. Pingback: New Paper Finds Water Vapor Feedback Is Strongly Negative : CLIMATE HIMALAYA

  5. Pingback: Clive Best gives evidence for negative water feedback in Earth’s climate system using the faint sun paradox | Watts Up With That?

  6. Russell says:

    The GRL Editor was right.

    Your first reference , on dust induced optical depth, is the one that inspired Steve Scheider to write of the the hype surrounding ‘nuclear winter’ , that Carl had ” proposed an invasion from Mars.”


  7. Mike Seward says:

    Thankyou for your paper which is about the most lucid accounting for the AGW vs Reality divergence problem I have come across and makes perfect sense as a mechanism.

    It says all you perhaps need to know about the mindset at GRL when even Hansen and co have been scratching their heads and publicly discussing the little problem that the models do not follow reality. It seems to me it is the central issue to resolve in advancing our proper understanding of the planets temperature mechanism yet the eco fundamentalists would have it that what they say is infallible truth.

    Like Martin Luther you just have to nail your ideas on the cathedral door because you know they will never open your letter in Rome.

  8. Alan S. Blue says:

    That’s going to leave a mark.

    Would there be any possibility of attempting ‘Spike/Impulse’ tests and other robustness tests from control theory?

    That is: How -big- a disturbance can hit Waterworld without rendering it unstable?

  9. In the conclusions, the dimensions are wrong.

    -2 watts/m/ºC –> -2 watts/m^2/ºC

    1.5+/-0.8 watts/m/ºC –> 1.5+/-0.8 watts/m^2/ºC

  10. Lars P. says:

    Clive, you are perfectly right.
    I have the feeling that the oceans play a much larger role to define earth average temperature then defined by consensus climatology.
    The water world is not so hypothetical after all, the Earth has lost about a quarter of its water during the ages:

  11. Robbie says:

    What do we know about Young Earth? Even this piece is still assuming and speculating about cloudcover being zero and the greenhouse effect causing the feedback necessary to create high enough temperatures for liquid water with help of a computer model.
    It could well be that Geothermal Heat was responsible for liquid water on Earth and not Greenhouse Gases. Shallower oceans probably warm up faster with geothermal heat (a more active planet) than perhaps deep ones do. It means that it doesn’t matter how much cloudcover there was 1 or 4 billion years ago. In time the Earth cooled down resulting in what we have today. The sun is 30% hotter now than 4 billion years ago and yet we are in the middle of one of the coldest periods in geological history.
    The ocean floor is “refreshed” with new rock every 200-250 million years. Oceans were shallower in the past, but we don’t know how deep they were 1 or 4 billion years ago. How thick was the continental crust for example? How geologically active was Young Earth?
    First try to explain an event like PETM that happened much more recently (55 mya) what caused a sudden global rise of 5-6 degrees Celsius (“The model leads to average temperatures increasing by just 5 degrees over 4 billion years” – Nobody really knows what temperatures were like 1 or 4 billion years ago. We are still arguing about global temperatures of the MWP) before trying to explain the Faint Young Sun Paradox with a negative or positive water vapor feedback mechanism.
    What feedback mechanisms were at play 55 mya to cause such a dramatic climate change?

    • Clive Best says:

      I am not trying to explain the faint sun paradox. I am drawing attention to the contradiction implicit in all models with built in positive feedback from water to increased radiative forcing. The oceans would have long ago boiled away with positive feedback.

      Otherwise I agree with you that geothermal heating, vulcanism, denser atmosphere may also have been important. Despite all this, and simply because we know that liquid oceans covered the young Earth, any positive feedback would have amplified the brightening sun in a run away effect.

