There’s no predicted hotspot in the upper troposphere, and cooling of the stratosphere is now the new indicator. New paper finds “greenhouse cooling” of the stratosphere over past 52 years
A new paper published in Atmospheric Chemistry and Physics finds the stratosphere of the Northern Hemisphere cooled over the past 52 years due to the increase of greenhouse gases. The paper suggests that stratospheric cooling is a “more suitable” signal of anthropogenic global warming than trying to find a mid-troposphere hot spot (which was previously considered to be the definitive “fingerprint” of man-made global warming, but still has not been found despite millions of weather balloon and satellite observations over the past 60 years):
According to the authors,
A major open question that still remains to be answered is whether the stratosphere can be considered as a more suitable region than the troposphere to detect anthropogenic climate change signals and what can be learned from the long-term stratospheric temperature trends. Indeed, the signal-to-noise ratio in the stratosphere is, radiatively speaking, more sensitive to anthropogenic GHG forcing and less disturbed by the natural variability of water vapour and clouds when compared to the troposphere. This is because (a) the dependence of the equilibrium temperature of the stratosphere on CO2 is larger than that on tropospheric temperature, (b) the equilibrium temperature of the stratosphere depends less upon tropospheric water vapour variability and (c) the influence of cloudiness upon equilibrium temperature is more pronounced in the troposphere than in the stratosphere where
the influence decreases with height (Manabe and Weatherald,
1967). Furthermore, anthropogenic aerosols are mainly
spread within the lower troposphere (He et al., 2008), and
presumably have little effect on stratospheric temperatures.
Another open question is whether the lower stratosphere
has been cooling in the time since a reasonable global network
became available, i.e. after the International Geophysical
Year (IGY) of 1957–1958. Such a long-lasting cooling
from the 1960s until today would need to be explained.
To what extent are the cooling trends in the lower stratosphere
related to human-induced climate change? Has the
cooling been accelerating, for instance at high latitudes in
winter/spring due to ozone depletion? Has it been interrupted
by major volcanic eruptions and El Niño events (Zerefos et
al., 1992) or large climatological anomalies.
This study addresses those questions and presents a new
look at observed temperature trends over the Northern Hemisphere from the troposphere up to the lower stratosphere in a search for an early warning signal of global warming, i.e. a
cooling in the lower stratosphere relative to the warming in
the lower atmosphere.
Further, many warmists claim any source of warming including solar activity, cloud changes, ocean oscillations, etc. would cause a mid-troposphere “hot spot” and overlying cooling of the stratosphere, and would not necessarily be a signal or “fingerprint” of anthropogenic global warming.
The authors also find from 1958-1979 the lower troposphere either slightly cooled or remained unchanged, followed by significant warming 1980-2010:
From 1958 until 1979, a non-significant trend (0.06 ± 0.06 °C decade−1 for NCEP) and slightly cooling trends (−0.12 ± 0.06 °C decade−1 for RICH) are found in the lower troposphere. The second period from 1980 to the end of the records shows significant warming (0.25 ± 0.05 °C decade−1 for both NCEP and RICH). Above the tropopause a significant cooling trend is clearly seen in the lower stratosphere both in the pre-1980 period (−0.58 ± 0.17 °C decade−1 for NCEP, −0.30 ± 0.16 °C decade−1 for RICH and −0.48 ± 0.20 °C decade−1 for FU-Berlin) and the post-1980 period (−0.79 ± 0.18 °C decade−1 for NCEP, −0.66 ± 0.16 °C decade−1 for RICH and −0.82 ± 0.19 °C decade−1 for FU-Berlin).
Thus, although it appears the stratosphere may be cooling, and this could be due to increased greenhouse gases, there is still no evidence of a mid-troposphere “hot spot” predicted by climate models. The slight cooling to no change of lower tropospheric temperatures from 1958-1979 found by this paper also don’t support AGW theory since CO2 levels rose ~7% during that period.
