What’s the worst case? Climate sensitivity

Posted on April 1, 2019 by curryja |

Reposted from Climate Etc.

by Judith Curry

Are values of equilibrium climate sensitivity > 4.5 C plausible?

For background, see these previous posts on climate sensitivity [link]

Here are some possibilistic arguments related to climate sensitivity.  I don’t think the ECS example is the best one to illustrate these ideas [see previous post], and I probably won’t include this example in anything I try to publish on this topic (my draft paper is getting too long anyways).  But possibilistic thinking does point you in some different directions when pondering the upper bound of plausible ECS values.

5. Climate sensitivity

Equilibrium climate sensitivity (ECS) is defined as the amount of temperature change in response to a doubling of atmospheric CO2 concentrations, after the climate system has reached equilibrium. The issue with regards to ECS is not scenario discovery; rather, the challenge is to clarify the upper bounds of possible and plausible worst cases.

The IPCC assessments of ECS have focused on a ‘likely’ (> 66% probability) range, which has mostly been unchanged since Charney et al. (1979), to be between 1.5 and 4.5 oC. The IPCC AR4 (2007) did not provide any insight into a worst-case value of ECS, stating that values substantially higher than 4.5 oC cannot be excluded, with tail values in Figure 9.20 exceeding 10 oC. The IPCC AR5 (2013) more clearly defined the upper range, with a 10% probability of exceeding 6 oC.

Since the IPCC AR5, there has been considerable debate as to whether ECS is on the lower end of the likely range (e.g., < 3 oC) or the higher end of the likely range (for a summary, see Lewis and Curry, 2018). The analysis here bypasses that particular debate and focuses on the upper extreme values of ECS.

High-end values of ECS are of considerable interest to economists. Weitzman (2009) argued that probability density function (PDF) tails of the equilibrium climate sensitivity, fattened by structural uncertainty using a Bayesian framework, can have a large effect on the cost-benefit analysis. Proceeding in the Bayesian paradigm, Weitzman fitted a Pareto distribution to the AR4 ECS values, resulting in a fat tail that produced a probability of 0.05 of ECS exceeding 11 oC, and a 0.01% probability of exceeding 20 oC.

The range of ECS values derived from global climate models (CMIP5) that were cited by the IPCC AR5 is between 2.1 and 4.7 oC. To better constrain the values of ECS based on observational information available at the time of the AR5, Lewis and Grunwald (2018) combined instrumental period evidence with paleoclimate proxy evidence using objective Bayesian and frequentist likelihood-ratio methods. They identified a 5–95% range for ECS of 1.1–4.05 oC. Using the same analysis methods, Lewis and Curry (2018) updated the analysis for the instrumental period by extending the period and using revised estimates of forcing to determine a 5-95% range of 1.05 – 2.7 oC. The observationally-based values should be regarded as estimates of effective climate sensitivity, as they reflect feedbacks over too short a period for equilibrium to be reached.

Values of climate sensitivity exceeding 4.5 oC derived from observational analyses are arguably associated with deficiencies in the diagnostics or analysis approach (e.g. Annan and Hargreaves, 2006; Lewis and Curry, 2015). In particular, use of a non-informative prior (e.g. Jeffreys prior), or a frequentist likelihood-ratio method, narrows the upper tail considerably. However, as summarized by Frame et al. (2006), there is no observational constraint on the upper bound of ECS.

The challenges of identifying an upper bound for ECS are summarized by Stevens et al. (2016) and Knutti et al. (2017). Stevens et al. (2016) describes a systematic approach for refuting physical storylines for extreme values. Stevens et al.’s physical storyline for a very high ECS (>4.5 oC) is comprised of three conditions: (i) the aerosol cooling influence in recent decades would have to have been strong enough to offset most of the effect of rising greenhouse gases; (ii) tropical sea-surface temperatures at the time of the last glacial maximum would have to have been much cooler than at present; and (iii) cloud feedbacks from warming would have to be strong and positive.

An interesting challenge to identifying the plausible upper bound for ECS has been presented by a newly developed climate model, the DOE E3SM (Golaz et al. 2019), which includes numerous technical and scientific advances. The model’s value of ECS has been determined to be 5.3 oC, higher than any of the CMIP5 model values and outside the IPCC AR5 likely range. This high value of ECS is attributable to very strong shortwave cloud feedback. The DOE E3SM model’s value of shortwave cloud feedback is larger than all CMIP5 models; however, shortwave cloud feedback is weakly constrained by observations and physical understanding.  A stronger argument for placing the DOE E3SM value of climate sensitivity in the ‘borderline impossible’ category is Figure 23 in Golaz et al. (2019), which shows that the global mean surface temperature simulated by the model during the period 1960-2000 is as much as 0.5 oC lower than observed, and that since the mid-1990s the simulated temperature rises far faster than the observed temperature. This case illustrates the challenge of refuting scenarios associated with a complex storyline or model, which was noted by Stevens et al. (2016).

An additional issue regarding climate model derived values of ECS was raised by recent paper by Mauritsen et al. (2019). An intermediate version of the MPI-ESM1.2 global climate model produced an ECS value of ~ 7 oC, caused by the parameterization of low-level clouds in the tropics. Since this model version produced substantially more warming than observed in the historical period, this model version was rejected and  model cloud parameters were adjusted to target a value of ECS closer to 3 oC, resulting in a final ECS value of 2.77 oC. The strategy employed by Mauritsen et al. (2019) raises the issue as to what extent climate model-derived ECS values are truly emergent, rather than a result of tuning that explicitly or implicitly considers the value of ECS and the match of the model simulations with the historical temperature record.

Was Mauritsen et al. (2019) justified in rejecting the model version with an ECS value of ~ 7 oC? Is the MPI-ESM1.2 value of ECS of 5.3 oC plausible? Observationally-derived values of ECS (e.g. Lewis and Curry, 2018) are inadequate for defining the upper bounds of ECS. There are two types of constraints that in principle can be used: emergent constraints and the Transient Climate Response.

Emergent constraints in principle can help narrow uncertainties in climate model sensitivity through empirical relationships that relate a model’s response to observable metrics. These analyses have mostly focused on cloud processes. The credibility of an emergent constraint relies upon the strength of the statistical relationship, a clear understanding of the mechanisms underlying the relationship, and the accuracy of observations. Further, the most robust emergent constraints are for model parameters that are driven by a single physical process (e.g. Winsberg, 2018). Investigations of integral constraints related to cloud processes have mostly concluded that the climate models with ECS values on the high end of the IPCC AR5 likely range show best agreement with the integral constraints (e.g. Caldwell et al., 2018). However, Caldwell et al. (2018) and Winsberg (2018) caution that additional processes influencing the metric and other biases in the model may affect the analysis. While the robustness and utility of these emergent constraints continues to be investigated and debated, this technique is not very helpful in identifying a plausible upper bound or in rejecting high values such as obtained by Golaz et al. (2019) and Mauritzen et al. (2019).

The Transient Climate Response (TCR) in principle can be of greater utility in providing an observational constraint on climate sensitivity. TCR is the amount of warming that might occur at the time when CO2 doubles, having increased gradually by 1% each year over a period of 70 years. Relative to the ECS, observationally-determined values of TCR avoid the problems of uncertainties in ocean heat uptake and the fuzzy boundary in defining equilibrium owing to a range of timescales for the various feedback processes. Further, an upper limit to TCR can in principle be determined from observational analyses.