      • Robbie says:

        Thanks for the reply.
        Just take a look at the graph at 8:09 in this video.
        Even a negative feedback can produce a significant amount of extra warming (blue line up). It just doesn’t get out of control.
        I accept the fact that water vapor feedback is negative. A very simple explanation is this one: Total greenhouse effect (TGE) on Earth is apporximately 33°C (Schmidt et al 2010 – http://meteo.lcd.lu/globalwarming/Schmidt/attribution_present_GH_effect_2010.pdf ).
        Without clouds the TGE turns into 60°C ( . Source: Roy Spencer – Climate Confusion) which means that clouds and thus water vapor produces a 45% negative feedback in the current situation. But this is a situation with clouds.
        You are speaking of a cloudless situation 4 billion years ago but with high enough water vapor concentrations to keep the planet warm enough for liquid water. Water cover on Earth would be >70% (which I accept in a shallow ocean situation).
        The other situation is complete nonsense to me. No clouds mean simply a very low concentration of water vapor in the atmosphere and thus a very cold Earth where liquid water is quite impossible. You’ll get the Snowball Earth condition.
        A thin crust with a shallow ocean on a very geologically active planet (after all it is Young Earth we are talking about) that releases enough heat to warm up the ocean is a much more plausible explanation. But how on Earth do you prove that scientifically?????
        There may be one: Mars seemed to have liquid water in exactly the same period (Hesperian epoch 3.7 bya) as well. How would that be possible? A planet even further away from the sun with also liquid water when the Sun was 30% dimmer. No modern climate model can make that plausible if they already have trouble producing liquid water on Earth with a dimmer Sun 4 bya.

  12. Excellent!
    Clive, thank you very much.
    I’m linking to this article from my climate and weather pages.

  13. David Hugh-Jones says:

    Forgive me for asking, but has this been peer-reviewed?

  14. peter azlac says:

    A most interesting paper but can you dissect the data further by influence of ocean basin and oscillation(s) – PDO, AMO, AO, IO etc. as MAST values are a combination of ground effects and the prevailing weather. This has been looked at in a more direct way using pan evaporation values from irrigation stations. These have shown that over the warming period of the last 30 – 50 years the rate of evaporation of water from the surface has decreased, thus falsifying AGW “theory” that claims an increase in atmospheric carbon dioxide will result in increased evaporation of water from the surface and casting doubt on the use of temperature anomalies to measure climate change. There are several papers on this but one by Roderick et al referred to by Pielke Sr will suffice:
    Roderick, Michael L. , Michael T. Hobbins and Graham D. Farquhar, 2009: Pan Evaporation Trends and the Terrestrial
    Water Balance. I. Principles and Observations. Geography Compass 3/2 (2009): 746–760, 10.1111/j.1749-8198.2008.00213.x
    Abstract “Pan evaporation is just that – it is the evaporation rate of water from a small dish located at the ground-surface. Pan evaporation is a measure of the evaporative demand over terrestrial surfaces. Declines in pan evaporation have now been reported in many regions of the world. The trends vary from one pan to the next, but when averaged over many pans, they are typically in the range of ?1 to ?4 mm a?2 (mm per annum per annum). In energetic terms, a trend of ?2 mm a?2 is equivalent to ?0.16 W m?2 a?1 and over 30 years this is a change of ?4.8 W m?2. For comparison, the top-of-atmosphere forcing due to doubled CO2 is estimated by the Intergovernmental Panel on Climate Change (IPCC) to be ~3.7 W m?2. Hence, the magnitude of the pan evaporation trend is large. What is of even greater interest is the direction – a decline – given the well-established warming of the last 30–50 years. “ Also:
    Changes in Australian pan evaporation from 1970 to 2002 (PDF)

    • Clive Best says:

      Thanks. I was unaware of the Pan evaporation data. At first sight it seems counter-intuitive, since warmer air can hold more water vapor. There must be something subtle going on here, which needs thinking about and explaining.

      regarding AMO PDO etc. The global temperature data show clear 60 year oscillations which support the idea of natural regular climate variation. I made a fit to hadcrut3 data which tried to quantify this. ” rel=”nofollow”>see here. There remains a logarithmic underlying trend which could be associated with AGW predicting a maximum climate sensitivity of 1.7 degrees to a doubling of CO2, which is far less than models predict.

