Guest Post by Willis Eschenbach
OK, a quick pop quiz. The average temperature of the planet is about 14°C (57°F). If the earth had no atmosphere, and if it were a blackbody at the same distance from the sun, how much cooler would it be than at present?
a) 33°C (59°F) cooler
b) 20°C (36°F) cooler
c) 8° C (15°F) cooler
The answer may come as a surprise. If the earth were a blackbody at its present distance from the sun, it would be only 8°C cooler than it is now. That is to say, the net gain from our entire complete system, including clouds, surface albedo, aerosols, evaporation losses, and all the rest, is only 8°C above blackbody no-atmosphere conditions.
Why is the temperature rise so small? Here’s a diagram of what is happening.
Figure 1. Global energy budget, adapted and expanded from Kiehl/Trenberth . Values are in Watts per square metre (W/m2). Note the top of atmosphere (TOA) emission of 147 W/m2. Tropopause is the altitude where temperature stops decreasing with altitude.
As you can see, the temperature doesn’t rise much because there are a variety of losses in the complete system. Some of the incoming solar radiation is absorbed by the atmosphere. Some is radiated into space through the “atmospheric window”. Some is lost through latent heat (evaporation/transpiration), and some is lost as sensible heat (conduction/convection). Finally, some of this loss is due to the surface albedo.
The surface reflects about 29 W/m2 back into space. This means that the surface albedo is about 0.15 (15% of the solar radiation hitting the ground is reflected by the surface back to space). So let’s take that into account. If the earth had no atmosphere and had an average albedo like the present earth of 0.15, it would be about 20°C cooler than it is at present.
This means that the warming due to the complete atmospheric system (greenhouse gases, clouds, aerosols, latent and sensible heat losses, and all the rest) is about 20°C over no-atmosphere earth albedo conditions.
Why is this important? Because it allows us to determine the overall net climate sensitivity of the entire system. Climate sensitivity is defined by the UN IPCC as “the climate system response to sustained radiative forcing.” It is measured as the change in temperature from a given change in TOA atmospheric forcing.
As is shown in the diagram above, the TOA radiation is about 150W/m2. This 150 W/m2 TOA radiation is responsible for the 20°C warming. So the net climate sensitivity is 20°C/150W-m2, or a temperature rise 0.13°C per W/m2. If we assume the UN IPCC canonical value of 3.7 W/m2 for a doubling of CO2, this would mean that a doubling of CO2 would lead to a temperature rise of about half a degree.
The UN IPCC Fourth Assessment Report gives a much higher value for climate sensitivity. They say it is from 2°C to 4.5°C for a CO2 doubling, or from four to nine times higher than what we see in the real climate system. Why is their number so much higher? Inter alia, the reasons are:
1. The climate models assume that there is a large positive feedback as the earth warms. This feedback has never been demonstrated, only assumed.
2. The climate models underestimate the increase in evaporation with temperature.
3. The climate models do not include the effect of thunderstorms, which act to cool the earth in a host of ways .
4. The climate models overestimate the effect of CO2. This is because they are tuned to a historical temperature record which contains a large UHI (urban heat island) component. Since the historical temperature rise is overestimated, the effect of CO2 is overestimated as well.
5. The sensitivity of the climate models depend on the assumed value of the aerosol forcing. This is not measured, but assumed. As in point 4 above, the assumed size depends on the historical record, which is contaminated by UHI. See Kiehl for a full discussion.
6. Wind increases with differential temperature. Increasing wind increases evaporation, ocean albedo, conductive/convective loss, ocean surface area, total evaporative area, and airborne dust and aerosols, all of which cool the system. But thunderstorm winds are not included in any of the models, and many models ignore one or more of the effects of wind.
Note that the climate sensitivity figure of half a degree per W/m2 is an average. It is not the equilibrium sensitivity. The equilibrium sensitivity has to be lower, since losses increase faster than TOA radiation. This is because both parasitic losses and albedo are temperature dependent, and rise faster than the increase in temperature:
a) Evaporation increases roughly exponentially with temperature, and linearly with wind speed.
b) Tropical cumulus clouds increase rapidly with increasing temperature, cutting down the incoming radiation.
c) Tropical thunderstorms also increase rapidly with increasing temperature, cooling the earth.
d) Sensible heat losses increase with the surface temperature.
e) Radiation losses increases proportional to the fourth power of temperature. This means that each additional degree of warming requires more and more input energy to achieve. To warm the earth from 13°C to 14°C requires 20% more energy than to warm it from minus 6°C (the current temperature less 20°C) to minus 5°C.
