Thin Polar Bears Called Sign of Global Warming

I was listening to RCI tonight. Canadians are too busy fighting over a stuffed grizzly to worry about
Pally McBear. At least the the ones in BC are.

However, the US has this overweight Senator who'd I'm sure wouldn't mind driving a snowmobile
under-the-influence while looking to be part of an Eskimo sandwich.

Probably find a good spot to put up a couple of windmills too, away from his "view".

Now there you go again, confusing everyone with the facts.

It's just a bad habit I picked up somewhere.

The wife tells me I ought to find a support group somewhere and get some help for the problem ;O)

http://www.giss.nasa.gov/edu/gwdebate/gwdebate.pdf

is the slide and accompanying text for Dr. Hansen's debate with Patrick Michaels of the University of Virginia. Click on the link to read it (you have to have Adobe Acrobat Reader to read a PDF document). Most of the figures in this document used to be in an HTML rendering of Dr. Hansen's testimony to Congress on the issue. For some reason those Web pages have been removed. I don't know why -- I wish they hadn't. They were very informative.

On page 2 of the document you can read the text accompanying Slide 7. On page 12 of the document you can view Slide 7.

Does not address the issue of the magnitude of climate temperature sensitivity to CO2 concentration.

I thought the issue we were trying to discuss was climate sensitivity to total forcing. To sum up what Hansen says, on average during the Ice Ages the Earth was 5 deg. C colder than now. That's a known. By summing the known forcing factor differences between now and then, which is what Slide 7 illustrates, the total forcing is estimated at 6.6 W m-2. (Note that one of the main differences is due to the increased albedo of the ice sheets.) That gives a climate sensitivity of 0.75 deg C per 1 W m-2 of forcing -- whatever the radiative forcing factor is.

Using iceage derived data as you infer, current temperatures would be rising at a rate of 6oC for each 100ppm change in CO2 concentration from the last glacial period to the current interglacial we are now experiencing.

No, geez, you missed that. It's not primarily CO2! CO2 and other greenhouse gases induce a positive feedback (primarily due to increased atmospheric water vapor; other factors are ice sheets and cloud albedo). Note also that the increase in CO2 between the last glacial period and now was Milankovitch-driven: warming oceans release CO2.

Now this figure I can show you:

See CO2 there on the left? It's about 1.3 W m-2 of forcing. That's 1 deg. C of climate response, not 6 deg. C.

Now, looking at all your numbers (i.e. 1-7), they appear a bit lower than the forcing ascribed to CO2 by Hansen, except for the last one, which is essentially similar (there are error bars on all of these, obviously).

I can't tell if we're talking past each other or if we essentially agree. It seems that we do agree on the sensitivity of climate to forcing, i.e., 0.75 deg. C per 1 W m-2 of radiative forcing is accurate. If I'm correct in that assessment, then it seems our disagreement is in how much forcing can be ascribed to CO2. Do you agree? If so, do you agree that the apparent range of estimated forcing for the increase in atmospheric CO2 from 1850 to present is 0.30 - 1.30 W m-2?

I thought the issue we were trying to discuss was climate sensitivity to total forcing.

Total forcing includes changes in solar irradiation and all factors not just the anthropogenic greenhouse gas forcing of CO² that IPCC & the GCMs postulate.

Climate sensitivity to the IPCC anthropogenic doubling of CO² concentration to 700ppm is what I thought we are discussing, not "total forcing", it is irrelevant as to what the source of heat is, heat(measured in wm^-2 ) is the same regardless of source.

A point of fact, IPCC's GCMs assume no change in solar irradiation and constant aldebo a condition that is not true of the glacial -> interglacial data.

In reference to the Hansen article:

http://www.giss.nasa.gov./research/intro/hansen_05/

"The strongest evidence is the empirical fact that the warmth of the current interglacial period, with Earth 5°C warmer than during the ice age 20,000 years ago, is maintained by a forcing between 6 and 9 Watts/m²."

The data contains substantial solar irradiation changes(astronomical forcing) and aldebo changes from meteoric dust causing changes in high level(noctilucent) clouds and many indeterminate factors not accounted for.

The statement ignores basic thermodynamics and IR absorption characteristices of GHG's.