      • JoNova says:

        Pan evaporation rates are also dependent on windspeed. I’ve heard that winds decrease in El Nino (hot) years, and increase in la nina’s (colder ones). I don’t know if that is just limited to certain oceanic winds. But if so, it might in part explain evaporation rate changes?

        “Indicators for a La Niña include:
        • The Walker Circulation strengthens leading to stronger than normal (easterly) trade winds across the Pacific Ocean.”

        Since evaporation rates are very dependent on temperatures above 30C, I expect the windspeeds would have most effect over cooler areas, but that includes a large part of the planet.

        Humidity also reduces evaporation, and will affect rates too.

  15. peter azlac says:

    Re my previous comment, I should have added that the lowered pan evaporation values support the link made by Professor Salby between increased atmospheric carbon dioxide and surface temperature/soil moisture values via increased production of biomass, such that both the carbon dioxide and temperature-water uptake aspects of the IPCC “theory” are falsified.

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  18. Clive,

    You said:

    ..All other explanations of the faint sun paradox seem to me contrived, relying on artificially exaggerated levels of CO2 or CHO4..

    Can you cite papers or textbooks, their values and their reasons and explain why they are “artificially exaggerated”?

    And then later:

    I am drawing attention to the contradiction implicit in all models with built in positive feedback from water to increased radiative forcing. The oceans would have long ago boiled away with positive feedback.

    This is a common area of confusion for people approaching climate science. A typical engineering problem with positive feedback results in an output going to infinity (until it hits some input restraints). Positive feedback from water vapor is simply an amplifier with other effects that are negative feedbacks – like the 4th power relationship between temperature and flux.

    It is “easy” to demonstrate that it doesn’t lead necessarily lead to runaway temperatures, for example, Water Vapor Feedback and Global Warming, Held & Soden (2000) – on p8 & 9 of the paper (around p449 in the journal page number).

    In fact this paper is an excellent resource for understanding climate science view of the water vapor effect and very readable. You are clearly interested in the subject, and I would recommend that you read it.

    You also say “..implicit in all models with built in positive feedback.. – again a common claim of people unfamiliar with models. The positive feedback is not built in, it is a result of the model.

    This doesn’t mean models are “right”.

    Plenty of websites sound off and enjoy the experience, with little interest in finding anything out. I think you are interested in understanding climate and to do that you need to represent current climate science fairly. My suggestion is you read more textbooks and papers.

  19. Clive Best says:

    That is a nice paper – thanks. As I understand it most models derive/assume a fixed relative humidity with rises in surface temperature leading to an enhanced H2O greenhouse effect as the total water column increases – Beta~0.4 increasing CO2 sensitivity by 1.7. Working the other way is the decrease in lapse rate as the atmosphere gets saturated – so the 150m or rise in height of the net radiation level is not as cold as before – a negative feedback. Then we have high cirrus clouds which act as a greenhouse cover – positive feedback, whereas low clouds increase albedo a negative feedback. The biggest uncertainty is low level cloud cover. However it seems to me that the tropics already show how the water cycle limits temperature rises as thunderstorms are triggered when temperature rises too much over the ocean. They rain out the humidity at night for the cycle to be repeated. Yes I know this is hand waving.

    Yes the models do not have a built in positive feedback. They rather have built in algorithms for water cycle which result in positive net feedback.

    The geochemical evidence is against massive concentrations of either CO2 or methane in the early Earth Atmosphere. It could be that atmospheric pressure was much higher then which would have kept temperatures higher.

    See: Possible Bounds on the Earth’s Surface Temperature, HSIEN-WANG OU Journal of Climate 14 2976, 2000
    and: No Climate Paradox under the Faint Sun, Nature 2010, Minik T. Rosing et al. download here

  20. Clive Best says:


    I forgot to say that I have been running an early GISS GCM to understand better what is going on. This led me to look at the time delay in warming (from ocean heat) that is often quoted as being pent up in the system. Please have a look at Thermal inertia and climate feedbacks.Here I fit the temperature data and get a net positive feedback of ~ 2.0 watts/m2K.

