Guest essay by Dr Doug Hoyt
In the past few years, three articles have come out that, taken together, lead one to conclude that climate sensitivity is very low, being less than 1 C for a CO2 doubling compared to the 3 C figure favored by the IPCC.
The first article is by Levitus et al (2005). They conclude that the oceans warmed by 0.06 C between 1948 and 1998. It represented an increase in heat content of 2 x 10^23 joules.
In 2006, Lyman et al. showed that the oceans cooled between 2003 and 2005 with a net loss of energy of 0.32 x 10^23 joules. Climate models do not predict or allow for such cooling of the oceans.
In 2007, Gouretski and Koltermann showed that the early heat content measurements were incorrect because they did not take into account changes in instrumentation. They concluded that between 1955 and 1996 that the oceans only gained 1.28 x 10^23 joules with an uncertainty of 0.8 x 10^23 joules. Essentially the earlier Levitus paper was wrong.
Combining the Lyman and Gouretski papers, the net ocean heat content between 1955 and 2005 seems to be only 0.98 x 10^23 joules with an error of (0.8 + 0.11) x 10^23 joules or 0.91 x 10^23 joules, adding the error terms of the two papers. The net heat content change is therefore essentially statistically indistinguishable from zero. The net warming of the ocean from 1948 to the present seems to be only 0.03 +/- 0.03 C.
The corresponding net radiative imbalance is about 0.1 W/m^2, well below the model predictions which equal 0.85 W/m^2 for 1993 to 2003 (Hansen et al., 2005). Instead of a climate sensitivity of 3 C for a CO2 doubling, the climate sensitivity is only about 0.4 C. There is little or no energy “in the pipeline” and thus a good reason to believe that all the observed warming of the atmosphere has already occurred.
The atmospheric warming of 0.6 C between 1900 and 2000 is presumably forced by 2.7 W/m^2 from all greenhouse gases. The forcing from a doubling of CO2 is about 3.7 W/m^2 which would correspond to a climate sensitivity of 0.8 C for a CO2 doubling if all the warming of the twentieth century was caused by greenhouse gases. Since even the IPCC concedes that half the warming may be coming from other causes (such as solar), the calculated climate sensitivity becomes 0.4 C for a CO2 doubling. This low sensitivity is consistent with the low values derived by Lindzen (0.5 C) and Idso (0.4 C) and others. It is also consistent with the analysis of the oceans discussed above.
There is no hiding of global warming in the oceans is as commonly argued. The results are consistent with the fact that 15 micron thermal radiation from carbon dioxide will only heat the upper 15 microns of the oceans, a topic to which we now turn.
Comments on why the ocean isn’t absorbing thermal infrared energy
The absorption coefficient for liquid water as a function of wavelength is given at www.lsbu.ac.uk/water/vibrat.html (see the figure near the end). Thermal infrared in the Earth’s atmosphere is around 10 to 20 microns where the absorption coefficient (A) is about 1000 cm-1. For the transmission in liquid water (T), we have
T = exp(-A*L)
where L is the depth of penetration. For the case where 1/e or 27% of the incident photons remain unabsorbed and with A=1000 cm-1, then L= 1/1000 cm = 0.01 mm. 98% of the incident photons will be absorbed within 3 times this distance.
So one can see from the figure, than practically no infrared photons penetrate beyond 0.03 mm. A more precise estimate of A is 5000 cm-1 at 15 microns where carbon dioxide is emitting radiation, so 0.006 mm is a more accurate number for the depth of penetration of 98% of the photons arising from carbon dioxide forcing. For the sake of argument, we will say that all the 15 micron thermal radiation at 15 microns arising from increased carbon dioxide in the atmosphere is absorbed in the upper 15 microns of the ocean, based upon electromagnetic theory. Since the liquid water is such an effective absorber, it is a very effective emitter as well. The water will not heat up, it will just redirect the energy back up to the atmosphere much like a mirror, but not exactly a mirror, and this is an important point.
For A = 5000 cm-1 at 15 microns, the implied water emissivity is 0.9998 implying that, of the incident radiation, only 0.02% of it will ultimately be absorbed in the water. The emitted radiation will closely follow a blackbody emission curve whereas the incident flux from carbon dioxide is confined to a band centered at 15 microns. The implication of this is that much of the radiation emitted will escape directly to space through the IR windows, so it could be viewed as a negative feedback. About 40% of the energy will escape this way. Alternatively, this mechanism implies that climate will be less sensitive to greenhouse gas warming than it would be to an equal solar radiation forcing. In addition, there are many moist areas over land and clouds are also moist, so this negative feedback or reduction in climate sensitivity is also operable nearly everywhere.
The above mechanism works because the initially absorbed infrared energy cannot be transferred to the ocean depths by conduction (too slow), by convection (too small an absorption layer compared to the size of convective cells), or by radiation (too opaque). It must escape by the fastest way possible meaning upwards radiation away from the water. Also since the surface layer where the absorption occurs is cooler than the water just below it, there can be no net transfer of energy by conduction, convection, or radiation downwards because it would violate the laws of thermodynamics.
Consequently, the only way to explain the ocean heating in depth is for the solar radiation to change and decreasing clouds between 1985 and 2000, as measured by ISCCP, indicate increasing solar radiation occurred at the same time that the ocean heating is reported to have occurred. Ocean warming papers do not even mention the ISCCP data that has a similar geographic distribution to the water warming. Simply put, where clouds decrease in amount, the water warms. It has nothing to do with carbon dioxide.
A handy plot of the ISCCP results can be found as Figure 3 at www.worldclimatereport.com/index.php/2006/01/11/jumping-to-conclusions-frogs-global-warming-and-nature/ where clouds are shown to decrease for 1987-2000. In a paper by Willis, his Figure 4b, covering 1992-2003, is the one that should be compared to Figure 3. Although the dates do not exactly overlap, the spatial patterns are very similar. There is a need to plot both variables over the exact same time interval, but it is unlikely it would change the major conclusions presented here. Clouds have large natural variations going up and down entirely independent of any greenhouse effect. The climate models do not predict these variations and apparently climate scientists are unaware of these variations and thus do not consider them.
In summary then, the net warming of the oceans since 1948 is small and statistically indistinguishable form zero. The best estimate for climate sensitivity is about 0.4 C for a CO2 doubling and you get this answer using either ocean temperatures or atmospheric temperatures. There is no delayed warming “in the pipeline”. The theoretical interaction of thermal radiation with water shows it cannot be the source of any observed ocean warming. The slight warming and cooling cycles in the oceans seem to arise from fluctuations in cloud cover that may be unforced oscillations, or perhaps may be forced by, for example, cosmic ray variations.
