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Tom Curtis at 11:34 AM on 19 February 20142014 SkS Weekly News Roundup #7
Could I make a request to other participants on this forum that they leave it to me to respond to Russ in relation to his responses to my post @28 and following discussion. I know there is plenty to respond to in what he writes, and of necessity I am not covering all points. However, just from the points I am covering it is becoming plain that Russ is very, and inconsistently selective in which evidence he will admit. Adding more voices to the debate will distract from that point, and also make it less likely the discussion will continue to the end where it covers those areas Russ incorrectly percieves as his strong points.
Moderator Response:[PS] This is a reasonable request and I would ask participants note the "No dogpiling" rule. Corrections or further elucidations of comments would help but please dont add new distractions.
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chriskoz at 11:27 AM on 19 February 20142013 Among Top Ten Warmest on Record
Dave@1,
I second that. And it's a pity that such good, information-rich article as this one receives so little commentary attention from our fellow bloggers while the Weekly News Roundup #7 thread is going haywire feeding a troller (user-named Russel R.) who has high-jacked it to feed his strawman arguments.
It's worth noting that the global temperature data used in this WMO report may be biased low if it does not include the CW2014 correction for lack of coverage in Arctic (look at figure 2 therein and compare to to figure 1 in this article, which one do you think should go to the resources page?) Looks like data the figure 1 in this article is based on combined NCDS/GISS/HadCRUT, so it's probably less biased than HadCRUT itself, but it's still revealing to compare it to CW2014 Hybrid data where 2013 comes up warmer than 1998.
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Tom Curtis at 11:26 AM on 19 February 20142014 SkS Weekly News Roundup #7
Russ @47:
1) Fundamentally the Transient Climate Response (TCR) is a function of feedbacks and thermal inertia. By definition, the Equilibrium Climate Sensitivity (ECS) is the response after thermal equilibrium with the oceans is reached, and, ergo, is not a function of inertia. On the other hand, thermal inertia is a confounding factor in calculating the ECS from empirical data. Getting these details right matters.
Turning to the substance of your comment, you claim that "...geological evidence points to a planet see-sawing between two relatively stable equilibrium climate conditions, which suggests high sensitivity in the middle of the range, and low sensitivity at either end of the range". That, however, is the reverse of the true situation. As global temperature falls, ice sheets creep towards the equator in the NH. As the edge of the ice sheet, and perhaps more importantly, the southern limit of winter snowfall creeps closer to the equator, it must deal with more direct sunlight, with the consequence that the albedo effect becomes greater and you have a stronger climate sensitivity. Conversely, with rising temperature, humidity rises, and with it the strenght of the water vapour feedback. In fact, water vapour concentration rises with the fourth power of temperature so that in the right conditions, increasing temperature mean that water vapour can force a runaway greenhouse effect. The right conditions include strong enough insolation, and fortunately for the Earth is safe from that outcome - but that does not preclude an increasing climate sensitivity with increased temperature due to a strengthening WV feedback.
As noted by Dikran Marsupial, your evidence for the convenient ECS plateau we are supposed to occupy also has it wrong. The Earth has in fact experienced at least two, and probably more runaway cooling events. Further, our nearest neighbour, Venus, has experienced a runaway warming event (which unlike the cooling events are not, for practical purposes, reversible). Physics does not change between planets. If increasing temperatures drives increasing climate sensitivity from the WV feedback (necessary for a runaway warming event) in Venus, then they drive the same effect here. Fortunately we are protected from the final outcome of such an event by lower insolation, and had greater protection in the past when the Sun was cooler, though CO2 concentrations were higher.
That raises another point, for the strength of feedbacks also depends on the strength of insolation. Consequently, climate sensitivity would have been lower in the deep past than now with the same configuration of continents (the additional factor effecting climate sensitivity). That is something that should be born in mind when looking at paleoclimate results, particularly from the deep past (pre-tertiary).
To summarize, your comforting belief is the opposite of what would be expected from basic principles. Further, it is based on claims that runaway cooling and warming events do not happen, despite the fact that several runaway cooling events have occurred on Earth, and a runaway warming event has occurred on our nearest, and most physically similar planet. Rather than being at a local high in terms of climate sensitivity, we are likely at a local low, with higher climate sensitivities likely for both warmer and cooler conditions.
2) Despite my heavy emphasis on observational estimates of ECS in my preceding post, many of which are paleo estimates (for which estimates of anthropogenic aerosol forcing, and thermal inertia are irrelevant), you again focus solely on computer models. The evidence climate scientists present for their theories are not restricted to the evidence you feel you may be able to rebut. Simply ignoring contrary evidence as you are currently doing is no basis on which to form views about scientific facts.
So, seeing you choose to ignore it, here is again a presentation of observational climate sensitivity estimates, in this case all from paleodata:
In addition to ignoring all the inconvenient empirical estimates, you again focus on Otto et al. The two main problems with Otto et al (IMO) are that they are only a partially observational estimate, and the method is erratic in its results, suggesting we should not place a large amount of weight on those results, and certainly not to the exclusion of other results.
First, to estimate ECS, Otto et al require an estimate of the increase in Global Heat Content (GHC) over the reference period from 1860-1879. There are no ocean heat content measures over that period on which to base an observational estimate. As they need a value for that period, they used model data to provide their baseline reference. Otto et al's result is critically dependent on this model determined value.
Further, Otto et al had no observational estimates of forcings over the period 2006-2010, and used the RCP 4.5 projections instead. Consequently their values for the final decade have even less of an empirical basis then the other values.
