My last post on Record Hot or Not stimulated some good discussion with the conformist warmists bringing some useful information to the debate. In particular, they drew attention to RATPAC and how this data, in their opinion, verified the surface thermometers, confirming 2015 as the warmest year since records began. So I decided to take a look. It is indeed another great data set that I’ve heard very little about and it certainly should not be ignored.
RATPAC stands for Radiosonde Atmospheric Temperature Products for Assessing Climate – are you any the wiser? It is in fact a global temperature model based on measurements made from weather balloons. RATPAC therefore provides vertical temperature gradients through the atmosphere and offers the opportunity to compare with the surface thermometer and satellite based analyses. There are 85 recording stations with good global cover (Figure 1) and data begins in 1958.
This post is a first look at the data intended to raise questions and issues for discussion. Part 1 is simple data description and presentation with a few key (and very interesting) observations. The second part (that will hopefully follow later in the week) compares RATPAC with surface thermometers and satellites.
Figure 1 Map showing the distribution of 85 RATPAC monitoring stations. A curious thing, I could not find a copy of a RATPAC map on the web. There was however this list of stations with lat lon and my friend Luis de Sousa kindly made this map.
RATPAC is managed by NOAA and the main “portal” is here. Documentation is sparse, for example you’d think they would provide a map. We have to look at the photo caption to learn:
… a hydrogen-filled balloon that will carry a radiosonde up in the air to measure temperature, humidity, and atmospheric pressure and transmit the data back to a ground station.
And the text says…
RATPAC data come from 85 stations with near-global coverage. NCEI provides data on 13 atmospheric pressure levels: the surface, 850, 700, 500, 400, 300, 250, 200, 150, 100, 70, 50, and 30 mb. Where available, data begin in 1958 and extend through the present. Some of the 85 stations have discontinued observations since the 1990s, and not all stations have observations at all levels.
Seasoned surface temperature analysts will be familiar with issues like this…
The temporal homogeneity of many radiosonde time series is questionable due to historical changes in instruments and measurement practices.
Two products are provided RATPAC A and B. NOAA recommend using the former and I have not looked into B at all. All the data presented here are RATPAC A and this is how NOAA describes the data:
RATPAC-A contains adjusted global, hemispheric, tropical, and extratropical mean temperature anomalies. From 1958 through 1995, the bases of the data are on spatial averages of LKS adjusted 87-station temperature data. After 1995, they are based on the Integrated Global Radiosonde Archive (IGRA) station data, combined using a first difference method (Free et al. 2004). For analyses of interannual and longer-term changes in global, hemispheric, and tropical means, the team recommends use of RATPAC-A since it contains the most robust large-scale averages.
All this sounds too familiar. I fully endorse the need to apply corrections to data where the physical need is identified and understood. But I’m afraid that NOAA and NASA have undermined their own credibility by continually adjusting surface temperature records. When sceptical scientists read here that temperatures have been adjusted they will wonder by how much and why.
The data were easy to download from this link provided by NOAA. It contains three files. I have looked at “RATPAC-A-annual-levels.txt” that gives global average T anomalies for 13 levels defined on atmospheric pressure (Figure 2) and “RATPAC-A-year-to-date-layers.txt” that provides the averages for three layers – 1) the Lower Troposphere 2) the Upper Troposphere and lower Stratosphere and 3) the Stratosphere. Data for individual stations and raw temperatures are not obviously available.
So lets get straight to the point and have a look at the data:
Figure 2 There is clearly a lot going on here. The convergence of all profiles in the interval 1973 to 1993 suggests this is approximately the datum period used to calculate anomalies. And clearly something dramatic has happened post-1992. To get a better picture of what is going on the following charts show the traces for the three layers used in the merged data sets.
Before proceeding I’m sure readers will appreciate some guidance converting milli bars (mb) to height. I’m an old fashioned Brit and still understand height measured in feet better than meters and so only give feet here. This web site was used for the conversion.