Climate Catastrophe, A spectroscopic Artifact?
Effects of Doubling CO₂ from 300ppm to 600ppm
A Lukewarm Greenhouse

The assumption of IPCC & their GCMs, is there are no significant astronomical or solar irraditation changes in forcing for the period they project, that the entire change is a concequence of anthropogenic GHG's (with CO₂ the dominant factor).

Compensating for the astronomical forcings of the glacial period data set

yields:

Effects of Doubling CO₂ from 300ppm to 600ppm

"0.45 C (empirical, calculated from ice core carbon dioxide and temperature variations, after de-trending both time series to remove orbital effects)."

leaving 0.11^oC/wm^-2 climate sensitivity to GHG forcing that IPCC is looking at (i.e. no solar irradiation change as assumed by IPCC projections for the next 100yrs).

The IPCC claim is that a doubling of CO² concentation from "anthropogenic" sources induces a 4.3wm^-2 or greater radiative forcing which will give rise to a measureable temperature increase.

Using the value of 0.75oC for 1wm^-2 (the IPCC low estimate for the Climate sensitivity coefficient) temperature should increase by 3.4^oC for a doubling of CO² concentration to 700ppm by 2100 according to IPCC & their GCMs.

I do not dispute that there can be some warming as a consequence of that IPCC "story line", (i.e. aprior assumption of CO² doubling from anthropogenic sources) should it come about. The question is a matter of the degree that 4.5wm-2 manifests itself as a change in atmospheric temperature.

The IPCC's GCMs do not track with the tropospheric observations of the last century. Hansen's article(that you reference) postulates corrections to the IPCC position regardiong GCM projections, and proposes modifictation to the GCMs to make them conform to observed tropospheric global temperture change.

In reference to the article

http://www.giss.nasa.gov./research/intro/hansen_05/

& specifically the bar graph(fig2) you refer to:

You will note, upon adding up the forcings that Hansen includes for "total forcing", the sum is -0.1wm^-2 ±0.3 (error is the rms value of the of all the quoted errors taken together)

That is a general COOLING.

Using (the IPCC 0.75wm^-2) coefficient of climate sensitivity,
that comes to a 0.075^oC loss in temperature.
Using Hansen's 0.3wm^-2 sensitivity coefficient,
we calculate a 0.023^oC loss.
Using the theoretical 0.15wm^-2 sensitivity coefficient as established by other authors in my prior reply,
we calculate a 0.011^oC loss.

The question becomes, what will the future total forcings be over the next 100 years (for the factors discussed by Hansen to correct IPCC's GCMs storyline projection to observation of the last century).

If we assume the Hansen corrections remain constant, or increase cooling (as CH₄ is decreasing) the corrections introduce additional cooling greater than the 2.4wm^-2 cooling Hansen's corrections postulate for the last 100yrs.

This brings the IPCC "story line" 4.5wm^-2 anthropogenic CO2 warming down to 2.1wm^-2 total warming for the next 100 years.

Using (the IPCC 0.75wm^-2) coefficient of climate sensitivity,
that comes to a 1.6^oC gain in temperature by 2100.
Using Hansen's 0.3wm^-2 sensitivity coefficient,
we calculate a 0.63^oC gain in temperature by 2100.
Using the theoretical 0.15wm^-2 sensitivity coefficient as established by other authors in my prior reply,
we calculate a 0.32^oC gain in temperature by 2100.

For your information Hansen uses a statistical approach based in Chaos theory for his analysis.

Forcings and Chaos in Global Climate Change

That is one of the reasons his numbers and projections do not track with the IPCC GCMs. His articles argue for the IPCC to adopt his modelling and way of doing things.

It seems that we do agree on the sensitivity of climate to forcing, i.e., 0.75 deg. C per 1 W m-2 of radiative forcing is accurate.

This is one of our disagreements, I support a 0.15^oC wm^-2 climate sensitivity per

Effects of Doubling CO₂ from 300ppm to 600ppm & A Lukewarm Greenhouse

Hansen uses 0.3^oC/wm^-2 in his own modelling;

IPCC uses 0.75 - 1.1^oC/wm^-2 depending on which GCM they are looking at at any particular time.