The paper:
Atmos. Chem. Phys., 14, 7705-7720, 2014
www.atmos-chem-phys.net/14/7705/2014/
doi:10.5194/acp-14-7705-2014
C. S. Zerefos, K. Tourpali, P. Zanis, K. Eleftheratos, C. Repapis, A. Goodman, D. Wuebbles, I. S. A. Isaksen, and J. Luterbacher
Abstract
This study provides a new look at the observed and calculated long-term temperature changes from the lower troposphere to the lower stratosphere since 1958 over the Northern Hemisphere. The data sets include the NCEP/NCAR reanalysis, the Free University of Berlin (FU-Berlin) and the RICH radiosonde data sets as well as historical simulations with the CESM1-WACCM global model participating in CMIP5. The analysis is mainly based on monthly layer mean temperatures derived from geopotential height thicknesses in order to take advantage of the use of the independent FU-Berlin stratospheric data set of geopotential height data since 1957. This approach was followed to extend the records for the investigation of the stratospheric temperature trends to the earliest possible time. After removing the natural variability [it is impossible fully distinguish natural variability from anthropogenic] with an autoregressive multiple regression model our analysis shows that the period 1958–2011 can be divided into two distinct sub-periods of long-term temperature variability and trends: before and after 1980. By calculating trends for the summer time to reduce interannual variability, the two periods are as follows. From 1958 until 1979, a non-significant trend (0.06 ± 0.06 °C decade−1 for NCEP) and slightly cooling trends (−0.12 ± 0.06 °C decade−1 for RICH) are found in the lower troposphere. The second period from 1980 to the end of the records shows significant warming (0.25 ± 0.05 °C decade−1for both NCEP and RICH). Above the tropopause a significant cooling trend is clearly seen in the lower stratosphere both in the pre-1980 period (−0.58 ± 0.17 °C decade−1 for NCEP, −0.30 ± 0.16 °C decade−1 for RICH and −0.48 ± 0.20 °C decade−1 for FU-Berlin) and the post-1980 period (−0.79 ± 0.18 °C decade−1 for NCEP, −0.66 ± 0.16 °C decade−1 for RICH and −0.82 ± 0.19 °C decade−1 for FU-Berlin). The cooling in the lower stratosphere persists throughout the year from the tropics up to 60° N. At polar latitudes competing dynamical and radiative processes reduce the statistical significance of these trends. Model results are in line with reanalysis and the observations, indicating a persistent cooling (−0.33 °C decade−1) in the lower stratosphere during summer before and after 1980; a feature that is also seen throughout the year. However, the lower stratosphere CESM1-WACCM modelled trends are generally lower than reanalysis and the observations. The contrasting effects of ozone depletion at polar latitudes in winter/spring and the anticipated strengthening of the Brewer–Dobson circulation from man-made global warming at polar latitudes are discussed. Our results provide additional evidence for an early greenhouse cooling signal in the lower stratosphere before 1980, which appears well in advance relative to the tropospheric [assumed] greenhouse warming signal. The suitability of early warning signals in the stratosphere relative to the troposphere is supported by the fact that the stratosphere is less sensitive to changes due to cloudiness, humidity and man-made aerosols. Our analysis also indicates that the relative contribution of the lower stratosphere versus the upper troposphere low-frequency variability is important for understanding the added value of the long-term tropopause variability related to human-induced global warming.
(this post via the HockeySchtick)
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About that missing hot spot in the upper troposphere
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GregL says:
August 4, 2014 at 8:57 am
==
Question: If I remember the physics correctly from the radiative transfer classes I took (I am not a radiation physics person), is it not true that if you have a gas that is a preferred absorber/emitter of radiation at certain wavelengths whose concentration decreases with height, then there will be some altitude/layer at which an increased overall concentration of it will cause a net increase of radiation out to space? If I remember correctly, this is because the decreasing concentration of it past a certain level means that more absorbed/re-emitted radiation in the preferred wavelengths will then be able to escape preferentially towards space as it will encounter fewer of the absorbing molecules in that direction. In other words, a heat trapping gas with decreasing concentration with height would be expected to have some higher level in the atmosphere with a net cooling effect owing to the vertical concentration gradient. Anyway, is this correct? This is what I remember from radiative transfer equations courses I took 20 years ago, but I may be remembering it incorrectly.
==
Agreed, per the radiative transfer properties there are 4 mechanisms of concern:
– Absorption of photons by GHGs in the appropriate frequency range. The result is an excited GHG molecule
– Spontaneous emission of photons by excited GHG molecules
– Molecular collisions which can excite a GHG molecule a small percentage of the time
– Molecular collisions with will de-excite an excited GHG molecule almost 100% of the time
In dense air (near the surface), GHG molecules tend to absorb photons then that excitation energy is converted to kinetic energy by a collision before it is spontaneously re-emitted. Thus the theory call for localized warming as the kinetic energy increases.