This means that as the temperature rises, each additional W/m2 added to the system will result in a smaller and smaller temperature increase. As a result, the equilibrium value of the climate sensitivity (as defined by the IPCC) is certain to be smaller, and likely to be much smaller, than the half a degree per CO2 doubling as calculated above.
Steve Goddard
How can you separate out the radiation from the Sun from the radiation from the atmosphere?
Dave Springer (05:37:48)
First, my “continued silence” on this is because (as I said I would) I’ve been skipping over anything containing the word “moon”. I only caught this one by chance. So you can stuff your “tacit admission” where the sun don’t shine, it is unpleasant, unwarranted, and untrue.
Next, why is the regolith the temperature it is? I don’t know … what temperature is it? Probably somewhere in one of the moon posts I skipped over, hang on, let me look … OK, here we go:
Well, that’s plenty confusing. First, the surface “averages” 40-45°C cooler than it is a metre down … why would that be? I mean, why would the interior of the moon be warmer than the surface, when it is well known that it doesn’t have a molten core? Can you explain that one, Dave? Or is your continued silence on that one a tacit admission that rather than admit an error you are choosing to simply ignore the inconvenient data?
And the regolith a meter down is a “nearly constant -35°C” … oh really? They know this from the hundreds of metre-deep holes we’ve drilled at various widely-separated locations to randomly sample the lunar sub-surface and then monitor its changes over time? …
Next, they give “average” temperatures. But when we are dealing with long, slow swings of 300°C in an environment where radiation is the only way to gain or lose heat, you can’t just “average” the temperatures, that’s nonsense. You have to convert them to the equivalent radiation temperatures, average their integrals over time, and convert back.
So as far as your question about the regoliths goes, until we have some real figures, I’m going to pass on guessing, and so should you. Those figures are from folks who think you can “average” lunar temperatures … riiight.
Bryan,
Good question. Solar radiation comes at much shorter wavelengths than radiation from the atmosphere.
http://www.globalwarmingart.com/wiki/File:Atmospheric_Transmission_png
JAE (09:17:27)
If you have data on this question I’d love to see it …
w.
Bryan (12:02:11)
Take the measurements at night …
w.
Willis Eschenbach (12:01:17) :
why is your reconstruction a degree warmer than theirs 500 years ago if their error bar is only a tenth of a degree?
There are random errors and systematic errors [e.g. depending on site distribution]. The systematic error is unknown and can [and probably does] explain the difference.
We’re not dealing with borehole scientists. We’re dealing with borehole acolytes.
I think you have a bad case of ‘confirmation basis’ [actually anti-confirmation], but to each his own bias 🙂
I would separate the technique [I think it will be useful on the Moon too – also no water 🙂 ] from current practitioners [or at least the ones you have had a run-in with].
Beng-
“The cold deep-water is a remnant of the previous ice-ages. ”
This occurred to me but I find it surprising. If heat were able to conduct through seawater at just 1 meter per year and the average ocean depth is just 3.7 km that would only take us back to a couple thousand BC, and I usually think of the last ice age as ending something like 10,000 BC. I wonder if there could be another phenomenon having to do with a pressure gradient and/or density at work “fighting” against downward heat conduction in the ocean?
If it is true that deep ocean coldness is an ice age remnant, it raises more questions. Now I wonder in maintaining the equilibrium you mention how much heat is extracted in a year and whether it is something worth putting into the models…. or is it all a subsystem that can be disregarded?
Steve Goddard:
“Nights in the desert are much warmer when it is humid, due to the increased GHG.”
Some data would be nice here. In summertime, it is much warmer at night in the dry desert (say, Phoenix) than it is at humid areas at the same lat. and long. (say Atlanta). Why?
Steve Goddard (10:57:07) :
?? I fail to see how the lapse rate supports your position. I don’t understand the other reference, so if it proves anything, I cannot tell.
Willis:
“If you have data on this question I’d love to see it …”
It’s mostly from experience that I say it. I don’t know where to get long-term daily temp., humidity, and cloud-cover records. However, if you look at the Phoenix weather for February and the first 18 days of this month, selecting only those days which have a cloud cover of 0 or 0.1 (11 days during the period), you will find that the high daily temperature varies betwee 85 F to 46 F, and the daily low relative humidity readings vary from 13-29 percent. There is a slight NEGATIVE correlation between the high temp. and humidity (r^2 = 0.33). At night there is also a negative correlation–it is generally warmer when the r.h. is LOWER (r^2 = 0.46). Not a lot of data, I know, but something to start with….