It is possible to eliminate the model dependence by applying their method, and using 1970-1979 as the reference period. The results for each decade is as follows:
1980s: 3.49 C/doubling
1990s: 2.70 C/doubling
2000s:2.58 C/doubling
The range of values obtained in that excercise also indicates the erraticness of the method. This method is heavilly influenced by decadal variations in the data, and effect partially concealed in their published results by the long time span used in the estimate, and by an odd discrepancy between their estimate of GHC in the 1970s and that obtained from other sources.
For completeness, two further problems with Otto et al are the use of HadCRUT4 which does not include the Arctic and hence underestimates recent warming. In addition, the HadCRUT4 record prior to 1880 consists effectively of the North Atlantic region (including the east coast of the US, and Western Europe), plus the sea routes to Brazil, South Africa, India and Australia. It is not a global record, and is heavily biased by data from the North Atlantic. There is a reason, a very good reason, why GISS and the NCDC start their temperature records in the 1880s (by which time temperature records are almost global, with the exclusion of Antarctica).
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mgardner at 11:21 AM on 19 February 2014How we know the greenhouse effect isn't saturated
HK @43
A noble effort, but I already understand all this, and it doesn't answer my question or my concern about communicating it to others, which I thought was a major purpose of the blog. KR@44 is saying that it is possible to answer my question, but apparently I have to acquire and become proficient with MODTRANS, run my numbers, and whip up the graphics on my own time.
Here's an example of what I'm looking for:
A nice image and explanation, I think. If I were explaining this to someone, I would use it, and I think most sincere 'students' would get it. But if someone then asked me "what about that saturation thing I've heard about", I would like to be able to zoom in on the zone at the top of the troposphere, and show a similar diagram with some approximate values.
I could elaborate, but I'm not sure if there is any point if there's no source of information.
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Rob Honeycutt at 11:07 AM on 19 February 20142014 SkS Weekly News Roundup #7
Russ... I have to ask you honestly when you read this...
"The most likely value of equilibrium climate sensitivity based on the energy budget of the most recent decade is 2.0 °C, with a 5–95% confidence interval of 1.2–3.9 °C,..."
Do you not get what they are talking about when they say "based on the energy budget of the most recent decade"?
They're not saying the most recent decade gives them a better estimation of ECS (which you seem to be implying). They state that that may not be the case, and that their estimations remain consistent with previous estimates of ECS.
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Rob Honeycutt at 10:09 AM on 19 February 20142014 SkS Weekly News Roundup #7
Russ... But can you not see that you're doing exactly what Otto et al are cautioning against?
Their conclusion is not that ECS is lower that other estimates. They're saying their results are consistent with other estimates.
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Russ R. at 09:10 AM on 19 February 20142014 SkS Weekly News Roundup #7
Rob Honeycutt,
"You might actually take the time to read Otto 2013 before making such assertions as that they estimate CS at 2C."
I did read Otto et al (2013).
Quote:
"The most likely value of equilibrium climate sensitivity based on the energy budget of the most recent decade is 2.0 °C, with a 5–95% confidence interval of 1.2–3.9 °C,..."
Moderator Response:[PS] It would save a lot of tedious detail if you would spell out why you think a CS of 2 is nothing to worry about, preferably with reference to impacts in the IPCC WG2. Since I would assume that you reject the Stern review, it would also help discussion if you spell out what sources inform your opinion when discussing impacts and costs. Thank you.
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Russ R. at 08:47 AM on 19 February 20142014 SkS Weekly News Roundup #7
Dikran Marsupial,
In one post @49 you managed the trifecta of: a) quoting me out of context, b) making a strawman argument, and then c) accusing me of trolling.
First, you ignored the first half of my comment, thereby distorting my argument. If you hadn't selectively quoted me you would have seen that my full comment was:
" I would make a case that climate sensitivity was both higher and lower at different points in our planet's history, and will diminish if temperatures continue to rise. Were this not the case, the planet would have experienced runaway warming (or cooling) in the past when temperatures and CO2 levels were much higher (and lower) than they are today."
You only quoted the second part, starting at "Were this not the case..." Then you linked to a reference that has nothing to do with the point I was making.
Why do I say the post had nothing to do with my argument? Because it concluded:
"Thus arguments that Ordovician glaciation disproves the warming effect of CO2 are groundless. On the contrary, the CO2 record over the late Ordovician is entirely consistent with the notion that CO2 is a strong driver of climate."
Since I'd already acknowledged above that "the forcing component of increased GHG concentrations is straightforward enough," I'm already on-the-record as being in agreement with this article's conclusion.
I wasn't arguing that CO2 doesn't impact temperatures. I was arguing that sensitivity is not a constant across all climactic states. An argument which you selectively omitted.
Lastly, you accused me of trolling because before responding to Tom Curtis I failed to consult with a 3+ year old SkS post on the Late Ordovician, which refuted a claim I never made. Really?
Moderator Response:[PS] Snark, accusations, some attitude issues and a failure to read comments and responses carefully by both sides are creating unnecessary heat in an otherwise useful discussion. Could everyone please dial it back and focus the issues? kudos to Russ R for spelling out his position in @41 and to Tom Curtis for a considered response. More like this please.
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How we know the greenhouse effect isn't saturated
mgardner - The interception probabilities are due to the total GHGs above the emission point and atmospheric temperatures, which are entirely quantitative but not reducible to a simple expression. That's why tools such as MODTRAN are used, running line-by-line computations with discretization over many layers.
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How we know the greenhouse effect isn't saturated
mgardner & others:
Let’s try another approach and see if it helps:
1. The Earth receives 240 watts of solar energy per square metre on average when its spherical shape and albedo is taken into account.
2. To maintain a stable temperature, each square metre has to lose 240 watts back to space. This heat loss can only be in the form of infrared radiation because convection (dominant within the troposphere) and conduction is impossible in a vacuum.