    I would be interested in your comments.

  21. There’s some good reasoning in your article which I’ll come to in a minute but what looks like basic physics confusion in your comment above.

    Yes the models do not have a built in positive feedback. They rather have built in algorithms for water cycle which result in positive net feedback.

    What exactly do you mean by “algorithms for water cycle”?
    The models use conservation of mass and energy. This means water vapor has to condense out into water or stay as water vapor. If you are sure what a given model does, reference the model and explain specifically what you think happens in the model and why it is unphysical.

    The geochemical evidence is against massive concentrations of either CO2 or methane in the early Earth Atmosphere. It could be that atmospheric pressure was much higher then which would have kept temperatures higher.

    This is the bit that makes me wonder. If you believe high pressure causes high temperature then you are not alone in the world but you are in science. Measure the temperature of air in a tire. Pump up the bike tire and measure the air temperature (hotter). Then remeasure it after 10 minutes (back to normal). Putting in the work increases the temperature. Long term the temperature is determined by the energy balance not by the pressure. As you can see explained in the first part of Convection, Venus, Thought Experiments and Tall Rooms Full of Gas – A Discussion.
    I’m hoping you meant something else and expressed it badly.

    As far as your main hypothesis goes I challenge the idea that there is a constant called climate feedback.

    In Measuring Climate Sensitivity – Part One I referenced Stephens (2005):

    The relationship between global-mean radiative forcing and global-mean climate response (temperature) is of intrinsic interest in its own right. A number of recent studies, for example, discuss some of the broad limitations of (1) and describe procedures for using it to estimate Q from GCM experiments (Hansen et al. 1997; Joshi et al. 2003; Gregory et al. 2004) and even procedures for estimating  from observations (Gregory et al. 2002).

    While we cannot necessarily dismiss the value of (1) and related interpretation out of hand, the global response, as will become apparent in section 9, is the accumulated result of complex regional responses that appear to be controlled by more local-scale processes that vary in space and time.

    If we are to assume gross time–space averages to represent the effects of these processes, then the assumptions inherent to (1) certainly require a much more careful level of justification than has been given. At this time it is unclear as to the specific value of a global-mean sensitivity as a measure of feedback other than providing a compact and convenient measure of model-to-model differences to a fixed climate forcing (e.g., Fig. 1).

    And if your current hypothesis explains the faint sun paradox (which needs more thought on my part) it struggles to explain the last 1M years of climate history – the rapid changes in temperature in and out of ice ages.

    Climate history is very valuable and there are lots of hypotheses that tackle the temperature history of the planet. They all seem to have problems. One day when I understand it enough I will write an article on it.

    • Clive Best says:

      Thanks for you comments.

      What exactly do you mean by “algorithms for water cycle”?
      This may be naive but – I believe that the algorithms for cloud cover are the most suspect example. The early GCMs (GISS II as far as I know) used a random number generator to decide if a grid cell was cloud covered or not. If the random number was greater than a calculated saturation level then cloud was assumed otherwise not. Likewise precipitation is triggered if humidity exceeds 100%. Modern models may be more sophisticated – I don’t know.

      Pressure v Temperature. What I mean is that higher pressures at the surface increases the height scale of the atmosphere and the total amount of water vapour that the atmosphere can hold. This would then increase H2O greenhouse effect without increasing cloud cover. The lapse rate must change as well. Temperature would only increase with Pressure (PV=RT) if the system was isolated – which it isn’t.

      The simplistic “water world” model I proposed does not have a constant climate feedback. It actually varies between positive at early epochs and negative values at later epochs. I was just using the “constant” feedback values as quoted by S. Bony et al. from their analysis of GCM models to show that this is not compatible with the faint sun paradox. As far as I understand it, the models do assume more evaporation = more H2O greenhouse effect – by taking a constant relative humidity.

      I don’t think anyone has a real explanation of Ice Ages. Here was my try.