Data here: http://www.nws.noaa.gov/climate/index.php?wfo=psr
Nuts, I used relative humidity, rather than absolute humidity. When abs. humidity values are used there is essentially no correlation between daytime high temperatures varying between 66-85 and daytime low abs. humidities varying from 2.9-5.9 (essentially a doubling of the amount of water in the air had no discernable effect on temperatures). Same with nighttime.
Doesnt the earth surface, and all the layers upwards obey Zeroth Law of Thermodynamics?
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/thereq.html
And doesnt that mean CO2 cannot increase the temperature?
Except, say if Co2 increased to the double amount overnight, the temperature would increase for a short time, and then fall back to the original value?
Or have I totally misunderstood the situation?
Leif Svalgaard (12:31:38), thanks for your answer. You say:
In other words, their error estimate is nonsense … which is what I said.
Anti-confirmation bias? That’s when results don’t agree with what we know about the past (e.g. no sign of a Little Ice Age in their records, when it is well documented by a host of proxies and contemporary accounts), so we should look on the results with suspicion? Yeah, I have that, so should you. The anti-confirmation bias motto is “extraordinary claims require extraordinary evidence” …
Regarding current practitioners, remember that these are the ones you recommended. These are the ones whose results differ from yours by 1°C, at a time when they are claiming a standard error of a tenth of a degree. My run-in with them establishes a history of scientific malfeasance, but that’s not why I think their results are bogus. I think they are bogus because a) they don’t show the LIA and b) their claimed accuracy is a joke.
Can boreholes give us a thermal history? Assuredly. Can we use them without a complete record of the underground geology at the site, particularly including water seeps? No way, and that’s what they’re doing.
Can we use them with such a record? Possibly, but even then it is difficult. How much water is leaking down the borehole, not just at a given instant, but on average over the year? Exactly what is the rate of heat loss through a given geological layer? What is is rate of heat loss at the boundaries between the layers? Until we can answer these questions very exactly, the results are very suspect.
So I agree with you that yes, theoretically, borehole records could give us historical temperature records. But as always, the devil is in the details, and with boreholes there are a lot of details, those details are often unknown, and are always way underground where we can only measure them indirectly. Not a good combination.
JAE (14:35:49)
Thanks, JAE. It’s very hard to prove that way. The difficulty is that deserts get rain. When the residual moisture in the soil evaporates, we get water vapour, which tends to hold the heat in.
However, as you point out, at those times we also get evaporation and sometimes clouds … which makes it very hard to separate out the effects.
kwik (14:56:35)
This is a common misconception. The zeroth law only applies to net flows, not individual flows. So while CO2 cannot increase the temperature, it can reduce the drop in temperature, which comes to the same thing. See my post above on the difference between net and individual flows.
Willis:
“However, as you point out, at those times we also get evaporation and sometimes clouds … which makes it very hard to separate out the effects.”
I hope you noticed that these were all virtually cloudless days (less than 10% cloud cover). And most of the days were in sequential periods, indicating no rainy periods.
“Thanks, JAE. It’s very hard to prove that way. The difficulty is that deserts get rain. When the residual moisture in the soil evaporates, we get water vapour, which tends to hold the heat in.”
Within this small amount of data, there is certainly no indication that more water vapor meant more heat, either in the day or the night. I’ll try to get more data somewhere.
Note, also that the amount of water vapor in the air down where you are is about 6-7 times what it is in Phoenix this time of year (during the day). Yet your temperatures are about the same… The negative feedbacks evidently keep any “greenhouse effects” well in check.
Apologies if this has already been covered.
Joel Shore (19:30:38, 18MAR10) wrote:
“What they are saying is that the direct effect of the IR absorption by CO2 will be to increase the TOA downwelling radiation by 3.7 W/m^2 but that the total increase, once you consider all the feedback effects will be an increase in the TOA downwelling radiation by almost 3 times this (where I am using the result that a 3.7 W/m^2 increase in TOA downwelling radiation produces a temperature rise of about 1 C, as calculated by the S-B Equation). ”
and Bill Illis (21:46:42, 18MAR10) wrote:
“- then there is feedbacks from increased water vapour and albedo which add another 6.5 to 7.4 W/m^2 after this initial forcing;
– the layer now increases in temperature by 3.0C (11.5 extra watts on top of the original 240 watts).
– the layer where the equilibrium emission temperature of 255K occurs is now 461 Metres higher.
– the adiabatic lapse rate of 6.5C/km stays intact and the surface warms by the same 3.0C.