3. The Earth’s average surface temperature is about 288 K (15oC), which corresponds to an IR emission of 390 watt/m2. That’s 150 watt/m2 more than needed to balance the energy received from the sun.
4. In order to avoid a dramatic cooling, the Earth’s heat loss to space has to occur from a level in the atmosphere where the emission equals 240 watt/m2. By using the Stefan-Boltzmann law (j* = T4 x 5.67x10-8) one find that this emission intensity corresponds to a temperature of 255 K (-18oC).
5. This means that the average altitude of heat loss to space is (288-255)/6.5 ≈ 5 kilometres above the sea level. Note that this altitude depends very strongly on the frequency of the emission. Some frequencies are hardly absorbed at all and therefore able to escape directly to space from the surface (see image in my post @23), while others can’t escape before they reach the lower or middle stratosphere because CO2 absorbs so strongly even in very low concentrations.
6. More CO2 and other greenhouse gases make the atmosphere at the altitude of heat loss more opaque to infrared, so the IR emissions from this altitude can’t escape to space so easily any more. As a result, the altitude of heat loss is pushed upwards to a thinner part of the atmosphere with fewer CO2 molecules above.
7. This new altitude of heat loss is colder and emits less heat to space, meaning that the Earth as a whole loses less heat to space than it receives from the sun.
8. As a result, the Earth has to warm until its heat loss to space increases enough to restore the balance between incoming and outgoing energy.
Did this help, or did I just create more confusion?
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sidd at 06:43 AM on 19 February 20142014 SkS Weekly News Roundup #7
Re:Climate sensitivity as a function of CO2
from
Climate Sensitivity, Sea Level, and Atmospheric CO2
James Hansen, Makiko Sato, Gary Russell and Pushker Kharecha
NASA Goddard Institute for Space Studies and Columbia University Earth Institute, New YorkFig 7b)
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Rob Honeycutt at 06:31 AM on 19 February 2014Customizable Global Warming Widget Metrics
Maurice... The temperature has gone up at a rate of something around 0.11C per decade since 1998. So, you're wrong from the outset here. Add to that the increase in ocean heat content and you have quite a lot of heat accumulating in the climate system.
If you believe the figures are in error then it is incumbent upon you to demonstrate how you would calculate the figures and show how they are correct.
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Composer99 at 06:28 AM on 19 February 2014CO2 was higher in the past
eric7866:
First, solar output, on the largest scale, changes extremely slowly over geological timescales, but is extremely significant when it changes. A few % increase in solar output will, in a billion years or so, render the Earth uninhabitable. So it's no surprise that a few % decrease in solar output going back into the geological past requires an immense amount of atmospheric greenhouse gases to compensate. That said, geologically-significant changes in solar output are not something that has the effects consistent with what we have seen of global warming over the last 150 years.
Second, today's global mean surface temperatures are cold compared to most of the Phanerozoic. (Although given sufficient unabated warming our species may yet have the opportunity to experience surface temperatures consistent with, say, the Late Cretaceous).
Third, if you think that scientists studying present and paleoclimates are "discounting" any forcing agent in any situation, you are simply mistaken.
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Rob Honeycutt at 06:11 AM on 19 February 2014CO2 was higher in the past
eric... Next, you need to consider what 4% actually means relative to solar output.
Our sun is a relatively stable star which varies only ~0.1% over the 11 year solar cycle. Solar irradiance is measured at around 1361W/m^2. Four percent of that is 55W/m^2, which is a significant difference of forcing on the climate system.
The change in solar forcing since ~1900 is on the order of 0.5W/m^2. So, we're talking about 2 orders of magnitude difference.
Others can check, but I think I have my figures correct.
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Rob Honeycutt at 06:03 AM on 19 February 2014CO2 was higher in the past
Eric... One simple question. Do you honestly think the entire scientific community is fitting science to a desired result? Or, perhaps, might it be that you haven't yet grasped what the science says relative to your question?
The first act of skepticism should be to ask a question, as you've done, and then see if you can find the answer.
Your comment seems more leading than "just an observation." It sounds more like you're headed off into territory where you are forming conclusions based on a lack of knowledge.
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eric7866 at 05:42 AM on 19 February 2014CO2 was higher in the past
If high CO2 levels of the past ages can be discounted by claiming the sun was 4% cooler back then, couldn't the slightly higher temps today be attributed to the sun being that much warmer than in the past? And not necessarily due to the CO2 levels? To discount levels in one scenario and not the current one? That seems like making the science fit a desired result rather than analysing the science to find the results...just an observation...
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Dave Evans at 05:15 AM on 19 February 20142013 Among Top Ten Warmest on Record
Good article John. Are you going to add the first graph to your resources page? I'd find it very useful.
Moderator Response:[JH] No. The two graphs embedded in the OP were produced by the WMO, not SkS.
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Rob Painting at 05:13 AM on 19 February 2014Extreme weather isn't caused by global warming
Cedders - the simple answer is that there isn't a linear relationship between the two - the moisture-holding capacity of the air increases faster for any given increase in atmospheric temperature. See the Clausius-Clapeyron relation.
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Rob Honeycutt at 04:13 AM on 19 February 2014IPCC overestimate temperature rise
Just to further clarify DM...
You can't do this (red circle):
That is a single year, cherry picked, baseline. It's something you see Chris Monckton constantly doing in his presentations.
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Dikran Marsupial at 03:56 AM on 19 February 2014IPCC overestimate temperature rise
Here is an example of what I mean (vai woodfortrees.org):
Here I've shown the HADCRUT4 datase, along with two lines representing completely accurate representations of the rate of warming, but only differing in the vertical offset introduced by the choice of baseline year.