In essence the climate models are wrong in their physics, and wrong in predicting large future warming.
Major references with abstracts:
Levitus, S., Antonov, J. and Boyer, T. 2005. Warming of the world ocean, 1955-2003. Geophysical Research Letters 32: 10.1029/2004GL021592.
The abstract reads:
We quantify the interannual-to-decadal variability of the heat content (mean temperature) of the world ocean from the surface through 3000-meter depth for the period 1948 to 1998. The heat content of the world ocean increased by ~2 × 1023 joules between the mid-1950s and mid-1990s, representing a volume mean warming of 0.06°C. This corresponds to a warming rate of 0.3 watt per meter squared (per unit area of Earth’s surface). Substantial changes in heat content occurred in the 300- to 1000-meter layers of each ocean and in depths greater than 1000 meters of the North Atlantic. The global volume mean temperature increase for the 0- to 300-meter layer was 0.31°C, corresponding to an increase in heat content for this layer of ~1023 joules between the mid-1950s and mid-1990s. The Atlantic and Pacific Oceans have undergone a net warming since the 1950s and the Indian Ocean has warmed since the mid-1960s, although the warming is not monotonic.
Lyman, J. M., J. K. Willis, and G. C. Johnson (2006), Recent cooling of the upper ocean, Geophys. Res. Lett., 33, L18604, doi:10.1029/2006GL027033
The abstract reads:
“We observe a net loss of 3.2 (± 1.1) X 10**22 J of heat from the upper ocean between 2003 and 2005. Using a broad array of in situ ocean measurements, we present annual estimates of global upper-ocean heat content anomaly from 1993 through 2005. Including the recent downturn, the average warming rate for the entire 13-year period is 0.33 ± 0.23 W/m2 (per unit area of the Earth’s surface). A new estimate of sampling error in the heat content record suggests that both the recent and previous cooling events are significant and unlikely to be artifacts of inadequate ocean sampling.”
Gouretski, V. and Koltermann, K.P. 2007. How much is the ocean really warming? Geophysical Research Letters 34: 10.1029/2006GL027834.
The abstract reads:
We use a global hydrographic dataset to study the effect of instrument related biases on the estimates of long-term temperature changes in the global ocean since the 1950s. The largest discrepancies are found between the expendable bathythermographs (XBT) and bottle and CTD data, with XBT temperatures being positively biased by 0.2–0.4°C on average. Since the XBT data are the largest proportion of the dataset, this bias results in a significant World Ocean warming artefact when time periods before and after introduction of XBT are compared. Using bias-corrected XBT data we argue reduces the ocean heat content change since the 1950s by a factor of 0.62. Our estimate of the ocean heat content increase (0–3000 m) between 1957–66 and 1987–96 is 12.8·1022 J. Because of imperfect sampling this estimate has an uncertainty of at least 8·1022 J.
Ellis T.D., et al., 2004. Evaluation of cloud amount trends and connections to large scale dynamics. 15th Symposium of Global Change and Climate Variations, Paper No. 5.7, American Meteorological Society.
This paper shows the trends in cloud cover for 1987-2001. The spatially patterns are very similar to the spatial patterns for ocean warming.
Willis, J. K., D. Roemmich, and B. Cornuelle (2004), Interannual variability in upper ocean heat content, temperature, and thermosteric expansion on global scales, J. Geophys. Res., 109, C12036, doi:10.1029/2003JC002260.
This paper shows the spatial patterns of ocean warming for 1992-2003, which are very similar to the spatial patterns of cloud change shown by Ellis (2004).
Hansen et al., 2005. Earth’s Energy Imbalance: Confirmation and Implications. Science, 308, 1431-1435.
This is the paper that claims a 0.85 W/m^2 energy imbalance for the Earth. It has now been completely debunked by the papers listed above and by basic physics.
Hansen et al., 1985. Climate response times: Dependence on climate sensitivity and ocean mixing. Science, 229, 857-859.
This paper was not mentioned in the above, but it is the primary paper upon which the idea of a high climate sensitivity, a slow response time, and “in the pipeline” ideas originate. Of the many problems with this paper, a major one is that it assumes tritium atoms and infrared photons transport energy in an identical manner. If they don’t, the entire paper is nonsense.
On June 1, 2006, Ray Pierrehumbert and Rasmus Benestad posted an article, www.realclimate.org/index.php/archives/2006/06/on-a-weakening-of-the-walker-circulation/ “On a Weakening of the Walker Circulation” at Realclimate. Then in the 4th comment Ian K asked, “Ray, could you answer some relevant basic questions before I try to digest this article? There are certain basics of the absorption of heat by the ocean which are unclear to me and which seem relevant here. A skeptic’s website avers that, paradoxically, water is not warmed by infrared radiation because it is such a good absorber(!) ie this radiation is completely absorbed by a top skin layer. This leads to re-radiation and evaporation rather than heating of the bulk of the water! Perhaps he has a point, although commonsense suggests to me that if I have two, open-top, insulated, pans of water, in darkened rooms of, say, 10 and 20 C, then that in the warmer room will warm up further and faster.
A corollary of what he is saying is that the sea is basically heated by visible light absorption rather than by heat radiation and is pretty impervious to global warming!”
[Response: This line of argument is total nonsense, and your intuition about what happens to a can of water in a warmer vs. colder room is correct. While it is true that infrared is absorbed in a thin skin at the top of the water, even if the water were completely quiescent this would still lead to the skin layer heating up until emission (plus evaporation and all the other terms we include in the surface budget) equalled the energy input. By the way, if the fluid were quiescent, the solar heating which penetrates the water would cause the water to boil (or close to it) since the heat that enters would have a hard time getting out by diffusion, which is slow. However, the top 50-100 m of ocean is well stirred by turbulence, so energy dumped into the top skin of the ocean gets mixed downward quite rapidly
An addendum to the above remarks is that the skeptics’ site you refer to is probably trying to imply that the greenhouse effect couldn’t increase at all, if infrared can’t heat the ocean. Aside from the fact that infrared can heat the ocean, the argument is misconceived on another level. As explained in our article “A Busy Week for Water Vapor,” the anthropogenic increases in greenhouse effect do not heat the surface primarily by directly increasing downward infrared radiation at the surface. Primarily, they affect what’s going on higher up in the atmosphere, which warms the whole troposphere (which is yoked together by convection so it tends to warm and cool as a unit). The atmospheric warming then warms the surface through increasing all the heat fluxes which couple the surface to the air, not just the radiative ones. The downward radiation to the surface increases mainly because the low level air temperature increases, not because of the direct effect of increased CO2 in the air. –raypierre ]
Dr. Hoyt, I was wondering if you might respond to some of the points that raypierre makes but especially the two regarding the mechanism of heat transfer (“The atmospheric warming then warms the surface through increasing all the heat fluxes…”) and ocean turbulence (“However, the top 50-100 m of ocean is well stirred by turbulence, so energy dumped into the top skin of the ocean gets mixed downward quite rapidly…”). Another description I’ve read somewhere of how the ocean warms, besides the one described above and yours (essentially short wave radiation), is that as the atmosphere warms, the ocean “sees” a higher atmospheric temperature and therefore emits less. So it’s not a question of increasing the energy from an outside source but limiting the emission of outgoing energy. Perhaps this is one of the fluxes that raypierre refers to. Any thoughts on this one? Thanks.