So, the sensivitiy is calculated as 4.0 extra watts of GHG forcing eventually results in an increase of 11.5 watts (once all feedbacks occur) and temperatures rise 3.0DegC”
I don’t agree with either of these statements.
The Surface Balance Equation at Equilibrium (I’m not claiming we are ever at equilibrium, this is the simple KT model) is:
Absorbed Solar Radiation + Back IR Radiation from the Atmosphere = IR Radiation from the surface + Latent Heat in Evaporated Water Vapour + Direct Conduction to the Air from the Surface.
Differentiating, again at equilibrium,
Change in Forcings (absorbed solar +back Radiation) = Change in Radiation from the surface + Change in Evaporation + Change in conduction (assumrd to be nil, as at equilibrium the relationship between the surface and the boundary layer is likely to be unaltered for any small change in temperature).
Cranking in the numbers:
Change in Forcing = 4sT^3dT + 78xdT. (s is 5.67×10^-8, dT is change in temperature, x is percentage increase in evaporation per DegC).
The big unknown in this equation is x, the increase in ebaporation. The Clausius-Clapyeron equation gives an upper limit of 6.5%, and some scientists think it is as low as 2%. It’s not 0%.
For x=2% the surface sensitivity is 0.15DegC/W/m^2, and the Change in Forcing is 22W/m^2 if the temperature rises by 3DegC.
For x=6.5% the surface sensitivity is 0.095DegC/W/m^2 and the Change in Forcing is 32W/m^2 for a temperature rise of 3DegC.
I don’t know what the relationship of the forcing at the tropopause (11.5 W/m^2 according to Bill) is to Surface Forcing. But to get 3DegC at the surface you need to double or triple that already trebled Radiative Forcing. (The assumption that the Lapse Rate stays constant is no help – the Surface is massively imbalanced. It cannot maintain the 3DegC increase without additional flux, and it can’t get that from an inflexible Lapse Rate.)
I don’t know what forcing was assumed by Joel. If it’s say 12W/m^2, then you get around 1DegC at the surface. But again you need to double or treble that to get 3DegC.
What am I missing here? I get a really insensitive surface and a large mismatch in surface forcing to tropopausal “Radiative Forcing”. Is there a problem with the no-change-in-conduction assuption (It would have to decrease by 50%)?
Regarding Pollock and his boreholes:
Here’s a 1997 paper reporting boreholes showing an early holocene climate optimum, medieval warm period, and little ice age
http://www-personal.umich.edu/~shaopeng/97GL01846.pdf
a summary from 1998 addressing only the 20th century
http://www.sciencemag.org/cgi/content/abstract/282/5387/279
and a summary of a paper from 1999 addressing only the warming since the Little ice age
http://www.nature.com/nature/journal/v403/n6771/abs/403756a0.html
It looks like an example of “playing to the global warmers”, papers since 1998 only address the period since the little ice age
– evidently these warming results more easily make it iinto the approved journals
“HankHenry (12:54:15) :
Beng-
“The cold deep-water is a remnant of the previous ice-ages. ” ”
The deep ocean temperature is a reflection of the past several hundred years of the coldest, densest ocean water there is on the planet.
The coldest densest ocean water occurs in the thermohaline ocean sinking regions near the sea ice pack and under the sea ice pack in the Arctic and around Antarctica.
Ocean water is most dense at about 1.0C with high saline content. Fresh water is most dense at 4.0C but with the introduction of very high salt content, the density can maximize close to 0.0C.
If ocean water gets colder than the maximum density combination of temperature and saltiness, it becomes less dense and rises. If it gets warmer than this or less salty than this, it also becomes less dense and rises. If it freezes, it becomes the least dense water of all and it floats to the top or it only occurs at the surface in the first place. The saline content will then fall out of it as well and it becomes even less dense.
Even in the ice ages, the deep ocean temperature probably did not go much lower, maybe 0.0C, and it has never, ever in the history of the planet, been lower than this. The entire ocean has to warm up, especially in the polar regions for the deep ocean temperature to go higher than today. In other words, there can be no sea ice, even in the winter, to increase much from today’s level.
In the paleoclimate, there are estimates of the deep ocean temperature being as high as 10C above today’s level. That means, even in the winter, the poles did not go below 10C.
JAE,
One reason Phoenix is warm at night is because of the humidity from lawns, golf courses, etc. I have seen dew points in excess of 70 degrees there.
Also, why do you think it is extremely cold on the top of Mt. Everest? Could it have anything to do with the lack of atmosphere?
