A Few Things Ill Considered

A layman's take on the science of Global Warming featuring a guide on How to Talk to a Climate Sceptic.

Monday, February 27, 2006

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Warming Due to Urban Heat Island Effect

(Part of the How to Talk to a Climate Sceptic guide)

This article has moved to ScienceBlogs

It has also been updated and this page is still here only to preserve the original comment thread. Please visit A Few Things Ill Considered there. You may also like to view Painting With Water, Coby Beck's original fine art photography.



  • At March 14, 2006 2:58 AM, Blogger Christer said…

    Thank you for this, in fact, thank you for this whole site.

    Made a nice user-friendly image of the pictures from the two pages you linked too, just in case anyone needs it: http://img.photobucket.com/albums/v90/KRIGBERT/tempnight.png

  • At March 14, 2006 2:29 PM, Blogger coby said…

    Thank you for the graphic and the comment, Chris.

  • At March 15, 2006 12:38 AM, Anonymous Anonymous said…

    Urban Heat Islands are easy to see in satellite infrared imagery. See here:



  • At March 15, 2006 8:42 AM, Blogger coby said…

    Thanks for the additional evidence, nanny_govt_sucks. The important point to remember is that Urban Heat Islands are real, but they are well understood and have not contaminated the temperature trend.

  • At March 24, 2006 2:07 PM, Anonymous Anonymous said…

    You only can correct for UHI if you have nearby rural stations. Even in densely sampled areas giss goes terribly wrong by warming rural stations and cooling urban ones:


    We therefore cannot say what the temperature trend is in say, Africa.

  • At March 24, 2006 2:34 PM, Blogger coby said…

    I think the Petersen paper (and there have been others) is pretty conclusive that Urban Heat Island, though real, does not effect weather station readings, probably due to micro-site selection. They have even less effect on temperature trends. UHI has been studied and its influence on temperature trend searched for and it just is not there. The continued descriptions of why it should be do not change the fact that it isn't. Plus, the kind of correction by correlation you offered in your links flies completely in the face of all the other lines of evidence of global warming. The trend is undeniable.

  • At April 17, 2006 8:30 AM, Anonymous Anonymous said…

    One way to ensure that the heat island effect does not affect Global Temperature is to use data that cannot be affected by it.That is: use data from uninhabited Stations.There is a network of such Stations in the USA there are quite a few in Australia and others distributed throughout the earth.
    Such sites mostly show that the temperatures in the 1940s were as high or higher than recent temperatures.
    However many of these stations were shut down in 1970 and curiously many
    inhabited stations have been started up inthe last 50 years.
    There is no way that your claim that urban heat has not had any effect on the Global Temperature can be upheld.

  • At June 29, 2006 2:32 PM, Anonymous Anonymous said…

    David Parker's study that concluded that the Urban Heat Island is not responsible for the current records of large-scale global warming is featured in the current issue of Journal of Climate:


    (A subscription is required to view the full document)

    -Stephen Berg

  • At September 18, 2006 7:01 AM, Blogger Co2emissions said…

    I stumbled across this one from the Hadley Centre today while looking at heatwave deaths.

    Quote from page 15:

    Urban heat islands

    It is well known that temperatures over large urban areas sometimes exceed those in the surrounding countryside, due, for instance, to differences in how much light the ground absorbs, heat storage, different amounts of available surface moisture, and locally produced heat in urban areas. This is the urban heat island effect, and has led to concerns that urbanisation near weather stations may have affected temperature measurements, possibly explaining some of the global warming signal.

    The Hadley Centre has used one of the observed characteristics of urban heat islands — that they mainly occur at night at times when winds are calm — to investigate whether this concern is valid.

    The Figure below shows the increase in the minimum daily temperature, which usually occurs at night, for windy and calm conditions separately. Because the rate of warming is the same during calm and windy periods, these new results indicate that urban heat island effects have not introduced significant biases into estimates of recent global warming trends and, therefore, strengthen our confidence in them.

  • At January 29, 2007 9:47 AM, Anonymous Anonymous said…


    You shouldn't have provided the global average in your propaganda.

    Every starting year on all 4 maps is 1955, THE COLDEST YEAR ON RECORD FOR 90 YEARS TO THE PRESENT!

    This is a lesson on fudging your data to get a desired result. If that master propagandist would have used almost any other year then the very cold 1955 as a starting point, then the map would have been blue'r.

    If it were up to me I would cut the entire NASA's budget until the person responsible for this Socialist Propaganda is fired, blacklisted, and burned at the Heretic's stake.

  • At January 29, 2007 10:05 AM, Blogger coby said…

    What are you talking about? The graphs start at 1880 becuase that is the earliest they can given data availability and the anomaly maps are based on the 1951-1980 average becasue that is standard meteorology and is a rolling window.