In the laboratory, you can point a 10.6 micron laser at a body of water. Its intensity will be millions of times greater than the intensity increase due to a doubling of carbon dioxide. A thermometer placed just a few centimeters deep in the water will not rise in temperature. It is clear that infrared radiation cannot do bulk heating of water with any efficiency.
At best an increased amount of infrared radiation will slow down any cooling that is occurring. It will not cause a bulk heating.
To the last comment, I might add that dermatologists use the 10.6 micron laser in some of their work. It will cut and burn the upper layer of skin, but will not penetrate into the body because the body consists mostly of water.
I just want to add that for the ocean, heat transfer by convection is impossible since you heat from the top contrary to the atmosphere where you heat from the bottom. Ocean’s thermal layers are in a stable situation
RE: T = exp(-A*L)
What irritates me is the way that AGW fanatics repeat their mantra about “first principles” and “the Physics” when it is plain for anyone who made it through undergrad Quantum Mechanics to see that the fanatics must have flunked Physics 1.
Concerning the sad descent of once functional scientists such as Pierrehumbert into an altered state of reality, I live in the coastal mountains in the upper 30 deg N latitudes of North America’s Pacific Coast. I live at just under 1000 feet and as such, am right in the middle of the semi persistent Summer marine layer when it gets thick. The Pacific Ocean SST is …. 56 to 57 degrees F. When the onshore push is strong, and it is windy and foggy at my locale, I read the thermometer out back and it reads …… drumroll please …….. 56 to 57 degrees. Amazing thing, that! 🙂
Frederic, that is also a key point. Although the ocean may be an excellent heat sink, heating only the thin layer at its top will result is negligable heat flow downward by any means. It is simply far more efficient for the heat to reradiate into the air. The ocean can be viewed as a capacitor. The external discharge path has lower impedence than the internal leakage path. QED.
Steve,
As an electronician, your capacitor analogy strikes me a cord. But I’ll see it this way:
GHG forcing putting excess heat into the oceans is like charging a huge and leaky old capacitor with a high impedance source. What you put in it is immediately leaked (by wind & waves aided convection & radiation). The heat storage capacity of oceans theorized by Hansen is refuted by recent measurements.
Theory points to a climate sensitivity of 1.2 K/2xCO2
modtran modeling shows 0.98 K/2xCO2
home.casema.nl/errenwijlens/co2/howmuch.htm
Nir Shaviv found 1.3 K/2xCO2
www.sciencebits.com/OnClimateSensitivity
So I think the 0.4 – 0.5 values for climate sensitivity are too low.
At the AGU Symposium on Oceans in a Changing Climate: Global Heat and Freshwater Budgets at the American Geophysical Union Fall Meeting held on December 11-15, 2006, Stephen E. Schwartz had a paper entitled “Empirical Determination of the Time Constant, Heat Capacity, and Sensitivity of the Earth’s Climate System”. That paper used Levitus’s erroneous results and derived a climate sensitivity of 2.2 +/- 0.75 C for a CO2 doubling. Substituting the recent Lyman and Gouretski results, his climate sensitivity becomes 1.3 +/- 0.75 C for a CO2 doubling.
Schwartz claims that aerosols are masking about half the warming which would be 1.4 C in the twentieth century vs the 0.6-0.7 C observed warming. We dispute this claim on several grounds.
Measurements of aerosols did not begin in the 1970s as some people claim. There were measurements before then, but not so well organized. However, there were a number of pyrheliometric measurements made and it is possible to extract aerosol information from them by the method described in:
Hoyt, D. V., 1979. The apparent atmospheric transmission using the pyrheliometric ratioing techniques. Appl. Optics, 18, 2530-2531.
The pyrheliometric ratioing technique is very insensitive to any changes in calibration of the instruments and very sensitive to aerosol changes.
Here are three papers using the technique:
Hoyt, D. V. and C. Frohlich, 1983. Atmospheric transmission at Davos, Switzerland, 1909-1979. Climatic Change, 5, 61-72.
Hoyt, D. V., C. P. Turner, and R. D. Evans, 1980. Trends in atmospheric transmission at three locations in the United States from 1940 to 1977. Mon. Wea. Rev., 108, 1430-1439.
Hoyt, D. V., 1979. Pyrheliometric and circumsolar sky radiation measurements by the Smithsonian Astrophysical Observatory from 1923 to 1954. Tellus, 31, 217-229.
In none of these studies were any long-term trends found in aerosols, although volcanic events show up quite clearly. There are other studies from Belgium, Ireland, and Hawaii that reach the same conclusions. It is significant that Davos shows no trend whereas the IPCC models for anthropogenic aerosol increases show it in the area where the greatest changes in aerosols were occurring.
There are earlier aerosol studies by Hand and Marvin in the Monthly Weather Review going back to the 1880s and these studies also show no trends and all the astronomical observations show no trends.
A second argument against aerosols being a cooling agent that masks warming is that the claimed aerosol increases occur where the strongest warming is being observed, namely the Northern Hemisphere mid-latitudes and Europe. If anything, aerosols are an additional source of heating through soot which warms the atmosphere or soot on snow that will also warm.
Finally the Northern Hemisphere where the aerosols presumably are located is warming faster than the Southern Hemisphere where there are fewer aerosols.
In short there is no experimental evidence that increasing aerosols are masking any greenhouse warming or that they caused the 1940-1975 cooling.