TCR values cited by the IPCC AR5 have a likely (>66%) upper bound of 2.5 oC and < 5% probability of exceeding 3 oC. Knutti et al. (2017; Figure 1) show several relatively recent TCR distributions whose 90 percentile value exceeds 3 oC. Observationally-derived values of TCR determined by Lewis and Curry (2018) identified the 5-95% range to be 1.0–1.9 K. As discussed by Lewis and Curry (2015) and Lewis and Grunwald (2017), use of a non-informative prior or a frequentist likelihood-ratio method narrows the upper tail considerably. While the methodological details of determining values of TCR from observations continue to be debated, in principle the upper bound of TCR can be constrained by historical observations.

How does a constraint on the upper bound of TCR help constrain the high-end values of ECS? A TCR value of 2.93 oC was determined by Golaz et al. (2019) for the MPI-ESM1.2 model, which is well above the 95% value determined by Lewis and Curry (2018), and also above the IPCC AR5 likely range. Table 9.5 of the IPCC AR5 lists the ECS and TCR values of each of the CMIP5 models. If a TCR value of 2 oC is used as the maximum plausible value of TCR based on the Lewis and Curry (2018) analysis, then it seems reasonable to classify climate model-derived values of ECS associated with TCR values ≤ 2.0 oC as verified possibilities.

In light of the cited analyses of ECS (which are not exhaustive), consider the following classification of values of equilibrium climate sensitivity relative to the π-based classifications provided in the possibilistic post, which provides the expert judgment of one analyst (moi). Note that overlapping values in the different classifications arise from different scenario generation methods associated with different necessity-judgment rationales:

  • ECS < 0: impossible
  • 0 > ECS < 1 oC: implies negative feedback (unverified possibility)
  • 1.0 ≤ ECS ≤ 1.2 oC: no feedback climate sensitivity (strongly verified, based on theoretical analysis and empirical observations).
  • 1.05 ≤ ECS ≤ 2.7 oC: empirically-derived values based on energy balance models from the instrumental period with verified statistical and uncertainty analysis methods (Lewis and Curry, 2018) (corroborated possibilities)
  • 1.15 ≤ ECS ≤ 4.05 oC: empirically-derived values including paleoclimate estimates (Lewis and Grunwald, 2018)   (verified possibilities)
  • 2.1 ≤ ECS ≤ 4.1 oC: derived from climate model simulations whose values of TCR do not exceed 2.0 oC. (Table 9.5, IPCC AR5) (verified possibilities)
  • 4.5 < ECS ≤ 6 oC: borderline impossible
  • ECS > 6oC: impossible

In evaluating the justification of the high-end values of ECS, it is useful to employ the logic of partial positions for an ordered scale of events. It is rational to believe with high confidence a partial position that equilibrium climate sensitivity is at least 1 oC and between 1 and 2.7 oC, which encompasses the strongly verified and corroborated possibilities. This partial position with a high degree of justification is relatively immune to falsification. It is also rational to provisionally extend one’s position to believe values of equilibrium climate sensitivity up to 4.1 oC – the range simulated by climate models whose TCR values do not exceed 2.0 oC — although these values are vulnerable to improvements to climate models and our observational estimates of TCR, whereby portions of this extended position may prove to be false. High degree of justification ensures that a partial position is highly immune to falsification and can be flexibly extended in many different ways when constructing a complete position.

The conceivable worst case for ECS is arguably ill-defined; there is no obvious way to positively infer this, and such inferences are hampered by timescale fuzziness between equilibrium climate sensitivity and the larger earth system sensitivity. However, one can refute estimates of extreme values of ECS from fat-tailed distributions > 10 oC (e.g. Weitzman, 2009) as arguably impossible – these reflect the statistical manufacture of extreme values that are unjustified by either observations or theoretical understanding, and extend well beyond any conceivable uncertainty or possible ignorance about the subject.

The possible worst case for ECS is judged here to be 6.0 oC, although this boundary is weakly justified. The only evidence for very high values of ECS comes from climate model simulations with very strong positive cloud feedback (e.g. Mauritzen et al. 2019; Golaz et al. 2019) and statistical analyses that use informative priors. Further examination of the CMIP6 models is needed to assess the causes, outcomes and plausibility of parameters and feedbacks in these models with very high values of ECS before rejecting them as impossible.

With regards to the plausible worst case (lower bound of borderline impossible values) of ECS, consideration was given to the upper bound of verified possibilities (4.1 oC) and also the time-honored value of 4.5 oC as the upper bound as the ‘likely’ range for ECS. Consideration of the model’s value of TCR in comparison to observationally-derived values of TCR seems to be a useful constraint for assessing the plausibility of a model’s ECS value. However, further investigation is needed to understand the methodological differences in the varying estimates of TCR and the causes of varying relations between TCR and ECS values among different models.  This seems to be a more fruitful way forward than the emergent constraints approach.

Given that 4.5 oC was specified by the IPCC AR5 as the upper bound of the likely range (> 66% probability), the judgment here that specifies 4.5 oC as the maximum plausible value of ECS will undoubtedly be controversial. Other analysts may make different judgments and draw a different conclusion on this. Consideration of different rationales for making judgments on the maximum plausible value of ECS would illuminate the underlying issues and rationales for judgments.

Because of the central role that ECS plays in Integrated Assessment Models used to determine the social cost of carbon that is largely driven by tail values of ECS, the issue of clarifying the plausible and possible values of ECS is not without consequence.

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107 thoughts on “What’s the worst case? Climate sensitivity

  1. Oh if we are giving up science and it’s betting then I am going with > 10 degree, I always like the 100:1 outsider.

  2. What’s the worst case? Example: Venezuela with Russia and China coming to the rescue.

  3. Worst case scenario is if the current crop of Democrats such as Bernie Sanders and AOC become empowered. Then life as we’ve known it will be over.

  4. As a control systems engineer rather than a climate scientist, I’m suspicious of any system that exhibits long-term stability that does not also have strong negative feedbacks. Given that our climate has recovered from ice ages and (likely) large meteor impacts and has stayed in a relatively narrow band Especially relative to, say, Venus or Mars), I’d infer that there MUST be negative feedback mechanisms at work. Therefore I’d expect ECS values below 1.

    • Concur. So adaptation is dramatically better then futile attempts at prevention of that which is likely net beneficial.
      So lets simplify the problem- solution adoption for policy makers.

      6 inch SL rise. Install a curb
      Increased night T. 0 – less frost
      Drought. More water storage & CO2
      Heat wave. A/C cheep energy
      Less snow. Increased hikeing opp…
      Lower crop yields. More CO2

      Title of history book on CAGW in 2075. Much Ado About Nothing.

      • 6 inch SL rise. Install a curb
        Increased night T. 0 – less frost
        Drought. More water storage & CO2
        Heat wave. A/C cheep energy
        Less snow. Increased hikeing opp…
        Lower crop yields. More CO2…

        More snow: good skiing 🙂

    • I’d agree. Pretty much any complicated “system” has overall negative feedback. The snow/ice –albedo effect is positive feedback, but if that was the major overall effect, Earth would be a permanent snowball.

    • pbft,

      The climate is a passive system, i.e. no internal source of Joules powering the gain, so its relative stablilty has nothing to do with feedback, nor does feedback have anything to do with how it operates. Take a good look at the analysis underneath Bode stability plots to see how crucial powered gain is to potential instability.