If I'm correct in that assessment,

I don't agree that you are correct in that assessment, for fundamental theoretical and empirical grounds with the following being just one of a dozen or so:

Climate Temperature Sensitivity Calculation
Since the atmosphere must emit radiation to balance Solar input, we can use the Sefan-Boltzman relation relating total radiation emitted to temperature
http://apollo.lsc.vsc.edu/classes/met130/notes/chapter2/sb_law.html

E=sT⁴

And The change in tropospheric temperature is less than +0.5^oC since 1850:

T₍₁₈₅₀₎ = -0.2^oC, 272.8^oK
E₍₁₈₅₀₎ = 5.67 x 10^-8 x (272.8)⁴ = 314.022 wm^-2;
T₍₂₀₀₀₎ = T(1850)+0.5^oC = 273.3^oK
E₍₂₀₀₀₎ = 5.67 x 10^-8 x (273.3)⁴ = 316.33 wm^-2;

Climate Temperature Sensitivity = 0.5^oC/(2.309 wm^-2) < 0.2^oC/wm^-2 to the accuracy of our assumed change in Tropospheric temperature 1850 -> 2000 of less than +0.5^oC.

then it seems our disagreement is in how much forcing can be ascribed to CO2. Do you agree?

That is another of our disagreements

IPCC uses 4.3wm^-2 projected CO2 forcing for the next century or thereabouts in its statements. It varies somewhat depending on the particular GCM they refer to at any particular time.

If so, do you agree that the apparent range of estimated forcing for the increase in atmospheric CO2 from 1850 to present is 0.30 - 1.30 W m-2?

I will agree that global Tropospheric temperature has increased less than 0.5^oC since 1850 for numerous causes including changes in solar irradiation, aldebo, & GHG's.

I will agree that CO₂ concentration has increased from 290ppm to 365ppm at present. That becomes a 75ppm increment for the period.

IPCC figures 4.3wm^-2 CO₂ forcing for 365ppm increase, therefore the IPCC figure for 75ppm would be approximately 0.9wm^-2. That is about the center of your range and upheld in Hansen's fig2 in my prior reply.

However, in accord with experimental observations by Dr. Heinz Hug,

Climate Catastrophe, A spectroscopic Artifact?

The CO₂ IR absorption from the surface and subsequent heat transfer to the atmosphere via CO₂ molecular interactions and re-radiation induces a very small heat transfer.

"Conclusions
It is hardly to be expected that for CO2 doubling an increment of IR absorption at the 15 µm edges by 0.17% can cause any significant global warming or even a climate catastrophe.
The radiative forcing for doubling can be calculated by using this figure. If we allocate an absorption of 32 W/m² [14] over 180º steradiant to the total integral (area) of the n3 band as observed from satellite measurements (Hanel et al., 1971) and applied to a standard atmosphere, and take an increment of 0.17%, the absorption is 0.054 W/m² - and not 4.3 W/m²."

Using the IPCC center range estimates 0.9wm^-2 CO₂ forcing for the industrial period, which accords with the Hansen bar chart fig2 displayed in my prior reply. That makes for 0.011wm^-2 CO₂ forcing based on the experimental science in regards CO₂ capacity for IR absorption above.

Seems we differ by one or more orders of magnitude difference, whatever we look at.

1) If we look only at IPCC's 4.3wm^-2 estimated CO₂ forcing for anthropogenic doubling and use 0.15^oC/wm^-2 climate sensitivity we calculate a temperature change due to that forcing of 0.65^oC by 2100
2) If we look at experimental result of CO₂ forcing provided by Hug, of only 0.054wm^-2 CO₂ forcing and use 0.15^oC/wm^-2 climate sensitivity we calculate a temperature change due to that forcing of 0.0081^oC by 2100

Case 1) would be barely discernable and not easily distinguished from background variation across a century.

Case 2) would be totally swamped out by background variation.

You are riding with the IPCC and its modellers. I look at the science that must constrain any model output for it to be in accord with thermodynamic theory, experiment and observed facts.

You must remember that the IPCC is a UN sponsored political body, that starts out with the assumption

http://www.ipcc.ch/about/about.htm

"Recognizing the problem of potential global climate change"

and

"The role of the IPCC is to assess ..."

"It does not carry out research nor does it monitor climate related data or other relevant parameters."

It is not a body of scientists doing independant science. It has shown itself to be very selective in assessing scientific literature to support its core assumption that there is a "problem of potential global climate change." and rejecting significant science counter to it bottom line apriori assumption.

