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What is the correct value of Climate Sensitivity?

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96.999% more to go and maybe we'll start taking you seriously too.Maybe even sooner if the rate of scientists abandoning the consensus position takes off.

Eyeball, I have a question. Do you think I am being a climate change 'denier' in anything that I've written in this thread? Or that my calculations somehow refute the 'concensus'?

Edited by -1=e^ipi

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Eyeball doesn't know enough to understand whether your posts in this thread support or oppose the "consensus" or, fall into the realm of "denial" or "alarmism", or anything else. He just wants to poke at you for being all nerdy-like.

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Another issue I just noticed. The decay time of temperature response to an initial change in atmospheric CO2 should depend positively on the equilibrium climate sensitivity (I've seen some arguments for a proportionality relationship). This suggests that the ratio between the TCR and the ECS should be lower than the 1.8 that was used in the Loehle paper and my calculations. If this is the case, then that is another reason why my estimate should be lower than 2.95C.

There is also a response to the Loehle paper that is going to be published on the 10th of February.

http://www.sciencedirect.com/science/article/pii/S0304380014004876

It suggests that the uncertainty suggested by Loehle is too small (by over a factor of 2) and that the signal decomposition technique was not optimized. Though it does make a mistake in suggesting that Loehle not taking into account CO2 emissions prior to 1950 results in an underestimation of climate sensitivity (when in fact it results in an overestimation).

Edited by -1=e^ipi

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Eyeball, I have a question. Do you think I am being a climate change 'denier' in anything that I've written in this thread? Or that my calculations someone refute the 'concensus'?

No, I get the impression you're bored and looking for amusement.

Eyeball doesn't know enough to understand whether your posts in this thread support or oppose the "consensus" or, fall into the realm of "denial" or "alarmism", or anything else. He just wants to poke at you for being all nerdy-like.

Please...it was obvious from practically day one where ipi wasn't coming from on this issue.

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No, I get the impression you're bored and looking for amusement.

So... Someone can't just find climate science interesting on its own?

Please...it was obvious from practically day one where ipi wasn't coming from on this issue.

Where wasn't that? Irrational climate alarmism?

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So... Someone can't just find climate science interesting on its own?

In today's political climate? Maybe.

Where wasn't that? Irrational climate alarmism?

No, rational climate reassurance.

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Can you define that for me?

Okay, everyone deserves the benefit of doubt. Rational climate reassurance is just the opposite of Irrational climate alarmism.

You look like you've been trained to use your brain and obviously fairly effectively, have you considered putting it to more rational use than rubbing people's noses in their alarmed ignorance? Seems a rather unbecoming pastime for someone who's so edumacated.

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Found another flaw with the Loehle paper. The assumption of a constant rate of 'natural' warming from 1850-2010 is not true and results in an underestimation of climate sensitivity.

Look at past solar activity over the past 1500 years as well as expected future solar activity.

planetcycles.jpg

The rate of increase in solar activity from 1850-2010 has been decreasing and has basically peaked around 2000 (There probably will not be comparable solar activity for another ~800 years). As a result, the rate of natural warming from 1850-1950 should be larger than the rate of natural warming from 1950-2010.

This probably dominates the reasons I mentioned why 2.95 C might be an overestimation of climate sensitivity.

So should I just go with the 'consensus' position that the best estimate for equilibrium climate sensitivity is ~3 C?

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So should I just go with the 'consensus' position that the best estimate for equilibrium climate sensitivity is ~3 C?

A mean that is somewhere between 2 and 3 degC is probably not as important as the probability distribution which is most often used to exaggerate alarm. i.e. two people could agree on the mean but disagree on the size of the tail at the higher end. Alarmists need a big fat tail to rationalize their claims.

Here is a fascinating PhD thesis on the problems with climate models:

http://judithcurry.com/2015/02/02/questioning-the-robustness-of-the-climate-modeling-paradigm/#more-17736

The state-of the-art fully coupled AOGCMs do not provide independent evidence for human-induced climate change. GCM-based multi-model ensembles are likely to be (implicitly) tuned to earlier results. The confirmation of earlier results by GCMs is therefore no reason for higher confidence.

...

Shortcomings, like the huge biases and ignorance of potentially important mechanisms, have been routinely and dutifully reported, but a rosy presentation has generally prevailed. Large biases seriously challenge the internal consistency of the projected change, and consequently they challenge the plausibility of the projected climate change.

...

Most climate change scientists are well aware of this and a feeling of discomfort is taking hold of them. Expression of the contradictions is often not countered by arguments, but with annoyance, and experienced as non-constructive. “What else?” or “Decision makers do need concrete answers” are often heard phrases. The ’climate modelling paradigm’ is in ’crisis’. It is just a new paradigm we are waiting for.