      If you can design an unstable system using only passive components like resistors, inductors and capacitors, then you can prove me wrong.

      • ..or they could just explain how…no matter how high CO2 got…..we crashed back into an ice age

        so much for feedback

    • Pbft: just doing system identification on the temperature data would return a better model than most of the blundering that’s often taken to task here.

    • As a control systems engineer, and one who is also familiar with the behavior of non-linear complex systems, and the limitations of modeling even simple systems, I agree.

      Indeed, I disagree with Curry that ECS (a unicorn itself) below 0 is impossible.

      None of us have any ability to predict the behavior of the numerous emergent (and phase-change-related) behavior mechanisms of the “climate system”, whether a Bayesian approach is used or not.

      Distillation columns do NOT run at equilibrium. An equilibrium-modeled distillation column has little resemblance to its real counterpart. I believe the same limitation applies to atmospheric physics.

    • pdft; I 100% agree with you. I also studied control theory and systems without significant negative feedback are very rarely stable. In particular I would point to the dual action of water vapour and clouds. The former yields logarithmically increasing warming whereas the latter yields close to linear cooling (cloud cover is no where near 100% as yet). At very low temperatures the warming from increasing water vapour dominates but as the temperature rises the incremental impact of water vapour declines whereas cloudiness increases due to increased evaporation/rainfall. Thus with increasing temperature incremental cloud cooling dominates over water vapour warming. A classic scenario of a negative linear plus positive non linear feedback duo establishing a setpoint which is maintained by negative feedback.

    • I agree with you! A system that remains in a range of + – 2 degrees for more than ten thousand years can not work without a corresponding counterregulation!

  5. 1.0 ≤ ECS ≤ 1.2 oC: no feedback climate sensitivity (strongly verified, based on theoretical analysis and empirical observations).

    I don’t know of anyone who disagrees with that. A higher ECS requires some kind of positive feedback. Systems engineers will point out that positive feedback systems tend to be unstable. Stability analysis is bread and butter for system design. It is possible to design a mostly stable positive feedback system. What are the chances that such a system would naturally evolve? Not much.

    During the current interglacial, temperatures have been higher than they now are. Things have been relatively stable with no runaway heating. Given that, I think there is little likelihood of significant positive feedbacks in the climate system.

    • The tropical mid-tropospheric hotspot was billed in both CMIP3 and CMIP5 eras as the finger-print of water vapor amplification that raised ECS to the 2X – 3X of the no feed back value.
      The Hot Spot is of course, as we all know, MIA (missing in action).

      Pseudoscientists like Benji Santer and NOAA’s Tom Karl all hand-waved away the MIA hotspot as simply “largely resolved” obfuscation language.

      The fact that a key prediction of theory (strong GHG amplification) is MIA in the observational records (the balloon and satellite MSU data) would demand that any real branch of science reject the theory/hypothesis. So that anything but a conclusion of 1.0 ≤ ECS ≤ 1.2 oC: no feedback climate sensitivity is all that is left. The fact that the Cargo Cultists model ever-onwards with model ECS outputs, tells us that what they do is not science. It is simply selling climate porn stories for a continuing fat paycheck.

    • I work with control systems (sub-micron motion control at high accelerations and velocities…and the electronic sensors and drivers needed for the motion control).

      My take on climate and feedbacks:

      The virtually linear “runaway” temperature rises coming out of every glaciation always stop at about the same temperature.

      That indicates a 100 % certainty of temperature related emergent negative feedback(s)… That or some physical limit is being approached…like the speed of light…or a phase shift temperature. There is no such physical limit here…so the negative feedbacks are a certainty.

      The most obvious “control loop” that comes to mind (Re: the nearly linear rapid temperature rises at the end of glaciations *that stops*) is that a Milankovitch “tipping point” starts some warming. Then a CO2 positive feedback cycle from CO2 oceanic outgassing (with temperature increasing) drives the “rapid” (6000+ year) ~linear temperature rise (CO2 levels are very low at the end of glaciations — so a CO2 increase has a more significant warming capability)…until CO2 levels reach a saturation point where other normally weaker negative feedbacks begin to dominate (probably cloud behaviors)…and any further increase in CO2 has a diminished effect.

      That “feedback stopping” temperature (where the driver peters out and other negative feedbacks dominate) is about 2 C above the current GAT. Negative feedbacks or drivers have been pushing GAT’s slowly downward the last 10,000 years.

      The Earth (and every species currently alive) survived quite well during those milder climates. And the added CO2 of today feeds life… Win-Win and no climate sensitivity > 1.5 is likely.

      • Paraphrasing Upton Sinclair, the situation we have is where a man’s paycheck depends on his not understanding something obvious to others.

      • Speaking as a controls engineer, the above comment—and Dr. Curry’s analysis too—would be more comforting if account were taken of the inherent time lags in climate-stabilizing feedbacks.

        Suppose for example that ECS > 6℃ is “impossible”, precisely as Dr. Curry’s analysis concludes, due to climate-stabilizing feedbacks that however act over spans of several thousand years (carbon sequestration by forests for example).

        In which event, short-term climate excursions of 10℃, 15℃, or even higher — devastatingly large planet-wide temperature surges that are sustained over centuries — are entirely consonant with stability arguments in particular, and with analyses like Dr. Curry’s in general.

        In consequence, Dr. Curry’s analysis provides scant reassurance in respect to the sobering scientific realities of climate change.

        • Once again, people, the climate has not changed. The past minor warming is but one of the many climate metrics that must be considered. There has been no detectable adverse changes in any climate metric; none. It also appears that plants like more CO2 and benign temperatures.

          Anybody stating that storms, etc. are getting worse is ether lying or misled by the strident messaging.

          • What HAS happened is extreme scrutinization of weather and climate. We’re able to detect so much more than we could even 30 years ago. So, of course, we’re going to see things that haven’t been seen since people started keeping records. That doesn’t mean these things haven’t happened before, we just don’t know. But the alarmists are saying these “unusual” things are due to evil humans, without evidence to back it up.

        • If you can find these “scientific realities of climate change”sobering or not, would you please list them.

    • I don’t know of a system that has a “mostly stable positive feedback system” without external limits. Something like a current limited power supply that won’t let power exceed a certain amount. Does the earth have one or more “limiting” factors that stops positive feedback from passing the “tipping point” and progressing to full on catastrophe? I have yet to see any discussions about what these could be.

      In a system with feedback > 1 the process will continue until a limit is reached or something burns up! I agree that the earth would have done this sometime in the past if positive feedback was possible.

      • Jim,

        Actually, if a feedback system has unit open loop gain, then positive feedback can be stable. The gain equation is 1/Go = 1/g + f, where Go is the open loop gain, g is the closed look gain and f is the fraction of the output fed back to the input between -1 and 1 whose sign indicates the direction of the feedback.

        If Go is 1, we get 1 = 1/g + f, or g = 1/(1 – f) which you might recognize as the gain equation specified by Schlesinger in his climate feedback paper which implicitly assumes Go = 1, yet his analysis assumes a non unit Go converting W/m^2 into degrees. This is completely stable for f < 1 and unstable only when f = 1 which represents 100% positive feedback.

        Note that this is only true when COE is not applied between the input and output of the gain block, as Bode requires. If you apply COE between the input and output, as required by the climate system, then it's completely stable as the output of the gain block can be either feedback power or output power, but not both.