    Otherwise, very astute criticisms!

    "If it were up to me I would cut the entire NASA's budget until the person responsible for this Socialist Propaganda is fired, blacklisted, and burned at the Heretic's stake."

    Please, tell us your name so we can all write you in on the next presidential ballot!

  • At January 29, 2007 10:42 AM, Anonymous Anonymous said…


    ^^^These 4 maps plus 1 annual mean. ok thats 5 maps. They all start in the very cold year of 1955.

    If I were to try to make the most exadurated picture of Global Warming, I would use the coldest year as the starting point.

    This is pure propaganda, simply because they used the coldest year (1955) as the starting point, to exadurate the results and make the maps red'r.

    What other numbers does NASA fudge to befuddle the public? This is classical manipulation of hard data to produce the desired results, and completely unethical for a scientist to do.

  • At January 29, 2007 12:28 PM, Blogger coby said…

    Thanks for being specific enough to identify the source of your confusion. The first important point is that 1955 is simply 50 years ago, so there is no cherry picking, this is a standard time period for an anomaly map. Five years ago the staring point was 1950, five years from now the starting point will be 1960 (2006 data is not available yet, should be soon).

    The second thing you are confused about is that starting in 1955 does not mean starting with that particular year's average temperature, rather it means starting with the five year mean centered on that year, which if you look here you will note is some .15oC higher than the temp that year. So if in fact some kind of cherry pick were desired they should have chosen 1966 when the five year mean was in fact even lower than in 1955. It would also be more dramatic because more warming would have occured in a shorter time.

    Thanks for the comments, I hope that reassures you.

  • At January 30, 2007 6:08 AM, Anonymous Anonymous said…

    Thanks for being specific enough to identify the source of your confusion. The first important point is that 1955 is simply 50 years ago, so there is no cherry picking, this is a standard time period for an anomaly map. Five years ago the staring point was 1950, five years from now the starting point will be 1960 (2006 data is not available yet, should be soon).

    The second thing you are confused about is that starting in 1955 does not mean starting with that particular year's average temperature, rather it means starting with the five year mean centered on that year, which if you look here you will note is some .15oC higher than the temp that year. So if in fact some kind of cherry pick were desired they should have chosen 1966 when the five year mean was in fact even lower than in 1955. It would also be more dramatic because more warming would have occured in a shorter time.

    Thanks for the comments, I hope that reassures you.


    Where in the source info, does it state that the 5-mean was used instead of the cherry-picked (Coldest Year since 1929) 1955?

    I see no information to lead me to believe that I shouldn't take your source literally when the map plainly states 1955-2005.

    If it was the 5-year Mean, then the map would have shown (5-year mean of 1955)-2005.

    What tricks, slight of hand, are we up to now.

  • At January 30, 2007 6:31 AM, Anonymous Anonymous said…

    ...and furthermore.

    If the 5 year mean was used for the starting point, why wasn't the 5-year mean used as the ending point. Surely even the year of 2005 has a 5-year mean even if it has to be 2000-2005 averaged.

    You say the 50 year was used because it is an even number, 5 decades, 5*10. Is this numerology? 50 years is no better then 49 years, or 48 years, or 47 years. Are we going to being counting in multiples of 7 for the Christian-Judeans, multiples of 5 for the Muslims, or multiples of 4 for Buddhists? What makes 10 a sacred multiple?

    If I were partisan and I wanted to prove that Global Warming did not exist, using your source's own data, I would use 1944-2004, a 60 year span. 6*10, 6 decades, has a zero on the end of it so it is sacred. 1944 was the hottest year until 1981. Not to mention 2004 was relatively cold.

    Or 1944-1993. From 1944-1994 there is in actuality a drop in global temperature. But nobody ever see's big maps of the earth from 1944-1993, where red=bad and blue=good, they are never published.

  • At January 30, 2007 6:46 AM, Anonymous Anonymous said…

    ....and furthermore take 2.

    Has anyone reviewed the Alaskan and Siberian anomolies? No? I didn't think so.

  • At January 30, 2007 12:32 PM, Blogger coby said…

    What do you mean by the Alaskan and Siberian anomalies?

    As for your psycho analysis of the choice 50, I think your are squinting awfully hard trying to see a problem. 50 is an obvious round number. What is sacred about base 10? Well, I've always thought it was because hat is the number of fingers most of us have. Sure it is arbitrary, so go back to the site and generate your own anomaly map. My observation that 1966 would be a better year if the goal were simple cherry picking stands.

    You will have to drill down into the details of the studies to find documentation of what smoothing is applied.

    BTW, what is your main point? Do you think there is no warming or very little warming going on? I think you are just being paranoid and silly.

  • At January 31, 2007 6:51 AM, Anonymous Anonymous said…

    My observation that 1966 would be a better year if the goal were simple cherry picking stands.


