Sorry about the "its". I always get confused about that one...

Let's try this: can the lapse rate of a planet with a non-condensing atmosphere be determined by insolation, rotation, gravity and atmospheric mass, regardless of chemical composition?

(I hope at least I got the apostrophe right).

Chandra, you say "The desert lacks water vapour. If it also lacked CO2, it would get colder". So have night temperatures in the desert increased, as the concentration of CO2 in the atmosphere has increased (for whatever reason)?

Those are just distractions. Your (or Geronimo's) assertion, "in the absence of water vapour there is very little heat retained by CO2 on its own", is what you need to understand and justify.

Oh, I didn't see that one (10:26) before posting.

"So have night temperatures in the desert increased, as the concentration of CO2 in the atmosphere has increased (for whatever reason)?"

That is what I was asking you earlier, but I think you said you could not find any data on it.

As far as I can tell the answer is: night time temperatures in the arid deserts have not increased during the instrumental record, while the concentration of CO2 in the atmosphere has increased by about 30% over the last 50 years.

But my search has not been exhaustive. Can anybody either confirm or deny this?

Chandra, a final point before I go out - if nightime desert temperatures have not increased while atmospheric CO2 has, and without water to complicate matters with its phase changes and feedback effects (either positive or negative, real or imaginary), do you agree that the CAGW hypothesis has been invalidated?

Roger: "I think that H2O is the working fluid that regulates average planetary surface temperature (minimises entropy rise), with CO2 being an insignificant player....."

Water vapour is sparse above 10km and about half is within the first 1.5km. CO2 is equally dispersed throughout the atmosphere. As transports of energy they are different animals. They are both radiative and because of that are singled-out as anomalies within the atmosphere. However, as constituents of the system operating on planetary temperatures, they behave the same as surfaces in that they can absorb, emit and conduct energy. It is in fact the non-radiative gases that are anomalous in this system. It is my contention that the conduction of energy into those gases that gives rise to the 'greenhouse effect'. The delay in energy transport within the system caused by this process gives the additional energy storage capacity when compared to an atmosphere devoid of radiative gases. I am talking here of a steady-state condition of course. You can visualise this process when looking at a graphic of the energy absorption bands in the IR spectrum. It is the energy in those bands that is conducted to the non-radiative gases as entropy dictates.

"Forget Mars, please justify your assertion: "in the absence of water vapour there is very little heat retained by CO2 on its own". "

Chandra you're beginning to look out of your depth, "in the absence of water vapour there is very little heat retained by CO2 on its own". is not an assertion, it's an observation. One makes an assertion by saying something is true/happening without empirical (observation/experimental) evidence. An assertion can be true, or false through chance.

A good, current example of an assertion, is "It is extremely likely that human emissions caused most of the rise in temperature in the 20th century." There is no empirical proof for that.

It matters no whether the temperatures went up in the deserts for the sake of this argument, it's whether water vapour is the major greenhouse gas or CO2 is. The diurnal temperatures in the tropics and the deserts respectively point to CO2 having very little effect as a GHG. At least in the deserts. I doubt there will be any temperature records for deserts before the satellite era, if you want to investigate the actual temperatures you could try the RSS or UAH records.

There are other, some say more important, things that affect temperature, one of them being atmospheric pressure, to which according to the gas laws, temperature is directly proportional. Hence, with a climate over 90% CO2 Mars is freezing, well actually it ranges from -55C to -100C. It is 50% away from the sun so will have considerably less TSI, nonetheless an atmosphere almost 100% CO2 would certainly show some warming.

Just been informed that next door's rabbit has died, must go.

Although most deserts are freezing overnight, Death Valley isn't although the diurnal temperatures follow that of other deserts with temperature swings of up to 20C.

Roger, you'll have to do better than that. To turn your assertion that night time temperatures have not changed into something worth considering, you need to provide some evidence. Like a link to a suitably researched paper in a reputable journal.

Geronimo, forget Mars and its characteristics. They add nothing to the debate. Your problem is the "very little" in, "in the absence of water vapour there is very little heat retained by CO2 on its own", and the conclusion you draw from it. There is no disagreement that water vapour is a much stronger greenhouse gas than CO2. So take away water vapour and we expect the temperature to be much lower. Take away the CO2 and it will be lower still by this "very little". If instead of removing the CO2 you doubled it, the temperature would be higher. The fact that changes due to CO2 are small when compared with those due to water vapour is irrelevant. They are still changes and they have a global effect.

"The fact that changes due to CO2 are small when compared with those due to water vapour is irrelevant. They are still changes and they have a global effect."

The fact that desert temperatures have not changed while CO2 has increased by 30% means that it has a negligable effect. Do you not agree?

As I said, you need to provide some evidence that desert temperatures have not changed.

geronimo,

Your observation on night-time arid and humid areas is correct and useful. The temperature difference between the surface and the intercepting atmospheric gas affects the radiation flux. As water vapour is closer on average to the surface than the average of CO2, its temperature is higher due to adiabatic lapse rate. In a humid area the flux is first governed by the temperature difference between surface and average water vapour temp, then between there and average CO2 temp and then to space. In an arid region, that first step is near to insignificant, hence the higher flux and associated faster cooling. Additionally, at higher altitudes, there is less chance of transfer of the radiation by collision with non-radiative gases in the short time period that an excited CO2 molecule holds that state.

