Climate Metrics - Temperature Averaging 8

[TGS4]

In our most recent "climate change" discussion, I made a point about temperature averaging that seemed to be misunderstood. Because of its importance (in my opinion), I wanted to make its own thread.

It is clear to me that there is significant confusion about the cp of air and a global average temperature. Perhaps an example will clear things up:

I have two temperatures: -30°C (for argument's sake, let's say that the RH is 50%) and +30°C with an RH of 50%. The mathematical average of the temperatures is 0°C. However, based on the specific heat capacities:
[ul]
[li]the energy in 1 kg of the -30°C (243.15K) air is 1.005 [kJ/kg*K] * 1 [kg] * 243.15 [K] = 244.36575 kJ[/li]
[li]the energy in 1 kg of the +30°C (303.15K) air is 1.03 [kJ/kg*K] * 1 [kg] * 303.15 [K] = 312.2445 kJ.[/li]
[/ul]
Now, average the energies to get 278.305125 kJ. If you wanted an average temperature based on average energy (something that can actually be averaged), you are stuck in the backwards calculation of which value of specific heat capacity to use.
[ul]
[li]If you use 1.005 [kJ/kg*K], you get an "average temperature" of 276.92K or 3.77°C.[/li]
[li]If you use 1.03 [kJ/kg*K], you get an "average temperature" of 273.20K or -2.95°C.[/li]
[li]If you use the "average" of the specific heat capacities (1.005+1.03)/2=1.0175 [kJ/kg*K], then you get an "average temperature" of 273.52K or 0.37°C.[/li]
[/ul] (Note that these calculations are all at sea-level).

So, which "averaging" calculation is correct? What is the true average temperature? Even IF you know the instantaneous humidity coincident with the temperature reading, you still have a problem in the averaging. But, here's another problem to highlight it even more:

I have two temperatures: +30°C (for argument's sake, let's say that the RH is 10% because it's in Denver) and +30°C with an RH of 100% (Miami). The average of the temperatures is, obviously, 30°C, right? However, based on the specific heat capacities:
[ul]
[li]the energy in 1 kg of the Denver air at 30°C (303.15K) air is 1.01 [kJ/kg*K] * 1 [kg] * 303.15 [K] = 306.1512 kJ[/li]
[li]the energy in 1 kg of the Miami air at 30°C (303.15K) air is 1.056 [kJ/kg*K] * 1 [kg] * 303.15 [K] = 320.1264 kJ.[/li]
[/ul]
Now, average the energies to get 313.1388 kJ. If you wanted an average temperature based on average energy (something that can actually be averaged), you are still stuck in the backwards calculation of which value of specific heat capacity to use.
[ul]
[li]If you use 1.01 [kJ/kg*K], you get an "average temperature" of 310.04K or 36.89°C.[/li]
[li]If you use 1.056 [kJ/kg*K], you get an "average temperature" of 296.53K or 23.38°C.[/li]
[li]If you use the "average" of the specific heat capacities (1.01+1.056)/2=1.033 [kJ/kg*K], then you get an "average temperature" of 303.14K or 29.99°C.[/li]
[/ul]

Again, what's the real metric here. It takes 4.5% more "energy" to heat the Miami air up an additional degree as compared to the Denver air. If we are truly "worried" about energies and fluxes, then why are we even using temperatures at all?

I am most certainly NOT talking about trends or anything else (yet). I am talking about the most basic of metrics used. Why are we using an average temperature?

 

[rb1957]

i get the technical point but i ask myself, "what's the point ?" ... we'll never know the global temperatures with a sufficiently fine grid to apply this detail. we can't do an energy balance of the earth, and again why bother ? ... i mean the total energy of the earth has been increasing and decreasing over time (increasing coming out of an ice age, decreasing going in) ... no?

is it reasonable to say that over geological time that the temperature of the earth's core has remained reasonably constant ? that the energy leakage to the atmosphere is negligible ? either way, does this mean much ?

why does an ice age start ? orbital and solar variations ??

clearly the global climate "tips" every so often.

the key question on climate change is "what impact is man having on the global climate?" ... and No one Knows. What effect is burning FF, releasing CO2, having on today's climate ? on tomorrow's ?? much of the discussion/argument centers on the response "well, it can't be good".