I distrust climate models for exactly the reasons stated. The fact that a PhD candidate was able to get this thesis published is a sign that change is coming to the field and that is a good thing. Edited by TimG

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A mean that is somewhere between 2 and 3 degC

I had that position ~ 1 month ago. But after doing the Loehle corrections, reading many other papers, and discussing things with people on science blogs I am becoming convinced that the best estimate is close to 3 C.

is probably not as important as the probability distribution which is most often used to exaggerate alarm. i.e. two people could agree on the mean but disagree on the size of the tail at the higher end. Alarmists need a big fat tail to rationalize their claims.

Any reasonable pdf is likely to have slightly longer tails for high sensitivity vs low sensitivity due to the nature of climate sensitivity (you can't have sensitivity less than zero; actually it shouldn't be below the no-feedback sensitivity of 1.15K). But yeah, I agree that this is a big issue that is used by the alarmists to push their data. The 'uncertainty' in climate sensitivity is likely greatly overstated by the IPCC (who's 90% confidence interval is 1.5 K to 4.5K), despite most of the more well done studies having a central estimate between 2.5-3.5K with much smaller 95% confidence intervals. From what I have read, the reason for such a large dispersion in the climate sensitivity estimates in the literature are due to people making incorrect assumptions (most of the higher estimates are due to GCMs overstating things). I think that any reasonable model should be calibrated to the empirical data before making predictions; if it can't properly explain the past then why expect it to predict the future?.

Here is an interesting talk on some of the things you mentioned. The issue of the overstated tail at the higher end is mentioned around 4:40. Though most of that yale seminar is beyond my understanding.

I distrust climate models for exactly the reasons stated. The fact that a PhD candidate was able to get this thesis published is a sign that change is coming to the field and that is a good thing.

I hope so. Though the 17 year slowdown sort of makes it difficult for things not to change. The predictions back in say 2000-2001 (IPCC assessment report 5) were way over confident and overpredicted things so much that what has been observed is well outside the IPCC confidence interval.

When you look at year ~2000 from a geological perspective, we have roughly a peak in the ~60 year solar cycle, a peak in the ~800 year solar cycle and the effects of the North Atlantic Multi-Decadal Oscillation and the Pacific Decadal Oscillation all converging to make things very warm. The 'consensus' climate scientists attributed too much of this natural warming to CO2 and we now see the result in 2015.

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Thought I would mention that I think this paper gives a good estimate of the Earth system sensitivity (ESS) to be 4.0-4.5 C.

http://www.researchgate.net/publication/40269214_Earth_system_sensitivity_inferred_from_Pliocene_modelling_and_data

So Earth system sensitivity is the climate sensitivity in the very long run (so includes all changes to ice sheets and vegetation) and takes millennia to get to. Where as the equilibrium climate sensitivity takes on the order of a few centuries to get to an is primarily due to fast feedback responses. In previous posts in other threads, I may have mixed up Earth system sensitivity with equilibrium climate sensitivity.

Comparing the Pliocene to the Holocene is probably a better way to get the ESS than looking at temperature changes during the Pleistocene (which James Hansen seems to like to do to get his crazy 6-8 C ESS estimates). Going from Holocene to Pliocene would represent a warming and higher CO2 levels, where as going from Holocene to a Pleistocene ice-age would represent a cooling and lower CO2 levels. Comparing Pliocene to the Holocene avoids all the complications associated with the Milankovitch cycles that one would need when using Pleistocene data. Using Pleistocene data means you are using ice core data, so you have to decide upon a polar amplification factor to obtain global temperature data (Hansen and most people assume a polar amplification factor of 2 by convention, where as there is a good chance that the polar amplification factor is more than this; so any estimates of climate sensitivity using ice core data are going to overestimate things by whatever factor they underestimate polar amplification). There is also the issue that the correlation between CO2 and temperature is different depending on if the initial forcing is due to CO2 or not, but Lunt et al. seem to avoid this; they even take into account continental changes that one should do when comparing such different points in time. Their result seems to rely on the equilibrium climate sensitivity being ~3.04 C, but the idea that the Earth System Sensitivity is roughly 1.4 times the Equilibrium Climate Sensitivity seems robust.

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Comparing the Pliocene to the Holocene is probably a better way to get the ESS than looking at temperature changes during the Pleistocene

I disagree with the assumption that the sensitivity is a constant across all geological epochs. e.g. the amount of plant matter @180 ppm is a lot less than at @600 ppm and this likely will affect everything from albedo to cloud formation. On top of that you have Milankovitch cycles, continental drift and poorly understood movement of heat between ocean layers.

Now this does not mean it is not useful to make assumptions and calculate a number but the "past performance does not guarantee future performance" caveat should not be forgotten.

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Oops, now we get to see ipi cut and paste some other flailing graph. GW is happening. Everybody knows that. Its a matter of how fast.

So you just look at random images and don't read the text that goes with it because text is too hard for you to read?

Go back to denying the basics of cellular respiration and photosynthesis.

I disagree with the assumption that the sensitivity is a constant across all geological epochs. e.g. the amount of plant matter @180 ppm is a lot less than at @600 ppm and this likely will affect everything from albedo to cloud formation.