In light of this, we reject Schwartz’s contention of aerosol masking and without it, the analysis of Schwartz gives a CO2 doubling sensitivity of about 0.65 C, close to the 0.4 to 0.8 C value we deduce.
Also like us, Schwartz concludes that there is minimal warming “in the pipeline”.
It seems like the upper limit on climate sensitivity is 1.3 C with evidence it may well be much lower.
In a recent interview with Roger Pielke Sr, Robert Corell, director at the Heinz Foundation (the same that granted Hansen 1 quarter million $ prize for his “outstanding contribution to climate science”) uses the image of “supertanker” (subliminal links to pollution and SUV spewing fossil fuel CO2 unintended of course) instead of “pipeline” to justify that the ocean stores excess heat, hence the inertia in temperature rise.
I wonder how long will they be able to paint themselves in the corner and keep the house of card from collapsing ?
Dough your calculations don’t make sense to me.
If we consider the CO2 only forcing of 5.35ln(369.4/296.3), this yields a pure co2 forcing 1900-2000 of 1.17 W/m2
www.grida.no/climate/ipcc_tar/wg1/222.htm
A climate sensitivity of 3 K/2xco2 is then 0.46 degrees
A climate sensitivity of 1 K/2xco2 is then 0.15 degrees
A climate sensitivity of 0.5 K/2xco2 is then 0.076 degrees
Here is a summary of some of the recent determinations climate sensitivities or warming for a doubling of CO2:
0.4 C (Idso)
0.5 C (Lindzen)
0.6 +/- 0.2 C (analysis above)
0.65 C (Schwartz without aerosol masking)
0.98 C (Modtran)
1.3 C (Schwartz with aerosol masking)
1.3 C (Shaviv)
2.2 C (Schwartz with aerosol masking and using incorrect ocean warming values)
Excluding the last value since it is based upon incorrect measurements, the mean of the remaining seven values is 0.82 C. The standard deviation is 0.35 C.
From this small sample, the 95% confidence limits are 0.12 C to 1.52 C, or well below the IPCC theoretical values.
Hans,
I used 2.7 W/m^2, given by Lindzen, for the total forcing by all greenhouse gases (CO2, methane, SF6, etc.) rather than just the forcing from CO2 alone to derive climate sensitivities.
The problem with the non co2 ghg is that their optical activity is in the near infrared, where there is also a big water vapour interference. Which means that climate sensitivity is not identical for every forcing (ghg species).
Refinements in the analysis can be made, but the main conclusion of low climate sensitivity won’t change.
agree, but your low is lower than mine 😀
OK, let’s make Hans a little happier and throw out the three lowest climate sensitivities. In that case, we have:
0.65 C (Schwartz without aerosol masking)
0.98 C (Modtran)
1.3 C (Schwartz with aerosol masking)
1.3 C (Shaviv)
The mean is 1.06 C and standard deviation is 0.27 C. In this case, the emperical mean is 3.48 standard deviations away from the lower limit of IPCC climate sensitivity which equals 2 C.
In the previous case with a mean of 0.82 C and standard deviation of 0.35, the same difference is 3.37 standard deviations. So throwing out the lower sensitivities actually makes the theoretical IPCC lower limit sensitivity even more improbable than it would be if one kept the lower sensitivities in.
In both cases, the empirical results differ from the model results at a level that is significant at greater than the 99% level. It indicates the model sensitivities have less than a 1% chance of being correct.
Dr Hoyt-
Setting aside Dr Pierrehumbert’s vehement rant in support of 50-100m sloshing machine of “ocean turbulence” — I know H2O vapor absorption overlaps CO2’s lower 4 micron peaks; one presumes similar low ocean-heat absorption at those bands according to www.lsbu.ac.uk/water/vibrat.html and warming that occurs in the upper mm(s) of the ocean?
=====
Actually I’m more troubled by lack of thermodynamics in Dr Pierrehumbert’s, “By the way, if the fluid were quiescent, the solar heating which penetrates the water would cause the water to boil (or close to it) since the heat that enters would have a hard time getting out by diffusion, which is slow. Among his flaws, great knowledge what, that a quiescent and clear column of solar-spectrum penetrated ocean (penetrated to a depth of >100m) could be caused to “boil (or close to it),” after daily dose of the sun on a spinning earth. I must have misread this, but does anybody know what he was really tryng to say, when he posted that nonsense?
Correction: I know H2O vapor absorption overlaps CO2’s lower 4 micron peaks;
Of course there is convection or mixing in the upper layer of the ocean. It is driven by absorbed solar radiation which is absorbed many meters deep in the water which then causes convection that transports heat upwards to the surface where it is radiated and evaporated away. I don’t see what Pierrehumbert’s statements have to do with what I am saying.
For thermal IR, it is absorbed in the upper few microns of the ocean. This is the surface tension layer of the water and there are no convection eddies at the scale of a few microns. Convection won’t play a role and most of the energy will be radiated away, although some it will lead to evaporation and a very small portion will be conducted away.
Solar photons are about 30 times more energetic than thermal IR photons, so I would think they would also be more effective in evaporation.
Doug – on this very topic I’ve gotten into it with AGWers on multiple occasions. One of the typical foils is the argument that “the thin heated layer lessens the heat flow from the ocean into the atmosphere leading to ocean warming.”
Ponder that for a moment (while trying to keep a straight face!) This is a particularly amusing statement for anyone living along the California coast (or the South American coast between the equator and about 48S latitude). We worry about hypothermia in the ocean! Even when the air is 80 deg F! Bottom line is, for every net positive atmosphere to ocean thermal gradient there is an equal and opposite negative one elsewhere on the globe. That is so basic, that it is positively Newtonian!
Steve..This was the subject of a Guest commentary by Peter Minnett at Realclimate on 5 September 2006. It can be read at:
www.realclimate.org/index.php/archives/2006/09/why-greenhouse-gases-heat-the-ocean/
Slowing down a cooling of the oceans is not the same as heating up the oceans. Changes in infrared radiation cannot cause the water to warm.
An interesting picture of cloud cover variations from ISCCP can be seen at isccp.giss.nasa.gov/zD2BASICS/B8glbp.anomdevs.jpg
The plot shows decreasing cloud cover from 1986 to 2000 which corresponds to the time when oceans were warming. Since 2000, cloud cover has started to increase and the oceans are now showing a cooling. If you look at the temporal and spatial variations of cloud cover, they are close to the temporal and spatiial variations of ocean warming.