The green line represents a "skeptics" presentation, where the observations and projection were baselined to a peak in the observations so that the observations are then generally below the projection. "IPCC models over predict warming" is the headline.
The blue line represents an "alarmist" presentation, where the observations and projections were baselined to a trough in the observations, so that the observations are generally higher than the projection. "IPCC models underpredict warming" is the headline.
The magenta line represents the scientific presentation (in this case it is just the OLS trend line), where the offset hasn't been cherry picked to support the desired argument.
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mgardner at 03:49 AM on 19 February 2014How we know the greenhouse effect isn't saturated
KR@40
Please note: I'm the one who wasn't comfortable with the whole "layers" thing in the first place. Maybe you could take a look at my @41; I think that's the best I can do at posing the question.
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Dikran Marsupial at 03:43 AM on 19 February 2014IPCC overestimate temperature rise
jsmith, the image you have shown there is not actually "unadjusted". The model projections used in the 1990 IPCC report do not all agree exactly on the temperature in 1990, and they definitely didn't predict the observations exactly either. The thing that is wrong with the picture is that they have used a baseline of year (whci happened to be a peak in the observations), rather than the proper procedure of a 30 year baseline. The problem with a single year baseline is that you can make it give any result you want, you can make it look like the models over-predict temperatures by baselining to a warm year, or you can make them look as if they are running cooler by baselining to a cold year. Sadly this sort of thing is done all the time, but that doesn't mean that it is correct - far from it.
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jsmith at 03:35 AM on 19 February 2014IPCC overestimate temperature rise
Just out of curiosity, how do you "adjust" the IPCC's predictions to reflect observed GHG forcings? Because it seems as though there's a big difference between doing that (which results in the images shown above) and not doing it (which results in images like the one below).
In other words, what's wrong with this picture?
Also, I hate to sound like a broken record (as I said this about the "Southern sea ice is increasing" page too), but I don't see why we need both this page and the one called "IPCC global warming projections were wrong," as they both seem to cover the same topic.
Moderator Response:[Dikran Marsupial] Please can you limit your images to no more than 500 pixels wide. I have made the adjustment this time.
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Dikran Marsupial at 03:33 AM on 19 February 20142014 SkS Weekly News Roundup #7
Russ R wrote "Were this not the case, the planet would have experienced runaway warming (or cooling) in the past when temperatures and CO2 levels were much higher (and lower) than they are today."
Please take the time to see if your arguments have been discussed before on skeptical science. In the past, when CO2 levels were higher and lower, there was no runaway warming because the other forcings were different (principally solar brightening), runaway cooling actually did happen and runaway warming is pretty difficult to achieve as CO2 radiative forcing only increases logarithmically with concentration, but e.g. ocean degassing only rises linearly with temperature and the radiation of energy from the earth proportional to the fourth power of temperature (Stefan Boltzman law).
I suggest we DNFTT until Russ actually starts checking up on whether his arguments have any merit before he uses them.
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jja at 03:32 AM on 19 February 2014Vision Prize: scientists are worried the IPCC is underestimating sea level rise
The Vision Project results are revealing. It is clear that there is a very conservative bias in the attribution of effect of poorly understood, but potentially significant feedbacks.The following image static.visionprize.s3.amazonaws.com/Q4.jpg shows that a significant portion of the polled scientists expect a warming signal that would necessarily result in a final 2100 TCR of over 4'C.
In this case, there is indication for the Ross ice sheet dynamics that were present during MIS-31 to reoccur due to hemispheric climate changes associated with a slowdown of the MOC. adsabs.harvard.edu//abs/2010agufmpp43d..03b
This is a poorly understood dynamic that has a potentially high probability within the next 85 years. www.nature.com/ngeo/journal/v5/n3/full/ngeo1391.html
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mgardner at 03:26 AM on 19 February 2014How we know the greenhouse effect isn't saturated
DM @39 or anyone who can contribute:
I'll give it one more try; perhaps I'm not communicating very well, or I'm completely wrong in my understanding.
1) The probability of a photon being emitted depends on the temperature, which depends on the altitude.
2) The probability of that photon escaping absorption and re-radiation (meaning attentuation statistically) is dependent on the altitude and the density of CO2 above it.
So, there are some photons that escape completely, and there is some attenuation of the total transport from that level through absorption and re-radiation in the atmosphere above the level of emission. What I'm trying to find is the quantitative relationship between those effects. I don't require great certainty, just some relative values.
If this is something we don't know, that's fine, but does anyone know if we know or don't know? (No, I'm not Rumsfeld in disguise.)
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How we know the greenhouse effect isn't saturated
mgardner - Discretization of a continuous system is a useful approach for analysis, but one must always keep in mind that it is an approximation of a continuous reality.
There are certainly qualitative dividing lines that can be drawn - the top of the troposphere where convection ends and the still air of the stratosphere begins, for example. But the boundary for IR emission for each greenhouse gas (different for each) is a probabilistic one due to concentration based chances of interception - with < 50% of upward IR from slightly below that altitude escaping to space along with > 50% of upward IR from slightly above.
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Rob Honeycutt at 03:22 AM on 19 February 20142014 SkS Weekly News Roundup #7
Russ @41... You might actually take the time to read Otto 2013 before making such assertions as that they estimate CS at 2C. They state:
"Using up-to-date data on radiative forcing, global mean surface temperature and total heat uptake in the Earth system, we find that the global energy budget implies a range of values for the equilibrium climate sensitivity that is in agreement with earlier estimates, within the limits of uncertainty."
They very specifically argue that caution needs to be taken in doing exactly what you've done.