No Chandra - I have said that desert temperatures have not changed, it is up to you to provide evidence that they have. Scientific advancememt is based upon evidence, not a lack of evidence. If there is no evidence that temperatures have changed, do you agree that the CAGW hypothesis has been falsified?

Chandra,
I had a vague recollection about death valley in WUWT. I suggest you could have a read of the posting and comments which could lead to the answer which either proves or falsifies what Roger and geronimo are saying. Don't ask me to do it for you though. Looks like NOAA is the place to go for Death Valley.

http://wattsupwiththat.com/2013/06/30/it-seems-noaa-has-de-modernized-the-official-death-valley-station-to-use-older-equipment-to-make-a-record-more-likely/

and some more.
http://weather-warehouse.com/WeatherHistory/PastWeatherData_DeathValley_DeathValley_CA_April.html
http://www.myweather2.com/City-Town/Mongolia/UmnuGobi/climate-profile.aspx
http://www1.ncdc.noaa.gov/pub/data/cmb/bams-sotc/2006/077-082.pdf

I suggest that you follow these up to do the falsifying, as I think what Roger is saying makes a great of sense.

Chandra, we know what temperature rise a doubling of CO2 will give (as does everyone who's been looking at this issue, so I'm guessing you're new to it and have come on this thread to give a bunch of ignorant "deniers" a hard time for having the temerity to challenge the "scientists". As you will find out, many people on this blog have had careers, or are having careers in science and it is science that we are discussing). A doubling of CO2 will give a temperature increase of 1.2C, actually a pretty beneficial temperature increase and certainly harmless. The dangerous temperature rises come from "asserted" feedbacks for which there is no empirical evidence. Even if the 3C increase was true there is no empirical evidence that the foretold disasters will/can occur, it's the output of models.

As it happens we've had temperature rises of 1C in the recent past and there is no sign in the records of a concomitant rise of 3C.

I don't expect, or want, you to believe me, I want you to say "that's bollocks" (the Latin for which is Nullius in verba) and go and look for yourself, then come back here and show that the denizens of this blog are wrong by producing empirical data to support your arguments. It should be, I believe the scientific words are, "a piece of piss" for you to find the scientific facts that sink our "denier" arguments without trace. Go for it!

Atacama desert, 'driest place on Earth'. Temperature record since 1955 at single (unsurprisingly) station shows downward temperature trend. The four seasons can be seen here. I have not yet found the original data but looking at the site have no reason to consider them manipulated.

http://mathyear2013.blogspot.co.uk/2013_04_01_archive.html

Scroll about 85% of the way down to find them.

Thanks Sandy - nice find.

Eyeballing the Death Valley data I can not see any changes in temperature that would correlate with a 30% rise in atmospheric CO2 over 50 years.

I have been looking for data in the Sahara to see if nightime temperatures have changed, but all I can find are articles of snowfall in recent years that have been the "worst in living memory". But I admit, as evidence this is of little use.

OK Chandra, we have provided evidence - over to you.....

Roger, you are trying to overturn a theory. The onus is on you to prove your theory.

Geronimo, you should talk to Roger. He thinks that CO2 has a negligible effect, while you clearly don't.

I'll cross-post the following from another thread;

Chandra

In my opinion you are bogus, I asked you why you were here but got no answer. You complain about a number of issues and if someone attempts to answer one of them you quickly jump to another issue. I would be most grateful if you would find another discussion to wreck, preferably on another blog more deserving of your talents.

Sep 15, 2013 at 8:06 PM | Registered CommenterDung

Chandra, I am not trying to overturn a theory, I am trying to falsify a hypothesis. This is the scientific method. The empirical data that have been provided so far have gone some way to doing this. Do you agree?

Roger, the greenhouse action of CO2 is way more than a hypothesis. I'm not sure what the "empirical evidence" you refer to is. If it is the Atacama desert stuff, that is just one station at high altitude and the graphs don't show night time temps. The Sonoran desert in the same page shows significant warming (but again no night time temps). If it is eyeballing Death Valley, very scientific.

Ssat, the similarity with the other thread (from which you cross posted) is that there too, someone was claiming something for which he had no evidence. In that case it was the suggestion that UK gas prices would fall and yet nobody on the thread could quantify how many well would be needed to shift the price (I'm not looking for the exact number, but the order or magnitude).

"Geronimo, you should talk to Roger. He thinks that CO2 has a negligible effect, while you clearly don't."

Which part of the deserts having very cold nights, while the tropics, with the same CO2, and lots of clouds, having warm nights aren't you understanding?

"...nobody on the thread could quantify how many well would be needed to shift the price (I'm not looking for the exact number, but the order or magnitude."

None, we could simply remove the green taxes on our current gas supplies to lower the price of gas by around 6%.

Can I suggest you stop demanding that people answer your questions and answer a few yourself.

Do you think that Trenberth can't do sums? If you do please explain, if you don't give us an example. If that's not what you want to discuss, then you're on the wrong thread and I suggest you go to "Unthreaded", but before you do you really do need to read around the topic, you're out of your depth and it shows.