It seems that a number of folks have missed one of the more important conclusions from our first paper on the surfacestations project. Co-author Dr. John Nielsen-Gammon has some things to say about it the finding that is the title.
For layman readers that don’t know what diurnal variation is, it is the daily variation of temperature due to the variation of incoming solar radiation from rotation of the earth on its axis.
It looks like this:
Source: http://apollo.lsc.vsc.edu/classes/met130/notes/chapter3/daily_trend4.html
Fall, S., A. Watts, J. Nielsen-Gammon, E. Jones, D. Niyogi, J. Christy, and R.A. Pielke Sr., 2011: Analysis of the impacts of station exposure on the U.S. Historical Climatology Network temperatures and temperature trends. J. Geophys. Res., in press. Copyright (2011) American Geophysical Union.
Fall et al. 2011: What We Learned About the Climate
By Dr. John Nielsen-Gammon
Our paper has a lot of info and analysis about temperatures and temperature trends and their correspondence to siting class. Perhaps the most important question, “Is the mean temperature trend different from previous estimates?” is answered in the negative, albeit with an asterisk associated with the limited scope of the study. While negative results are useful, they’re also boring. So in this post I’ll talk about something we did learn about the climate that’s new and different, and why I think it matters.
This new finding is stated succinctly in the abstract as: “According to the best-sited stations, the diurnal temperature range in the lower 48 states has no century-scale trend.”
The diurnal temperature range is simply the difference between the daily maximum temperature and daily minimum temperature, “diurnal” being a more impressive way of saying “daily”. It’s conventionally abbreviated DTR.
…
The change in global DTR trends roughly coincides with the change in phase of the Pacific Decadal Oscillation, for example, so it’s hard to tell whether the DTR trends were natural or forced.
That’s where Fall et al. 2011 comes in. The figure below shows the change in DTR anomalies over time over the United States, as estimated using data from each of the four classes of station siting. The data goes all the way back to 1895, making this (as far as we know) the longest evaluation of regional DTR trends done anywhere.
Dotted lines represent average values and are plotted 1.5 C apart from each other
All four classes of stations show the decline from the 1950s through the 1970s. But if you take a broader view, you see that the black line, representing the estimate from the best-sited stations, has a long-term positive (!) trend using unadjusted data or time-of-observation adjusted data, and has no trend at all for fully adjusted data (top set of curves). The lower-quality siting classes all show a negative long-term trend, and the worse the siting, the larger the trend.
These results suggest that the DTR in the United States has not decreased due to global warming, and that analyses to the contrary were at least partly contaminated by station siting problems. Indeed, DTR tended to increase when temperatures were fairly stable and tended to decrease when temperatures rose. Maybe DTR really isn’t a robust signal of global warming, and maybe the discrepancy between models and observations is primarily a problem with the observations rather than the models!
I’ve used the words “suggest” and “maybe” here. That’s because I regard our results as tentative. The zero trend estimate is based on only 80 stations, which might be only marginally adequate. The systematic change in trend with station siting quality makes me more confident, but the fact that the closest poorly-sited stations have a weak but positive DTR trend suggests that DTR may be strongly site-specific and makes me less confident. Maybe the best-sited stations have actually improved their siting over time, and maybe the adjustments haven’t fully corrected for this. Because of all this, I think these results need to be confirmed through other means or in other parts of the world before I will wholeheartedly believe that the real DTR has not been decreasing.
Nonetheless, all the ongoing work to understand the consequences of a faster rise in minimum than maximum temperatures for ecosystems and human health might, just might, be misguided.
Read the full post here
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May I, as a friendly gesture, recommend that, in future, one might better express oneself with shorter sentences and less circumlocution if one were just to …um, come right out and say what you mean?