It's goal is to justify "potential climate change" requires global government(i.e. UN) involvement to combat "the problem".

Interesting, the Hansen figures from the www.nasa.gov site do not seem to display properly on a FR page. You can only retrieve them by going directly to the site and loading them into your cache from there.

Once retrieved into your cache they will show up on the FR page. I suspect the nasa site is blocking transmission of there graphs & pictures to html pages not associated with an access to their site to preseve bandwidth.

If you are going to use their graphs and stuff, make sure you provide the URL of the page they are found on. Otherwise they are difficult to retrieve, and we mess up on communications.

I finally found Hansen's statement concerning climate sensitivity of 0.75^oC/wm^-2.

I had downloaded the pdf file and the file name was so similar to another I had on my machine I initially grabbed the wrong one to look at. Sorry for the confusion.

In reference to Hansen's pdf discussion of slide 7.

"7. Ice age bar graph
Averaged over several thousand years the Earth must be in radiation balance with space (emitting the same amount of energy that it absorbs from the sun) within a fraction of 1 W/m 2 , as we can easily see by cal-culating the energy it takes to melt the ice sheets or raise ocean temper-ature by a plausible amount. So the world provides an empirical measure of climate sensitivity, which is just the ratio of the observed global temperature change, about 5°C, divided by the forcing that maintained that temperature change, which was somewhere between 6 and 9 W/m 2 ."

He doesn't tell us where he gets the 6-9wm^-2. Is it from someone elses back calculation using 0.75^oC/wm^-2 as their parameter? Like IPCCs 0.75-1.10.75^oC/wm^-2. It is interesting that the ratio of 6wm^-2 to 9wm^-2 is consitant with IPCC's GCMs assumed value which, as I pointed out earlier, no one can find a study or calculation supporting it.

Climate sensitivity is the amount of heating required to raise a body's radiative surface (i.e. the troposphere) into radiative balance with solar influx.

The current average solar radiation incident with the earth is 341.6wm^-2

For a +5^oC change in radiative forcing from surface 268^oK(temperature 20kyrs ago) to 273^oK of today takes: E₍₀₎-E_(-20k) = 22.44wm^-2 (not the mere 6-9wm^-2 stated):

E_(-20k) = 5.67 x 10^-8 x (268)⁴ = 292.50 wm^-2 radiative forcing;
E₍₀₎ = 5.67 x 10^-8 x (273)⁴ = 314.94 wm^-2 radiative forcing;

That computes to a max 0.22^oC/wm^-2 climate temperature sensitivity(0 aldebo) with respect to glacial period radiative forcing. The number today would be somewhat smaller as the rate of change in temp for given radiative forcing decreases as absolute temperature increases and aldebo tends to rise with temperature & cloud forcing from current conditions.

If we were to add 5^oC today, it would take at least (338-314.66)wm^-2 = 24.00wm^-2.

which yields a max climate sensitivity of 0.208oC/wm^-2 and we could only do that by reducing aldebo to near .011 becoming a virtually totally absorbing blackbody(no clouds and a black surface or atmosphere.)

The current average solar radiation incident with the earth is 341.6wm^-2

We would have to absorb 338/341.6 = 98.9%(aldebo drop to 0.011) of the incident radiation of the sun on earth to achieve that high a forcing.

The earth's aldebo is much higher than that and thus such a temperature would not be achievable under any rational scenario. At those temperatures the cloud cover alone would significantly increase aldebo far above what we have today, not lower it, thus reflecting more solar energy away from the earth's surface which nearly all heating derives.

Take away the sun, the earth is a very cold critter, you don't get energy from nowhere.

The greenhouse effect derives from absorption and reradiation of solar energy and an insulation effect retaining higher temperatures near the surface as compared to the upper atmosphere. But the greenhouse cannot derive energy that is not incident on the planetary surface or absorbable in the atmosphere in the first place.

The whole concept of greenhouse warming requires short wavelength radiation to be incident on the surface to be converted to IR wavelengths absorbed by the atmosphere and transfered upward through many mechanisms(convection, re-radiation, diffusion etc.) then re-radiated from the top of the atmosphere as black body emission + reflection balancing with total incident Solar radiation. Increase the cloud cover or otherwise increase aldebo(i.e. reflection) at the top of the atmosphere, less energy is available for absorption to increase temperature at the surface that establishes the temperature differential necessary for heat transport to the top to be emitted as blackbody radiation.