        The implicit power supply also infers a high input impedance and low output impedance thus feedback is only measured by the input of the gain block and not consumed as it would be for the climate system where the origin of the output power is the input power plus the feedback power and not an infinite and implicit power supply.

    • Feedback, and in fact control system analysis, is irrelevant to a passive system like the Earth. The Sun is the EXPLICIT signal input, not the IMPLICIT power supply, and it can not be both. Feedback is only relevant to systems with active gain and the climate system has no active gain. The definition of active gain requires an implicit source of Joules to power the gain. You simply can’t design an unstable system using only passive components like resistors, inductors and capacitors.

      • I’m not sure I agree with you. To me the sun is the power supply and provides the energy to drive the system. From that power you bias the input to the operating point. This bias would consist of anything in the atmosphere that absorbs heat by convection or radiation, H20, CO2, O2, N2, SO2, etc. There is no feedback, but rather a variable voltage power supply control that will be derived from anything that reflects the suns energy, i.e. aerosols, ice, clouds, etc.

        As you increase the bias, the output would go up. As things that reflect the sun’s energy away goes up, you would decrease the power available and consequently the output voltage. From this, I conclude that water vapor is the biggest bias component and the biggest feedback component. Anything else is miniscule. Guess what happens? As water vapor goes up, the bias goes up causing rising temperatures. At the same time, the power supply voltage goes down (from clouds) and voila, temperature stays the same.

        This doesn’t totally disagree with your assessment though. I would have to sit down and do the math, but my gut tells me you could do this with passive components and no amplification at all.

      • Jim,

        The Sun is the forcing and can’t also be the implicit power supply. It supplies the input power to a passive system and in fact is the ONLY source of input power to the system, but in no way shape or form does this satisfy the criteria of the implicit power supply that defines an active amplifier.

        There’s no bias involved either, as a bias also requires the implicit power supply. Considering this to be a plausible option is a side effect of incorrectly considering that the average and incremental sensitivities can be different when ‘amplifying’ W/m^2, when in fact, they must be the same, as the planet has no way to tell the difference between the next Joule and any other.

        What you’re considering the operating point is the effect from the other 240 W/m^2 arriving from the Sun, but this distinction is irrelevant, as all W/m^2 have the same average effect, including the next one. The concept of an operating point is specific to an active amplifier whose necessary precondition is an implicit supply powering the gain, so that more power can come out of the gain block than goes in.

        Considering the surface as the output which emits more power than the forcing input is consistent with the output power being the sum of the input and feedback. However; the fraction of the output being fed back to the input can not be considered both output power and feedback power. The mathematical solution is to add delay between the output and the feedback term added to the forcing input so that after a sufficient amount of time, enough of the old power is available to be added to new power which results in more output power than the new power can provide itself.

  6. In the theoretical worse case how much do AvgTmax and AvgTmineach rise by? There are 4.5×2=9.0 deg C to share between the two.

  7. The likely upper bound is somewhere between 0 and what ever the highest temperature the earth has reached in the last billion or so years. Nothing man is doing can possibly match the ridiculous natural disasters the earth has gone through in that time period. If run away global warming was possible it would have already occurred somewhere along the line.

        • And we know, based upon the concern of which country Is To Blame and Must Be Punished, that the US-sourced CO2 is WAY worse than the China-sourced CO2. Because until we cut our CO2 output down to zero, there is no need to worry about China’s CO2 output.

          Thus our CO2 must be a LOT more harmful than their CO2. I guess our molecules are just that much more efficient at causing runaway destruction!

  8. Not sure the utility of such a data mining exercise. The way empirical test of theory should proceed is that we should be able to derive a testable implication of theory from the theory itself. Then we test that testable implication against the data. The problem is that no clear testable implication exists because the time scale and other details are a moving target. This means that if your result does not suit the needs of climate science they can simply claim that your time scale is not long enough to take the slow equilibrium with the ocean into account and so on and so forth.

    That we have now gone since 1938 still hunting for the GHG effect that Svante allegedly “demonstrated” (according to NASA GISS) means that this is a fishing expedition and a data mining exercise and nothing more. The real world conclusion should be that we don’t know that there is an ECS and if there is one we have no idea what its value is.

    It was on this basis that Knutti and Myles and a few other prominent researchers in the field had proposed that we must leave this ugly ECS thing behind and move on with thee TCRE (Knutti, Reto, Maria AA Rugenstein, and Gabriele C. Hegerl. “Beyond equilibrium climate sensitivity.” Nature Geoscience10.10 (2017): 727). Except of course that there are serious statistics problems with the TCRE as well that Reto and Myles will not acknowledge.

    TCRE link#1: https://tambonthongchai.com/2018/12/03/tcruparody/

    • Nice parody, but an obvious criticism is that while your parody provides no physical, causal mechanism (other than the vague statement about impact on gravity and magnetic fields), accumulation of CO2 in the atmosphere has an obvious and well established connection to warming. I’m not saying the effect of CO2 is exclusive to all other possible mechanisms, or that it is well understood and constrained, but it does exist.

        • I think you are misunderstanding my point. My point is that CO2 is an IR active gas. Thus, it has some effect on the radiation energy balance. This is true even in the case of a long lag between temperature increase and CO2 increase, which has to do with feedback mechanisms, apparently.

      • “The real world conclusion should be that we don’t know that there is an ECS and if there is one we have no idea what its value is.”

        Why can’t people be happy with that?

    • OK. Here’s a testable implication of the high ECS claimed by the IPCC.

      If 1 W/m^2 increases the surface temperature by 0.8C, as nominally claimed by the IPCC, the surface emissions must increase by 4.4 W/m^2. Since COE dictates that the Earth can not distinguish one Joule from any other, all W/m^2 must have the same average influence on the final result. If this is 4.4 W/m^2 of surface emissions per W/m^2 of forcing as claimed, the surface must be emitting 4.4*240 = 1056 W/m^2 corresponding to an average surface temperature of about 96C, or close to the boiling point of water. Clearly, of the ECS was as high as claimed by the IPCC, we would all be dead. The very fact that we’re not all dead falsifies the IPCC’s nominal ECS.

  9. Specific heat is defined as the amount of energy transferred to a unit mass to raise the temperature 1 degree.

    The energy transferred can be of any form.

    According to specific heat tables 1 kg of CO2 at 300 K the specific heat is .846 kj/kg K. Thermodynamics says we need 846 J to increase temperature 1 K. Q = Cp m dT.

    Now according to climate science if the energy includes IR we must add in the forcing equation. Or about 74 w of internal energy that causes a further increased temperature.

    Climate science is at odds with the specific heat tables. And at odds with thermodynamic statement of the energy can be of any form. Correct the tables and thermodynamics or fix climate science.

    • Kelly, the heating proposed is not that of a passive heating of a mass by adding joules, from an external heat source. The mechanism is rather absorption of specific bands of upwelling long wavelength infrared radiation by CO2, water vapour and a few other gases.

      Your mechanism would heat up all gases (say from a campfire). The bulk of the atmosphere, Nitrogen, Oxygen etc is tranparent to IR so are not heated by it. The CO2 molecule (and H2O molecule) resonates like a spring when iradiated by specific wavelenghths of IR because of its molecular geometry. This temporarily arrests and re-emits IR, slowing down the passage of IR through the atmosphere, causing heating.

      • “This temporarily arrests and re-emits IR, slowing down the passage of IR through the atmosphere, causing heating.”

        I believe Dr Happer says the IR energy is dissipated by collisions.(thermalization). 30,000 collisions before emission?