In less dense air (the stratosphere), GHG molecules will still experience millions or hundreds of millions of collisions per second (instead of billions). Some small percentage of those will excite the GHG molecule. Since the air is less dense there is enough time between collisions for spontaneous photon emission to de-excite the GHG molecule. Half of those photons will move away from Earth and into space. The end result is a net cooling.
Thus the radiative transfer model predicts warming at low elevation and cooling at high elevation.
For most sceptics I think there is little doubt in the basic radiative transfer physics, thus this paper supports something that both warmers and many/most sceptics agree on, so it is of little value except to confirm already agreed to physics.
If there are sceptics that believe that the radiative transfer physics itself is fundamentally flawed and does not occur, then this paper is one they should address.
From my understanding of the sceptic / warmer argument, the big question is what the sensitivity of the lower atmosphere is to CO2 warming. This paper has zero to say about that and as such is not relevant to the argument.
The implication here is that the troposphere grabs most of the incoming energy robbing the stratosphere of its share cooling it down with the assumption seeming to be that CO2 is causing that. A heat trapping troposphere might explain why the stratosphere is cooling down but that says nothing about why the troposphere is trapping heat, much less that CO2 is causing it, much much less that it’s the anthropogenic CO2 that’s doing it. We already knew the troposphere has warmed up so what does this study contribute to our understanding? And why does it have anything to do with all the models being completely wrong about the hotspot?
JohnWho: I’m so confused!
catweazle666 I don’t suppose the stratosphere could possibly be cooling because we’re around half way through the negative – ie cooling – phase of the ~60 year cycle
Claude Harvey says: So once again, “cooling proves warming”.
etc etc…..
Hey guys, ease up on the heavy sarcasm before thinking or reading the subject.
Stratosphere cooling usually acompanies tropo warming. If stratosphere blocks incoming solar, it warms, cutting down what gets to lower climate system, which cools.
“the evidence indicating persistent cooling over the 1952-2012 period (60 years) would seem to undermine this idea. ”
Well, the overall stratospheric cooling trend is clearly evident and consistent with radiative forcing estimates.
However, ‘persistent’ is probably not an apt adjective to describe the stratospheric cooling.
For the ten years before El Chichon, there is a strat warming trend.
For the years between El Chichon’s resolution and Pinatubo, there is a strat warming trend.
For the years since Pinatubo, there is cooling in the upper strat and no change in the lower strat.
By no means does that preclude CO2, but most of the cooling is actually observed as a step function from before to after volcano eruption:
http://1.bp.blogspot.com/-qBLJ6MR2dtk/TdUpDF5VdsI/AAAAAAAAADo/cDQqeUogo_Y/s1600/StratCoolingPlot_2011.png
Climate Weenie says:
August 4, 2014 at 9:59 am
Whoops posted without reading the last few posts. I see that CO2 causing stratospheric cooling has been explained . . . but it has nothing to do with anthropogenic CO2.
Steve,
Better fingerprint of what, Steve? More CO2 or anthropogenic global warming?
Lying by context is still lying!
John G,
It has plenty to do with anthropogenic CO2 but nothing to do with anthropogenic global warming. The myth that the stratosphere cools because CO2 traps lower IR is one of the worst myths in the entire debate and one that is wrongly believed by both sides thanks to a bad post by Gavin in 2004.
OH dear, more straight line science. When will these guys get beyond “trend” fitting everything.
Let’s look at TLS ( temp of lower stratosphere ) without a straight line to guide the eye and mind:
Let’s also drop the broken climate models , that will not tell us anything useful.
Observational data:
http://climategrog.wordpress.com/?attachment_id=902
Yes signal to noise is a lot better in stratosphere and we can see straight away what is causing the cooling. Volcanoes.
0.5K drop after each event.
Whether this is changes in ozone, which is reckoned to be reduced after Mt P. or whatever process that removes the volcanic aerosols also removes anthropogenic pollution, the cause of the changes seems to be clearly attributable to punctual events, not a long term CO2 driven decline.