🙂
As “sky” correctly noted, the diurnal chart can be easily explained in basic terms or ordinary heat transfer. More easily, there is a direct analogy (mathematical equivalence) between electrical circuits and heat transfer processes. Any electrical engineer would immediately recognize the chart as an ordinary non-ideal rectifier, with slightly nonlinear load. Thermal capacitor of surface-air gets “charged” when sun shines (through certain finite “resistor”), and discharges when not. The “leakage” is partly radiative, with addition of other resistive paths (convection/evaporation/precipitation). The temperature rises until the charge exceeds leakage, all very simple, regardless if this “leakage” is forth or any other degree, or even a constant. Therefore, the “answer” given in that lecture of department chief of Lyndon State College of Meteorology is fundamentally goofy and shows lack of in-depth understanding. I skipped across the rest of lecture, and it looks like a collection of cooking recipes to me. There are some good points presented, but overall I don’t think this class will prepare students for contributing to real science.
The confirmation of the trend found by all other scientists researching the instrumental temperature record is unsurprising.
The finding that in the best sited stations there is no change in the diurnal range confirms that the warming trend is NOT a solar effect and must be a ‘greenhouse’ effect.
Perhaps the reduced diurnal range in the ‘bad’ sites represents the greater effect of local CO2 levels that reduced the cooling at night?
-grin-
Why the lag? Well, because Lag is the norm in everyday empirical life.
June 21 … Typical NH Summer Solstice.
September 10 … Typical NH Minimum Sea Ice Extent.
——-> almost 3 months. Perfectly normal.
December 21 … Typical NH Winter Solstice.
February 15 … Typical NH freezer weather.
——-> almost 2 months. Perfectly normal.
High noon versus High Temp, approx 3 hours. Perfectly normal. Turn the stove on, boiling water, almost 3 minutes. Perfectly normal. Warming trend in the world, CO2 rises, 800 years. You get my drift.
What would be abnormal is if something had immediate influential effect (perhaps only seen in a controlled experiment, in a vacuum, without any atmospheric matter and possibly even gravity).
Think outside the box, free yourself from the artificial confines of models, theory and hocus pocus. Or remain stuck in the Matrix.
I wonder if you guys are perhaps all missing the point. I am missing whether or not it is maximum temperatures that are driving up the mean temperature or whether or not it is the minimum temeprature that are driving up mean temperature.
I would love to hear all your comments on the balls that are currently on my pool table:
http://www.letterdash.com/HenryP/henrys-pool-table-on-global-warming
(you do not want to know how much work this little compilation was)
John Finn says:
May 20, 2011 at 5:01 am
Should read like this
KAP says:
May 19, 2011 at 8:36 am
But should we expect to see a century-scale trend? It’s clear that the primary cause of the 1880-1940 temp increase was due to solar effects rather than greenhouse,
Is it really? could you just clarify – is this the solar effect with lags or the solar effect without lags? I only ask because when solar activity moves in synch with temperature then it shows a clear correlation, but when solar activity declines, as it has since ~1991, while temperatures continue to rise then it’s because of the lag effect.
It’s obviously a complicated mechanism.
Honestly I haven’t read all this..
But..during a scouting expedition on another area of interest.. ran across this..which may be part of the answer to “why lag,” in the first graph above..
“”FAST shows this convection time is as little as 2-3 hours.””
http://sprg.ssl.berkeley.edu/fast/scienceprod/nuggets/low_latitude/ring.current.viewgraph2b.pdf
Happpy Friday..
John Finn,
Without lags. As far as I’m aware, there are no century-scale climate lags from solar forcing.
The disconnect between declining solar activity and increasing temperatures since 1991 is due to increased greenhouse effect.
If you haven’t done so, read the original post. It is very illuminating.
I can help you with that. At his blog, R.A. Pielke, Sr., a co-author with Mr. Watts on this study, has made clearer and more informative comments on their findings, in my opinion.
Mean temperatures clearly increased for all qualities of surface station, and the difference they found is that at the best stations the difference between maximum and minimum temperatures did not show a trend, while at the poorly-sited stations, a trend toward less difference between minimum and maximum temperatures was detected. That is, they have a “smaller diurnal temperature range.”
As Dr. Pielke explains, a larger diurnal temperature range, which is what the best-sited stations exhibit, is indirectly bad for us because it is worse for plants including crops, but it is not as bad for humans directly, during heat waves. “Wintertime minimum temperatures help determine plant hardiness, for example, and summertime minimum temperatures are very important for heat wave mortality.”