  10. Okay, I’m just gonna blurt it out:

    “Climate sensitivity” [in reference to CO2] is a totally bogus concept, I have come to the conclusion.

    I’ve grown sick of the phrase.

    There — I said it.

    Delete me. Berate me. Correct me. Have it.

  11. “0 > ECS < 1 oC: implies negative feedback (unverified possibility)"

    Absence of evidence is not evidence of absence.

    The remarkably stable global temperature when viewed on the Kelvin scale instructs that a negative feedback exists. The earth's clouds always reflect much of the incoming radiation. Billions of years ago, with a weaker sun, the earth must have had lesser amount of clouds to stop from being an ice ball. The controlling variable is LWIR causing H2O evaporation on the surface. A weak sun caused less LWIR evaporation, less clouds, and thus increased short wave insolation, and thus more SW ocean warming. This gave a warm earth then.

    Our added CO2 increases evaporation, leading to a cooling. Superimposed on this, external factors such as amplified solar variances induce natural cycles of warming and cooling of the earth. No climate scientist with their CO2 controlled models can explain the 1910 to 1940 warming rate. Dr. Curry advised so to the Congress. (the uncertainty monster)

    Until satellites can measure cloud cover, thunderstorm activity, minute by minute, globally, over long periods, we will not be able to measure the size of the negative feedback. All it takes is for cloud/thunderstorm formation to start five minutes earlier on an average day for the negative feedback cooling effect to compensate for the heating effects of our additional CO2. The daily Max Temp reading does not even change. The daily Min Temp reading increases, with the slightly more lingering cloud cover.

    IMO, its long past due for climate scientists to admit they simply cannot measure ECS with the imprecise tools they have. IMO, the actual evidence is that the ECS is small, and we should calm down, stop wasting money, and get on with developing next generation nuclear. There is no fat tail.

  12. This is not a fruitful area of research, sorry.

    The entire notion of “climate sensitivity” based upon pretended reactions of a massively complex system of systems that constitutes the earth and the astrophysical system (i.e., the sun) that suppose the thermostat is determined by only one factor, CO2 concentration in the atmosphere, is patently riduculous and is not supported by any valid scientific observations of earth’s geophysical history as we know it today.

    All we know is that the prevailing planet wide climate has varied fantastically and radically over relatively short recent periods of geologic history – the last 2.6 million years. With varying periodicities of glaciation periods and interglacial periods, all without any evident ties to CO2 concentrations in the atmosphere.

    This is really nothing more than scientific masturbation.

    The earthian system’s complexities – including the known knowns, the known unknowns, and especially the unknown unknows, defies any attempt to “model” the earth with a computer.

  13. “0 > ECS < 1 oC: implies negative feedback (unverified possibility)"
    That possibility is ignored. It means essentially zero effect. To many $$$$ at stake.

  14. Sensitivity to CO2 emissions? Lets use observations over the last 50 or 60 years and say “sensitivity” is ZERO!

  15. “>>> ECS ECS < 1 oC: implies negative feedback (unverified possibility) <<<"

    I would suggest three papers for Prof. Curry to look at that demonstrate the two cases listed above to be quite possible. The first one, by Chilingar, Sorokhtin, Khilyuk, and Liu [1] demonstrates that, yes, CO2 and methane can actually cool the globe if convection is properly accounted for. In the presence of convection greenhouse gases work like a coolant in an AC. Yes, they absorb outgoing IR, but once they've done so, convection and buoyancy push them up into the higher levels of the atmosphere, where they emit IR into space more efficiently than would be the case without convection. Their calculations both for Venus and Earth show extremely close agreement with measurements. Schmithusen et al [2] even argue that the negative greenhouse effect is seen in Antarctica.

    The third paper to look at is by Smirnov in Journal of Physics D [3]. Smirnov shows that collision and radiative processes in emission of atmospheric carbon dioxide have been incorrectly calculated in the existing models. When corrected, climate sensitivity to CO2 turns out to be 0.4K/doubling only at the present level of the atmospheric CO2 concentration.

    [1] https://doi.org/10.4236/acs.2014.45072
    [2] https://doi.org/10.1002/2015GL066749
    [3] https://doi.org/10.1088/1361-6463/aabac6

  16. What’s the worst case? Climate sensitivity

    Equilibrium climate sensitivity (ECS) is defined as the amount of temperature change in response to a doubling of atmospheric CO2 concentrations

    Doesn’t matter, methane is 85 times more powerful than CO2
    Source:
    IPCC AR5 Chapter 8 Page 731

  17. ECS in my opinion (equilibrium climate sensitivity) is another buzz word for we really don’t know. A while back Willis had a nice piece on the opposite theme. What keeps the earth’s temperature so stable. We all have cruise control and it works hard to get 1% stability. We have thermostats and they do well to keep us at +/- 1 degree. Here the chaotic climate maintains the earth at better than 1 part in 250 stability. Mull this over for awhile.
    Al Brand

    • “Mull this over for a while”.

      I have and for a very long time. The chaos is only in the path from one steady state to another and has nothing to do with what that steady state will be. Confusion arises because many conflate the complex path to equilibrium as determining what the equilibrium state will be.

      What keeps the surface temperature stable is the relative stability of the Sun, where the resulting temperature is a function of COE and how W/m^2 are related to degrees by the Stefan-Boltzmann LAW. During the short amount of time that we have been accurately measuring the output of the Sun, it has varied by only about 1 part in 250 which easily explains the relative stability of the planets temperature.

      If the climate system was as unstable as the IPCC requires it to be, the average summer (or winter) temperatures would vary by 10’s of degrees from year to year.

      • The climate system is ALWAYS in a steady state equilibrium. It’s had nearly an infinite amount of time to arrive at the steady state response to varying solar input. Changing GHG concentrations or any small change to any attribute of the system has an effect on the steady state response, but that effect is manifested almost immediately upon the change. If the climate system responded as slow as the alarmists require, we wouldn’t even notice a temperature difference between night and day, much less seasonal variability.

        Even if a large change to the system occurs, for example an impact event or super volcano, the effects on the climate are noticed almost immediately.

  18. “… the DOE E3SM (Golaz et al. 2019), which includes numerous technical and scientific advances. The model’s value of ECS has been determined to be 5.3 oC, higher than any of the CMIP5 model values and outside the IPCC AR5 likely range.”

    At a time when the US Federal deficit is ballooning out of control, and neither party seems to care, Soooo [NOT] glad my tax dollars went to pay for this POS junk out of US DOE and Ben Santer’s propaganda production group. The corruption is so deep in these climate groups at NASA, DOE, NOAA, and their junk climate model love so extreme, the only rational course is the Lindzen defunding proposal. Rationality demands defunding all of CliSci to 10% or less of today’s monies.

    Continuing this path of more modelling by multiple groups is poly-Cargo Cult Science. Every modelling group is like its own island in an archipelago of Climate Cultist Tribes thinking their magic is the best of all the other islands’ magic. Every few years, all the island tribal leaders get together in a Cargo Cult Model Inter-comparison Project to compare whose junk model runway and bamboo control tower is most likely to bring back the cargo airplanes with their wondrous goods. Each tribal elder studies the others, makes pontificating gratuitous comments in arcane papers, makes meaningless critiques, drinks lots of fermented beverages, and secretly thinks their own model “runway” is the most faithful of what is a just a failure of rationality. All just delusional “make work” that does nothing to bring any understanding to the climate.