    Again, you are assuming that the 5-year mean is being used. Because you are a Democrat, who, "WANTS TO BELIEVE!" You, "WANT TO BELIEVE," so you assume the 5-year mean is used when it is not.

    Go back to watching the X-files, and leave the real science to the scientists, or at least the minimally educated ones.

  • At March 18, 2007 2:45 AM, Blogger Heiko said…

    Hi Coby,

    as you know, I don't think there's any good evidence that the urban heat island effect is significant.

    But, I've got to say that some of the arguments on real climate and in the wikipedia article are rather strange:

    1) Real climate take great pleasure in pointing out how satellite data have been through multiple revisions and therefore cannot be used to argue against models.

    Fine, but then they can't be used to argue against the urban heat island effect either, just because it so happens that these multiply corrected satellite data give slightly more warming over North America than ground stations.

    2) Trends over the oceans and over land are very different, so how can the wikipedia author claim that they are so similar as to disprove the urban heat island effect?

    3) Wouldn't it be precisely rural stations that are affected by the urban heat island effect?

    I mean cities are already warm, it's areas with extra building that should experience changes, ie rural areas that are becoming less rural?

  • At March 20, 2007 1:40 PM, Blogger coby said…

    I suppose one might expect the most UHIE from stations that changed from rural to urban due to sprawling cities. Perhaps also in long records from always urban stations where dirt and wood chaged to ashpalt and concrete.

    I haven't revisited the RC or wiki articles but ocean and land trends are similar in that they are both clearly up, that might be enough to justify saying they are the same depending on context etc. Ocean trends are certainly a good piece of evidence if you are tryin to refute the claim that all observed warming is an UHIE artifact. Regarding satellites, I suppose it is a temptation to accept unreliable data when it agrees with expectations/models even as you view it suspiciously when it does not. But you are right, one should be careful to be even handed in the standards used regardless of the argument you are supporting.

    Sorry for the slow response.

  • At April 18, 2007 2:59 PM, Blogger max anacker said…

    It appears that one of the weak points in the latest IPCC report is the UHI impact on the surface temperature record used by the IPCC to show significant global warming.
    Based on the uncorrected surface temperature record, the total warming over the 20th century (1900-1999) was 0.6°C, as reported in the IPCC “Third Assessment Report” of 2001 [1].

    The IPCC 2007 summary report (February 2007) uses the surface temperature record for the period 1906-2005. This shows a 100-year linear trend of 0.74 °C [2], somewhat higher than the 0.6°C shown in the earlier report. In effect, the “20th century” was shifted by six years: a cooling trend of –0.06°C from 1900-1906 was replaced by a warming trend of 0.08°C from 1999-2005, to change the “20th century” statistic in an upward direction.

    The surface temperature record shows an increase of 0.17°C over the latest decade; the IPCC increases this by 18% to project a warming of about 0.2°C/decade over the next two decades [1].

    Starting in 1979, tropospheric temperatures are being measured by satellites. These are being measured by NASA’s National Space Science and Technology Center at the University of Alabama in Hunstville (UAH). These provide millions of observations with uniform global coverage while surface measurements are based on weather stations that are much more limited in number and primarily on land and near urban areas, with limited coverage outside the USA and poor coverage in the southern hemisphere. The two temperature records are available to the public; the satellite record is more transparent and detailed than the surface record [3,4].

    The satellite record became a problem for the IPCC, since it did not show the degree or rate of warming as shown by the surface record or as predicted in earlier IPCC reports. It is not used as the standard by the IPCC, but only mentioned in passing with the statement: “New analyses of balloon-borne and satellite measurements of lower- to mid-tropospheric temperature show warming rates that are similar to those of the surface temperature record and are consistent within their respective uncertainties, largely reconciling a discrepancy noted in the TAR.” [2]

    This statement is incorrect. The surface temperature record shows significantly higher rate of warming than either the satellite record or the weather balloon record. For the latest decade the difference between the reported surface and troposphere temperature anomalies is around 0.4°C [3,4].

    A reanalysis of the satellite record was made by Remote Sensing Systems, an independent research oriented business located in Santa Rosa, California, to take into account errors resulting from orbital decay of the satellites. This study showed a calculated error of 0.097°C in the measured temperature anomaly [5].

    In a later study, the same authors claimed that the UAH processing algorithms were incorrectly adjusting for diurnal variations, especially at low latitude. If this were actually the case, correcting for this problem would raise the trend line 0.035°C/decade [6].

    The debate between UAH (Christy et al.) and RSS (Mears et al.) over how to interpret the same basic data has continued, with both sides claiming their interpretation is the correct one. UAH shows a trend of around 0.1°C/decade, after correcting for orbital decay, while RSS calculates a trend of 0.16°C/decade, somewhat closer to the surface record.