Quando Omni Flunkus Moritati

 

[TGS4]

My point is that if we are going to answer the question of "what's going on?", then we need to do it properly. As an anecdote, I have heard that the bulk of the recent "warming" has come from the polar regions, by way of the daily low-temp. If the tropics are not heating up, then the total amount of energy in the atmosphere can't really be increasing, can it?

I would also disagree with your assessment that the climate "tips". The difference between an ice age and an interglacial age is a continuum with respect to summer temperatures. There has never been a run-away (proof is that we are here...). Maybe there are multiple meta-stable "points"...

 

[rb1957]

if one region is heating up and the rest static then the total energy has increased, no?

as for "tipping" i meant that the state of the globe has changed significantly over the geological time record, sometimes quite quickly. clealry (in my mind, this means that the amount of energy arriving at the earth changes, the amount of energy the earth absorbs and reflects also changes over time.

Quando Omni Flunkus Moritati

 

[JohnRBaker]

While it may not be the 'tropics', have you looked at what's happening this 'Summer' in Australia? They've been setting some very high new records (remember, 50°C equals 122+°F).

http://www.abc.net.au/news/2014-01-02/records-tumble-as-central-australia-swelters/5182712

http://www.abc.net.au/news/2013-12-19/extreme-weather-southeast-australia/5166618

http://news.ninemsn.com.au/national/2014/01/02/08/30/2014-brings-heat-wave-for-australia

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
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To an Engineer, the glass is twice as big as it needs to be.

 

[zdas04]

What is the point? Really, you want to know what the point is. The point is that "temperature" is a horrible surrogate for "state". If I average the temperature in Denver with the temperature in Brisbane, I get a number that truly means nothing. I'm fine with saying "we'll never know the global temperatures with a sufficiently fine grid to apply this detail", but the next statement needs to be "so let's just stop talking about the whole subject. The metric for AGW is average temperature. As long as that is the metric, TGS4's point is the only valid one. His examples show that the uncertainty in taking a simple average is greater than the implied uncertainty of the projections. If I can get a range of answers in the +/-10C magnitude, do I really have data to support a contention that man is causing temperatures to rise 0.6C/decade?

A big part of my career has been spent specifying and designing compression equipment. It has mostly been air cooled. Without a humidity and elevation assumption I get the wrong cooler every single time. An air cooler designed for a platform in Lake Maricaibo, Venezuela will be grossly inadequate for Northern Colorado. That is a trivial example of the importance of fully defining the state of a gas before trying to aggregate it with other gases.

This is very much analogous to stating flow rates at standard conditions. If I have a 0.65 SG gas stream at 90F and 100 psia that has 100 MSCF/day volume flow rate at standard conditions (13.4 MACF/day at actual conditions), a second stream of the same gas with 200 MSCF/day at 1,000 psia and 60F (2.4 MACF/day) and a third stream with 500 MSCF/day at 15 psia and 120F (548 MACF/day). If I was foolish enough to just add the ACFs, I would get 564 MACF/day--a totally meaningless number. If I add the SCF's (which is reasonable) I get 800 MSCF/day, and if I add the mass flow rates I get 18 tonne/day (which I will get if I multiply the ACF times the actual density or the SCF times the standard density). The point of that exercise is that we all (except apparently climate scientists) know that you can't take averages (or any other calculation) of gases at different conditions. Adding apples to Volkswagens just doesn't yield a result that means much.

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[TGS4]

JohnRBaker - fascinating weather anecdotes (and data) from a region that makes up 1.5% of the planet's surface area. Any comments on-the-topic?

 

[Enginerd9]

My dad used to tell me when I was a kid "there's more nicotine in a head of broccoli than in one cigarette. So they can't tell me second hand smoke is bad for you!" I have a hard time believing that just because it's cold in the winter, climate change isn't real (because it's just as ridiculous a claim).

Don't we accept that Entropy is always increasing? Energy is becoming more disorganized by default? And displacing one form of energy to keep another organized / predictable doesn't stop the overall entropy? I'm just throwing that in the pot here... if left alone, a warm pot of water will be reduced to ambient temperature until the stove is turned on. We add energy to the global system every day, like turning the burner on.