    The fact that the AOGCMs are all just junk outputs and delusions of their designers was made quite clear where JCurry writes (above):

    “Since this model version produced substantially more warming than observed in the historical period, this model version was rejected and model cloud parameters were adjusted to target a value of ECS closer to 3 oC, resulting in a final ECS value of 2.77 oC. The strategy employed by Mauritsen et al. (2019) raises the issue as to what extent climate model-derived ECS values are truly emergent, rather than a result of tuning that explicitly or implicitly considers the value of ECS and the match of the model simulations with the historical temperature record.”

    After reading that, anyone who still calls the current state of climate modelling as “science” is simply delusional and/or doesn’t understand what science is.

    • Joel O’Bryan : [ … anyone who still calls the current state of climate modelling as “science” is simply delusional … ]

      And this from the article:

      “The range of ECS values derived from global climate models”

      They’re pulling value(s) for ECS from their own models?

      It’s self-referencing delusion

    • I forgot which modeler said this, but they tune the models to get an ECS that “seems about right.”

    • So called “Climate Science” is in effect a replacement for “Bible Study” with the supposed “Scientists” as a new Priesthood.
      Traditional Religious Fundamentalists cling to their beliefs unless someone could definitively show that God doesn’t exist.
      The new Priesthood cling to their beliefs unless someone could show definitively that CAGW could be ruled out.
      Judith certainly has more stamina and patience than I would have continuing with this discussion.

  19. Any ECS where 1 W/m^2 of forcing results in more than 2 W/m^2 of surface emissions is impossible. When converted into an ‘incremental’ temperature effect of doubling CO2, the theoretical upper limit is about 1.2 C.

    So many are horribly confused because the IPCC and its self serving ‘consensus’ specifies the ECS as the temperature effect from doubling CO2 and embodies 4 levels of obfuscation between the physically relevant ECS and the politically desirable ECS. It’s quite interesting how subtly tweaking the units of a metric can dramatically change the perceived impact of its effect.

    The physically relevant ECS is W/m^2 of surface emissions per W/m^2 of forcing where the input and output are expressed in the same units enabling COE to facilitate a linear analysis of power in vs. power out. The first level of obfuscation is to convert W/m^2 of output emissions into a surface temperature, thus disconnecting the relationship from the Stefan-Boltzmann LAW. The second level of obfuscation is burying the 3.7 W/m^2 of equivalent forcing from doubling CO2 thus separating the effect of CO2 forcing from solar forcing despite the fact that all Joules are the same relative to the work of warming the surface. The third level of obfuscation is to make the effect incremental, further disconnecting the next Joule of solar input from all of the preceding Joules completing the disconnection from COE. The fourth level of obfuscation is to add +/- 50% uncertainty to a value that can be ascertained to within 10% using a relatively simple analysis.

    The result is a range of ECS, all of which is precluded by basic physics and yet plausibly serves the purpose of inciting alarm. There can be no other reason to add this much obfuscation to something that’s relatively easy to predict and measure.

  20. We’ve had less than a degree of warming over the last 150 years, while CO2 levels have gone from around 250ppm to a bit over 400ppm.

    Even assuming that 100% of that warming is due to CO2.
    Even assuming that there is lot of lag due to oceans absorbing some of the heat.
    Given the near logarithmic nature of any warming that CO2 would produce.

    It’s clear that the absolute worst case for climate sensitivity isn’t much more than 1C.
    Knock out either of the assumptions (much less both of them) and climate sensitivity drops even more.

    • “t’s clear that the absolute worst case for climate sensitivity isn’t much more than 1C.
      Knock out either of the assumptions (much less both of them) and climate sensitivity drops even more.”

      I think that sums it up quite nicely.

      1C or less. Nothing to get excited about. Nothing to cause us to lose our minds and start building windmilss willy nilly with no regard to the consequences.

      People need to calm down.

  21. Several years ago I began a project of reading technical papers about climate sensitivity and documenting the value each research group came up with. Generally I thought the trend was a slow drift toward lower and lower values. Suddenly we get a flurry of work on new (improved) models which show a high value of ECS.

    We also have a trend toward a proliferation of concepts: climate sensitivity, ECS, TCR, TCRE, and so forth, which provides an opportunity to argue past one another since, apparently, the expenditure of 40 billion U.S. on the climatic impact of CO2 has carried us not very far from 1979. As Dr. Curry states here, ECS is a fuzzy sort of concept because of the abundance of feedbacks with varying time scales to reach equilibrium–one might add that for some of these mechanisms we even argue over the sign of the feedback (the most significant bit).

    For about twenty years I have wondered from time to time about the value of “mean earth temperature” in the first place. I wonder if the mean temperature, however one might estimate it, is just a random walk through a range of possible values all of which are consistent with a fixed energy balance through different mechanisms in different places. The earth certainly has any number of integrators in its control loop which would make a random walk possible.

  22. “Equilibrium climate sensitivity (ECS) is defined as the amount of temperature change in response to a doubling of atmospheric CO2 concentrations.”

    My guess : as an active gas in the infrared spectrum, CO2 constitutes a negative feedback with respect to temperatures change :

    ECS
    atmospheric warming (26 W/m²) -> contribution to upward convection ->
    Radiative heat tranfer from the upper troposphere and beyond into space ->
    atmospheric cooling (165 W/m²) -> contribution to downward convection -> brrrr !

    • Oups. Some sentences went away due to some XML characters I used.


      My guess … :

      ECS is negative or 0.

      The fact that active gases in the infrared spectrum absorb 26W/m² of the upward radiative flux from the surface is only half of the story. The atmosphere emit also 165W/m² into space in the infrared spectrum :
      – how could it be without active gases in the infrared spectrum (H2O vapor, CO2, …) ?

      Schematic process of atmosphere cooling by active gases in the infrared spectrum :

      atmospheric warming … brrrr !

  23. I do not agree that 0 degrees or less is impossible.
    CO2 has significantly over saturated the available near earth radiation. Combined with water vapor, this means more CO2 should be able to do pretty close to diddly squat. But, as it mixes through the entire atmosphere, increasing CO2 can effectively increase the amount of radiation the atmosphere sends to space. So, it can have a cooling effect.

  24. “”…extreme values that are unjustified by either observations or theoretical understanding, and extend well beyond any conceivable uncertainty or possible ignorance about the subject.”‘

    That kind of sums up the “whole thimbleful of fact lost in a bushel of propaganda” concept.

  25. I have kinda lost interest in models which simply dismiss substantve and variable effects in their initial assumptions, blame it all on CO2 and then overpredict reality by 100’s of %. I would like to onow one simple figure from climate modellers. What is the actual sensitivity of the ov ceanic feedback from evaporation, condesation and cloyd albedo, per degree SST anomaly. With that we can immediately see what the relative natural control of 1.6W/m^2 is, if it is correct and not a lot less, as it appears from actual data.

    I suggest Thor’s hammer has some similarities, and this control through the oceans has happily brought us through many ice ages, in fact mainataining euqilibirum across a few degress within a 10 degree max band at the polse. Why are we even talking about this when the records of the the current interglacial show continual variation of a degrees every 250 years or so, up then down, never stable, and a decline of the long term trend to the interglacial floor level that the last down took us through. We are lucky to have got back inside the interglacial range, just, and have another 1.5 degrees to go to reach the interglacial median.

