Warmer nights no proof of global warming

The diurnal temperature range (DTR) is the difference between the daily low temperature at night and the daily high temperature during each day. In some places this range is decreasing because the nights are getting warmer. Proponents of carbon dioxide induced warming (AGW) tout this as proof that carbon dioxide is indeed warming the planet.

In the following graph, compiled from the weather station at Phoenix Sky Harbor airport, we indeed see that the nightly minimums (red) are rising while the daily highs (blue) are fairly steady. This could imply that carbon dioxide is trapping heat at night and delaying the nightly cooling in absence of sunlight.


Apparently, however, carbon dioxide works only in the cities. The same kind of data collected near the airport in rural Childs, Arizona (near Ajo), show no such rising nighttime minimum temperatures.


Rising levels of atmospheric carbon dioxide fail to explain the different DTR responses between rural and urban stations. However, the urban heat island effect does provide an explanation. During the day, concrete and asphalt in cities absorb energy from the sun and radiate it back during the night, thereby making the nights warmer.

Many researchers have studied the urban heat island effect. For instance, Gallo et al., from the National Climatic Data Center found: “Those stations that were associated with predominantly rural land use land cover usually displayed the greatest observed DTR, whereas those associated with urban related land use or land cover displayed the least observed DTR.” That means the night temperatures in urban areas were warmer than those in rural areas.

The warming effect of urbanization is shown by many examples. For instance, the next graph compares the stations in urban Tucson versus rural Tombstone:

Tucson-Tombstone temp

You can see that Tucson temperatures have been rising but there is no trend in the rural Tombstone station. Carbon dioxide works in mysterious ways. This difference between urban and rural stations is not a local phenomenon, but a world-wide one. For instance, the next graph compares the temperature records of urban and rural stations in South Africa:


 This dichotomy of temperatures shows that land-based temperature data have an artificial warming bias since most stations are in or near urban areas. Of course, the keepers of the data say they can mathematically “correct” the data to account for the urban heat island effect. But too often, it seems that they are “correcting” away inconvenient records. For instance, read how NASA is “correcting” away the warming of the 1930s here.

Once again, the hypothesis of  carbon dioxide caused warming fails in the light of actual data.

Reference cited:

Gallo, Kevin P.; Easterling, David R.; and Peterson, Thomas C., “The Influence of Land Use/Land Cover on Climatological Values of the Diurnal Temperature Range” (1996). Papers in Natural Resources. Paper 191, Journal of Climate 9.


  1. Jon, a few days ago you asked me, “what is the evidence that ice core reading(s) are no longer uncertain even thought they disagree with other proxies?” Among other things I referred you to the work of Richard Alley. Since then I’ve come across a couple of other articles that explain how the work of Jaworowski, Z., Segalstad, T.V. misinterpreted what they called “physicochemical” (I know, I never heard it before either) activity in the ice cores. That information is here http://www.someareboojums.org/blog/?p=12. For a good case study see this: http://www.ncdc.noaa.gov/paleo/taylor/indermuehle99nat.pdf. Robert Mulvaney has a very interesting short piece titled “How are past temperatures determined from an ice core” in the June 2005 Scientific American.”http://www.nature.com/scientificamerican/journal/v292/n6/full/scientificamerican0605-116.html.

    Got a plane to catch, but I’ll address the Global warming signal of more warmer nights than warmer days later today. Can’t wait to talk about UHI. JP

    1. John,

      Your references discuss the uncertainties in ice core bubble analysis, but do little to convince one that such uncertainties are under control.

      “Physiochemical” refers to physical chemistry, a beginning chemistry course I had in college. Physical chemistry deals with measurement, description, and prediction of chemical systems and their interactions regarding transfers of mass and energy.

      1. Jon, Jaworowski used the word “physicochemical”. You used the word “physiochemical”. Not the same thing. Although I was merely pointing out a unique word choice on his part, the word you used refers to the chemistry of biological systems. JP

      2. Jon, Of corse there are “uncertainties” in nearly all proxy data. I’m beginning to see a trend. You talk up the uncertainties and ask for “unequivocal” evidence. I think you should look at the “preponderance of evidence” and overwhelming “multiple lines of corroborating evidence.” If “100% mathematical certainty” is your standard of evidence, there’s very little chance you’re ever going to get that. If we wait for anything approaching that sort of evidence, it’ll be to late to have a mitigating effect. JP

      3. “Preponderance of the evidence” may work in small claims court, but in science it takes only one instance of contrary evidence to falsify a theory.

      4. Your statement is correct only if your single piece of evidence proves the alternative hypothesis and that falsifies the null hypothesis. JP

  2. Looking at your first 2 charts , one ends 7 years ago, and the other ends 8 years ago. 
    WASHINGTON, Jan. 19, 2012 — /PRNewswire-USNewswire/ — The global average surface temperature in 2011 was the ninth warmest since 1880, according to NASA scientists. The finding continues a trend in which nine of the 10 warmest years in the modern meteorological record have occurred since the year 2000.

