Dr. Roger Pielke Sr. writes:
News Article On The Earth’s Heat From Radioactive Decay
An intriguing news article has appeared by Charles Q. Choi titled
Radioactive decay fuels Earth’s inner fires
The article includes the text
“Extraordinary amount of heat remains from primordial days, scientists say
The researchers found the decay of radioactive isotopes uranium-238 and thorium-232 together contributed 20 trillion watts to the amount of heat Earth radiates into space, about six times as much power as the United States consumes. U.S. power consumption in 2005 averaged about 3.34 trillion watts.
As huge as this value is, it only represents about half of the total heat leaving the planet. The researchers suggest the remainder of the heat comes from the cooling of the Earth since its birth.”
To convert the estimate in the MSNBC news article to watts per meter squared, 20 trillion watts must be divided by the area of the Earth [5.1 x 10^14 meter squared] which yields a heat source of 0.039 watts per meter squared.
This is well less than the significant radiative forcings as estimated in figure SPM.2 in the 2007 IPCC WG1 report and, except for local effects where lava flows and volcanic eruptions are occuring , this heat is of minor climatic importance [the outgassing of sulphur dioxide and other chemicals and of ash, of course, are a different issue]. The heating of the interior and resulting effect on currents in the Earth’s mantle, however, are important in climate on very long time scales as this helps drive plate tectonics, such as continental drift.
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I am happy I can still take out my CRC Handbook, c.r. 1971, and calculate that the earth radiates .082 watts per square meter. So not much has changed in 40 years…
@blade
> I’ve always wondered about something. Would it make sense to place on the moon …,
> a sensor … that measures whatever can be measured from 200,000+ miles away …
Satellite-born sensors provide the same capability. The diurnal variance from the Earth’s surface would greatly exceed any wobbles in the orbits (for which the data can be normalized).
What about sensing the Moon’s “heat” from Earth? Turns out this is mostly reflected IR from the Sun. Samuel Langley was the first to measure this IR radiation, back in the 1880’s[1], using a rock-salt prism to refract the ‘dark rays’ (as they were called then) into bands. He invented a gadget called a ‘bolometer’ to measure the heat in each part of the spectrum. Very impressive accomplishment, in light of the fact that he did this without any ‘modern’ electronics. Vacuum tube amplifiers weren’t invented until decades later.
Not all of the IR reaches the ground, of course. Some of it is absorbed by the Earth’s atmosphere by water vapor and other gases. Arrhenius used Langley’s lunar data as a basis to illustrate this phenomenon in his well-known paper [2] on CO2 absorption.
[1] Langley, “The Temperature of the Moon”, Memoirs of the National Academy of Sciences, vol iv, pg 193, 1890.
[2] Arrhenius, “On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground”, http://www.rsc.org/images/Arrhenius1896_tcm18-173546.pdf, 1894.
@Roy.
Iceland is the exception that proves the rule. If you live on the mid-Atlantic ridge then yes, you are good for geothermal and major volcanic activity. Otherwise, no. The sun generates so much more energy than the earth’s thermal gradient and yet solar panels aren’t powering the world either. The energy in a liter of gasoline is really amazing and it won’t be easily replaced any time soon.
Steve
They forgot Potassium 40! There is actually very little Uranium left but the real heat producers are Thorium and Potassium because there is so much of them.
@prjindigo
July 21, 2011 at 9:46 pm
“[…]
Using neutrino detection in the article’s way sounds much like trying to determine which fans in a full stadium are Ford owners based only on the sounds they make. It strikes me as an attempt to generate a data set simply to meld into whatever shape is wanted to support a pre-determined hypothesis. Politicians change the data to support hypothesis, scientists just raise their hands and say “its just a lot of noise”.
My posting on this site could easily statistically lead you to conclude to which I am more akin.”
You drive a Ford? ;o)
I didn’t get what you were after when you mentioned “doughhook” in your first post. That term conjured up the wrong mental image for me and it took a few comments by others to get me on the right track.
Mechanically generated heat can be significant. I particularly liked your example of bending #12 copper wire. I work with tube benders and it brought to mind what happens when we bend a 90 degree angle with a 150mm CL radius in a piece of 48.6mm OD x 5mm Wall steel tube: enough heat is generated that one cannot grab the tube at the bend for several minutes afterwards. It always startles new bender operators when they first handle a bent piece.