    The two records were put to an independent test by comparing the trend lines with the radiosonde balloon record. This gave a very close confirmation of the UAH (Christy et al.) record (less than 0.01°C/decade difference), but only a poor correlation with the RSS series (0.08°C/decade difference) [7].

    In effect, this validated the UAH record and confirmed that the discrepancy between the surface record on one hand and the satellite and balloon record on the other has not been resolved as the IPCC states.

    It is generally recognized that global warming from greenhouse gases must start in the troposphere, not on the ground, so the satellite measurements are a more pertinent indicator of the degree of warming that is actually occurring than are the surface records, particularly if the warming is being caused by the greenhouse effect.

    Satellite data also do not introduce any human error or distortions caused by the “urban heat island effect” and changes of weather stations.

    The comparison between temperature averages from land-based stations over time inevitably introduces an upward bias, as population and human activity increase along with economic prosperity.

    The measurement stations themselves also change over time. Many rural stations were closed down and replaced by stations with more modern, better-equipped facilities located nearer an urban center or airport. In addition many stations were upgraded with larger, more comfortable buildings with better heating, paved access roads, etc.

    There have been many studies, which show that the above-mentioned changes are not limited to the USA alone and have caused a significant spurious rise in measured global surface temperatures [8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25].

    Land surface air temperature anomalies are currently 0.14°C higher than the sea surface temperatures and 0.21°C above the night-time marine air temperatures as compiled by the UK Met. This gap has opened up since 1980 as surface readings have increased, and it shows again that there are spurious heating effects on land, which are not observed over the oceans [26].
    The MSU satellite temperature records of the lower troposphere (Microwave Sounder Units) carried by NASA satellites, detect genuine global climate variations which are also evident on the surface record, such as volcanic activity (notably that of Mount Pinatubo in 1992), ocean circulation (such as the El Niño event of 1998), and changes in solar activity (such as recently documented by Soon et al. in 2000).
    They do not detect, however, the regional hotspots, which are largely responsible for the apparent rise in surface temperature. The differences between the surface temperature record since 1979 and that recorded by the MSU satellites in the lower troposphere must therefore be largely due to local heating which is highly regional, and is particularly evident in cold climates. This cannot be regarded as a genuine climate change, but merely a local result of human activity, primarily improved comfort conditions.
    In other words, the MSU satellites give a true indication of global and regional temperature change, whereas the surface record is contaminated by the local effects cited above.
    The IPCC report states that: “Urban heat island effects are real but local, and have a negligible influence (less than 0.006°C per decade over land and zero over the oceans) on these values.”[2] From 1980 to 2006 this would represent an error of only 0.02°C.

    The many reports cited above show that this statement is incorrect and that the net error in the global anomaly as reported in the last decade due to the UHI effect is closer to 0.3°C. [8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25]

    If we make this correction to the surface record as used by the IPCC, we have reconciled the difference between the surface and satellite records to a discrepancy of less than 0.01°C over the latest decade. We would then also show a close correlation with the radiosonde balloon record.

    The IPCC report states that “Eleven of the last twelve years (1995-2006) rank among the 12 warmest years in the instrumental record of global surface temperature (since 1850)”.[2]

    This is obviously not the case if the IPCC used the satellite or weather balloon temperature record or if we make the correction to the IPCC surface temperature record to account for the Urban Heat Island effect.

    As climatologist Douglas V. Hoyt questions: “Would it not be far more important to adjust the accuracy of surface measurements to the standards set by balloon and satellite measurements, rather than to ignore the results of the latter two methods of measuring global temperature trends?” [27]

    With the IPCC making temperature projections and climate change predictions for the next 100 years based on model scenarios using only the questionable surface temperature trend as the basis, this seems to be a very valid question.

    Note: Douglas V. Hoyt is a solar physicist and climatologist who worked for more than thirty years as a research scientist in the field. He has worked at NOAA, NCAR, Sacramento Peak Observatory, the World Radiation Center, Research and Data Systems, and Raytheon where was a Senior Scientist. He has conducted research on issues related to climate change, changes in solar irradiance on all time scales, and the sun-climate connection. His most recent publication is the book "The Role of the Sun in Climate Change" . He has published nearly 100 scientific papers on solar irradiance variations, the greenhouse effect, atmospheric transmission, aerosols, cloud cover, sunshine, radiative transfer, radiometers, solar activity, sunspot structure, sunspot decay rates, and the history of solar observations. Dr. Hoyt has received no funding from any fossil fuel entity or government entity. His work is influenced only by the data and the study of the scientific literature.