What about the Antarctica data?

The article I read was talking about Antarctica !

That is in the Southern Hemisphere.

I think cogitator should organize a collection and ship some of the Polar bears south, lots of Seals down there!

I thought I saw on the news today that it was snowing in parts of Montana. On May 22nd?

Oh yea, never mind cogitator told me before that climate has nothing to do with weather.

I guess its like one of those addition subtraction versus new math kind of things.

I wonder what ever happened to that hole in the ozone everyone was so concerned about?

We are spending more tax dollars on this hunt for Global Warming! See this :

Sounding out the weather : satellite designed to improve forecasting and climate research.

The instrument is a desk- sized sounder that profiles the lower 21.7 miles of the atmosphere by analyzing the invisible infrared radiation, or energy, emitted from the land, sea and air. The profile samples the two main drivers of weather: temperature and humidity.

Hey! Here's another thread you and your friends can huff and puff on.

The key computer models that form the basis of forecasts disagreed. One said it would rain. The other said it wouldn't.

I've told all of my friends (both of them) That the weather guessers in Alaska moonlight forcasting the local salmon returns. Both are equally as accurate.

And I forgot to add taxpayer funded.

It's amazing to me that these people can keep the same job year after year.

I want to thank you for all the effort that you've put in on the recent posts. I do want to reply, because there are a number of points that need clarification. However, due to pressing demands I may not get to reply at length until mid-June (but I might be able to -- not sure yet).

I look forward to your contributions. If nothing else it helps me to investigate and further clarify and adjust my own position to more nearly conform to observational data.

Just to mix the issue up again, it appears that IPCC is moving to lowering its estimate of climate sensitivity for the GCMs.

Climate Change 2001
The Scientific Basis
IPCC

6.2 Forcing-Response Relationship

6.2.1 Characteristics

As discussed in the SAR, the change in the net irradiance at the tropopause, as defined in Section 6.1.1, is, to a first order, a good indicator of the equilibrium global mean (understood to be globally and annually averaged) surface temperature change. The climate sensitivity parameter (global mean surface temperature response DT_s to the radiative forcing DF) is defined as:

DT_s / DF = l(6.1)

(Dickinson, 1982; WMO, 1986; Cess et al., 1993). Equation (6.1) is defined for the transition of the surface-troposphere system from one equilibrium state to another in response to an externally imposed radiative perturbation. In the one-dimensional radiative-convective models, wherein the concept was first initiated, l is a nearly invariant parameter (typically, about 0.5 K/(Wm^-2); Ramanathan et al., 1985) for a variety of radiative forcings, thus introducing the notion of a possible universality of the relationship between forcing and response. It is this feature which has enabled the radiative forcing to be perceived as a useful tool for obtaining first-order estimates of the relative climate impacts of different imposed radiative perturbations. Although the value of the parameter “l” can vary from one model to another, within each model it is found to be remarkably constant for a wide range of radiative perturbations (WMO, 1986). The invariance of l has made the radiative forcing concept appealing as a convenient measure to estimate the global, annual mean surface temperature response, without taking the recourse to actually run and analyse, say, a three-dimensional atmosphere-ocean general circulation model (AOGCM) simulation.

The often quoted IPCC range of 0.75-1.1^oC/Wm^-2 is a measure derived from and applicable to their models which, for one thing, do not recognize water vapor as a component of GHGs.

Water vapor for one thing is treated as "feedback" not a "forcing" by IPCC in the GCMs and is not included in their measure of DF of the climate sensitivity parameter l. Thus their model l cannot be reflective of the observational and real world parameter based on total forcing from all factors, to which I refer.

The IPCC baseline assumption(a political decision rather than one rooted in science) is that mankind is the primary causative agent of warming through introduction of additional GHGs into the atmosphere, and that temperature and everything else derives from changes in those GHG additions that can be attributed to mankind.

The position that I and many others take is that climate temperature can vary for a multitude of reasons(variation in solar irradiation, astronomical primary and secondary effects, ...) and the increase in CO2(and other GHG's) arise from changes in temperature as well as contributions by man. The contributions of CO2 and other GHGs that are recognised by IPCC, do not have the degree of effect on the global climate temperatue the IPCC attribute to them in their Global Climate Models(GCMs).