    Warming is not our problem. Change is natural and we are, or were, due a rise. Neither is any such change catastrophic, even if it is down, the real problem, its 0.5 degrees per century, so several lifetimes of adapting and then relocate, 100 metres downhill?. This is all simple fact anyone can check for themselves, so why are we talking about something else that is quite unreal and has no supporting evidence. Here it is in case you didn’t know what happened for the 7,000 years before 1,000 AD. https://www.dropbox.com/s/vvyej6raim9hjic/Facts%20About%20Climate%20History.pdf?dl=0

  26. I’m an idiot. Got into other ares, Here is the key request from climate muddles. I would like two or three parametisations quantified in W/m^2, at current interglacial conditions will do, to compare their feedback with the supposed effect of AGW of 1.6W/M^2.

    I seek the sum of the effects of evaporation, condensation and resulting albedo in W/m^2 caused by 1 degree change in SST. Nice and simple. Never seen a figure, yet this is the single effect stablilising the SST against all change by modifying solar insolation and standing between us and Venus. I suspect the truth is inconvenient for disaster scenarios, and why we stayed inside 10 degrees range or so since we had oceans, etc.

  27. Climate sensitivity appears to be ripe for confounding factors. The “what if’s” of inadequately understood complicated systems. The evidence for one will likely be the oceans. As they continue disgorging heat likely put there during the last cold stadial period, the planet continues to green, which increases insect populations, and increases carbon from decay of all that green stuff, and oceans disgorge CO2. Under the warming atmosphere compliments of the disgorging oceans, greening will increase every year. Until that is the oceans are affected by orbital mechanics that starts putting heat back into the oceans as we fall back down to cold. CO2 is not the leader, it is the signal of some other process. One that has been going on for at least the past 800,000 years.

  28. > 5-95% range of 1.05 – 2.7 °C

    The problem with reasoned and supported conclusions like this is that the result is not scary. The other “problem” is that as it relies on observation, as time goes by it gains greater weight in the record.

    Question. RCP 8.5 is no longer remotely possible short of a cosmic event. Why is it not dropped from ensemble averages?

  29. I doubt very much that ECS is a constant. It varies based on temperature, humidity, altitude (pressure) and who knows what. Hence, anyone looking for some magic ECS will forever be disappointed.

    Now, it may be possible to compute an average ECS similar to the average surface temperature. However, that would probably be just about as useful.

    This is just another case of blind folks trying to tell us what the elephant looks like.

    • An average ECS would be like saying the average American has 1 boob, 1 ball, and 2 1/2 kids.

  30. Joel O’Bryan

    “All just delusional “make work” that does nothing to bring any understanding to the climate.”
    That pays the witch doctors very well.

  31. I had a critical, but polite post on this subject removed by mods in the first Curry posting. I’m glad to see a bit more critical to dismissive comments abound this time. We can’t have sacred cows in this battle.

    I have considerable respect for Curry. She’s been in the lion’s den of the climateers when she could have been a well paid, decorated, and highly respected cheerleader for the totes.But ceteris paribus nonsense on ECS in a system with so many confounding agents acting or waiting to act counter to ‘forcings’ (see Le Chatelier’s Principle even in Wiki) can only give encouragement to hangers on in a falsified meme.

    Willis, Lintzen and a few others have waxed strongly and convincingly on the existential necessity of the presence of negative feedbacks for there even to be a world that we and our millions of other specie fellow citizens of this planet can be alive on. What are the constraints on temperature range (nevermind ECS)? The two billion years of the chain of life is a powerful signal for the stability of earth climate. Mass extinctions appear to be from extraterrestrial catastrophic bombardment of large bolides that jerked climate to extremes with mechanical shock, horrific tsunamis, rain of hot glass, and longlasting dust that blocked the sun. We (collectively) barely survived, but, thanks to powerful negative feedbacks, the earth system righted itself and survivors re-spread around the earth. What was the ECS? Nothing that mattered.

  32. At least one negative feedback is obvious. Increasing temperature increases water evaporation (especially over the oceans where wind and wave action makes mass and heat equilibration rapid). More water vapor means more clouds. More clouds mean more diffraction of incident sunlight to space.

    The climatistas have to reduce cloud W/m2 effect in the models because if they had it at a more realistic value their models would no longer fit the 20thC training period. Likewise they can’t model clouds properly because if they did this negative feedback would overwhelm the effect of CO2 and model-derived ECS would be low. The ensemble climate models are notorious for poorly modelling clouds.

    All this fits with the view that solar modulation of cloud cover and the ~60 year ocean cycle caused most warming last century, and CO2 only contributed a small amount. I am sure if the modellers included those two significant variables correctly (and not the laughable 0.05 W/m2 for solar variability) then their models would forecast much much better.

    But if they did that the ECS value would be well under 1 K/doubling, global warming would be proven harmless and most climate programs would be defunded.

  33. “5. Climate sensitivity

    Equilibrium climate sensitivity (ECS) is defined as the amount of temperature change in response to a doubling of atmospheric CO2 concentrations, after the climate system has reached equilibrium. The issue with regards to ECS is not scenario discovery; rather, the challenge is to clarify the upper bounds of possible and plausible worst cases.

    The IPCC assessments of ECS have focused on a ‘likely’ (> 66% probability) range, which has mostly been unchanged since Charney et al. (1979), to be between 1.5 and 4.5 oC. The IPCC AR4 (2007) did not provide any insight into a worst-case value of ECS, stating that values substantially higher than 4.5 oC cannot be excluded, with tail values in Figure 9.20 exceeding 10 oC. The IPCC AR5 (2013) more clearly defined the upper range, with a 10% probability of exceeding 6 oC.”
    ——————————

    The paragraphs selected above are very interesting, I think.

    The first paragraph consist with the consideration of the ECS definition and the relation of its actual consideration.
    Definition of ECS as it stands, requires, needs and depends on a confirmation and support by the scenario discoveries, aka experiments, or as in the actual case the models…
    as it tightly relates in substance of it’s claim and existence as a concept to the origin of it, to the scenario discoveries of the “experiment”.

    None of proper models offers such support or confirmation, as far as I can tell… for a ECS > 3C.
    In consideration of such, the result from the models have ECS at < then 3C…even for the few that get to do a doubling of CO2….

    And when it comes to the second paragraph, the question to put forward is;
    The ECS as per the definition, does it really originates or stands as properly being proposed as a such concept, as considered these days, by the Charney et al. (1979), or is that linkage silly and over claimed and over pushed?
    I am not really sure about this one, that is why am asking…any info in this one very appreciated.

    ECS is not simply CS, is a special case of CS considered…in the "science" of AGW.

    cheers

  34. I’m sorry, but here is an excerpt from the post:

    “Emergent constraints in principle can help narrow uncertainties in climate model sensitivity through empirical relationships that relate a model’s response to observable metrics.”
    ===============
    I’ve tried reading it forwards and backwards, can anyone tell me in simple terms what it says ?

    • u.k.(us)

      Maybe it means that the most valid and proper models to consider in relation to ECS are the ones that may be considered “realistic”, the ones that do go through in realistic step with the CO2 concentration path scenarios as per merit of comparison with the reality in context of CO2 concentration path, or the models who do a very close enough CO2 concentration trend as in consideration of the CO2 concentration trend in reality.
      And there is no many such as…and as far as I can tell none do reach a doubling, and none of these do an ECS>3C.