    [1] Intergovernmental Panel on Climate Change (IPCC), “Third Assessment Report” (2001)

    [2] Intergovernmental Panel on Climate Change, “Climate Change 2007: The Physical Science Basis, Summary for Policymakers” (February 2007)

    [3] http://vortex.nsstc.uah.edu/public/msu/y2/uahncdc.mt

    [4] http://lwf.ncdc.noaa.gov/oa/climate/research/anomalies/anomalies.html
    [5] Mears, C., Schabel, M. and Wentz, F.J., “A Reanalysis of the MSU Channel 2 Tropospheric Temperature Record”, Journal of Climate, 16 (May 2003)
    [6] Mears, C. and Wentz, F. “The Effect of Diurnal Correction on Satellite-Derived Lower Tropospheric Temperature” Science Vol. 309. no. 5740, pp. 1548 – 1551 (2005)
    [7] Christy, J. et al. “Update on Microwave-based Atmospheric Temperatures from UAH”, Fifteenth Symposium on Global Climate Change and Climate Variations (2006)
    [8] Bohm, R. 1998. Urban bias in temperature time series - A case study for the city of Vienna, Austria. Climatic Change, 38, 113-128.
    [9] Bottyan, Z., Kircsi, A., Szeged, S. and Unger, J. 2005. The relationship between built-up areas and the spatial development of the mean maximum urban heat island in Debrecen, Hungary. International Journal of Climatology, 25, 405-418.
    [10] Chen, L., Zhu, W., Zhou, X. and Zhou, Z. 2003. Characteristics of the heat island effect in Shanghai and its possible mechanism. Advances in Atmospheric Sciences, 20, 991-1001.
    [11] Chung, U., Choi, J. and Yun, J.I. 2004. Urbanization effect on the observed change in mean monthly temperatures between 1951-1980 and 1971-2000. Climatic Change, 66, 127-136.
    [12] De Laat, A.T.J. and Maurellis, A.N. 2004. Industrial CO2 emissions as a proxy for anthropogenic influence on lower tropospheric temperature trends. Geophysical Research Letters, 31,1029.
    [13] Frauenfeld, O.W., Zhang, T. and Serreze, M.C. 2005. Climate change and variability using European Centre for Medium-Range Weather Forecasts re-analysis (ERA-40) temperatures on the Tibetan Plateau. Journal of Geophysical Research, 110, 1029.
    [14] Gonzalez, J.E., Luvall, J.C., Rickman, D., Comarazamy, D., Picon, A., Harmsen, E., Parsiani, H., Vasquez, R.E., Ramirez, N., Williams, R. and Waide, R.W. 2005. Urban heat islands developing in coastal tropical cities. EOS, Transactions, American Geophysical Union, 86, 397, 403.
    [15] Hinkel, K.M., Nelson, F.E., Klene, A.E. and Bell, J.H. 2003. The urban heat island in winter at Barrow, Alaska. International Journal of Climatology, 23, 1889-1905.
    [16] Houghton JT., Meira Filho LG, Callander BA, Harris N, A. Kattenberg A, Maskell K , (1996), Climate Change 1995 : the science of climate change, Cambridge University Press. Cambridge.
    [17] Jáuregui, E. 2005. Possible impact of urbanization on the thermal climate of some large cities in Mexico. Atmosfera,18, 249-252.
    [18] Kalnay, E. and Cai, M., 2003. Impact of urbanization and land-use change on climate. Nature, 423:528-531

    [19] Karl, T.R., Diaz, H.F. and Kukla, K., 1988. Urbanization: its detection and effect in the US climate record, Journal of Climate, 1: 1099-1123
    [20] Liu, X. and Chen, B. 2000. Climatic warming in the Tibetan Plateau during recent decades. International Journal of Climatology, 20, 1729-1742.
    [21] Oke, T.R. 1973. City size and the urban heat island. Atmospheric Environment, 7, 769-779.
    [22] Ren G. Y., Z. Y. Chu, Z. H. Chen, Y. Y. Ren (2007), Implications of temporal change in urban heat island intensity observed at Beijing and Wuhan stations, Geophys. Res. Lett., 34, L05711, doi:10.1029/2006GL027927.
    [23] Streutker, D.R. 2003. Satellite-measured growth of the urban heat island of Houston, Texas. Remote Sensing of Environment, 85, 282-289.
    [24] 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.
    [25] Zhou, L., Dickinson, R.E., Tian, Y., Fang, J., Li, Q., Kaufmann, R.K., Tucker, C.J. and Myneni, R.B. 2004. Evidence for a significant urbanization effect on climate in China. Proceedings of the National Academy of Sciences, 101, 9540-9544.
    [26] Parker DE, Folland CK, Jackson M, 1995 Marine surface temperature observed variations and data requirements Climatic Change 31:559-600
    [27] Hoyt, Douglas V. Greenhouse Warming: Fact, Hypothesis, or Myth?
    dhoyt1@erols.com (March 24, 2001)

  • At April 19, 2007 12:21 AM, Blogger coby said…

    "The IPCC report states that “Eleven of the last twelve years (1995-2006) rank among the 12 warmest years in the instrumental record of global surface temperature (since 1850)”.[2]

    This is obviously not the case if the IPCC used the satellite or weather balloon temperature record or if we make the correction to the IPCC surface temperature record to account for the Urban Heat Island effect."

