Guest post by Dr. Roger Pielke Senior
As discussed in the post
the global annual average surface temperature trend has become the icon of communicating climate change to the policymakers and even within the climate science community.
However, as I have written previously; e.g. see
The Terms “Global Warming” And “Climate Change” – What Do They Mean?
Pielke Sr., R.A., 2003: Heat storage within the Earth system. Bull. Amer. Meteor. Soc., 84, 331-335
and as presented elsewhere; e.g. see
An Important Weblog Post On “The Air Vent”
Misconception #2: The global average annual temperature average is an appropriate metric to diagnose global warming.
Global warming, of course, is just a subset of climate variability and long-term change [see], which I will discuss further in a later post.
A change in heat (e.g. global warming) is defined in Joules [not degrees Celsius by itself) and can be written for the climate system as
ΔH = MA * [CA * ΔT + L Δq] for the atmosphere + MO* [CO* ΔT ] for the ocean + ML* [C L* ΔT + heat from phase changes of soil water] for land + MI* [CI * ΔT + heat from phase changes of ice] for continental glaciers and sea ice
where H is heat in Joules, M, C and ΔT represents the mass, the heat capacity and the temperature change for the respective components of the climate system, respectively. L is the latent heat of vaporization and q is the specific humidity.
As clearly overviewed in the excellent post on the Air Vent
Global Temperatures and Incomplete Rationale of My Own Skepticism
where a figure from that weblog is reproduced below
the ocean is a much larger reservoir of heat changes. A similar plot for land, and the continental glacier and sea ice would show a similar very large disparity between the oceans and the other reservoirs.
Where does the global annual average surface temperature trend fit into this framework? I present four reasons below that document why this temperature fails to accurately diagnose global warming. Other reasons are discussed in several of our research papers; e. g. see
Pielke Sr., R.A., C. Davey, D. Niyogi, S. Fall, J. Steinweg-Woods, K. Hubbard, X. Lin, M. Cai, Y.-K. Lim, H. Li, J. Nielsen-Gammon, K. Gallo, R. Hale, R. Mahmood, S. Foster, R.T. McNider, and P. Blanken, 2007: Unresolved issues with the assessment of multi-decadal global land surface temperature trends. J. Geophys. Res., 112, D24S08, doi:10.1029/2006JD008229.
First, as seen in the above figure from the Air Vent the absolute value [MA * [CA * ΔT + L Δq] for the atmosphere] << absolute value [MO* [CO* ΔT ] for the ocean]
Thus we can define that
Global Warming is an increase in the heat (in Joules) contained within the climate system. The majority of this accumulation of heat occurs in the upper 700m of the oceans.
Global Cooling is a decrease in the heat (in Joules) contained within the climate system. The majority of this accumulation of heat occurs in the upper 700m of the oceans.
Even over the ocean, the surface air temperature (marine air) is only a small part of this heat accumulation, and then only if it is well correlated with temperatures over at least a few meters of depth.
Second, over land, there is another issue, heat is not only contained in the temperature but also the moisture content of the air. The moist enthalpy [CA * ΔT + L Δq] is the appropriate measure of atmospheric heat content; e.g. see
Pielke Sr., R.A., C. Davey, and J. Morgan, 2004: Assessing “global warming” with surface heat content. Eos, 85, No. 21, 210-211.
Thus, in using the global annual average surface air temperature trend to diagnose global warming and co0ling, the contribution to heat changes of the air by concurrent water vapor changes [L Δq], an important fraction of the heating/cooling is missed.
Third, there is issue of the height at the air temperature measured? As we have shown in
Steeneveld, G.J., A.A.M. Holtslag, R.T. McNider, and R.A Pielke Sr, 2011: Screen level temperature increase due to higher atmospheric carbon dioxide in calm and windy nights revisited. J. Geophys. Res., 116, D02122, doi:10.1029/2010JD014612.
Lin, X., R.A. Pielke Sr., K.G. Hubbard, K.C. Crawford, M. A. Shafer, and T. Matsui, 2007: An examination of 1997-2007 surface layer temperature trends at two heights in Oklahoma. Geophys. Res. Letts., 34, L24705, doi:10.1029/2007GL031652. [see correction also]
air temperature trends are a function of height above the surface.
Fourth is the complex spatial and temporal heterogeneity of surface air temperatures. The assumption that a single trend value can characterize the heating and cooling of the climate system is based on an oversimplistic assumption based on an object with a uniform mass and temperature change (such as a metal sphere of a few centimeters in size). I discuss this issue in my post
The Computation Of A Global Average Surface Temperature Anomaly
Below are the latest anomaly plots (for February 2011) from http://earthobservatory.nasa.gov/GlobalMaps/view.php?d1=MOD_LSTAD_M&d2=AMSRE_SSTAn_M#
“Fourth is the complex spatial and temporal heterogeneity of surface air temperatures.”