    Read more here: http://www.sacbee.com/2012/01/19/4199913/nasa-finds-2011-ninth-warmest.html#storylink=cpy

  3. NOAA –
    The warmest years on record were 2010 and 2005, which were 0.64°C (1.15°F) above average. Including 2011, all eleven years in the 21st century so far (2001–2011) rank among the 13 warmest in the 132-year period of record. Only one year during the 20th century, 1998, was warmer than 2011.

      1. Or see this, from the Proceedings of the National Academy of Science:
        James Hansen, Makiko Sato, Reto Ruedy, Ken Lo, David W. Lea, and Martin Medina-Elizade, Global temperature change, Proc. Nat. Acad. Sci. 103 (2006), 14288-14293.
        Looks like you’ll have to go back a little farther in time. The point I believe Bob was making was it’s hot and getting hotter. The Eocene was nice if you were a lizard and the last Ice age if you were a Wooly Mammoth. If you are a human, you might want to keep it about the way it’s been for the last ten thousand years or so. JP

  4. Where’s the warming?
    Currently were at -0.01C (Jan 2012) and falling pretty dramatically. With this drop once again (past 30 years), we can virtually write off the whole AGW theory or scam or whatever you want to call it. There is no statistically significant warming trend in this data (AMSU lower troposphere)

  5. Jonathan, your articles are always more thoughtful and empirically based than the run-of-the-mill pieces challenging climate change.  In this case, though, I think you have missed an important point.  The technical term used in climatology is “diurnal temperature range” and the findings of several studies is that minimum diurnal temperatures have been increasing during the past 50 years or so.  Minimum temperatures generally occur at night.  So, in fact nights are warming–on average.  The latter is the point you missed.  Yes, you can find examples where this is not the case but, on average, nights are getting warmer.  You have to look at this on a world-wide scale.  The two most often cited studies showing this are  Braganza 2004 and Alexander 2006

    1. I agree that nights are getting warmer — in cities due to the urban heat island effect, that’s the point I was trying to make. And it takes only one piece of evidence, one exception to falsify a theory.

      1. Poppycock. You need more than one piece of evidence to falsify a hypothesis or Theory. In order to falsify a null hypothesis you need evidence that proves the alternative hypothesis. You only need one proven alternative hypothesis to falsify the null hypothesis, but not a single piece of evidence. In Jon’s scenario, the Theory of Evolution would have been disproven thousands of times. JP

      2. No amount of experimentation can ever prove me right; a single experiment can prove me wrong.
        Albert Einstein

      3. “A single experiment” is not the same as a “one piece of evidence”. A single experiment could theoretically be designed that might falsify the null hypothesis. Einstein’s statement is correct. If Jon wishes to falsify the hypothesis that human CO2 emissions, if continued at or near the present rate, will warm global temperatures over the present century by ~2C to~ 5C; let’s hear his hypothesis. It’s the validity of the alternate hypothesis that counts. If he can prove his hypothesis using an experiment with “one piece of evidence”, so much the better. If so, his place in the history of science would be a lofty one indeed. What’s the hypothesis, Jon?

      4. Then why is the greatest warming in Alaska, Northern Russia, Greenland and the Arctic? An Urban Heat Island in Greenland? JP

      5. On warming Arctic: That’s nothing new, the same thing happened during the last interglacial period. “The warmest millennia of at least the past 250,000 years occurred during the Last Interglaciation, when global ice volumes were similar to or smaller than today and systematic variations in Earths orbital parameters aligned to produce a strong positive summer insolation anomaly throughout the Northern Hemisphere.” CAPE Project Members, 2006. Last interglacial Arctic warmth confirms polar amplification of climate change. Quaternary Science Reviews, 25, 1383-1400.

        In other words, it is part of the natural process and has nothing to do with carbon dioxide emissions from burning fossil fuels.

      6. I, and many others here, have shown evidence over and over that solar insolation can not be the cause of the warming we have seen in recent decades. You repeatedly dismiss the science in favor of the idea that: that’s what caused it before, so that must be what’s causing it now. You provided a graph to support your theory at one time. But that graph (Tim Patterson) was shown to you to be incorrect. Tim admitted that to me personally and it’s well known in the literature. What’s your evidence that the evidence provided in the Lockwood, 2006 paper is incorrect? What’s your evidence that the evidence gathered by the NASA Earth Observatory is wrong? Because an affect had a certain cause at one time in the past is not evidence that each time that affect is noticed, it must have the same cause. JP

      7. You are correct about polar amplification. I hope you’re not suggesting that the UHI warming is sufficient to cause the level of warming we see in the Arctic. JP

  6. Jon, I must compliment you on your first graph. It actually covers a statistically significant (re., climate) period of time. But one immediately sees a problem. Your chart unfortunately, shows only nighttime minimums versus daytime highs. The data we need to see is the occurrence of nighttime lows versus nighttime highs over the time period and the occurrence of daytime lows versus daytime highs over the same period. Then we could see if there was a trend toward  more warm nights compared to warm days (see below for the results). You conflate this trend with DTR. Not the same thing. I think you should be complimented however for what appears to be original research. 