Knowing these details will be invaluable in mitigation efforts, but by far the most important finding is that after all, just as Dr. Muller has found, the global mean temperature trend has been correct all along and is not an artifact of urban heat, surface station siting, or any other systematic bias.
Global warming is settled science.
The confirmation of the trend found by all other scientists researching the instrumental temperature record is unsurprising.
The finding that in the best sited stations there is no change in the diurnal range confirms that the warming trend is NOT a solar effect and must be a ‘greenhouse’ effect.
Perhaps the reduced diurnal range in the ‘bad’ sites represents the greater effect of local CO2 levels that reduced the cooling at night?
Settled Science says:
May 20, 2011 at 1:53 pm
“…by far the most important finding is that after all, just as Dr. Muller has found, the global mean temperature trend has been correct all along and is not an artifact of urban heat, surface station siting, or any other systematic bias.”
Inasmuch as Fall et al. confine their findings to the US station records based on PRESENT-DAY siting ratings, this is a staggereging leap of illogic. If anything can be deduced physically from the lack of long-term trend in DTR is that the capacitance of the atmosphere has NOT changed. Thus whatever the course of long-term temperature changes, they are NOT due to any enhancement of the “greenhouse effect.” We have no comparable studies globally, where well-sited small-town stations with long, intact records are generally unavailable and urban records thus are used by default. Conclusions drawn from such records based on the pretense that systematic UHI bias doesn’t exist are scarcely science–let alone a wholly settled matter.
Hua Hin says:The finding that in the best sited stations there is no change in the diurnal range confirms that the warming trend is NOT a solar effect and must be a ‘greenhouse’ effect.
Perhaps the reduced diurnal range in the ‘bad’ sites represents the greater effect of local CO2 levels that reduced the cooling at night?”
Henry says
We have reasonable accurate data from weather stations all over world for the past 35 years. I do not trust most of the data from long before 1975 unless it can be explained exactly how the measurements were done and recorded. (like in the example of the station in Armagh – Northern-Ireland).
So far, the score on my pool table of global warming is as follows (I have just added the results of Bodo (in the arctic, Norway) and Honolulu (in the pacific, USA):
MAXIMA: rising at a speed of 0.04 degrees C per annum
MEANS : increasing at a speed of 0.02 degrees C per annum
MINIMA: no change at 0.00 degrees C per annum
HUMIDITY: decreasing at a rate of -0.02% per annum
PRECIPITATION: decreasing at a rate of -0.11 mm /month /year
This means that, on my pool table so far, the global warming trend that is observed on earth is natural (coming from outside) and is not caused by an increase in greenhouse gases.
If it had been the other way around, i.e. minimum temperatures rising, that pushes up the average temperature, (i.e heat being trapped), we should agree that the increase in greenhouse gases on earth was the cause.
http://www.letterdash.com/HenryP/henrys-pool-table-on-global-warming
Not so?
[You don’t get posting privileges here when you call the site owner a “fraud” elsewhere on your website for publishing a science paper, and hiding in anonymity, what a pathetic cheap shot ~mod]
Are there ANY conclusions and recommendations of the AGW-Krew that aren’t “misguided”?
Perhaps the most important question, “Is the mean temperature trend different from previous estimates?” is answered in the negative, albeit with an asterisk associated with the limited scope of the study. While negative results are useful, they’re also boring.
…These results suggest that the DTR in the United States has not decreased due to global warming, and that analyses to the contrary were at least partly contaminated by station siting problems. Indeed, DTR tended to increase when temperatures were fairly stable and tended to decrease when temperatures rose. Maybe DTR really isn’t a robust signal of global warming, and maybe the discrepancy between models and observations is primarily a problem with the observations rather than the models!
Anthony – are you in agreement with these statements by your co-author ?
It seems he is suggesting your paper is additional evidence towards AGW theory
Anthony – see thesis towards a masters: http://etd.ohiolink.edu/send-pdf.cgi/Kolan%20Sreekanth.pdf?osu1259613805
See pages 46/74, actual page numbered 36 & 69/74, actual page numbered 59.