      Maybe…

      cheers

  35. Complex (highly evolved) life requires a relatively stable climate for tens of millions of years (at least) to exist.
    Therefore, this planet has a self regulating climate system which keeps it within the temp range where said life continues and saying that adding a few ppm co2 will change that is some kind of loopy joke.
    I mean how obvious does it need to be?
    All talk of feedback mechanisms is purely academic.

  36. Pretty certain we’re at about 0.55°C before the cloud cover starts to drastically increase with increase average sustained minimum winds.

    That was the whole problem with the “global weirding” theory: that it was going to primarily increase the maximums of things but when you put more energy into a shuddering and halting system it only increases the lower end activity.

    The “climate” is perfectly capable of dealing with a 10% increase in solar input without turning the planet uninhabitable.

    Or we wouldn’t be here at all.

  37. errm; the claim is that doubling CO2 (from 280 to 560 ppm) adds about 3 watts/sqM of warming and that this, with feedbacks, causes what? 3C, 4.5C maybe 6C warming. Lets go with the lowest 3C then ECS is 1watt/sqM/C. But the total energy contribution from CO2 is claimed to be 30 watts/sqM. Sure absolute sensitivity is not the same as incremental sensitivity but 30 watts/sqM is still a pretty small fraction of the total green house gas contribution of about 160 watts/sqM so the non linear effect should be relatively small. So the total contribution of CO2 should be about 30K. That means without CO2 earths temperature would be not 288K but 258K. But as has also been repeatedly pointed out, without green house gases Earth’s temperature would be about 255K. So all of water vapour and clouds contributes 3K of warming. If its so small it can hardly exert much feedback so where does the massive positive feeedback come from?

  38. The climate sensitivity of CO2 is zero as a worst case. It is all a matter of science. The radiant greenhouse effect has not been observed in a real greenhouse, in the Earth’s atmosphere, or anywhere else in the solar system for that matter. The radiant greenhouse effect is science fiction so hence everything based on the radiant greenhouse effect is science fiction including the AGW conjecture.

  39. “The radiant greenhouse effect has not been observed in a real greenhouse, in the Earth’s atmosphere, or anywhere else in the solar system for that matter.”

    Tell that to your miitary.
    Modtran and Hitran (LbL radiative models) are used to keep you safe and were developed as such.

    https://en.wikipedia.org/wiki/HITRAN
    https://en.wikipedia.org/wiki/MODTRAN

    “HITRAN – HITRAN (an acronym for High Resolution Transmission) is a compilation of spectroscopic parameters that a variety of computer codes use to predict and simulate the transmission and emission of light in gaseous media including the atmosphere, laboratory cells, etc. The original version was compiled by the Air Force Cambridge Research Laboratories (1960s). HITRAN is maintained and developed at the Harvard-Smithsonian Center for Astrophysics, Cambridge MA, USA.

    HITRAN is the worldwide standard for calculating or simulating atmospheric molecular transmission and radiance from the microwave through ultraviolet region of the spectrum.[citation needed] The current version contains 49 molecular species along with their most significant isotopologues. These data are archived as a multitude of high-resolution line transitions, each containing many spectral parameters required for high-resolution simulations. In addition there are 320 molecular species collected as cross-section data. These latter include anthropogenic constituents in the atmosphere such as the chlorofluorocarbons.”

    Oh BTW:
    Neither is the trapping of heat in your garden greenhouse anywhere near an analogue for what happens in the atmosphere.
    Try educating yourself…..

    https://scienceofdoom.com/roadmap/atmospheric-radiation-and-the-greenhouse-effect/

  40. “ECS < 0: impossible" – as others have commented above, I disagree with Dr. Curry on this point. To the extent that the atmosphere is conceived as a static radiative insulating blanket in respect to the surface, one would expect warming of the surface with increased concentration of CO2. But more realistically conceived as a heat engine, driven by intense radiative coupling with the surface, one has to consider the possibility that an increased concentration of CO2 improves the effectiveness of the working fluid of the machine. The heat engine should perform better with a slightly more intense radiative coupling at the surface, so why would it be impossible to drive the same amount of heat to high altitude with a slightly lower surface temperature?

  41. I made a machine learning app that predicts,for 20 by 20 km patches of earth, monthly and annual average temperatures from monthly average surface and top of atmosphere visible power flux, altitude, monthly rainfall, surface albedo and a few other inputs. . The resulting learned function is differentiable and can be used to calculate climate sensitivity to visible light and, after accounting for surface albedo, sensitivity to IR flux. It show sensitivities well below 0.2 C w/m2. Code and lots of graphs are here: https://github.com/ndbucksmith/tf.climate

  42. We have nearly 80 years of good data. We don’t need to guess at this and we can make much better estimates.

    Since 1945, Co2 has risen 30% from 310 to 410. Temperatures have risen between 0.3-0.8C depending on the data you use. TCS therefore is between 1.0-2.4C. ECS is not much higher. The reason is simple. We have 75 years of data and if anything the rate of increase since 1945 has been decreasing not increasing even as we add more co2 at higher rates. If there was latent heat or effects in the system we would be seeing that already.

    The El Nino of 2015 was an event that triggered high temperatures that have diminished over the last several years as expected. We were told by prominent climatologists that there would be no drop off in temperatures after this El Nino. As usual they were wrong. I was told by a climate modeling leader in my Global Warming class at Stanford years ago that El Ninos would disappear as Co2 effects dominated. Didn’t happen.

    We got an El Nino after nearly 15 years of no temperature change. Without that the temperature change over 20 years would have been nearly 0. This is after we are pouring into the atmosphere at the most prodigious rate ever and faster than even their models anticipated.

    The highest rate of change in temperatures happened from 1978-1998 which coincided with a positive PDO/AMO cycle and increasing Co2. For the 30 years prior to 1978 temperatures barely moved and may have gone down not up even though this is the period of most active Co2 output in mans history to that time.

    About 95% of all Co2 ever produced by man has occurred since 1945. Thus this is the only period we can use as reference.

    If you use data prior to 1945 it acts as a control. From 1880-1945 temperatures rose about the same as during the Co2 phase. Thus it is not possible to conclude that Co2 has any effect on temperature. During the period for which we poured in 1/20th the Co2 we got the same temperature change as when we poured in 20 times as much. The two causes can’t be from Co2. Therefore we need to know the specifics of what caused what warming to be able to deduce what %age may have come from Co2 vs other unknown causes.

    Climate Scientists cannot explain adequately the decline in temperatures between 1945-1975 while we massively increased Co2. They claim pollution or aerosols. However, studies have shown this is very speculative. Since we don’t know these things and we have the prior 80 year period exhibiting the same temperature change with virtually no co2 increase we can conclude that the sensitivity of the atmosphere to Co2 could very well be only a fraction of the 1.0-2.4 TCS range.

    When this alarmism started we saw graphs showing 8C change from a little over 100ppm change just since 1945. Instead we’ve seen 0.3-0.8C or 1/10th the effect they postulated. Their models are actually conservative compared to the theories they had. Yet, today we see the models are hot, very hot compared to reality.

    Yes, it is remotely possible that ice fields might suddenly collapse and disintegrate or that giant volcanoes will go off and asteroids will strike the Earth or that any number of things might go wrong.

    It would be unscientific to quote a change in temperature greater than we’ve seen in the last 75 years for the next 75 years given the Co2 levels will rise a similar 30% to the last 75 years. This is how the atmosphere reacts to Co2 and its proven by 75 years of data. To say anything else is not scientific.

    This is not really in dispute.

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