"We note, too, that caution is required in interpreting any short period, especially a recent one for which details of forcing and energy storage inventories are still relatively unsettled: both could make significant changes to the energy budget."
Otto et al are not making an argument against the current central estimates of 3C for ECS. In fact, they are saying quite clearly their estimates support those earlier figures.
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Russ R. at 03:15 AM on 19 February 20142014 SkS Weekly News Roundup #7
Tom Curtis,
Glad to see we agree on most of the issues. That leaves only two... climate sensitivity and the magnitude (and sign) of expected net costs for given amounts of warming.
Each of these is a subject weighty enough to be it's own PhD thesis, so a blog post won't really do justice to either. Plus, I'm tight on time this morning, being at work, so this will have to be brief.
Let's start with climate sensitivity (we'll get to net cost/benefits later). I have two main issues that cause me to be skeptical of arguments for high sensitivity.
1. Fundamentally, climate sensitivity is a combination of forcing, feedbacks and thermal inertia. The forcing component of increased GHG concentrations is straightforward enough, the planet's thermal inertia is a bit less straighforward (since nobody seems to know exactly when all the supposed "warming in the pipeline" should appear), but the feedbacks are most assuredly not straightforward at all. There are countless feedback mechanisms in operation at any point, some positive and some negative. The magnitude of each will vary under different climactic conditions (e.g. ice albedo feedback can be a factor only at the margin of ice extent, which is of much greater magnitude when ice sheets extend down to 45N latitude instead of 70N). I wouldn't treat the sum total of all feedbacks as a linear multiplier and extrapolate it into the future. (Which is exactly what is being done when using ECS to forecast temperature changes.)
I would make a case that climate sensitivity was both higher and lower at different points in our planet's history, and will diminish if temperatures continue to rise. Were this not the case, the planet would have experienced runaway warming (or cooling) in the past when temperatures and CO2 levels were much higher (and lower) than they are today. Instead, geological evidence points to a planet see-sawing between two relatively stable equilibrium climate conditions, which suggests high sensitivity in the middle of the range, and low sensitivity at either end of the range. We can get into this in greater detail if you like.
2. Second, the model-derived estimates of sensitivity are a function of the assumptions relating to aerosol forcings, which vary significantly. Rather than retype the whole argument, I'll link to a post that summarizes it: http://www.coyoteblog.com/coyote_blog/tag/ecs. I agree with Meyer on this specific issue, with one exception... where he estimates ECS at 1.2C, I'd go with 2.0C based on Otto et al (2013).
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gws at 02:55 AM on 19 February 2014Methane emissions from oil & gas development
Two new, contrasting studies addressing air pollution from shale areas have been published:
1. A study published by a Houston company in Science of the Total Environment found no significant impact from oil and gas extraction activities in the Barnett shale region of Texas for a selected subgroup of air toxics (the paper title is thus somewhat misleading).
2. An investigation by a 3-member consortium (Center for Public Integrity, InsideClimate News and The Weather Channel) found that, in the Eagle Ford shale region of Texas, an ever increasing amount of emission permits given to frackers and limited state oversight suggests that air toxics emissions have strongly increased in a previously low emissions region, leading to very significant impacts.
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Dikran Marsupial at 01:57 AM on 19 February 2014How we know the greenhouse effect isn't saturated
I don't think I am saying anything substantially different from KR, I was just giving the caveat that there probably isn't a clear boundary between the "opaque layer" and the "translucent layer", just that the probability of an IR photon escaping into space depends on the height at which it is emitted, and that as more CO2 is added, the higher the mean altitude will be. The boundary between the layers is equivalent to the height at which the p.d.f. starts rising quickly, but it isn't a distinct boundary. If it makes more sense to think of a p.d.f. than in terms of layers, then think of a p.d.f.
Layers are often useful in explaining concepts about the atmosphere, but they layers don't always correspond to physically distinct layers in the atmosphere (like the trophosphere and stratosphere). Like all analogies/models, there comes a point in the discussion where you need to move onto a lower level of abstraction. IIRC layered models are often used in practice (atmosphere and ocean) as it is easier to model a continuously varying atmosphere as a number of thin homogenous layers.
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mgardner at 01:42 AM on 19 February 2014How we know the greenhouse effect isn't saturated
KR and DM
Thanks; I do understand the principles as described. I guess my problem is with this language of 'layers'. It seems that even you guys aren't quite in agreement on how to characterize what's happening when you try to employ it.
The analogy I used @28 fails in a strict sense because it is restricted to radiative transport; there would have to be some other metaphor for mass effects (convection), to account for the gradient or thermocline through this upper zone of the troposphere where the action is. (I'm still hoping someone can refer me to a source that gives a higher-resolution picture of that area.)
But maybe the real source of confusion is that opacity to 'original photons' makes us think of 'layers' when there are no layers with respect to radiative transport? Or do I have that wrong?
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PluviAL at 01:13 AM on 19 February 2014Customizable Global Warming Widget Metrics
Thanks for the restatement of what would seem to be obvious but is not. I started to put this on my website, now I am motivated to finish. Just to be sure, the terms are very generous. I understand that it can even be put into an e-book. Please correct me if that is not correct. I'll read terms again, but I don't want to missinform.
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Cedders at 01:09 AM on 19 February 2014Extreme weather isn't caused by global warming
Please excuse a very basic question, prompted by the flooding here in the UK and a report on it at <http://www.metoffice.gov.uk/research/news/2014/uk-storms-and-floods>. I understand (a) CO2 etc will raise the temperature and moisture content of warm air; (b) precipitation generally occurs when warm moist air meets colder air. Is the strength of precipitation proportional to the difference in temperature between the two air masses (that causes water vapour to condense)? If so, will not the colder air mass on average also be warmer, so the differential remains roughly constant with rising SST, and precipitation is not necessarily heavier? (If the answer requires maths, please include.) Thanks.