“The myth that the stratosphere cools because CO2 traps lower IR is one of the worst myths in the entire debate and one that is wrongly believed by both sides thanks to a bad post by Gavin in 2004.”
So, a radiative model of an increased CO2 atmosphere will yield reduced net longwave at the troposphere.
That being the case, the layers above experience less energy.
Which part is a myth? and why?
@gregfreemyer: Thanks! I had thought it had been something like this. Others prior to your post were getting at this answer as well, though not directly.
To everyone else: Please avoid bad physics and knee-jerk reactions. This entire climate science issue is badly politicized – a fact beyond dispute – but please don’t contribute to it immediately based just upon paper titles. The central real science issues are these:
1) What is the water vapor feedback as a forcing response to the small heating that occurs directly as a result of increased CO2? If it exists, it would be a powerful amplifier, but also imply a highly unstable climate system that should respond to any warming (hence why did the earth’s temp not “run-away” during the warmer period of the Holocene Maximum?). Given the importance of this and other highly nonlinear reactions to forcing, we truthfully do not fully know how this works and are highly unlikely to model it correctly at present knowledge levels. This should be the proper skeptical position as none of this is in dispute, and claims of certainty as to how these forcings interact is clearly junk science at present.
2) How much of warming during the 20th century is “real”, versus how much was thermometer-adjustment errors and thermometer siting/land-use-change issues?
3) What would be the present “global temperature” (a terrible and hard to define metric for atmosphere/ocean heat content) absent forcing driven by increased CO2 levels? A related question is what amount of the increased CO2 levels is directly attributable to the sum of all anthropogenic effects (emissions, land use changes, etc)? Is it even possible to know this without being a deity that could create a replicate earth complete with no humans?
Steven Mosher says: “Stratospheric cooling is the better fingerprint.”
Yes, but whose ? Not mine and yours.
The best thing to do with fingerprints is to look at them and see who’s they are before arresting the usual suspects because you have “a fingerprint”. 😉
in their abstract the authos say they filtered the data to remove natural variation.
How did they filter out natural variation? how do you tell signal from noise if you dont understand the statistical properties of the noise?
The first trend has an error rate as large as the trend (0.06 +- 0.06) and for the second trend it is half the trend. I’ll say it again. When the error rate is a significant percentage of the answer (trend), the theory cannot be proven. Statistics that take numbers and average them and have a large or significant percentage error rate are guesses, not facts. My whole problem with AGW is that. I mean in physics we have the Heisenberg Uncertainty Principle, The more precise the supposed average, the less likely they are to be correct due to the variations in equipment, calibration, location, human error, etc.
@Bill H. says:
August 4, 2014 at 9:49 am
Bill,
It’s a simple matter that the AGW theory says there should be a hotspot in the mid-troposphere and there ain’t. This observation means the AGW theory is invalid because the observation doesn’t match the results.
In lieu of snarky comments, I’ll wait for a theory which agrees with observations.
“in their abstract the authors say they filtered the data to remove natural variation.”
This is second mistake after the straight line fitting. They have already decided what the natural and ‘unnatural’ signal are. The result is induced from their preconceived ideas.
There is no “linear trend”, it’s two steps. It’s natural. You need to start by looking at the data _before_ drawing the straight lines that will guide the eye and prejudice the analysis.
Copied and pasted from their abstract:
The data sets include the NCEP/NCAR reanalysis, the Free University of Berlin (FU-Berlin) and the RICH radiosonde data sets as well as historical simulations with the CESM1-WACCM global model participating in CMIP5. The analysis is mainly based on monthly layer mean temperatures derived from geopotential height thicknesses in order to take advantage of the use of the independent FU-Berlin stratospheric data set of geopotential height data since 1957. This approach was followed to extend the records for the investigation of the stratospheric temperature trends to the earliest possible time. After removing the natural variability with an autoregressive multiple regression model our analysis shows that the period 1958–2011 can be divided into two distinct sub-periods of long-term temperature variability and trends: before and after 1980.
=============
So if they are using reanalysis “data” and mixing in a CMIP5 GCM output, how is that not self fullfilling for a priori assumption on GHG effects?