850: 4,779 ft (Ben Nevis)
300: 30,053 ft (Mount Everest)
100: 51,806 ft
50: 63,367 ft
Figure 3 The 5 levels between 850 and 300 mb are highly congruent and show a familiar warming pattern. Spikes associated with the 1998 and 2010 el Ninos are clear to see. Is that a pause 1958 to 1978 and again 1998 to 2015? Or is it a single warming trend? Remember that each level is successively colder than the one below and these absolute differences are removed by the normalisation procedure. These levels encompass most of the troposphere. The surface measurements are not included because NOAA do not include the surface in their layer models and as we shall see there are issues with the surface data. Amongst other things, not all surface stations are at sea level.
Figure 4 I am skipping over the 300 to 100 layer for the moment, the reason for this will become clear when we get to it in Figure 5. The 100 to 30 mb layer is in the stratosphere and has some of the most interesting information.
The key observations:
- There is a very distinct and large overall cooling trend of about 2.25˚C from 1958 to 2015.
- The three large volcanic eruptions of Agung, El Chinon and Pinatubo resulted in pronounced warming spikes in the stratosphere.
- Pre-Pinatubo these 4 layers were fairly congruent but post Pinatubo the 100 mb level defines a separate trend.
- The Agung eruption did not warm the 100 and 30 mb levels but all 4 levels were warmed by the El Chinon and Pinatubo eruptions.
- Post-Pinatubo there was severe cooling of levels 70, 50 and 30 that seem to have become “detached” from level 100.
- El Nino warming in 1998 and 2010 is clearly visible in the 100 mb level but mainly absent in the higher levels.
There is a lot going on here and I will defer commenting further until the discussion.
Figure 5 The 5 levels between 300 to 100 mb present a somewhat chaotic picture. One reason for this will be the fact that the tropopause boundary between troposphere and stratosphere occurs in this interval and since the height of the tropopause is not constant across the Earth some of these layers will receive mixed messages. The 100 mb level is also included in the previous chart and is the only level to display stratospheric warming during volcanic eruptions AND tropospheric warming during el Ninos. Its possible that the stratosphere signal comes from high latitudes and the troposphere signal comes from low latitudes. RATPAC provides the latitude bands to examine this, but I have not had time to do so. Levels 300 to 150 mb all show el Nino warming but none show either warming or cooling associated with the three large volcanic eruptions.
Figures 6, 7 and 8 provide the averages for the three layers selected by NOAA: 1) 850 to 300, 2) 300 to 100 and 3) 100 to 50 mb. The N and S hemispheres are also plotted. Figure 6 shows that the S hemisphere troposphere is warming less rapidly than the N, confirming what we already know from surface thermometers and satellites. RATPAC data indicate 1.9˚C per century in the N and 1.3 ˚C in the S. The difference in the Stratosphere is less pronounced. The N hemisphere is cooling at a whacking 3.9˚C per century and the S at 4.5˚C per century.
A curious feature of the stratosphere cooling is that it goes down a step across the El Chinon eruption and then down an even larger step after Pinatubo. Beween Agung and El Chinon the trend is relatively flat as it is post-Pinatubo. It is as if these large eruptions have left a lasting imprint on the stratosphere.
One final observation from Figure 6 is that despite assertions made by the climate science community that these large volcanic eruptions cool the troposphere I can see no evidence for it in these data. Any blips down, if they exist, have no significance compared with the year to year noise. I have been puzzled by this for many years. Earth science is empirical. We develop theories based on observations and the lack of volcanic cooling in the troposphere has puzzled me for many years. I once wrote to the UK Met Office to enquire and was told by a renowned expert that cooling must be masked by El Nino warming. Alleged volcanic cooling plays a crucial role in the overall global warming modelling argument.
Figure 7 shows that the chaotic 300 to 100 mb mixed layer averages to a flat line.
Comparison Thermometers, Satellites and Balloons
Before moving on to the discussion I want to post just one chart comparing surface, satellites and balloons to give a flavour of what this shows.
What we see is that the RATPAC 850 to 300 layer shows the same high amplitude variance seen in the satellite data. RATPAC actually seems to follow the satellite trend more closely than it does the surface thermometers. But the temperature gradient through RATPAC is virtually identical to the surface thermometers. The adjusted RATPAC A and the adjusted surface thermometers are in exact agreement with each other. In 2008, RATPAC A and satellites were exactly aligned. Since 2011, the trends are blown apart.