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Dikran Marsupial at 00:30 AM on 19 February 2014How we know the greenhouse effect isn't saturated
mgardner, the top of the opaque layer is determined by the bottom of the translucent layer, rather than the translucent layer being determined by the top of th opaque layer.
Imagine we needed a layer 1km thick to be completely opaque. That doesn't mean that the atmosphere above 1km is traslucent, the next 1km layer will also be opaque. However the energy from IR emitted from the surface that is absorbed by the first opaque layer is still transfered to the one above it by conduction, convection and radiation. There could be several such saturated opaque layers from which IR cannot pass through from thelayer below, even though some of the heat energy does pass through them.
IIRC the lower atmosphere isn't completely opaque to IR, so it probably isn't best to think too strongly about it in that way, instead there is a band in the atmosphere from which the bulk of IR is radiated. Some may come direct from the surface, but not much as it is absorbed in the trophosphere, most will be emitted from the air higher up in the atmosphere, which is cold. The more CO2 you add, the higher in the atmosphere it needs to be radiated from in order not to be absorbed before it escapes. I suspect there is a probability distribution that shows the density of the height in the atmosphere from which IR photons escape; the mean increases with increasing CO2.
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How we know the greenhouse effect isn't saturated
mgardner - The opacity to IR in absorbance bands is set by the total amount of GHGs. As the concentration of GHGs increases, the atmospheric pressure where that total amount is small enough for IR to reach space decreases, meaning it occurs at a higher (and colder) altitude.
In short, as GHG concentrations increase, the bottom of the 'translucent' layer becomes IR IR absorbing, and the radiation altitude increases - the thickness of atmosphere wherein IR is captured does indeed become thicker.
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Tom Curtis at 00:05 AM on 19 February 20142014 SkS Weekly News Roundup #7
Russ @41, breaking the list down with description and your position grouped we have, to start:
(1) "In a BAU scenario GHG emissions will continue at a rate faster than can be absorbed by the biosphere, resulting in significantly and unsustainably rising concentrations"
"The evidence is abundant and highly compelling."
Agreed.(2) "The expected increase in atmospheric GHGs will result in a significant amount of warming"
"The evidence is mixed. Computer models show high sensitivity, whereas estimates derived from observations are more borderline. (e.g. Otto et al (2013) best estimate of ECS was 2.0)."
The evidence is mixed. Just addressing the evidence before the IPCC, we have OAGCCM models with equilibrium climate sensitivities ranging from 2 to 4.6 C/x2CO2 (IPCC AR5 WG1, Chapter 9, see figure 9.42). Empirically, from the instrumental record, we have values from 0.8 (Lindzen and Choi) to 5 C/x2CO2, with 8 out of 20 being below 2 C/x2CO2, and 5 being 3 C/x2CO2 or above. Empirically, from climatological constraints we have three results, all lying between 3 and 4 C/x2CO2. Also empirically, from paleoclimate, we have just one from eleven results lying below 2 C/x2CO2, and one lying above 4 C/x2CO2, with the remainder lying between 2 and 3.5 C/x2CO2. There are also six results from attempted combined assessments, of which just one gives a result below 2 C/x2CO2, with the others all lying around 2.8 to 3 C/x2CO2. Of course, these are just modal (or mean or median in some cases) values, and the confidence intervals extend widely from the quoted values. In some instances as high as 9 C/x2CO2, but in no case below 0.5 C/x2CO2. (Data from IPCC AR5 WG1 Chapter 12, Box 12.2 Fig 1)
The mixed results in this case mean we have significant error margins in estimates. It does not mean there is a contrast between the range of values from empirical estimates and model estimates as you have suggested. That is a cannard formulated by focussing on just two or three studies that have conveniently low values, and not considering the full range of available evidence.
Given this, whether guided by empirical studies or the models, it is difficult to arrive at an estimate ECS range much different from the IPCC estimate that "...ECS is likely in the range 1.5°C to 4.5°C with high confidence, extremely unlikely less than 1°C (high confidence) and very unlikely greater than 6°C (medium confidence)."
I look forward to your ingenious argument that policy makers should ignore the assessment of experts on the topic, looking at the full range of evidence in favour of the opinion of non-experts looking at two or three cherry picked studies. Alternatively, I will be pleased to hear that you accept the IPCC assessment of climate sensitivity, and with it the likely temperature consequences for BAU.
(3) "The warming and related changes (sea level rise, etc.) will occur over time periods that are meaningful relative to human lifespans"
"The evidence is compelling."
Agreed.
(4) "The changes will meaningfully impact ecosystems, economies, societies and individuals (considering both positive and negative impacts)"
"The evidence is compelling."
Agreed.
(5) "The net cost / benefit of the expected changes will be negative"
"The evidence is conditional. (Modest amounts of warming would be beneficial, greater warming would likely be negative. http://www.skepticalscience.com/copenhagen-consensus-center-climate-change-costly.html)"
Actually, the evidence is more equivocal than conditional. From the article we link to we find this graph, showing the cost estimates for the three major economic models for the costs of climate change:
As you can see, just one of three models shows benefits for small amounts of global warming, with the other two showing costs at all levels of warming. Claiming the "evidence is conditional" implicitly assumes that model is correct, in contrast to the other two. I do not see how that can be justified. As with the empirical climate sensitivity results, it looks a lot like choosing to pay attention only to those studies which give you the result you like.