    Your post and its sources do not dispute the rise, merely its slope so I am a bit at a loss as to how you reach the above conclusion.

    There are many difficulties with the satellite records, I don't know why you would chose to rely on them so heavily. Regardless, the evidence of warming comes from a great many and varied sources including sea level rise and glacier mass balance surveys.

    I am curious as to what your answer is to my comparison of urbanisation patterns and warming anomalies. Why don't warming anomalies match urbanization if global warming is an artifact of UHI effect?

    Please only put original material here, if you are using another source then just quote it with the proper attributions.

    Thanks for the visit and sorry for the tardy response.

  • At April 19, 2007 2:12 AM, Blogger max anacker said…

    Thanks for reply and comment.

    Don’t believe anyone disagrees with IPCC that there is warming today, as the record shows there has been for two hundred years, excluding a few short cooling periods.

    Disagreement centers on how much warming has taken place over the past 2 decades, i.e. the “slope” of the rise, and on whether or not the current trend is unprecedented.

    Another disagreement centers on whether this is largely caused by anthropogenic or natural factors, but that is another debate.

    Global warming is not an artifact of UHI effect alone. Its magnitude is only exaggerated by this effect, that’s all.

    The satellite record, validated by the balloon record, shows that in the troposphere this warming has been at about half the rate shown by the surface record.

    There is a significant difference in the anomaly as reported by the two referenced records.

    It is the extrapolated “slope” of the IPCC projected rise for next 100 years that gets everyone’s attention, and if this is based on exaggerated data it will show an exaggerated prediction for the future.

    Extrapolating 0.1 deg C per decade for 100 years gets us a 1.0 deg C rise, which is not very exciting. Taking IPCC lowest “best estimate” of 1.8 deg C by 2100 gets more interesting and using the highest “best estimate” of 4.0 deg C becomes almost alarming.

    That is my point.

  • At April 19, 2007 4:37 PM, Blogger coby said…

    Hi max,

    I don't think any of the lower troposphere satellite records only show half the degree of surface warming. Regardless there are I believe five different ones each with slightly different results.

    The wikipedia article and the RealClimate post linked to from my "satellites show cooling" article are both very well sourced and informative. (I know you don't claim cooling).

    As for future rises, the IPCC is not extrapolating past trends, these are projections from complex models. That is not to say that if the warming of the past three decades had been significantly less than thought it would not be a problem for the models, but it is not so simple as you seemed to represent. BTW, if ever this were the case, such a discrepancy could have several explanations including underestimated aerosol effects. Judging from the satellite record's very recent past, I personally am very hesitant to put too much stock in it. It has changed so much, so frequently why on earth should I be confident it won't change again?

  • At April 19, 2007 4:40 PM, Blogger coby said…

    Oh, I forgot to make the point that even if the current warming were not unprecedented, its cause is so there is no reassurance in that fact. I disagree strongly that there is any disagreement on the mostly anthropogenic cause of today's warming (within the scientific community that is, opinions like Glenn Beck's are quite irrelevant to reality).

  • At April 20, 2007 1:32 AM, Blogger max anacker said…

    Thanks for reply. Think we've beaten the "slope of line" discussion to death. But I come to another point you made.

    “I strongly disagree that there is any disagreement on the mostly anthropogenic cause of today’s warming (within the scientific community)”

    What about Israeli astrophysicist, Nir Shaviv; MIT professor, Richard Lindzen; Harvard astrophysicists, Sallie Baliunas and Willie Soon; University of Virginia climatologist, Patrick Michaels; solar physicist, Douglas Hoyt, just to name a few. Are these not part of the “scientific community”?

    Coby, if you had said that those disagreeing are a minority, I could have bought your argument. But when you strongly disagree that there is ANY disagreement in the scientific community, you are on thin ice. It’s just not so.


  • At April 20, 2007 9:16 PM, Blogger coby said…

    Hi max,

    You're correct I should have qualified my statement with "virtually" or something similar. 100% unanimity is probably unacheivable on any issue. I would note that in your list at least Lidzen and Michaels do not deny the observed increase or its largely anthropogenic attribution, rather they doubt the IPCC projections of the future. I know that Soon and Baliunas have in the past promoted a solar theory but I have the imression they have abandoned it, I could be wrong. Shaviv is working on his GCR-climate connection hypothesis but has he actually made any string statements claiming this is the primary driver? I know he says it may be an underestimated factor.