As discussed above, the RATPAC A data for the 5 levels in the 850 to 300 mb troposphere layer are to varying degrees the same as what we already know from surface thermometers and satellites. The troposphere is warming. The exact pattern and rate of change is disputed, as is the cause. The interesting part of the troposphere debate will have to wait.
In my opinion, the really interesting data here is from the stratosphere, Figures 4 and 8. What has caused the steep stratosphere cooling trend and should we be worried about it? What causes volcanic eruption warming of the stratosphere? And do CO2 emissions have anything to do with this at all?
As stated at the beginning of this post, all these points are up for discussion. Informed commenters are invited to give their informed opinions. I find myself on unsure ground. Skating out on thin ice. Normally Google would provide instant back up, but in this case not, which I find curious. There must be a wealth of research out there. But it hasn’t jumped out at me yet.
Ozone is a molecule of oxygen. O2 is the stuff we breath. O3 is ozone. Ozone is manufactured in the stratosphere by incoming solar ultraviolet (UV) radiation from the Sun, and once it is formed it also absorbs incoming UV warming the stratosphere. That is why the stratosphere gets warmer as you go up, ozone is absorbing a large amount of the incoming UV, protecting the surface. The UV that gets through is absorbed by the surface and re-emitted as infrared (IR) that is trapped by green house gas (mainly water vapour) warming the surface.
Everyone has heard of ozone holes and ozone depletion caused by chemicals released by Man. This is a vast subject I don’t have time to go into. But a simple summary would say that stratospheric cooling is caused mainly by ozone depletion (regardless of the cause). The simple idea is that less ozone means less UV intercepted in the stratosphere that results in cooling.
What you don’t hear so often is that less ozone means more UV landing at Earth’s surface that when re-emitted means more outgoing IR that would warm the surface via the greenhouse effect. I haven’t a clue if the increased UV at surface resulting from ozone depletion is sufficient to cause significant warming of the troposphere. I’m hoping that Clive Best may be willing to provide some answers to that.
Large volcanic eruptions can inject vast quantities of sulphur dioxide into the stratosphere where it is converted to sulphuric acid which condenses to form sulphate aerosols. I am borrowing heavily from this United States Geological Survey source.
The sulphuric acid / aerosols do three things:
1. They are supposed to reflect incoming UV back to space cooling the planet. There is little observational evidence for this (see discussion of Figure 6 above).
2. They trap outgoing IR radiation warming the stratosphere. This could be described as a sulphur borne stratospheric greenhouse effect. There is clear evidence for stratosphere warming associated with large volcanic eruptions. If sulphur compound greenhouse warming is the cause, I don’t know.
3. Sulphate aerosols destroy ozone. The USGS link says this:
The sulfate aerosols also promote complex chemical reactions on their surfaces that alter chlorine and nitrogen chemical species in the stratosphere. This effect, together with increased stratospheric chlorine levels from chlorofluorocarbon (CFC) pollution, generates chlorine monoxide (ClO), which destroys ozone (O3).
There is clear evidence from the stratosphere temperature record that the large volcanic eruptions may have destroyed ozone leading to stratosphere cooling.
To sum up, large volcanic eruptions that inject large quantities of sulphur compounds into the stratosphere, are alleged by climate science to cool Earth’s surface but there is little evidence for this happening. The evidence that does exist shows quite clearly that large volcanic eruptions lead to temporary warming of the stratosphere and longer lived cooling that could be explained by destruction of ozone. The latter may lead to more UV arriving at surface that would cause warming not cooling of the troposphere.
CO2 greenhouse causes stratosphere cooling
The climate science community has gathered around the idea that the obvious cooling of the stratosphere is caused by the CO2 greenhouse induced warming of the surface. It seems so simple, less heat escaping the surface leads to cooling of higher layers. Too simple I’m afraid because the higher layers are normally warmed by incoming not outgoing radiation.