I don’t think the IPCC people have a valid argument when they say all the ocean temperature changes are caused by infrared radiation changes and cloud cover variations have nothing to do with. The opposite is the case.
;
That range isn’t even considered in Modtran, because the Planck curve has little contribution anyway.
Here is my bold attempt for a far cooler business-as-usual scenario, using the 1.3 K/2xCO2 of Nir Shaviv
tech.groups.yahoo.com/group/climatechangedebate/message/5121
Correction attempt #2 for “I know H2O vapor absorption overlaps CO2’s lower 4 micron peaks”
I know H2O vapor absorption overlaps CO2’s lower less than 3 micron, but not so much the greater than 4 micron peaks
Sorry — in my previous 2 attempts, using the mathematical symbols for “less than” and “greater than” in this context, unpredictably truncated my post. BBCode [] instead of HTML … live and learn.
First of all, it should be relatively easy to test the ocean-as-negative feedback theory in a lab, simply by shining 10,6 micron light into water with various amounts of waves and turbulence. If stirring makes a difference, then it should be easily measurable.
Second, I’ve been thinking a bit about this. Is this cooling behavior limited to oceans only? I would think that the surface is also an almost equally good absorber and hence emitter of IR. If so then the whole planet has this negative feedback built into it, not just the oceans.
RE: Richard Hanson Says:
February 12th, 2007 at 1:04 pm
So, let us assume an elevated skin temperature, on average, world wide. Let us assume, for the purposes of a “set initial conditions” exercise, that air temperature has not changed. Initial conditions are therefore, T(x,y,z)1 = air temperature at the ocean – air interface at a given point, T(x,y,z)2 = ocean temperature below the skin just below that point and T(x,y,z)3 = skin temperature just below that point. Consider cases where the mean air temperature at that point exceeds the mean ocean temperature below that point (e.g. anywhere in the range of lower mid latitudes down to the equator where there is a cold current). So, if we raise the skin temperature due to increased IR, the gradient between the air and skin decreases and the gradient between the skin and ocean increases. The component eat flow flux from the air into the skin and hence, into ocean, will therefore decrease. The component of heat flux from the skin into the ocean will increase. In the reverse scenario, the heat flux from the ocean into the skin (and hence the air) decreases but the heat flux from the skin into the atmosphere increases. Only if the skin is heated to a temperature that exceeds both the air and the ocean, with the ocean being warmer than the air (in other words, T3 > T2 > T1) could there be a net heat gain by the ocean due to skin heating. I am definitely skeptical that this rare combination exists in all but a few very small areas of the sea surface. I therefore conclude that this “ocean heating by skin heating” effect is negligable.
RE: Richard Hanson Says:
February 12th, 2007 at 1:04 pm
So, let us assume an elevated skin temperature, on average, world wide. Let us assume, for the purposes of a “set initial conditions” exercise, that air temperature has not changed. Initial conditions are therefore, T(x,y,z)1 = air temperature at the ocean – air interface at a given point, T(x,y,z)2 = ocean temperature below the skin just below that point and T(x,y,z)3 = skin temperature just below that point. Consider cases where the mean air temperature at that point exceeds the mean ocean temperature below that point (e.g. anywhere in the range of lower mid latitudes down to the equator where there is a cold current). So, if we raise the skin temperature due to increased IR, the gradient between the air and skin decreases and the gradient between the skin and ocean increases. The component heat flux from the air into the skin and hence, into ocean, will therefore decrease. The component of heat flux from the skin into the ocean will increase. In the reverse scenario, the heat flux from the ocean into the skin (and hence the air) decreases but the heat flux from the skin into the atmosphere increases. Only if the skin is heated to a temperature that exceeds both the air and the ocean, with the ocean being warmer than the air (in other words, T3 > T2 > T1) could there be a net heat gain by the ocean due to skin heating. I am definitely skeptical that this rare combination exists in all but a few very small areas of the sea surface. I therefore conclude that this “ocean heating by skin heating” effect is negligable.
Dr Hoyt provides very convincing arguments that IR radiation cannot do what the AGW brigade push. However all this stuff on oceans heating due CO2 radiative forcing (from AGW’ers) seems such a waste of time unless there is strong understanding how warm oceanic waters are generated in the first place. Viz discussion of this post and link provided to RealClimate item.
Firstly the studies purporting to be measuring temperatures at depth, the relevant issues are:
1) laws of thermodynamics, hot water rises.
2) placement/distribution of the measuring devices w.r.t major oceanic currents (even if there are issues with time series, & calibration) AND their location from major submarine volcanic/hydrothermal activity. Examples of loci of major hydrothermal activity are along the Mid Atlantic Rift/Ridge, East Pacific Rise, intra-oceanic plate hotspots such as Hawaiian chain. There is a paucity of studies and data from these (as Temp – Depth –Salinity transects) across and laterally along these geological features (difficult access). But what is known, are the high temperatures and salinities of the hydrothermal fluids (often greater than 300deg.C direct measurement, and > 40eq wt%NaCl as inclusions; from ore deposit studies). Does anyone know how these hydrothermal fluids convect/conduct heat into the overlying ocean?
These volcanic centres are pumping out vast quantities of heat, there must be vast entrained hydrothermal convection cells around the Mid- Atlantic rift that go thousands of km’s. Variations in oceanic heat are caused by waxing and waning of volcanic activity/tectonic movements. Therefore, how can these people measuring these temperatures at various depths over relatively short time periods say it is due to radiative affects of atmospheric CO2?
Secondly when you exclude volcanic sources of heat, how are warm oceanic waters generated? What fundamental studies / hypotheses have been forwarded? You’ll have to forgive my ignorance on the following basic ideas as I’m only an Exploration Geologist.
The movement and generation from equator to poles of warm tropical oceanic waters could be achieved by two possible methods?:
1). Tropical rainstorms remove heat from atmosphere over the oceans via precipitation of warm lower density fresh water onto relatively cooler ocean? Upon hitting ocean evaporation and latent heat transfers back to atmosphere may be controlled by cloudness? Hence do not have invoke conduction via “turbulent mixing of the IR heated surface”, but can invoke conduction by turbulent mixing of warmer rainwater and cooler ocean? Rotation of the planet/ prevailing winds /salinity differential (+ upwellings ; a change in gravitation due to planetary alignments? or in case of PDO Length of Day effect) explains why these currents move.