    And, although I like the idea of bringing your local area into the discussion, it does bring up another obvious problem with your analysis. Local evidence for a Global phenomenon. Here is a quote from a paper where the authors did use Global measurements, “Over 70% of the global land area sampled showed a significant decrease in the annual occurrence of cold nights and a significant increase in the annual occurrence of warm nights. Some regions experienced a more than doubling of these indices. This implies a positive shift in the distribution of daily minimum temperature throughout the globe.”[Alexander, et al 2006, J. of Physical Research]. It would be interesting to see if the Tucson area is part of the 30% or part of the 70%. If it turned out to be the former, it would be interesting to find out what is uncommon about thenTucson area.

    The comment that, “Apparently, however, carbon dioxide works only in the cities.” is just silly. More on UHI later. JP

    1. The graphs show the difference between daily highs and lows (averaged of course), that is the definition of DTR. Something is causing the DTR to decrease in cities. You claimed that the cause was carbon dioxide, but that is falsified by the rural data. If carbon dioxide were delaying cooling at night we should see that effect in both urban and rural areas. You seem to be talking about record highs and lows which are just a reflection of weather. If that’s not what you are talking about how do you define the nighttime low versus nighttime high? Midnight and 4am?

      Your contention “Over 70% of the global land area sampled showed a significant decrease in the annual occurrence of cold nights and a significant increase in the annual occurrence of warm nights” is misleading because I’m guessing about 70% of weather stations are in or near urban areas. Furthermore, the way the data are interpolated sometimes incorporates much land with few if any stations, thereby inflating the land of the warming.

      I used the South African data to show a worldwide phenomenon, and I’ve been to both South African locations.

      1. Jon,

        AGW Theory predicts more warm nights than cold nights versus more warm days than cold days. Your graph simply shows the relationship between the daytime highs and the nighttime lows, DTR. To measure the trend predicted by AGW, you need four parameters not two. You need the number of record low temperature nights versus the number of record high temperature nights as well as the number of record low temperature days versus the number of record high temperature days. In other words, the frequency of extreme cold and warm days AND the frequency of extreme cold and warm nights.  I know it can be confusing, but it’s really rather simple. You are comparing two trends, not simply establishing a single trend. You’re comparing two trends, each of which has two variables. See the difference?

        Jon, you cannot make a claim about Global Climate by citing two measurements for two cities in Arizona and two cities in S. Africa. Even if you are talking about DTR. JP

  7. You say, ” Of course, the keepers of the data say they can mathematically “correct” the data to account for the urban heat island effect.” You may be being a little too cynical of statistical analysis. Believe me, statisticians are only too eager to show other statisticians where they are in error. Richard Muller specifically formed the BEST group (including a Nobel laureate)  to address the issue of how GST’s were dealt with in the various major data sets. One of the four papers to come from their research was specifically designed to address the manner in which UHI was dealt with in those data sets. This is a group of professionals at the very top of their fields. Importantly they are not part of the “usual suspects” or IPCC “gatekeepers”. The leader of the group was an avowed skeptic who was “surprised” to find that the UHI problems had been dealt with properly in the past studies. Not only were they independent in every sense of the word, the used different methodologies only to arrive at the same conclusion. Again, multiple lines of evidence.

    Jon, it walks like a duck. It quacks like a duck. It’s peddling Aflac insurance for chrissake. Jon, it’s a duck.

  8. Finally, another way to explore UHI would be to look at where the majority of warming has occurred across the globe. If the UHI effect were the cause of the warming anomalies we see, it should match the areas of greatest urbanization. However, if you look at the 2006 global temperature anomaly data from NOAA, you find that the greatest difference in temperatures for the long term averages were across Russia, Alaska, far north Canada, Greenland and the Arctic;  not areas where major urbanisation has occurred. It is, however, precisely what AGW Theory predicts. JP

  9. I have shown in many posts that the current warming is neither unprecedented nor unusual. The climate is always in flux. Except for the contribution of geothermal energy, the sun is the source of energy that drives climate, both by insolation and magnetic flux. The solar effect is modified by the positional relation of sun and earth, by atmospheric cycles such as ENSO, PDO etc., by cloud cover and many other factors. Warming similar to that of recent decades has happened before from natural causes. You still have presented no compelling evidence that natural forces have been suspended and carbon dioxide emissions, which represent a very small percentage (about 3%) of total carbon dioxide flux, are now the major cause of recent warming. Your arguments remain pedantic.