    What do you think a lay person should do when there is only 99% agreement in the scientific community?

  • At April 22, 2007 10:11 AM, Blogger max anacker said…

    Hi Coby,

    Thanks for reply. Sorry for delayed response.

    None of the scientists I mentioned deny the observed increase, although they may have reservations about the “slope of the curve” we talked about earlier.

    Shaviv has made a statement that there is no scientific evidence that the anthropogenic increase of CO2 and other greenhouse gases is the cause of the warming we are experiencing. Check http://www.sciencebits.com/CO2orSolar

    Others have made similar statements. Soon and Baliunas have shown that current warming is not unprecedented.

    Yes, they all also doubt the IPCC projections for the future.

    “What do you think a lay person should do when there is only 99% agreement in the scientific community?”

    A lay person should use his common sense and not believe everything he hears from the media or from politicians, in particular, scare stories. He should not “a priori” believe what a largely political UN commission (the IPCC) has published as a “Summary for Policymakers” without checking out the science behind it and getting other opinions.

    Your 99% figure is not based on any kind of poll, I take it. I sort of doubt that 99% of the scientific community supports the IPCC projections, but, like you, I do not have any hard numbers, either.

    But whether it is 90%, 80% or 51%, I agree it is probably the majority; this does not convince me that they are right, however.

    Believe we are back to a similar debate as the “slope of the curve” we discussed earlier.

    You believe one thing. I believe another. And neither of us has been able to convince the other to change his standpoint.

    But it has been an interesting conversation. Thanks for taking your time.


  • At August 07, 2007 6:31 AM, Anonymous Anonymous said…

    The urban heat island.

    Remember the old storage radiators.
    You warmed a stack of bricks housed in a metal jacket during the night with off peak electricity, you then slowly released the heat during the day. That warmed your house and it was definitely a significant warming not 0.01 of a degree.Forget about computer models and complex maths, use your senses, your eyes and sense of touch. The urban heat island is caused by the retention of heat during the day by all the hard surfaces within the urban area, walls, tarmac etc, then released at night.

    The suns heat during the day is radiated back off these hard surfaces and hence raises the surrounding temperature. The temperature rise is only seen over land. As water covers 2/3`s of the planets surface plus there are no weather stations in the deserts how can anyone possibly say there is global warming. Its all rubbish and the rise is all local.

    Exactly the same local as the local medieval Warm period and the local little ice age according to the global warming fanatics.


  • At February 05, 2008 10:20 AM, Anonymous Anonymous said…

    I know that there are a lot of problems that are connected with the largest cities, but they excite me!

  • At February 17, 2008 3:49 PM, Blogger kate@warrenandkate.com said…

    Your analysis borders on the silly. Obviously, urban heat islands, since they are local, do not have a huge effect on average world temperatures... BUT

    The issue is whether they have an impact on surface temperature measurement. And, unlike satellite measurement, the surface temperature record is made up of discrete measurement points.

    If you were to plot these measurement points, they would be clustered extremely similarly to the urban lights in the satellite image you linked.

    Trying to compare the urban lights satellite photo to the GISS temperature plot you linked next to it is plane wrong. The GISS temperature plot gives the impression of measuring the whole earth, but in fact many of the temperatures on that map are extrapolated from thermometers as far as 1200 KM away. If you instead showed the GISS 250KM gridcell map, which still exaggerates the extent of the surface temperature coverage, you would see a high correlation between available grid cell data and urban lights on the satellite map.

  • At February 20, 2008 7:17 AM, Anonymous Anonymous said…

    And the person making the adjustments to the GISS data just happens to be one of the biggest promoters of the Global Warming Hoax.

    It's like letting GWB count the disputed ballots in Florida and declaring himself the winner.

  • At February 28, 2008 7:01 PM, Blogger barry said…

    This comment has been removed by the author.

  • At February 28, 2008 7:08 PM, Blogger barry said…

    Anthony Watts at surfacestations.org has been looking at US surface stations. With a team of dedicated skeptics he's been collecting photos and data on weather stations that are likely biased by local conditions (biased upwards temps), on the premise that the US temp record fails to properly account for the UHI effect.

    Watts and his team have collected a good number of sites they think are of good standard. At the time of this post, they're about a third of the way through the project.

    Excising sites they think corrupted, they have plotted the US temperature profile using only the sites they think sound, and have compared with the profile as given by the US Climatology Network (http://cdiac.ornl.gov/epubs/ndp/ushcn/newushcn.html), which is used by GISSTEMP and HADCRU.

    So far, the results provide a very good fit.


    That article links to climateaudit, a well-known skeptical site run by Stephen McIntyre, which has been working on the data from the 'good' weather stations as determined by Watts' team. In the thread doing the math on the preferred data stations, this is the post (below) where one of the skeptics, John V, compares the surfacestations.org data with USCHN.