Again it’s tricky to find sources for CO2 causing the troposphere to warm and the stratosphere to cool. But here’s an old Real Climate post by Gavin Schmidt, the current director of the NASA Goddard Institute For Space Studies (NASA GISS) and one of the most pre-eminent climate scientists in the world.
In the case of the Earth, the solar input (and therefore long wave output) are roughly constant. This implies that there is a level in the atmosphere (called the effective radiating level) that must be at the effective radiating temperature (around 252K). This is around the mid-troposphere ~ 6km. Since increasing GHGs implies an increasing temperature gradient, the temperatures must therefore ‘pivot’ around this (fixed) level. i.e. everything below that level will warm, and everything above that level will cool.
Even though the stratosphere has an opposite lapse rate to the troposphere because of the ozone absorption, the effect of increasing GHGs is the same, i.e. since it is above the effective radiating level, it will cool. The cooling will be greatest as you go higher. In the troposphere, there are important other effects that change the temperature, chiefly moist convection, and that smears out the temperature changes you expect from a pure radiative atmosphere. So while the troposphere does warm as a function of increasing GHGs, the maximum change is not at the surface, but actually in the mid-troposhere.
There’s so much to say about this I don’t know where to begin. But I just want to focus on my understanding of how the CO2 greenhouse works on Earth that is based entirely on the writings of Clive Best.
The main IR absorption bands of CO2 are saturated at surface. Therefore increasing CO2 ppm does nothing. All the IR radiation that CO2 can absorb is already absorbed. This theoretically sets up a radiative cascade chain where tropospheric CO2 emits, absorbs and re-emits IR in the chosen bands upwards through the atmosphere until a level is reached where the density of CO2 molecules is too low to capture and re-emit IR and at that level the IR emits directly to space by passing all that overlies that critical level. The critical level is known as the emission height which lies just below the tropopause. Observations from space confirm this theory. Note that this is quite different to what Gavin Schmidt has described. I appreciate that the Real Climate post is dated 2004 and may require updating. It is in fact labelled as obsolete and points instead to this post.
As CO2 ppm increases in the atmosphere, the density of CO2 molecules at altitude also increases and this raises the emission height, which in the troposphere means a colder emission temperature. The colder emission temperature at altitude means that the surface must warm to maintain radiative energy balance. That at least is how the story goes.
One consequence of this yarn is that the stratosphere is and always has been bypassed by outgoing IR in the CO2 absorption bands. The CO2 greenhouse is diagnostic of the troposphere and its absence is diagnostic of the stratosphere. IR radiation trapped by CO2 warms the troposphere and then escapes to space. Increasing CO2 may warm the troposphere a bit more before escaping to space. According to theory, outgoing IR in the CO2 bands bypasses the stratosphere emitting directly to space and always has done.
Thus, increasing CO2 does not cool the stratosphere. Depleting the amount of ozone does.
Finally, there is the curiosity of Figure 2 that seems to show the 100 mb (52,000 ft) level belonging to the stratosphere pre-Pinatubo, but joining the troposphere post- Pinatubo. Convective storms, associated with el Ninos have clearly lifted water vapour into this level post-Pinatubo eruption. One rational explanation is that the Pinatubo eruption destroyed ozone and raised the level of the tropopause. Should this be true, understanding the exact physical reasons for this appears to be vital.
Since 1958, the troposphere has warmed and the stratosphere has cooled. These observations may be linked, not by manmade CO2 emissions but by ozone depletion triggered by the 1982 El Chinon and 1991 Pinatubo volcanic eruptions.
Ozone depletion leads to less incoming UV trapped in the stratosphere, cooling that layer, and more incoming UV reaching surface warming the troposphere by greenhouse effect. The cooling stratosphere causes a warming surface and not vice versa.
Climate science seeks to explain the observations by increased manmade CO2 emissions and a cooling effect on the surface by volcanic eruptions. There is no evidence from the data presented here that large volcanic eruptions cool the surface. And the physical science does not permit the explanation of increased CO2 cooling the stratosphere.
I have gone skating on the thin ice of science tonight. Fire away and provide greater and better insight, links to charts and data. The emphasis here is on greater, better and validated.