2). A small amount of conduction does occur on land-sea interfaces (any beach confirms this, warm water right against beach, heated by conduction from warm sand), but probably dominated by fresh water run-off from numerous tropically located land masses into oceans (again a lower density water, does not mix with higher density salty water). Variations in geographic distribution of tropically centered monsoons in during northern and southern hemispheric wet seasons thus would affect fresh water run-off flux and hence heat and distribution of these warm tropical currents??
Inturn both points above simply explains inter-annual temperature variability of the oceanic currents?
But does anybody know?
Further, in regards to temperature and salinity/density contrast, and heat conduction between two oceanic currents. Sometime ago I watched a documentary about the movement of warm and cold oceanic currents on Pacific coast of South America and there was a distinct visual boundary laterally between hot and cold waters at same depth (no obvious mixing taking place, density/salinity diff??, a fish was sticking to only the low temp water (at the centimetre scale).
Anecdotally …. When scuba diving around Los Cabos (southernmost point of Baja California) there is a distinct and drastic thermal difference in waters west and east of the point. West of it, lie the waters of the California Current, east of it, waters in the Sea of Cortez sheltered from it. While the Sea of Cortez’ warmth is no doubt partially attributable to local heating from the sun and from eddies bringing tropical waters into it, one must wonder the degree to which having the East Pacific Rise (and its black smoker hot water vents) also contributes to the warmth.
Often the IPCC scientists claim a high climate sensitivity using climate models forced by volcanic eruptions, such as Pinatubo in 1992. A recent paper by Boer et al shows that such an approach is not valid. Both high and low sensitivity climate models respond in the same way and one cannot deduce climate sensitivity using this approach. The paper and its abstract are:
Boer, George J., Markus Stowasser, and Kevin Hamilton, 2007. Inferring climate sensitivity from volcanic events. Climate Dynamics Vol. 28, No 5, pp. 481-502, April 2007.
Abstract
The possibility of estimating the equilibrium climate sensitivity of the earth-system from observations following explosive volcanic eruptions is assessed in the context of a perfect model study. Two modern climate models (the CCCma CGCM3 and the NCAR CCSM2) with different equilibrium climate sensitivities are employed in the investigation. The models are perturbed with the same transient volcano-like forcing and the responses analysed to infer climate sensitivities. For volcano-like forcing the global mean surface temperature responses of the two models are very similar, despite their differing equilibrium climate sensitivities, indicating that climate sensitivity cannot be inferred from the temperature record alone even if the forcing is known. Equilibrium climate sensitivities can be reasonably determined only if both the forcing and the change in heat storage in the system are known very accurately. The geographic patterns of clear-sky atmosphere/surface and cloud feedbacks are similar for both the transient volcano-like and near-equilibrium constant forcing simulations showing that, to a considerable extent, the same feedback processes are invoked, and determine the climate sensitivity, in both cases.
(Thanks to Timo Hameranta for pointing this out to me.)
Doug, this is a fascinating essay. However, you say:
As a long time surfer and diver, I’d like to clarify this. In general, thermal convection in the quiescent ocean is limited to the night-time. During the day, as you point out, the deeper oceans (metres) are heated. However, the further you go down, the less light there is available to heat the water, and thus the heating is less. This leads to a stable condition, not convection. On a warm, calm afternoon, the usual result is a distinct thermocline at about a meter or less, which I have felt many times while surfing – if I hang my arms straight down over the edge of the board, they will be in cold water.
At night, the ocean radiates and cools. When it cools enough, the cool water mixes downwards and is replaced by warmer water from below. This has the effect of cooling the ocean faster than it would cool if there were no convection, since warm water is constantly being moved to the surface to radiate away its heat. As a result, by morning the thermocline is gone.
In fact, however, the ocean is rarely calm. Thus, while the IR can only heat the skin layer, this layer often does not stay at the surface for long. It is constantly mixed by wind and waves. Thus, the absorption will be larger than theory would indicate. This does not, however, change your underlying point.
w.
I can’t add your feed to Feedburner. How I do this?
This news item appeared today at planetgore.nationalreview.com/post/?q=ZDc0MTY2NmVlOWNiNjc4ODk0NGUzMDE2YTRlMjMxNzc=
Overturning the “Consensus” in One Fell Swoop [Joel Schwartz]
New research from Stephen Schwartz of Brookhaven National Lab concludes that the Earth’s climate is only about one-third as sensitive to carbon dioxide as the IPCC assumes. Schwartz’s study is “in press” at the Journal of Geophysical Research and you can download a preprint of the study here.
According to Schwartz’s results, which are based on the empirical relationship between trends in surface temperature and ocean heat content, doubling the CO2 concentration in the atmosphere would result in a 1.1oC increase in average temperature (0.1–2.1oC, two standard deviation uncertainty range). Schwartz’s result is 63% lower than the IPCC’s estimate of 3oC for a doubling of CO2 (2.0–4.5oC, 2SD range).
Right now we’re about 41% above the estimated pre-industrial CO2 level of 270 ppm. At the current rate of increase of about 0.55% per year, CO2 will double around 2070. Based on Schwartz’s results, we should expect about a 0.6oC additional increase in temperature between now and 2070 due to this additional CO2. That doesn’t seem particularly alarming.
A couple of other interesting implications of Schwartz’s results:
Aerosols have a relatively small effect on temperature. A doubling of CO2 has an estimated climate “forcing” of 2.7 watts per square centimeter (W/cm2). In contrast, actual aerosol concentrations during the 20th Century had a forcing of -0.3 W/cm2 with a large uncertainty range that could mean either net cooling or net warming from aerosols.
The response time, or “time constant”, of the climate to greenhouse gas forcing is relatively small—only five years. In other words, there’s hardly any additional warming “in the pipeline” from previous greenhouse gas emissions. This is in contrast to the IPCC, which predicts that the Earth’s average temperature will rise an additional 0.6oC during the 21st Century even if greenhouse gas concentrations stopped increasing.
Schwartz is careful to include the appropriate caveats to his results. But he also shows that his estimates are consistent with much of the previous literature on the subject. His study also has the virtue of relying largely on empirical measurements of actual climate behavior during the 20th Century, rather than on climate models.
Stephen Schwartz is a pretty mainstream climate scientist. Yet along with dozens of other studies in the scientific literature, his new study belies Al Gore’s claim that there is no legitimate scholarly alternative to climate catastrophism.
Indeed, if Schwartz’s results are correct, that alone would be enough to overturn in one fell swoop the IPCC’s scientific “consensus”, the environmentalists’ climate hysteria, and the political pretext for the energy-restriction policies that have become so popular with the world’s environmental regulators, elected officials, and corporations. The question is, will anyone in the mainstream media notice?