Tom T says:
August 4, 2014 at 10:20 am
Right I should have said anthropogenic warming . . . I certainly fell for the implication that somehow the troposphere was stealing the stratosphere’s heat causing it to cool but even if that was true it wouldn’t imply CO2 had anything to do with it.
Next we need to look at TOA changes in reflected SW and compare to TLS.
http://climategrog.wordpress.com/?attachment_id=955
There’s one of those fingerprints again.
Less SW getting scattered back into space means more making it into the climate system. It’s not heating the stratosphere ( since it’s cooling ) so it must be making it into the lower climate system.
That is a least one factor that caused ‘global warming’ between 1980 and 2000: the OMG years.
Climate Weenie,
Its entirely a myth.
The stratosphere cools because of the presence of O3. The presence of O3 makes the stratosphere considerably warmer than the tropopause below it can considerably warmer than it would be under just under long wave forcing. Therefore, added CO2 increases the stratospheres ability to radiate the heat that the O3 is absorbing but it doesn’t significantly increase its ability to gain heat because the lion’s share of the stratospheric heat content comes from O3 absorbing SW radiation. Were there no O3 or little O3 and the atmosphere un-stratified then CO2s absorptive effects would dominate all the way to the top of the atmosphere. This is the greenhouse gas effect and it does not cool the stratosphere.
gregfreemyer says:
August 4, 2014 at 10:05 am
“GregL says:
August 4, 2014 at 8:57 am
Agreed, per the radiative transfer properties there are 4 mechanisms of concern:
– Absorption of photons by GHGs in the appropriate frequency range. The result is an excited GHG molecule
– Spontaneous emission of photons by excited GHG molecules
– Molecular collisions which can excite a GHG molecule a small percentage of the time
– Molecular collisions with will de-excite an excited GHG molecule almost 100% of the time
In dense air (near the surface), GHG molecules tend to absorb photons then that excitation energy is converted to kinetic energy by a collision before it is spontaneously re-emitted. Thus the theory call for localized warming as the kinetic energy increases.
In less dense air (the stratosphere), GHG molecules will still experience millions or hundreds of millions of collisions per second (instead of billions). Some small percentage of those will excite the GHG molecule. Since the air is less dense there is enough time between collisions for spontaneous photon emission to de-excite the GHG molecule. Half of those photons will move away from Earth and into space. The end result is a net cooling.
Thus the radiative transfer model predicts warming at low elevation and cooling at high elevation.”
Notice that you have introduced a claim that does not belong to radiation theory alone. You appeal to the relative density of the air. There is not a lot of water vapor in the stratosphere. There is a huge amount of water vapor in the troposphere. So, your explanation appeals to factors that fall outside of radiation theory. Radiation theory alone does not imply that radiation passing through a dense cloud of CO2 will cool the area above it that is less densely populated with CO2.
The important point here is that the good reputation of radiation theory cannot be used to support the claim that high concentrations of CO2 in the troposphere cool the stratosphere. Some other claim must be added. Maybe a claim about relative concentrations of water vapor. Your rather generic claim is about the relative density of air at various heights.
Now I’m really sad.
Of all people fricking Connolley is the only one who has this right.
What is the world coming to!!!!
Tom T. and Jim Steele: Thank you for your inputs. They are both clear. They also seem to be orthogonal, which is okay.
What I haven’t teased out is the mechanism Tom T. implies. The cooling results from a reduction in the amount of (dare I say it) back radiation–presumably longwave–that reaches the stratosphere?
Greg Goodman says:
August 4, 2014 at 10:35 am
Excellent post. The mystery continues. Why is it that Alarmists simply cannot get their minds around the concept of natural variation?
Climate Weenie says:
August 4, 2014 at 10:27 am
“Which part is a myth? and why?”
Lots of myths…
First being that its evidence of global warming.
Second being that it can even be used as relevant information.
As you yourself say the model that is correct has nothing to do with global warming. Just because the model is correct doesn’t much of anything in the debate…. It kind of like saying that a model showing the reduction of water in a lake proves global warming because some other models shows that global warming would reduce the lake level. All the time however someone’s just letting water out of the spillway.
This paper is nothing but a post facto excuse to try to shift the goal posts so that once again well known natural effect = doom.
Where is the comparable 2000 to 2014 graphic? Is the graphic a static picture of what was and was supposed to be in 1999? What does it look like in 2013-2014?