Tsk, tsk. Leif Svalgaard has made clear to all that this is “spatiotemporal cult” “mumbo-jumbo”. Thanks for the laugh Leif!
[ See here: http://wattsupwiththat.com/2011/04/10/solar-terrestrial-lunisolar-components-of-rate-of-change-of-length-of-day/ .]
Paul Vaughan says:
April 14, 2011 at 8:35 pm
“Fourth is the complex spatial and temporal heterogeneity of surface air temperatures.”
Tsk, tsk. Leif Svalgaard has made clear to all that this is “spatiotemporal cult” “mumbo-jumbo”. Thanks for the laugh Leif!
Indeed it is when you could simply say that the temperature varies with location and time. There is one little difference: a cult member would have said ‘spatiotemporal’ instead of ‘spatial and temporal’.
“All the energy emitted from the planet is radiated from the top of the atmosphere and gets there from below. But the energy of the radiated IR is proportional to the fourth power of the temperature of each unit area of the radiating surface(s); i.e. the radiated energy is proportional to T^4.”
Doesn’t the average energy the earth receives from the sun equal the energy radiated from the TOA or the earth would not be in equilibrium? In other words, temperature ^ 4 is proportional to the energy received from the sun.
ferd berple:
At April 14, 2011 at 10:51 pm you quote from my post at April 14, 2011 at 4:43 pm where I wrote:
“All the energy emitted from the planet is radiated from the top of the atmosphere and gets there from below. But the energy of the radiated IR is proportional to the fourth power of the temperature of each unit area of the radiating surface(s); i.e. the radiated energy is proportional to T^4.”
Then you ask and say;
“Doesn’t the average energy the earth receives from the sun equal the energy radiated from the TOA or the earth would not be in equilibrium? In other words, temperature ^ 4 is proportional to the energy received from the sun.”
The answer to your question is, yes.
And the response to your statement is, no.
My post tried to explain this, but I will illustrate it with an analogy that I hope will make the matter clear.
1.
Consider a laboratory experiment that establishes two surfaces each of unit area
where
2.
one of the surfaces is heated by a radiant input and the other is not heated
but
3.
there is a connection that permits heat to flow from the heated surface to the unheated one
so
4.
both surfaces lose heat by radiation
and
5.
the described system is in thermal equilibrium such that the radiated heat into the surface(s) equals the radiated heat out of the surfaces.
The described apparatus is a crude analogy to a unit area of the tropics (heated by the Sun) and a unit area of a polar region (that gets almost no solar heating) with the thermal connection between them being ocean currents.
Now let the temperatures of the two surfaces be
40 deg. C (i.e. 313 K = Th)
and
10 deg. C (i.e. 283 K = Tc).
The average temperature of the two surfaces of equal area is 25 deg. C.
The total radiated energy (e) is a constant and is proportional to the fourth power of the surface temperature(s). Therefore, the radiation from the surfaces is in the ratio
Th^4 : Tc^4 = 313^4 : 283^4
Now, drop the value of Th by one degree, so Th1 = 312 K
but the total radiated energy (e) remains constant, so
Th^4 : Tc^4 = 313^4 / 283^4 = Th1^4 : Tc1^4 = 312^4 / Tc1^4
i.e.
Tc1^4 = 312^4 / (313^4 / 283^4) = 8567625486
So, Tc = 304.2 K which rounds to 304 K
Thus, a fall of one degree in the temperature of the ‘hot’ surface causes the temperature of the ‘cold’ surface to rise by (304 – 283) = 21 K
So the average temperature of the two surfaces increases from 25 deg. C to over 35 deg.C.
The change in average temperature is because an effect of a fourth power is to amplify small changes.
Richard
ferd berple at 10.51PM, the earth is never in equilibrium. The oceans have a huge heat capacity. 0.1K change has has a very large effect on temperature of the lower atmosphere- look at the graph in the post. Further, having an average temperature over all the surface for one year makes provides no information about climate or weather in any part of the world. I am sure Dr Pielke has put that in refereed articles.
“Does this light any bulbs out there?”
Also interesting is the fact that the direction of the temperature gradient in the rock/soil deeper than that point of constant temperature (no influence of diurnal and seasonal changes) is inwards. That means the direction of the net heat flux is outwards.
So, the net heat flux in the deeper ground is outwards. The earth is transfering heat from the depth to the surface.
I think this “geothermal” heat flux is actually a net (total) flux at the respective depth. You can not calculate it and compare it to solar heat flux and say it’s neglibile compared to the solar flux. The solar flux is already in the equation.
ferd berple says:
April 14, 2011 at 10:51 pm
Doesn’t the average energy the earth receives from the sun equal the energy radiated from the TOA or the earth would not be in equilibrium? In other words, temperature ^ 4 is proportional to the energy received from the sun.