    Even the skeptics are getting the same result as the mainstream. If anyone is sincerely interested in this subject, the surfacestations/climateaudit project now spans three threads (the post above is from the second one, which is 300 posts long), and it will be interesting to see the results when they complete their project.

    As a side note, I consider the discussion going on in this climateaudit thread to be the very best example of the skeptical community putting their money where their mouthes are. It is a substantive, polite investigation, and while they have begun with their conclusion (not very scientific), they are genuine in their efforts. When so much skepticism (and advocacy, for that matter), is couched in ignorance and vitriol, this project champions the best of the skeptical community. Let it be a standard-setter for all sincere discussion on climate change.

    And, the US temperature profile looks almost exactly the same when all the urban data is excluded, which is one thing that is done to test for UHI.


  • At March 19, 2008 9:53 AM, Anonymous Anonymous said…

    I absofrigginulutly (quote from "the G") agree with Max! He is absofrigginulutly right.


    This link is to a graph which shows that if one disregards the small dip way at the end of the graph, (since it is highly probable that this is only a small "valley" in the Global temperature just like the dips in temperature in 2004 and 2005.)The GISTEMP temp. has risen by around 0.4 degrees more than the satellite trend.

    A study by Ross Mckitrick and PAtrick J MIchaels in December
    2007 also found that the UHIE could account for up to half of the land based warming trend. It also showed that even satellites are influenced by UHIE.

    Nice site,
    and thank you for providing the opportunity to debate some issues.

  • At March 19, 2008 9:55 AM, Anonymous Anonymous said…

    Whoops! sorry for the incomplete link. The page cut it of.

    Here is the complete one:


  • At April 23, 2008 11:59 AM, Anonymous Anonymous said…

    If you're interested in hearing the other side of the argument, realclimate.org have posted a response to this paper.


    (and if that link gets cut off, here is a split version)


  • At May 19, 2008 2:24 PM, Anonymous Anonymous said…


    Bisrat Kifle, National meteorological agency

    Addis Ababa, Ethiopia.

    The total population increase in the 18 years (1967-1984 was 739, 591 and the annual mean maximum temperature in the same period became warmer by 1.7 degrees C. The annual mean maximum temperature attained lt`s peak in the year 2000. It is interesting to observe that the urban population was also the highest in that same year.


  • At June 11, 2008 4:10 AM, Anonymous Anonymous said…

    Unfortunately the temperature record of Ethiopia is fragmentary outside of Addis Ababa. It would be good to compare rural with urban warming to see how much difference there is. Rural parts of the city are mentioned in that study, but no long term data are given, just a comparison of the temps on a given day.

    Found this abstract to a study on the past 100 years of rainfall and temperature records.


    Is the 1.7C increase in temps at Addis Ababa over 18 years reflected in the long-term trends in this paper? Not really.

    Analysis of the records shows increasing trends in annual minimum and maximum temperatures from 1951 to 2002 (0.4 °C/decade and 0.2 °C/decade, respectively).

    Urbanisation does make the area hotter, which is why UHI is studied and accounted for in temperature profiles.

  • At June 11, 2008 6:14 PM, Anonymous Anonymous said…

    That's a bit quick...
    using the same image method, looking at the map of ozone layer thickness, you'll conclude someone in Antarctica is using his car too much, burns tires in his backyard, and maybe uses too many fridges!

  • At June 13, 2008 9:25 AM, Anonymous Anonymous said…

    I'm not quite sure what point you're making in response to anything on this thread, but there is no controversy about why ozone depletion is greater at the poles and greatest over Antarctica. Ozone depletion occurs most strongly at very cold temperatures where there are stratospheric clouds. The atmosphere above Antarctica is colder than in the Arctic, so most of the action happens there. Ozone depletion is also detected at lower latitudes and hardly at all in the tropics where the atmosphere is warmer.

    Unlike CO2, ozone-depleting reactions are not well-mixed but concentrated in the coldest parts of the atmosphere, especially in the stratosphere above the poles.


  • At July 04, 2008 6:14 PM, Anonymous Anonymous said…

    All these articles read like propaganda and spin. They say, Yes, you were correct, but from a certain angle and a certain way of thinking AGW is still happening. I still haven’t found the link that explains away the relationship between observed sun-spots and the emanated radiation which results interrelating with cosmic rays to affect cloud cover and so follows Earth’s service temp. The graph of the before mentioned much more closely correlate with observed temp change. I noticed the proposed “carbon tax” is carefully avoided, and the push for world government is not mentioned. This web-site is clearly one-sided and political. I see a lot of extra words that make the sentences convoluted. I do not sense straight talk. This web-site stinks of wrong-doing.

  • At July 11, 2008 11:00 PM, Anonymous Anonymous said…

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