That alternative position makes for a substantially different view of the world and conforms more readily to observational data. It also allows us to examine the real physical phenomena for true causitive factors rather than staying with models based in an apriori underlying premise and agenda to perceive mankind as the primary causitive agent of climate change.

The IPCC claims (and cogitator agrees) that towns with populations of 5000 and less have no urban heat islands. The article below (summarized by co2science.org) points out that towns of population of 1000 have heat islands of 2.2 C. The article implies a town of 100 has a heat island of 1.0 C and a town of 10 has a heat island of 0.4 C. The entire surface network is contaminated and that is why it heating rapidly compared to the satellite and balloon observations. Also the growing season in Siberia has been getting shorter over the last half century and tree rings there are getting narrower, but the urban heast island contaminated stations there show marked warming. Without this faulty claim of Siberian warming, there is almost no global warming.

From www.co2science.org:

Urban Heat Islands in Australia

Reference

Torok, S.J., Morris, C.J.G., Skinner, C. and Plummer, N. 2001. Urban heat island features of southeast Australian towns. Australian Meteorological Magazine 50: 1-13.

What was done

The authors studied the characteristics of urban heat islands in several cities in Australia with populations ranging from approximately 1,000 to 3,000,000 people.

What was learned

The maximum urban-rural temperature differences of the Australian cities were found to scale linearly with the logarithms of their populations. The authors noted that the same was true for cities in Europe and North America, but that the heat islands of Australian cities were generally less than those of similar-size European cities (which were less than similar-size North American cities) and that they increased at a slower rate with population growth than did European cities (which increased slower than did cities in North America). The regression lines of all three continents essentially converged in the vicinity of a population of 1,000 people, however, where the mean urban-rural temperature difference was approximately 2.2 ± 0.2 °C.

What it means

The results of this study suggest that very small towns, with populations measured in mere hundreds of inhabitants, likely have urban heat islands that are on the order of the entire amount of global warming that is believed to have occurred since the end of the Little Ice Age. With such small aggregations of people having such a dramatic impact on air temperature, it is ludicrous to believe that on top of the natural warming experienced by the earth in recovering from the Little Ice Age we can confidently discern an even more subtle increase in background temperature caused by concomitant increases in greenhouse gas concentrations. Changes in population, which have generally been positive nearly everywhere in the world over this period, could easily explain whatever tiny bit of warming is left after the natural component of warming (which must be substantial, relatively speaking) is subtracted from the total amount of warming recorded by the totality of earth's thermometers over the past century or so.

Reference:

Reconciling Observations of Global Temperature Change
(read on-line version by clicking on Special Offers left side of HTML page)

Summary as regards Tropo vs Surface temp measurements:

http://users.erols.com/dhoyt1/nas-table.htm

Quotes from and comments on the NRC Report, "Reconciling Observations of Global Temperature Change" (National Research Council, 2000).
The case for recent global warming is not nearly as strong as one might think from reading the Executive Summary.