I hadn’t thought about gravitational contributions to the earth’s heat budget. It’s not discussed much. Good point and I thank you very much.
richard verney says:
July 21, 2011 at 8:11 am
No, the ~25 degrees C geothermal gradient is from surface, not from mean sea level. So thats either the land surface or the sea bed. In the oceans the geothermal gradient is a bit higher because the crust is thinner but is mainly depends on the tectonics and type of rocks.
Barry Day says: July 22, 2011 at 12:49 am
Tim, What happens when the Ocean current travels same direction as the plate boundaries and the heated water gets continually reheated time and time again.Wouldn’t that make your equations meaning less?There would be a localized strip of heated water alongside a landmass which would most certainly NOT be “minor”.!!!
I find that equations are are rarely meaningless. 🙂
A global average is a global average. If one subset of the ocean water gets extra thermal energy, then that would mean other parts would get less thermal energy. That would not change the fact that 0.1 W/m^2 is “minor” compared to 240 W/m^2.
I agree that where that energy surfaces will make some difference. If a concentrated dose surfaces in one spot, then there will be local warming effects. But then the rest of the globe would get less warming.
Another issue is the amount of change. The various radiative forcings are on the order of 1 W/m^s. Unless the change in geothermal energy is ~ 1 W/m^2, its affect on climate change would be expected to be minor.
Yes, thermal effects of tidal forces on the earth have been studied.
Even if this is off a bit, this ~ 4 trillion watts is considerably less than the 20 trillion watts from radioactive decay, which is less than the total geothermal energy, which is much less than the solar energy.
prjindigo says: July 21, 2011 at 9:24 pm
There is no radioactive material which would survive several billion years of active half-life in a heated (accelerated) environment.
Temperature has no noticeable affect on decay rates. U-238 has a half life of 4.5 billion year — which by coincidence is the age of the earth, so 1/2 the U-238 that the earth started with is still here.
Again, the amount of heat (or energy) in watts (J/s)? That’s like amount of water in a tank in l/s. Or gasoline.
Anyway, the geothermal flux could easily be underestimated. Think of all the undersea volcanoes and vents.
“The December 12, 2005, issue of National Geographic News carried a story about a hydrothermal megaplume in the Indian Ocean that is almost 1 mile long and is thought to have the energy equivalent of 100,000 MW. The story went on to estimate the thermal output of all the known vents in the world at about 17,000,000 MW—about the same as current worldwide power generating capacity. Other major vents are known to be located off the coasts of the U.S., China, Japan, Korea, and South America, and in the Mediterranean Sea and Dead Sea. And there remain tens of thousands of miles of ocean ridges yet to be explored.”
http://www.powermag.com/issues/features/Tapping-seafloor-volcanic-vents_128_p3.html
Regarding energy balance, the averaged net heat flux at TOA is averaged insulation minus averaged Earth’s outgoing radiation:
Etoa = Einsol – Eout
At the lower system boundary (~10 m under the surface/sea floor), the averaged net heat flux is the geothermal flux:
Esurface = Egth
The change in internal energy of the system (accounting only for the heat fluxes) is:
dU = Egth + Etoa (input positive sign)
Assuming dU = 0 (averaged over periods with no significant trend in internal energy):
Etoa = -Egth
The average heat flux at TOA (over periods with no significant trend in internal energy of the system) is negative (heat loss) and is equal in magnitude the average geothermal flux.
ferd berple says:
July 21, 2011 at 9:47 am
“Are we that certain that the 30C or so extra warming of the earth as compared to what is calculated from the sun’s energy is due to GHG in the atmosphere?”
No. GHGs have very little effect over the ocean because the ocean doesn’t absorb long wave infrared. Infrared shined on the surface of a body of water merely raises the evaporation rate and water temperature is unchanged. Conversely visible light is almost completely absorbed by a body of water warming it to some depth. The energy from visible light absorption cannot escape the way it entered (radiatively) because water is opaque to infrared. It largely escapes by evaporation and before the deeper sun-warmed water can evaporate it must somehow reach the surface. The ocean is responsible for most of the greenhouse heating because, just like greenhouse gases, it is tranparent to visible light but opaque to infrared. The GHG effect is confined to land which limits its potential to raise global average temperature. The so called “missing heat” is not missing. It never made it into the ocean in the first place. It was rejected at the ocean surface through increased evaporation rate. The water cycle speeds up and you get more cooling from clouds and rain. The entrained energy is invisibly lifted from the surface in latent heat of vaporization and transported to the cloud deck where it is released and at that altitude the path of least radiative resistance is upwards as the denser layer of greenhouse gases are now below it and make it more difficult for downwelling infrared from the cloud deck to make it back to the surface.