 

[TGS4]

We add energy to the global system every day, like turning the burner on.

Interesting assertion. Please explain.

Just as a hot day here, or a cold day here don't really mean anything in a global context, I am still deeply troubled by the "averaging" metrics.

 

[Enginerd9]

We move. We create friction. We burn fuel. We introduce waves of energy into the atmosphere (cell phones, radios, etc). We eat and give off waste. We introduce chemicals into the atmosphere which react with other chemicals to form variances in the "fluid." All of those things add (if even only slightly as individuals) some amount of energy to the system.

Although, I will agree with the averaging metrics problem. I think we share an opinion that more data from many more sources would help substantiate global climate claims either way.

Experience: accumulated knowledge over time.

Talent: the ability to use experience.

Which is more valuable?

 

[TGS4]

Did you see my comment in the other thread that if ALL of our (humanity's) energy usage were converted to heat, it would still only account for 0.0097% of the energy we get from the sun? Our direct contribution to the thermal balance of this planet is so insignificant.

 

[JohnRBaker]

OK TGS4, let's deal with a part of world, the Northern Hemisphere, where most of land mass IS found (BTW, anyone ever lose any sleep over this? If you want to blow you mind and you've got one of those nice 'World Maps' from the National Geographic Society, try hanging it on the wall upside-down.): It's January 13th and here in SoCal it's 82°(F) outside my office, or at least it was awhile ago when I got back from lunch. I know this isn't any sort of record, but it's hardly something that's expected, even here in SoCal (Orange County), this time of the year.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[TGS4]

JohnRBaker - one single data point among thousands. Interesting weather. I would expect, generally, SoCal to be warmer than Calgary in the Northern Hemisphere winter, which it is today.

That your current temperature is not a record, based on records being kept for 100-120 years, tells me that it is somewhere in the "normal" range.

Not even remotely interesting w.r.t. climate.

What's your opinion on the topic - temperature averaging?

 

[JohnRBaker]

I was posting it more as some sort of 'smart-ass' comeback to your implication that what's happening in Australia was somehow irrelevant due to it's lack of land mass ;-)

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[dvd]

One kg of moist air at 50% RH and -30C contains less H2O than one kg of moist air at 50% RH at +30C. When averaging the temperature, how does one account for the moisture changes? Where does the air go when adding moisture in order to keep just one kg? Is any energy involved in adding/removing moisture from the air?

 

[TGS4]

The additional water vapour is accommodated by the different value of specific heat capacity. See

http://www.coolit.co.za/airstate/airmoistobject.htm

(or really any psychrometric chart) for specifics on how much water vapour g/kg is in the various relative humidities.

Is any energy involved in adding/removing moisture from the air?

There sure is - think thunderstorm...

 

[rb1957]

the only thing a global average temperature does is reduce a very complex situation (global climate) to a single (not very meaningful) number that we can look at and wring our hands over as it changes from day to day.

Quando Omni Flunkus Moritati

 

[zdas04]

I'd be OK with that as the single metric if they used an energy-weighted average instead of a "simple" average. No single metric is going to convey the whole picture, but using density and heat content to weight the temperature readings would be a step in the right direction.

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[Enginerd9]

Isn't there a field of study which deals specifically with all of this? I don't remember it being in my Engineering curriculum, but I think it's called something like "meteorology." And there's people who are really good at it. And those people, even within their own circles, debate the topic like we are.

Just saying, it's possible we may be grasping at straws.

Experience: accumulated knowledge over time.

Talent: the ability to use experience.

Which is more valuable?

 

[rb1957]

ok, so we could add humidity, and pressure, and heat content, to all the temp moitoring stations (you'd imagine that if these are "proper" weather monitoring stations that they'd have much of this already) and replace surface average temperature with surface average energy (maybe per sq mile). so what ? that's not doing an energy balance, it is a better average single parameter. maybe it's a step along the path for getting more detailled atmospheric data, but the energy balance of the globe is still decades (centuries?) away. still, the more we understand about the globe then the better questions we can ask.

enginerd9 ... is that a "piss-take" ? sometimes it's hard to read scarasm.

Quando Omni Flunkus Moritati