Quote from NRC Report	Comments
"The most common method for determining trends - least squared deviations - indicates linear trends from the time series of +0.053, +0.059, and +0.053 C/decade for the period 1890-1998 and +0.17, +0.19, and +0.13 C/decade for 1979-98 for Quayle et al. (1999), Jones et al. (1999) and Hansen et al. (1999) respectively." [p. 36]	The linear trend in surface temperature over the last two decades is about 0.16 C/decade. The models upon which the Kyoto Protocol is based however predict warming of 0.3 to 0.4 C/decade (IPCC, 1995; Hansen et al., 1988).
"Surface temperature has been increasing at a rate of about 0.1-0.2 C/decade, whereas tropospheric temperature has changed so little that a different sign for the trend is obtained, depending on whether or not the final year of the record is included." [pp. 62-63]	There is a difference between the MSU satellite trends for mid-tropospheric temperatures and trends based on surface observations. For greenhouse warming,climate models predict the trend should be larger in the mid-troposphere than at the surface, the opposite of what is observed.
"The models indicate that natural variability may indeed have contributed to the observed discrepancy, but unless the models are seriously underestimating the natural variability, it is highly unlikely that a differential trend as large as the one observed during the past 20 years could be entirely due to the internal variability of the climate system. [p. 69]	The climate models indicate the above discrepancy is highly unusual and the present models do not provide a believable explanation for the differences.
"Part of the observed difference between global-mean trends in surface temperature and tropospheric temperature may be a reflection of the incomplete coverage of surface data, which are sparse over the higher latitudes of the Southern Hemisphere. Recent calculations of Santer et al. (in review), based on the sub-sampling methodology described earlier, indicate that perhaps as much as one-third of the difference may be due to this effect." [p. 67]	About one-third of the trend in surface temperatures is caused by incomplete spatial sampling (similar to our result of about one half). Correcting this single error source in the surface temperature measurements reduces the surface temperature trend in the last 20 years to about 0.1 C/decade, which is consistent with a warming of 0.8 C for a doubling of carbon dioxide. [Error of the first type: insufficient spatial-temporal coverage]
"The uneven spatial distribution of in situ data, and the change in their distribution over time, can also potentially create biases." [p. 39] "Biases due to discontinuities in the observing network are a much more difficult problem to resolve." [p. 39]	At the end of 1989 more than half of the stations in the USSR were shut down. The bulk of the difference between the MSU and surface trends occurs at the time and location where this network discontinuity occurs. We estimate that this second major error in the surface network accounts for about 0.05 C/decade of observed surface warming, reducing the real climatic warming at the surface to about 0.05 C/decade, bringing the MSU and surface trends essentially into agreement. The corresponding warming for a doubling of carbon dioxide then becomes 0.4 C. [Error of the second type: inhomogenieties within a grid box due to changing number and quality of stations]
"Unfortunately, most long-term climatological time series have been affected by a number of non-climatic factors that make these data unrepresentative of the actual climatic variation occurring over time. These factors include changes in: instruments, observing practices (e.g., depth of the water intake for SST measurements), station locations, formulae used to calculate means, and station environment (e.g., urbanization)." [ p. 37]	Here are listed just a few additional problems plaguing the surface network. These problems are generally most severe at remote island stations and in third world countries. [Error of the third type: inhomogeneity in the record of a single station]
"The data can be erroneous due to instrument problems (e.g., a bubble in the liquid-in-glass thermometers), or contain errors caused by faulty transcription, digitization, or transmission of the data. Such quality control problems add noise to the data, but are not likely to add a bias to the results because of the large number and variety of sites monitored." [p. 37]	We are less confident than the authors of the NRC report that the errors are unbiased. For example, in the transcription of data a "7" is sometimes written in place of "2" whereas the reverse transcription seldom happens. This type of error is more frequent in recent years. The net result: a non-climatological warming. In short, the assumption of unbiased errors seems optimistic and needs proof. [Also error of the third type]
"Some changes cause sharp data discontinuities, while other changes, particularly change in the environment around the station, can cause gradual biases. All of these inhomogenieties can bias a time series and lead to misinterpretations of the studied climate unless they are accounted for by adjusting or 'correcting' the data." [p. 37]	Subtle changes in the environment about stations is probably more prevalent than assumed (e.g., changing skyline hypothesis). The corrections to the data may be of the same order of magnitude as the long-term trends and it would be helpful to quantify them. Finally, there are few stations existing now that are in the identical location and with identical instruments as they were in 1900. A list of such stations would be helpful. [Yet other errors of the third type]
"However, global coverage of in situ data can never be achieved, particularly historically." [p. 40]	The error bars on the trends in temperature must be considered to be larger the further one goes back in time where fewer stations exist. The trends in the Southern Hemisphere must be very unreliable before 1957 when the observation network was sparse.
General comment: Changes in glaciers and Arctic sea ice coverage and thickness are cited as evidence supporting recent warming.	Changes in tree rings do not support warming in the last two decades. Changes in lower tropospheric pressure using radiosondes do not support recent warming trends. Surface pressure measurements in Russia are not supportive of warming there. None of this evidence is mentioned in the NRC Report.

The IPCC claims (and cogitator agrees) that towns with populations of 5000 and less have no urban heat islands.

Heat islands are not the only problem.

see http://users.erols.com/dhoyt1/index.html

What happens when base time interval is changed? The trendline changes due to
   Temporal variations in Area Coverage
   Drifts in surface temperature network
   Changing Skyline