Nuke says:
Slightly OT: The lead story on ABC’s World News Tonight last night was the heat wave spreading through the middle of America. Not one mention of climate change, global warming, etc. Was this deliberate or accidental?
+++++++++++
CBC Toronto interviewed a senior climatologist from Environment Canada who also avoided any mention at all of ‘global warming’ or ‘climate change’. Immediately afterwards a woman was interviewed who was obviously well prepared to state very clearly that the current heat wave is indeed the result of climate change, and later that it was becoming easier to be able to attribute this type of event to climate change which we know is induced by Man. The contradictions (it is/it could be/it is becoming easier/maybe/surely/almost proving/detectable) was not lost on me. It was nearly a word for word repetition of a paragraph I have read elsewhere.
The importance for me was the lack of alarm from Environment Canada who have slavishly spoken the party line thus far. Perhaps the hammering the warmists took for claiming the Moscow heat wave last year was caused by climate change, not a stalling high, sunk in. Expect specious, weasling, contradictory claims in the coming weeks.
Interestingly the number of deaths atttributed to the heat (22) is far lower than the cold wave in the UK this year.
Sure would be nice if we could harness all this heat for energy.
I did a science course with the Open University in the seventies in which I found out that the Earths mantle heats up by pressure the mantle heats up with the extra pressure with depth until it melts and then with greater depth and pressure it becomes solid again.This reason for heating of the mantle is not mentioned here.
@ur momisugly SteveE says: July 22, 2011 at 5:30 am
///////////////////////////////////////
The oceanic crust is very different to the continental (land) crust. The oceanic crust is very much less thick (circa 7-10km in thickness) than the continental crust (circa 25 to 70 km in thickness). There are diifferences in density and latent heat capacity.
There is probably some data for temperature gradient obtained from oil wells drilled in the sea bed, however, these are situated on the continental shelves and are no doubt not representative of conditions that would be encountered if we were to drill in deep oceanic crust, ie., if we were to make a bore hole in the sea bed lying at say 4.5km depth. I envisage that temperature gradients in such crust would be significantly different but I have seen no data and as far as I know, man has never drilled there (but I stand to be corrected on that).
My point is not what geothermal energy is available in the depths of oceanic crust compared with that found at depth in continental crust. The point I am mooting (and I have no firm views on it), is whether if the seas were to be drained, ignoring the atmosphere and adiabatic lapse and ignoring convection. would the land temperature at the very deepest valleys of the oceans be warmer than the land temperature at the top of Everest? After all, at the foot of the deepest oceanic valleys, the distance to the warmer parts of the mantle is significantly less (say 7 to 10km compared to 70 to 100km). logic dictates that the nearer you are the mantle, the less impedience there is to heat being conducted/radiated away from the core and isn’t this what drilling boreholes on land bears out. Put another way, would I be warmer standing at the foot of the deepest oceanic valley than if I was standing on top of Everest?
If I would be warmer standing at the foot of the deepest oceanic valley than when standing on top of Everest, I am mooting the possibility that this heat source may not have been properly accounted fr in the models since it is additional to that produced by volcanic outgasing. I doubt that it would be large (at least not in comparison to the energy received from the sun) but when one is only talking about changes caused by approximately 2 or 3 w per sq m, even relatively modest factors could be significant contibutors.
.
Yeah, but this is exactly what I am worried about.
I’m also thinking that no bird except those at a Lagrange point are truly reliable as the inevitable decay needs retasking and corrections, this human intervention step makes the data less than reliable, at least to me.
We’ve got this stable platform, the moon, sitting up there. I look at it and think, heck, we can get great photos and measurements of it from here, through our thick atmosphere. The Earth is even larger in the sky from the moon, there is almost no atmosphere, it is only a second ot two away in real-time comm, it is tidal locked and we know every little thing about its orbit. It seems the only problem would be lack of shielding from solar radiation and micrometeorites (both problems exist with satellites anyway).