Willis Eschenbach says:
I suggest you read what Bill Illis wrote in his comment on 18/03/2010 (21:46:42). At the end of the day, the original forcing of ~4 W/m^2 from doubling CO2 results in another ~7 W/m^2 of “forcing” (in the sense of change in downwelling radiation at the TOA).
The IPCC is not saying that ~4 W/m^2 increase in downwelling radiation at the TOA leads to a 3 C temperature rise…They are saying that ~4 W/m^2 of forcing results in feedback that increase the downwelling radiation by considerably more than that.
Francisco says:
That is not really relevant as the rate of transfer to the deep ocean reservoir is rather small. So, you have to consider the amount we are adding to the other reservoirs (that exchange fast enough that they can be thought of as a rapidly-equilibrating subsystem that exchanges carbon only very slowly with the deep oceans. Also, note that if you add only 1% annually to a reservoir that is not able to get rid of it, you will double the amount in that reservoir in 100 years.
Ah…Do you mean no basis beside the overwhelming empirical evidence that we have increased the levels of CO2 in the atmosphere from the pre-industrial baseline of 280ppm to the current ~390ppm?
Reasonable compared to what? And, the fact is that CO2 levels on geological timescales has been much higher than they are now, with the correlated effects of warmer temperatures, higher sea levels and everything else.
I think you are woefully misunderstanding the science. There was some confusion regarding exactly what fraction of that carbon that is not accumulating is going into the ocean and what part into the biosphere (and soils). There was not confusion about the basic fact that about half of it was not remaining in the atmosphere.
Well, you are welcome to believe what you want to believe but it certainly isn’t a belief based on the scientific evidence.
Brian G Valentine says:
Debunking of G&T’s Second Law argument in 3 easy steps:
(1) The Second Law statement about heat flowing from hotter to colder applies to net flows; it does not mean that no heat can be radiated by a colder body and absorbed by a hotter one. This should be obvious from an understanding of the basic statistical physics from which the Second Law derives, but even if one is ignorant of that, we know that all bodies radiate when they are at a nonzero temperature; if you have a hotter body near a colder body, the colder body is not going to magically detect the hotter body and stop radiating. The Second Law is not about magic. The Second Law means simply that the colder body will absorb more radiation emitted by the hotter body than the hotter body will absorb radiation emitted by the colder body.
(2) All reasonable models of the atmospheric greenhouse effect, whether toy models like Willis’s steel greenhouse or Trenberth and Kiehl’s energy budget diagrams or line-by-line radiative transfer calculations, have the net flow of heat being from the warmer earth to the colder atmosphere, as the Second Law requires. If you believe otherwise, show us.
(3) Despite the fact that the net flow is from earth to atmosphere, the effect of an IR-active atmosphere is still to produce warming relative to the case of an IR-transparent atmosphere. This may be the point that trips the most people up….It seems like an almost unstated assumption in many arguments of a Second Law violation that in order for the greenhouse effect to occur, the net flow must be from atmosphere to Earth. ****THIS IS WRONG.**** The reason that this is wrong is because in the comparison case, of an IR-transparent atmosphere, all the radiation emitted by the earth escapes into space. Hence, anything that causes some of that radiation to be returned to the earth will cause warming relative to that case. The greenhouse effect just says that SOME of the radiation that would otherwise escape from the Earth into space finds its way back to the Earth; it makes no claim that the amount that finds its way back is greater than the amount that the atmosphere absorbs from the earth, as such a claim would be a violation of the Second Law (and just plain silly to boot).
Bryan:
Arthur has troubles with them in the same way that I would have troubles with a particularly dense and opinionated student who had all sorts of wrong-headed ideas about physics and did not have the necessary combination of knowledge, intellect, and ability to listen to things that go against what they want to believe to understand when I tried to explain things to them. I suppose that someone reading the exchange who does not have the necessary background to evaluate the scientific arguments might find Fred Staples or Terry Oldberg’s arguments compelling; those of us who do, do not find them at all compelling and are actually somewhat amused to hear that people take them at all seriously.
Joel, I appreciate very much your understanding and interest of the forcings at the tropopause and the associated feedbacks. I really do, I know you have labored and contributed extensively. Your understanding of the climate sensitivity corollaries is as extensive as anyone I know.
But if we come back to the same old problem above, Joel, this trying to move heat from cold to hot without compensating work … we know that space is something of a homogeneous radiation source or sink at a temperature of like 2.9K – one looks at that and thinks, the heat has to be going the other way …
The bottom like to all the feedback stuff, Joel, is that it doesn’t look right, what more can anyone say?