      The discussion on your site shows there is still much confusion about back radiation !.

  22. You write:

    “There is a clear trend in the data that ARID stations warm faster and cool faster than WET stations.”

    Isn’t this what we would expect even if there were no feedback, positive or negative? Water vapor is a greenhouse gas. The more greenhouse gas in the atmosphere, the less the effect of adding a bit more of another greenhouse gas–you can’t block the same photon twice. So increased CO2 will have a larger effect the drier the atmosphere–feedbacks aside.

    Am I missing something?

    • Clive Best says:

      Everyone assumes that CO2 concentrations in air are the same everywhere ~0.04% . So if an increase in CO2 levels causes an increased greenhouse effect then the effect is the same everywhere – i.e. a doubling of CO2 leads to ~ 1 degree C increase in surface temperatures (ignoring feedbacks). Now we compare areas where there is an infinite amount of water available for evaporation – Wet Tropics with those with essentially zero water surfaces for evaporation: Arid areas – deserts and polar regions. If more evaporation leads to an enhanced greenhouse effect (positive feedback) than we would expect Wet areas to warm faster that dry areas. Instead we find the opposite if the case.

  23. Coldish says:

    Interesting article and discussion. Thank you. I’d also be interested in your (or anybody’s) comments/ criticism of a blog article by Kevan Hashemi, who also argues in favour of a net cooling effect from increased atmospheric H2O. See http://www.homeclimateanalysis.blogspot.de/2012/03/anthropogenic-global-warming.html

    • Clive Best says:

      I think the blog by Kevan Hashemi is very thorough and objective. There are two opposing effects from water in the atmosphere. Firstly H2O is a greenhouse gas and traps some IR heat radiating from the surface – this gives a positive feedback. However clouds reflect incident solar radiation back to space thereby cooling the planet. Anyone who has sat on a beach in the UK can confirm that the temperature drops significantly when the sun goes behind a cloud. The decreasing lapse rate is also a negative feedback mechanism. I think the overall net feedback depends on the temperature. When the earth is too cold (near 273K) the warming effect wins, but in todays climate negative feedback wins. 70% water cover on Earth stabilizes temperatures.

  24. Coldish says:

    Are you still interested in comments on the May 2012 version of your Water Feedback article? If so, I could make some suggestions, more about presentation than content.

  25. Coldish says:

    Hi Clive,
    Just a few thoughts.
    I’m not sure that GRL was the best choice as it is a generalist journal, which covers several other fields in addition to climate. However the editor seems to have been confident enough of his (or her) own knowledge of the subject matter to assess your article without sending it out for peer review. He did consider it ‘represented an … advance in our understanding…’ which would seem to me to be a reason for accepting the paper. But perhaps he thinks ‘incremental’ means ‘small’….also you could write to ask him for some references to articles in the peer-reviewed lit which already cover the ground of your paper.
    Anyway I hope you will be resubmitting your results to another journal. Perhaps one specialising in climate.
    If, so I would suggest tidying up your reference list. Every journal has its own style for references, and it’s a simple courtesy to reformat these to comply with the style used by the journal one is submitting to. It at least shows one is familiar with the journal. For some reviewers the refs list is the next thing they look at after the abstract.
    I haven’t read the article carefully enough to comment on the content. But you seem (apologies if I’m wrong about this) to be combining two distinct arguments – one relates to modelling feedback and the early sun paradox, the other to ‘Direct evidence for negative water feedback … found in CRUTEM4 station data…’. Both arguments may support your thesis, but if they are independent, it might be neater to write a separate (and shorter) paper for each. Otherwise a reviewer’s objection to one argument can become grounds for rejecting both.
    I confess to prejudice against the style of your abstract – which I’m sure you’ll agree is the most important part of any paper insofar as getting into print is concerned. I have a printout of a short (1 page) article called ‘Abstracts: good and bad’ , which I’ll try to locate online; otherwise I can scan it for you as pdf.