My feeling is a consequence of the current state of human nature and science itself these days. When I hear that someone needs to adjust data to compensate for something peculiar to a satellite, I immediately lose trust. And considering that NASA employs people like Hansen, I know that agenda driven scientists *do* exist. Means, motive and opportunity.
I simply do not trust them any longer. Thus my idea. Plant sensors up there that cannot be tampered with and let the raw data speak for itself.
@Lichanos, Andrew
I just read War of the Worlds while on holiday, which was written by HG Wells in 1897. It gives an interesting insight into the state of astro / geophysical knowledge at the time. Basically both the planets and the sun were considered to possess only residual, primordial heat, and were thus steadily cooling. There was indeed no conception of a heat source within either, such as as then unknown nuclear processes (although Roentgen must have been discovering radioactivity around that time). Thus Mars was cold due to its greater age than earth, and in the past had been warmer and more habitable. The freezing Martians thus envied our warmer Earth and hence the invasion of London.
Wells considered Mars older than earth, contrary to current ideas of the genesis of the solar system which gives all planets more or less the same age.
richard verney says:
July 22, 2011 at 11:52 am
————-
That has been studied over a decade ago, while I was at uni studying geology:
http://www-odp.tamu.edu/publications/heatflow/ODPReprt.pdf
Page 15 average sea floor temp of 4.2 degrees C, page 19 shows data coverage. Think you can rest assured that’s all pretty pretty well covered.
An additional couple of sources for earths budget sure to cause debate.
1: the global electrical circuit, telluric currents, etc.
2: Modulation of earths magnetic field by external fields, and the inductive kickback or inductive heating that occur to earths “dynamo” molten rotating core.
Blade says: July 21, 2011 at 11:14 pm
I’ve always wondered about something. Would it make sense to place on the moon (the side always facing us), a sensor (or perhaps 3 to eliminate any error between them) that measures whatever can be measured from 200,000+ miles away in a constant orbit (albeit receding a few mm a year).
There is certainly some sense in this suggestion. One challenge i see is the long period of the orbit. With low-earth orbits, you get around the earth every 1.5 hours, so you can get frequent measurements of the spots under the orbit (which would be the whole earth for polar orbits). For Geosynchronous orbits, you get a continuous look at one part of earth.
But from the moon, you get a view that switches from the day to the night side once every 4 weeks or so. For some measurements that is would work quite well, since the earth spin under the sensors once per day. For temperature measurements, this would be problematic. You could measure the mid-day temperature of a location for a week; then measure the the dusk temperature for a week; then the night temperature for a week, then the dawn temperature for a week. It would be very difficult to get a global average temperature this way.
@SteveE says: July 23, 2011 at 7:19 am
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Thanks fir the paper. Interesting read. I note that the study found the seafloor temperature as high as18.7 deg C in some places. Unfortunately without sight of the files referred to in the paper, it is not possible to consider the situation and distribution of seafloor temperatures.
If you do have the files referred to in the paper, I would very much you posting a pdf of them.
thanks again,
Actually, since Trenberth’s missing heat never existed, 20 trillion watts is slightly smaller in climate modelling terms.
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richard verney says:
July 23, 2011 at 1:17 pm
Google ocean drill program, their website has quite a lot of data. The higher temps are most likely drilled on hot spots like Hawaii and Iceland or spreading ridges.
phlogiston says:
July 23, 2011 at 6:45 am
“I just read War of the Worlds while on holiday, which was written by HG Wells in 1897. It gives an interesting insight into the state of astro / geophysical knowledge at the time. Basically both the planets and the sun were considered to possess only residual, primordial heat, and were thus steadily cooling.”
Sure. I’m working from memory but as I recall it was Lord Kelvin about that time, or sometime between Charles Darwin publishing of Origin of Species and the turn of the century, who’d worked out the age of the earth at 100 million years by way of calculating how long it would take heat of formation to dissipate enough to reach current temperature. Back then the earth at 100 million years old was both religious and scientific heresy where the religionists pegged the age in the thousands of years using bible references and where science of the time (mostly through geology) held it to much older than 100my. Kelvin’s estimate was too short a period of time for Darwinian evolution and too long for bible literalists.
History of science can be fascinating reading and very enlightening.