Of course, I am inclined to give little weight to all three. That is because:
a) The models are not able to include a number of known and significant costs due to lack of data;
b) The models assume a prescribed economic growth, and therefore cannot include the costs of any reduced economic growth either due to global warming, or due to mitigation measures. As alterations in the rate of economic growth are likely to have far more effect on total costs and benefits than factors covered in the models, that renders them of dubious value. I should note that several global warming related weather disasters have already significantly impacted economic growth.
c) The models are unable to realistically cost the effects of loss of major eco systems, such as the Arctic, the Great Barrier Reef (both near certainties) and potentially the Amazon Rainforest. That means the costs they show are, in effect, best case scenarios rather than realistic estimates of the actual costs of global warming.
It seems a general feature of these economic models that they show little bearing to the kinds of impacts scientists tell us certain temperatures will have. It is telling that the FUND model, for example, shows only a loss of 7.5% of GDP at temperatures which scientists tell us will make the tropics seasonally uninhabitable for part of the year. The situation appears to be that the scientists cannot tell us the likely economic cost of global warming because they do not have the economic training necessary; but the economists cannot tell us either because global warming will likely take us to conditions so far outside normal conditions that the economists do not in fact have tools to deal with it. The general effect is that the uncertainty is much larger than indicated by the economic models, and while this allows the possibility of overall economic benefits to relatively high temperature increase (3 C), it also allows the possibility of catastrophic results at quite low levels of temperature increase (2, or even 1.5 C).
I will leave discussion of the policy issues until you have had a chance to respond on the science (and economics) issues.
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mgardner at 00:03 AM on 19 February 2014How we know the greenhouse effect isn't saturated
@32 Dikran Marsupial
"As CO2 is added, this thickness decreases and so the bottom of the layer becomes higher."
Perhaps I really do need to have a picture drawn to have this make sense. Let's say there's an altitude h which represents the top of the top opaque layer O. Above it there is a translucent layer, Lt1. For the bottom of Lt1 to move up, the top of O must also move up, but if it is already saturated, then adding CO2 should have no effect on O; its thickness remains constant. It seems more logical that the top of Lt1 moves down in altitude.
What effect am I missing?
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Dikran Marsupial at 23:55 PM on 18 February 2014How we know the greenhouse effect isn't saturated
In short, the Earth's energy budget is determined by the balance of incoming and outbound radiation, so rather than thinking about what happens to the IR radiation that is emitted by the surface, you need to think of where the IR that actually does escape the Earth comes from. The key is to think about the IR radiation that isn't absorbed by CO2, rather than the IR that is.
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How we know the greenhouse effect isn't saturated
@30:
Actually, Venus gets even less solar energy than the Earth does!
Most sources I’ve found state that Venus’ albedo is about 75%, while the Earth’s albedo is 30%.
Taking into account the 91% higher insolation because of the shorter distance to the sun, the net result is that Venus receives about 32% less solar energy per unit of area than we do.If Venus had no greenhouse effect at all, its average temperature should be about -40oC, or more than 500oC colder than it really is! (Assuming the solar energy was evenly distributed. The temperature variations caused by the day-night cycle and different latitudes would lower the average temperature even more)
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Dikran Marsupial at 23:42 PM on 18 February 2014How we know the greenhouse effect isn't saturated
gws wrote: "on your 1): see the post by Glenn @24: convection is contributing to heat transport from the surface to the atmosphere, but not the majority; that is still IR radiation"
I suspect you have misunderstood Glenn's post, IR radiation transfers heat from the surface to the layer of air immediately above the surface, where it is absorbed. Convection then transfers this heat to the bulk of the trophopshere.
"but "moving up" is not meant literally"
No, the height at which IR is radiated into space really does move up as more CO2 is added to the atmosphere. Think of the thickness of the layer required to obtain a certain level of opacity at the top of the atmosphere. As CO2 is added, this thickness decreases and so the bottom of the layer becomes higher. The bottom of this layer is then cooler (due to the lapse rate) and so emits less IR, creating the energy imbalance.
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mgardner at 23:29 PM on 18 February 2014How we know the greenhouse effect isn't saturated
@29 gws
Thanks for your response, but I think you are misreading Glenn and the others. See Tom @21.I also think you are missing the point on the altitude question.
I'm hoping those guys can turn their attention to this when they are done pummeling Russ. I would have lost patience long ago.
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michael sweet at 21:14 PM on 18 February 20142014 SkS Weekly News Roundup #7
Russ,
I am amazed that you want to continue. Did you read my post at 40? As Tom pointed out there were many more hot all time records during the time you are claiming it was cold. The winter is almost over so few additional all time records will be set, the summer has not started yet.
You said:
"Global warming? Are you serious? It's below freezing in Atlanta"."So what if it's hot in Australia. That's only a local weather event. Weather is not climate."
I am using the 2012 US weather instead of Australia, the Australia data are comparable to the US weather. In 2014, Georgia had it's 4th coldest January. It was the coldest state in the USA. This is not exceptional at all in a 120 year record. In March, 2012, 25 states had their all time heat records. There were 21 instances where the cold temperature at night was hotter than the previous high temperature ever recorded during the day. In a movie you would not believe it.
Do you really want to argue that a single state fourth coldest is equivalent to 25 all time record hot events? That is just the start. Here is the 2012 annual report.
In 2012 19 states recorded their all time record hot year, most were extreme hot, much hotter than previous years. 25 additional states had a top 10 year for a total of 45 out of 48 states. The remaining three were 11, 12 and 30th hot. The temperature was 1.0F hotter than the previous hot record from 1998, an unbelievable amount higher, these records are usually broken by hundredths of a degree. Billions of dollars of damage was recorded. Your pitiful daily records cannot be compared to this record breaking heat. It is expected that with thousands of locations that some records will be broken every year. It is becoming tedious to transfer these sad records from the NCDC archve, read the rest yourself.