Yes, on average. But not at every instant, e.g. the temperature doesn’t instantly fall to zero at night.
Dr Pielke:
One small suggestion; Great post. I enjoy all of your series posts. My only helpful advice would be to include more quotes in your running text whenever you site outside source material, such as journal publications.
Thanks and keep up the great work.
Gary
Chuck L. – Your question is an excellent one. Our interpretation (which we have published on) is that their is a systematic warm bias in the land surface portion of the surface temperature trend data; e.g. see
Klotzbach, P.J., R.A. Pielke Sr., R.A. Pielke Jr., J.R. Christy, and R.T. McNider, 2009: An alternative explanation for differential temperature trends at the surface and in the lower troposphere. J. Geophys. Res., 114, D21102, doi:10.1029/2009JD011841. http://pielkeclimatesci.wordpress.com/files/2009/11/r-345.pdf
Klotzbach, P.J., R.A. Pielke Sr., R.A. Pielke Jr., J.R. Christy, and R.T. McNider, 2010: Correction to: “An alternative explanation for differential temperature trends at the surface and in the lower troposphere. J. Geophys. Res., 114, D21102, doi:10.1029/2009JD011841”, J. Geophys. Res., 115, D1, doi:10.1029/2009JD013655.
http://pielkeclimatesci.wordpress.com/files/2010/03/r-345a.pdf
Christy, J.R., B. Herman, R. Pielke, Sr., P. Klotzbach, R.T. McNider, J.J. Hnilo, R.W. Spencer, T. Chase and D. Douglass, 2010: What do observational datasets say about modeled tropospheric temperature trends since 1979? Remote Sensing, 2(9), 2148-2169.
http://pielkeclimatesci.files.wordpress.com/2010/09/r-358.pdf
Richard S Courtney says:
“Thus, a fall of one degree in the temperature of the ‘hot’ surface causes the temperature of the ‘cold’ surface to rise by (304 – 283) = 21 K”
Not even close! The TOTAL stays the same, not some ratio.
If the hot surface cooled from 40C to 39C, the cool surface would warm from 10C to 11.33 C. The average temperature will indeed rise, but only to 25.17C
Thus, a fall of one degree in the temperature of the ‘hot’ surface causes the temperature of the ‘cold’ surface to rise by 1.3 C
The average rises by ~ 0.17 K
Even if both were the same temp, both would be ~ 26.15 C, an average rise of only ~ 1.15 C.
There IS a change in the average when radiation is held constant.
The change IS due to the T^4 nature of the radiation.
The difference IS significant.
But it is nowhere near 10 K!
Tim Folkerts:
With respect, your comment at April 15, 2011 at 10:39 am is mistaken.
You state the source of the error when you say;
“There IS a change in the average when radiation is held constant.”
But the radiation is NOT held constant. The total energy flux of the radiation is held constant.
Your failure to understand this point is explicitly stated by you when you wrote:
“Even if both were the same temp, both would be ~ 26.15 C, an average rise of only ~ 1.15 C.”
But the illustration specifically stipulated that the two surfaces were at very different temperatures and then the temperature of the hotter one was reduced slightly. It is hard to equate that stipulation with “Even if both were the same temp”.
Anyway, this is an ‘angels on a pin’ argument.
1.
I said the average temperature would rise if the hotter temperature were reduced and I tried to explain why by using what I stated is an unrealistic simplification.
2.
You agree that the average temperature of that simplification would rise but not by the amount of my estimation.
3.
So what? If you are right and I am wrong then you have agreed my point: viz. the average temperature would rise.
Indeed, the temperatures of my simplistic illustration were 40 deg.C and 10 deg.C but the real world has a larger range of temperatures, and I only changed the hotter temperature by one deg.C, but temperature usually varies by more than that over 24 hours at every real location. And your figure for the change to the average is ~0.2 deg.C so your calculation would support my case if it were right.
Richard
“
Ira says:
April 14, 2011 at 11:33 am
‘The satelite record measures W/m^2 emissions of Oxygen, I believe, for cloud-free areas of both ocean and land surfaces, or at least of the lower Atmosphere adjacent to these good storage masses for heat energy. Is there a way to use these W/m^2 values as a proxy for the underlying ocean or land mass heat content, or to use them to calculate the same? ”
Not really. The radiative intensity of any gas in the atmopshere depends not only upon the the heat content of the underlying ocean/land, but upon the local atmospheric pressure, temperature, and moisture, i.e., its enthalpy. Although the units are the same, it is not an energy-conserving measure of thermal flux from the surface.
Leif Svalgaard wrote,
“[…] ‘spatiotemporal’ instead of ‘spatial and temporal’.”
‘Spatial’ & ‘temporal’ are adjectives describing marginal distributions, whereas ‘spatiotemporal’ is an adjective describing a joint distribution — conceptually different things and the distinction is NOT trivial.