—————-
My comments:
1. Schwartz’s climate sensitivity is 1.1 C/doubling and based upon recent revisions to the Levitus results, my number would be 0.8 C/doubling.
2. Schwartz’s time constant is 4-6 years. In 1979, I said 4-5 years so we agree (Hoyt, D. V., 1979. Variations in sunspot structure and climate . Climatic Change, 2, 79-92.) I also recall that Lindzen said about 5 years based upon volcanoes. So GHG, volcano, and solar forcing all yield a short time constant in contrast to IPCC time constant of many decades. A short time constant means a low climate sensitivity.
3. I think these results show a net negative feedback although Schwartz still argues that it is positive. If it is positive, it is a very small positive, perhaps an additional 0.1 C/doubling.
All in all, bad news for the modelers and good news for those who pay attention to the data.
An observation on Dr. Hanson’s assertion that ‘downward mixing’ is going to heat ocean depths:
Deep sea temperatures seem to have been stable for long periods of time, despite acknowledged wide ranging surface temperature fluctuations over the same periods of time. Heat from AGW is no different from other sources of heat, so it does not seem reasonable to brush off this latest failure of the AGW models so lightly by offering such a weak rationalization.
It also seems at least intuitively more reasonable to assume that surface ocean wave action and evaporation would be sufficient to mitigate any heating from CO2 induced infrared increases. On a possibly off topic suggestion: perhaps it would be useful to study what very small soot particles distributed on ice could do to increase melting of ice despite ambient temperatures.
#36 Doug Hoyt, citing Stephen Schwartz:
V. Ramanathan & G. Carmichael published a study in Nature showing tropospheric soot – in conjunction with bright aerosols – in fact causes a net positive heating, 60% of CO2’s warming effect (a 38/57 soot:CO2 mix). Wouldn’t this further vindicate Schwartz’ study by reducing variability otherwise ascribed to CO2?
I believe Roy Spencer has some extremely interesting results from the Aqua satellite proving a *negative* feedback of water vapor as CO2 increases (as opposed to the positive feedback the IPCC claims and programs into their models). I do hope he seeks publication of his findings. That could put AGW “science” on it’s ear.
I know that the Harry Horvath comment about warm tropical rain is a long time ago (Feb 18, 2007), “1). Tropical rainstorms remove heat from atmosphere over the oceans via precipitation of warm lower density fresh water onto relatively cooler ocean”, but having just found it, I’d like to comment.
Living, as I do, on a tropical Island, Tortola, Virgin Islands, I am frequently made aware that, far from being warm, tropical rains can be bloody cold. One explanation for this was given me by a pilot friend. His observation was that, flying at several thousand feet in a small plane, he often sees snow forming which melts while descending. If it is snow at, say, five thousand feet, it’s certainly not going to be much warmer when it reaches my back
Otherwise, very interesting paper and borne out by the recent ARGO reports that the ocean depths are showing no warming
icecap.us/index.php/go/political-climate/the_oceans_have_stopped_warming/
I concur with Tony E., HH has it exactly wrong. Condensation dumps 70cal./cc H20 into surrounding troposphere. Evaporation removes same 70cal./cc H2O from oceans.
This effect dwarfs radiation of GHG gases at these temperatures and pressures. CO2 emissivity=absorptivity=9*10^-4 at STP per Hottel 1942. Gas emissivities cannot be calculated as they do not follow Kirchoff’s relation for solids: e=C(1-a).
In solids, absorbed energy is emitted in relation to the temperature. In gases, the energy is converted to kinetic energy and emitted in relation to temperature and pressure.
Therefore, moving from Beer’s Law estimating the absorption of the incoming signal to estimating gas emissivity is not practicable. This is a fundamental flaw of Climate Science.
Time for a little update on climate sensitivity. I now think that Schwartz is overestimating climate sensitivity since he is ignoring unforced internal oscillations of climate.
Below are some comments on why and how climate change seems to be occurring with a few comments on climate sensitivity.
1. Cloud cover is varying over the oceans. Evidence (see Palle abstract below).
2. The cloud cover causes changes in ocean temperatures by modulating the amount of solar radiation being absorbed.
3. The changes in ocean temperatures cause much of the observed changes in temperature over land (see Compo abstract below).
4. Part of the changes in land temperatures are also caused by land use changes (Pielke, Sr.), urban heat islands (McKitrick and Michaels), and poor siting of thermometers (Watts).
Additional comments:
1. The Compo paper states: “Indeed we find compelling evidence from several atmospheric general circulation model simulations without prescribed GHG, aerosol, and solar forcing variations (Table 1) that the continental warming in Fig. 1a is largely a response to the warming of the oceans rather than directly due to GHG increases over the continents (Table 2).” In other words, they simulate the observed climate changes without any changes in greenhouse gases.
2. The cloud cover variations reported by Palle are consistent with the recent cooling of the oceans based upon the Argo buoys and are inconsistent with the GHG warming theory.
3. The oceans cannot be warmed by additional downward radiation from additional greenhouse gases since this radiation is absorbed in the upper few microns of the oceans. Indeed Compo says the heat is flowing out of the oceans and not into it, so this also eliminates the hypothesis the greenhouses gases warm the air which is mixed into the oceans warming them (as argued earlier by some in this thread).
4. Cloud cover over the oceans varies and this modulates the amount of solar radiation reaching the surface which modulates the ocean temperatures. Cloud cover variations are probably natural unforced internal variations of the climate system. It is unlikely that cloud cover and ocean temperatures are ever in equilibrium and hence one can expect oscillations over decades and centuries as seen by El Nino, PDO, AMO, NAO, the 1500 year cycle, etc.
5. Palle reports that the internal forcing is several watts per square meter. The observed temperature variations are in the tenths of a degree. The implied climate sensitivity therefore is very low. The low climate sensitivity means that the postulated forcing by greenhouse gases will have little effect of temperatures.
6. Studies that neglect internal unforced variations in cloud cover will lead to an overestimation of climate sensitivity (for example, Schwartz). You would need to remove all the unforced variations from the temperature record and then apply Schwartz’s techniques to calculate climate sensitivity. I am not sure if this is possible.
7. Some of the cloud cover variations may be forced by solar variations as suggested by Svensmark.
8. Spencer seems to hold views similar to the ones above.
Pallé E., P. Montañés-Rodriguez, P. R. Goode, S. E. Koonin, M. Wild, and S. Casadio, 2005: A multi-data comparison of shortwave climate forcing changes, Geophysical Research Letters.