    1. There exists a widely accepted theory that we call AGW. The evidence for this theory is overwhelming, and is freely available to all.You can accept it or you can propose an alternative hypothesis. Saying that that warming has happened before is a correct statement. Saying that it’s natural is a correct statement. But neither is a hypothesis that explains the facts explained by the null hypothesis, AGW.

      Jon has recognized that our planet is warming. Once that is recognized, the null hypothesis is assumed to be correct unless or until it is falsified. That can only be done scientifically by providing an alternative hypothesis. As a scientist, I would be interested to see one. JP

      1. John,

        You keep saying that the evidence for AGW theory is overwhelming, but you haven’t produced that evidence. The attempts at evidence you mentioned so far are not overwhelming because there are valid alternative explanations. Climate has always been changing, sometimes quickly and drastically, due to natural variations. Those natural variations are complicated but still are in operation. Just how complex the natural system is, is listed here: http://wattsupwiththat.com/2012/01/21/the-ridiculousness-continues-climate-complexity-compiled/#more-50595
        You have not shown that changing just one substance, carbon dioxide, from, as you allege, 0.028% of the atmosphere to 0.039% of the atmosphere has produced drastic or dangerous effects or even produced any major effect. You also seem to ignore the fact that this planet is normally much warmer than it is now and that life, both plants and animals, flurished during these warmer times, and that brings up another question: if AGW were in fact true, so what?

      2. Jon, The evidence is not “my” evidence. The evidence supporting the AGW hypothesis has been compiled by thousands of earth scientists from all over the world. It has been made available to all by the IPCC. THAT is the overwhelming evidence. I assume you have studied that evidence. That is the evidence I’ve put before you and your readers. No one can make you, or anyone else, accept that evidence. There are hundreds of millions of people that do not accept the overwhelming evidence for the Theory of Evolution. However, because no alternative hypothesis has been proposed that has falsified that Theory, the vast consensus of the scientific community accept it. The same is true for the Theory of AGW.

        You say, ” You also seem to ignore the fact that this planet is normally much warmer than it is now and that life, both plants and animals, flurished [sic] during these warmer times….” I don’t ignore that. I believe that is a fact. You seem to ignore the fact that those conditions never existed while a complex civilization of eight billion people lived in, and depended on, that biosphere.

        “So what?”, you ask. That’s the question. What are we going to do about the changes we are making to our biosphere. We are going to mitigate and we are going to adapt. Scientists like you have training in costs versus benefits, and risks versus rewards. You very likely have valuable insights into how these efforts should be framed as policy choices. 

        Scientists generally agree that there is a 95% chance that humanity faces a monumental global problem and  we should take actions to mitigate, and plan to adapt to, this problem.  I agree. Apparently you do not. JP

      3. John,

        Now I see where you are coming from. The IPCC, the authority to which you appeal, has been shown to be a fraud, most recently by Donna LaFramboise in her book The Delinquent Teenager Who Was Mistaken for the World’s Top Climate Expert, an IPCC Exposé which I reviewed. Readers may also check my ARTICLE INDEX for posts about the IPCC, their modeling, their scandals, and their corruption. If you are invoking the IPCC as your source of “overwhelming” evidence, then I say you have none.

        And it wasn’t really “thousands of scientists” writing IPCC report. True, there were 2500 who merely reviewed some part of the massive studies, but the writing was by less than 100. BTW, that 2500 includes those that were highly critical and whose reviews and recommendations were rejected by the IPCC because they didn’t conform to the political agenda. Readers may refer to my post: http://tucsoncitizen.com/wryheat/2009/06/27/the-assumed-authority/ to see that the IPCC was foremost a political body, not a scientific one.

        Now you may claim that what I’ve written above is argumentum ad hominem, but I don’t refer to a person, but to a corrupt organization whose models have been proven wrong and whose methods of corruption revealed by the Climategate emails. As Dr. Timothy Ball wrote of the IPCC, “Science creates theories based on assumptions that are then tested by other scientists performing as skeptics. The structure and mandate of the IPCC was in direct contradiction to this scientific method. They set out to prove the theory rather than disprove it.” And in doing so, the IPCC ignored or supressed evidence that did not fit their theory.

      4. Jon, I concur. This exchange has been illuminating. And I’d like to pursue the IPCC issue further. Before I do, I’d like to know if you’ve studied the IPCC Working Group 1 report and/or the Synthesis Report. Could you let me know that? Thanks, JP

      5. I read much of WG1 several years ago. What I read showed that it was an error-filled political document.

        You should also realize that at this point there are few people reading this particular post, so continued argument here serves little purpose.

  10. Your links lead to other pseudoscience denier websites. Do those pseudoscience denier websites have links to your pseudoscience denier websites articles?

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