Well if you go from mid-Holocene to mid-Pliocene, you are only going from ~270 ppm to ~400 ppm, so it isn't that bad. Also, the Earth system sensitivity is supposed to include changes to vegetation, albedo and cloud formation (basically all long run effects that may occur over millennia). Realistically, the equilibrium climate sensitivity is a better representation of the maximum temperature change due to anthropogenic CO2 emissions because the time scale at which atmospheric CO2 is reabsorbed by the lithosphere is shorter than the time scale at which one moves towards the Earth system sensitivity.

On top of that you have Milankovitch cycles, continental drift and poorly understood movement of heat between ocean layers.

Milankovitch cycles are a bigger issue if you are trying to obtain the Earth system sensitivity from ice-core data in the pleistocene (since the variation in temperature and CO2 is due to Milankovitch cycles). Comparing the Pliocene to the Holocene tends to avoid this since the time scale is much longer. Also, the Pliocene maximum and the mid-Holocene correspond to rough maxima in the overall effect of the Milankovitch cycles, so there should not be too much difference due to this.

Continental drift is obviously a big issue, but Lunt et al. seem to take into account some of these changes in their paper (such as formation of mountains). I'm not sure if the formation of Panama around 3 million years ago is taken into account.

Edited by -1=e^ipi

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rvWeJd.gif

This was an image provided by someone on another site. Apparently past temperatures since 1880 can be very well predicted by only 7 variables using a simple regression (including logarithm of CO2 concentrations, solar irradiance, volcanic aerosols, length of the day oscillations, Pacific Decadal Oscillation and North Atlantic Multidecadal Oscillation). So a lot of the 'natural variability' we see in Loehle and other papers can be explained (and thus removed) in order to get more accurate estimates of climate sensitivity.

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Found another flaw with the Loehle paper. The assumption of a constant rate of 'natural' warming from 1850-2010 is not true and results in an underestimation of climate sensitivity.

Look at past solar activity over the past 1500 years as well as expected future solar activity.

planetcycles.jpg

The rate of increase in solar activity from 1850-2010 has been decreasing and has basically peaked around 2000 (There probably will not be comparable solar activity for another ~800 years). As a result, the rate of natural warming from 1850-1950 should be larger than the rate of natural warming from 1950-2010.

This probably dominates the reasons I mentioned why 2.95 C might be an overestimation of climate sensitivity.

So should I just go with the 'consensus' position that the best estimate for equilibrium climate sensitivity is ~3 C?

That graph of Medieval Warming is wrong and borrowed from climate change denier Douglas J. Cotton's blog. He's got a BSc and no graduate degree in science, but likes to run around the internet sowing uneducated garbage all over the place.

For information from practicing scientists who actually work in the field, check here. It explains the problem with Cotton's graph, but I suspect you don't really give a crap how wrong it is as long as it supports your biased goal of denying the settled science.

http://www.realclimate.org/index.php/archives/2004/12/werent-temperatures-warmer-during-the-medieval-warm-period-than-they-are-today/

http://www.realclimate.org/index.php?p=11#myth2

Edited by cybercoma

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That graph of Medieval Warming is wrong a...

They usually are. Even if they weren't, though, the argument seems to be that because there was a relative warming period in the past the CO2/warmth correlation we're seeing now shouldn't be looked at with concern ?

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@cybercoma -

Sorry I just took a random image of google for illustration purposes. Is this better?

2000px-Carbon14_with_activity_labels.svg

evanstotal-solar-irradiance-1-1.gif

Also, are you even capable of reading the text that goes with my posts? I was pointing to the fact that Loehle not taking into account the changes in solar irradiance results in an underestimation of climate sensitivity, and therefore there is a good argument that the best estimate of climate sensitivity should be above 2.95 C.

But I guess only a true believer in the climate alarmism religion would rather that climate sensitivity be underestimated than admit that solar irradiance has an effect on climate.

as long as it supports your biased goal of denying the settled science.

What 'settled science' am I denying? I see a lot of of alarmists here that deny even the basics of cellular respiration and photosynthesis.

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They usually are. Even if they weren't, though, the argument seems to be that because there was a relative warming period in the past the CO2/warmth correlation we're seeing now shouldn't be looked at with concern ?

Oh wow. No. Do you guys just see the image, ignore the text then replace the text I write with whatever you think should be there to fit your narrative?

Look it's not hard.

Loehle uses the assumption that the rate of natural warming (due to recovery from the Little Ice Age) is the same from 1850-1950 as it is from 1950-2010. However, if you look at changes in solar irradiance during this time, the rate of increase from 1850-1950 is higher than from 1950-2010. As a result, the assumption used by Loehle results in an underestimation of climate sensitivity, thus the ~3C best estimate of equilibrium climate sensitivity by the IPCC is validated by this correction.

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Oh wow. No. Do you guys just see the image, ignore the text then replace the text I write with whatever you think should be there to fit your narrative?

We see climate alarmism religion in your text which pretty much sums everything else up at a glance.

You seem to think you need to be a rocket scientist to figure out what you're saying but any grade school drop-out could do that.

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