Your assertion that your cold records are comparable to the heat records I have cited is absurd. I could match these records easily with the heat records from Australia. Your assertion that there is an equivalence between your "cold in Atlanta" and the scorching heat suffered across the country in 2012 is astonishing. I am stunned that anyone could write that with a straight face.
If you consider that one state fourth coldest for a month is equivalent to 25 hottest ever years shattering all previous records that we will have to end our discussion.
You are undoubtedly also ignorant about the economic effects of these heat waves. I will not waste my time documenting them for you since you have already made up your mind and are not open to reviewing the actual data. Read the comic I linked in 35.
God save us from this deliberate ignorance.
John Hartz: thanks for the ice water.
Moderator Response:[DB] You have made your point. That Russ refuses to concede does not overturn the fact that you have provided the strongest case. It is time to move on.
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AndrewDoddsUk at 20:44 PM on 18 February 2014How we know the greenhouse effect isn't saturated
Ultra Basic Rebuttal : Venus.
Interesting factoid: because Venus has such a high albedo, both Earth and Venus have about the same incoming solar radiation. But Venus is several hundred degrees hotter.
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Klapper at 17:31 PM on 18 February 2014Unprecedented trade wind strength is shifting global warming to the oceans, but for how much longer?
@HK #73:
Graph legend is in error running delta's are 15 year not 20.
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Klapper at 17:24 PM on 18 February 2014Unprecedented trade wind strength is shifting global warming to the oceans, but for how much longer?
@HK #73:
I've analyzed your results using a rolling delta OHC anomaly using data from these sources:
In your analysis, which you don't describe or source explicitly you compared a 37 year delta, to a 17 year (exclusive), to an 8 year (overlapping). I'm not sure what the significance of these periods are as you don't elaborate.
I used a rolling 15 year delta OHC (NODC ZJ anomaly, creating the 700-2000m delta from the 0-2000 and 0-700 datasets. Following is a graph of the results:
As you can see from the graph, there were 15 year periods ending in the early 70's where the deep ocean heat gain was over 50% of the shallow ocean heat gain; certainly more than the last 15 years where the % of deep ocean is only +35% or so. I'm not sure how meaningful this comparison since the data are very sparse for the deep ocean, but I don't agree there has been an unprecendented amount of heat gain by the deep ocean relative to the shallow in recent years. Your theory might still be correct if you compared 500 to 300 metre data, or some other depth ranges, but what I have easy access to does not have the resolution.
Moderator Response:[RH] Hotlinked URL's that were breaking page formatting.
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Klapper at 16:24 PM on 18 February 2014Unprecedented trade wind strength is shifting global warming to the oceans, but for how much longer?
@Michael Sweet #96:
My calculations weren't peer-reviewed, but then neither was anything in HK's post. In fact I used data used to produce all his graphs come from. However, that was on a different computer a long way's from me now and I note that currently links to ascii data on pentadal data seem to be broken, plus I can't find the composited pentadal data I used anyway, only gridded data.
I'll try to get the excel file sent from the computer's owner and post my graphs and numberical results.
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Russ R. at 15:08 PM on 18 February 20142014 SkS Weekly News Roundup #7
Dikran Marsupial,
"I didn't express any desire to debate each of the 12 questions, just the first one,..."
My apologies, I interpreted your initial question as a prelude to a point-by-point debate over each of the 12 questions... something that would take much more time than I could hope to have. Hence my desire to stay focused on the Cook et al paper.
Going back to your question from the other thread (I'm not sure if it's poor etiquette to cross threads like this, but if it is, I'll blame you for doing it first).
"Russ R O.K. lets take the first one, what do you think the uncertainty is on the subject of GHG emissions in a "business as usual" scenario? Do you think they are going to be substantially less than RCP 8.5? If so, please explain why."
If there were no uncertainty, only one scenario would necessary. Personally, I believe that the RCP6.0 scenario is far more plausible than RCP8.5 for two reasons: the relationship between population growth vs. economic growth, and the relative cost of fossil fuels vs. alternatives.
1. As nations industrialize, their fertility rates plummet. (See every developed country on the planet.) I don't think it's likely we'll see a scenario where economies continue to grow rapidly and populations continue to grow rapidly at the same time.
2. 10 years ago oil cost $30/bbl and a solar panel or geothermal system cost a fortune. Two things have happened in the past decade... technologies have advanced bringing down the cost of renewable, carbon-neutral energy, while non-renewable resources have become more scarce, driving up the market price of of fossil fuels. (I'm in the process of converting my own home heating from electric to biomass, simply beause it costs less.) I don't expect either trend to reverse.
That said, I believe that even RCP6.0 could be sufficient for a "serious problem" depending on other factors.
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John Hartz at 15:03 PM on 18 February 20142014 SkS Weekly News Roundup #7
All: It appears that this discussion will continue. Please keep it civil.
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Bob Lacatena at 14:47 PM on 18 February 2014Customizable Global Warming Widget Metrics
I'm afraid not. It wouldn't be an effective metric. The Tsar bomb is about 1,500 times the energy of the Hiroshima bomb, which means the counter would "tick" once every 375 seconds, or a little less than once every six minutes. That's just not an effective display.
Choosing an effective metric is challenging. It can't roll the counter either too quickly or too slowly, and it must also be something which is somehow within the range of human experience (not firsthand, obviously).
Ideas for metrics are welcome, but to be effective a person must be able to visualize it, and it must also represent a value between 1014 and 5*1014 Joules per second. Anything outside of that range doesn't make an effective counter.
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