  26. Coldish says:

    Clive: the article by Landes about abstracts is at http://www.aapg.org/bulletin/abstract_scrutiny.pdf

  27. Ken Gregory says:

    In part III Models, you say, “The sun has brightened 30% over the last 4 billion years and current average incident solar radiation is ~342 watts/m2.” This means the solar radiation 4 BYA (billion years ago) was 342/1.3 = 263 W/m2.

    In part III Water World, you say, “When the planet’s sun is 4 billion years younger its output is 33% less ~ 274 W/m2. Solar radiation slowly increases over the following 4 billion years to 342 W/m2.”

    But 33% less than 342 is not 274, it is 342 x (1-0.33) = 229. The sun now being 30% brighter than 4 BYA is inconsistent with the sun then being 33% less than now.

    The Introduction says, “The total change in solar radiation over this long period turns out to be huge ~ 87 W/m2.” This implies the solar radiation 4 BYA was 342 – 87 = 255 W/m2.

    So, was the solar radiation 4 BYA 263 W/m2, 274 W/m2, 255 W/m2 or 229 W/m2?

    You say the normalized greenhouse effect g = 0.3/X and you give the value at 4 BYA of 0.45. The value of X = 1 now, so 4 BYA the value of X = 0.3/0.45 = 0.67, which is 33% less than now. You defined X = So/342, so you are apparently using a 4 BYA solar flux of 0.67*342 = 229 W/m2 (not the 274 W/m2 you stated.)

    You write, “At low solar forcing epochs it is assumed that cloud cover is zero …”.
    This seems to say you used zero cloud cover at 4 BYA, but your equation for low cloud cover CC = 0.4X = 0.4*0.67 = 0.268. This contradicts the assumption of zero cloud cover at low solar forcing epochs.

  28. Ken Gregory says:

    I take Go = 0.30 C/W/m2. (1/Go = 3.3 W/m2/C) You used Go = 1/3.75 = 0.267 C/W/m2.

    From DT1/DT2 = 1 – GoF, F= (1 – DT1/DT2)/Go = (1 – 1.4)/(0.3 C/W/m2) = -1.33 W/m2/C

    You have labeled F as “net water feedback F”, but this value includes the feedbacks from water vapor, the lapse rate, clouds, and surface albedo. The IPCC separates feedbacks into these components, so we should avoid confusion between the IPCC water vapor feedback and your F, which is the sum of all feedbacks.

  29. Martin Lack says:

    In your abstract, Clive, you mention “authors” (plural). Who are the other co-authors (if you are not the sole author of this paper)? Given their history of publishing all sorts of poorly-executed research with indefensible conclusions, I think you should take heed of the response (rejection) you received from Geophysical Research Letters. If early Earth history and/or the presence of liquid water on Earth today contradicted the consensus view of climate sensitivity to the extent that you claim it does here, this would be on a par with Galileo’s proof that the Earth lies within a heliocentric solar system. Sadly, for you, it is not.

    Since climate “sceptics” are therefore not like Galileo – and given that the only obscurantist Establishment today is funded by the fossil fuel lobby – I have a question for you: Why do people who are not in denial about climate change and are not conspiracy theorists question the motives of the Met Office for saying what they do and rebutting the misinformation put about by (self-confessed) ideologically-prejudiced and unscientific journalists such as David Rose and James Delingpole?

  30. clivebest says:

    I am not questioning the motives of the Met Office for rebutting critical articles by David Rose and James Delingpole. It is normal that they defend themselves. However the data speaks for itself and clearly show that the rapid warming from 1970 – 2000 has stopped – as both Delinpole and Rose claimed. The new forecast up to 2017 essentially is saying that this stalling of global warming will continue. My view is that this slow down will continue until 2030 and thereafter there will be another 30 years of rapid warming (0.5C) until 2060, followed by another lull.

    Regarding the Faint Sun paradox – the “consensus explanation” is that huge quantities of CO2 in the early atmosphere is to blame. There is no agreement about this.

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