The abstract reads:
“Traditionally the Earth’s reflectance has been assumed to be roughly constant, but large decadal variability, not reproduced by current climate models, has been reported lately from a variety of sources. We compare here the available data sets related to Earth’s reflectance, in order to assess the observational constraints on the models. We find a consistent picture among all data sets of an albedo decreased during 1985–2000 between 2–3 and 6–7 W/m 2, which is highly climatically significant. The largest discrepancy among the data sets occurs during 2000–2004, when some present an increasing reflectance trend, while CERES observations show a steady decrease of about 2 W/m 2.”
Compo,G.P., and P.D. Sardeshmukh, 2008: Oceanic influences on recent continental warming. Climate Dynamics, in press.
The abstract reads:
“Evidence is presented that the recent worldwide land warming has occurred largely in response to a worldwide warming of the oceans rather than as a direct response to increasing greenhouse gases (GHGs) over land. Atmospheric model simulations of the last half-century with prescribed observed ocean temperature changes, but without prescribed GHG changes, account for most of the land warming. The oceanic influence has occurred through hydrodynamic-radiative teleconnections, primarily by moistening and warming the air over land and increasing the downward longwave radiation at the surface. The oceans may themselves have warmed from a combination of natural and anthropogenic influences.”
The first two studies cited for this article have since been updated.
ftp.nodc.noaa.gov/pub/data.nodc/woa/PUBLICATIONS/grlheat08.pdf
www.junkscience.com/Greenhouse/heat_2006_1.pdf
Reading the original studies, I find the comments therein are antithetical to those of this essay.
(Levitus et al 2005)
and
(Lyman et al 2006)
The last quote clarifies the rather muddy assertion in this article,
‘Such’ coolings? Coolings are ‘predicted’ for the time period specified (and longer). What is unexpected is simply the magnitude. I do not understand why the language in this article is so vague on that point.
As it turns out, the magnitude is not as great as thought (see corrected papers linked above), and the long-term warming of the oceans is considered to be consistent with climate models – this is so whether one refers to the original or the updated papers.
The first problem I can see with such a low climate sensitivity as posited here (in what is a rehash of Lindzen’s ‘Iris’ hypothesis), is that ice ages would be impossible. Mean insolation changes are too small, and ice sheet/allbedo changes would be offset by the ‘Iris’, reducing their effects – as well as that of GHG forcing. The Iris is a function of temperature change (not GHG change).
I am surprised this article has not been updated WRT the revisions in the updated studies. Perhaps a new article has been written absorbing the new findings? Please direct me where.
Barry.
I’ll just quote Roy Spencer’s latest finding on climate sensitivity at www.drroyspencer.com/2009/06/epa-endangerment-finding-my-submitted-comments/
where he finds a 0.6 C warming for a doubling of CO2.
“Using this new insight, if we now return to the linear striations seen in the satellite data plotted in Fig. 2, we find their slope to be about 6 Watts per sq. meter per degree C, which would correspond to strongly negative feedback. This is about the same feedback value that Spencer et al. (2007) found for a composite of tropical weather systems over a multi-year period. If this is the feedback operating in the real climate system on the long time scales involved with manmade global warming, then the amount of warming from a doubling of carbon dioxide would only be about 0.6 deg. C, which is at least a factor of 4 less than the IPCC’s best estimate for the future.”
One can’t use the ice ages to determine climate sensitivity because one does not know how cloud cover, thickness, height, phase, etc. has varied between modern values and the ice ages.
Lindzen has a publication coming out saying climate sensitivity is 0.6 C for a CO2 doubling. A summary can be found at masterresource.org/?p=4307
The figure shows that all the models are systematically wrong in the same direction.
Leaving aside the climate models, the IPCC climate sensitivity of ~3 deg per 2xCO2 seems to be heavily dependent on ice age forcings. Douglas Hoyt, in an earlier post (July 2nd 2009), quotes Roy Spencer’s comment, i.e.
“One can’t use the ice ages to determine climate sensitivity because one does not know how cloud cover, thickness, height, phase, etc. has varied between modern values and the ice ages.”
This is something that has occurred to me, but I rarely see the IPCC/AGW position challenged. Any mention of the water vapour/cloud effect is dismissed as a feedback response to the primary forcing(s). I can see where they are coming from, but as far as ice age/interglacial periods are concerned, CO2 can also be described as a feedback.
Some time ago I read an article by James Hansen where he claimed that, without CO2, there would be no (or very little) WV greenhouse effect. My crude interpretation, therefore, of the AGW (high CO2 sensitivity) position is
Increase in insolation -> Increase in CO2 -> Increase in atmospheric Water Vapour
Rather than
Increase in insolation -> Increase in CO2 + Increase in atmospheric Water Vapour
Are there any relatively simple calculations which show the rate of evaporation as a function of temperature and can, therefore, justify the high sensitivity (or other) position.
I also think I’m right in saying that Douglas Hoyt believes that the increase in albedo during ice ages has been under-estimated which, if correct, will again reduce the CO2 sensitivity.
The above statement was mine, not Roy Spencer’s. I think the IPCC folks get a high climate senstivity for CO2 from ice ages by foolishly assuming cloud cover is invariant over time. Thus, all the changes are attributed to CO2, making its sensitivity appear high.
On the water vapor feedback, Paltridge et al recently suggested it is a negative feedback if you believe the NCEP analysis.
Paltridge says:
Paltridge’s analysis, as it now stands, would be consistent with both Spencer’s findings and Lindzen’s conclusions that climate sensitivity is low. More discussion can be found at masterresource.org/?p=1280
The above statement was mine, not Roy Spencer’s.
Sorry, Douglas, I’d read it as a continuation of the account of the Spencer paper. My mistake.
it is interesting and informative article. This has been very helpful understanding a lot
of things. I’m sure a lot of other people will agree with me.
As far as I can see from the literature over the last 1000 years direct solar forcing has varied by between 3 and 4 w/m2 and this has resulted in a temperature change of between 0.8C and 1.0C according to most temperature series (excluding Mann). This includes any solar multiplier effects such as cosmic rays etc.
According to Gavin Smith a change of 7 w/m2 during the last ice age resulted in a drop in temperature of aproximately 5C. This is an enormous difference in temperature sensitivity to the last millenium, particularly since the ice ages were caused by the Milankovich cycles and therefore were not effected by solar multipliers.
Has anybody done any work on the effect of icesheet albedo that might explain this discrepancy.