Guest post by Mike Crow
Figure 1 Night time temperature profile of a clear sky night in NE Ohio. 8:28pm Sunset/6:16am Sunrise
Climate science is all about surface temperature trends. The problem with this is that the CAGW is a rate of cooling problem, not a static temperature problem. Is Co2 changing the rate of cooling, thereby altering the expected surface temperature, are the hypothesized positive feedbacks actually there, are there any actual measurements of these parameters. I think there is. Every night the Sun sets on every location on Earth, and the surface starts to cool by radiating heat into the cold black of space. What can weather station data tell us about this?
Figure 2 Count of NCDC Daily station records by year (2011 is partial year)
The temperature record has daily min and max temperatures. When the Sun comes up in the morning, on most days it warms the surface from the minimum temp of the day peaking late in the afternoon. Then the Sun sets and temperatures start to plummet. I live at 41 N Lat, and on a clear night the temperature will drop 20-30 F (Figure 1), over a degree F per hour. If there’s a CO2 effect in the temperature record, it should show up in night time cooling. The question is, does this loss of cooling actually show up in the data?
I went in search of an answer, I started with NCDC’s global summary of day’s data set which contains over 120 million station records, and starts late 1929. The first thing to notice is how few samples there are each year prior to 1973 (Figure 2).
What I wanted to look at is how much the temperature went up “today”, and how much does it drop “tonight”. Today’s Rising temp is today’s T-max –today’s T-min. Falling temp is today’s T-max – tomorrows T-min, the drop in temp over night. Difference is Rising – Falling.
To do this, you have to have good records for both today and tomorrow, so as part of my data import process, I validate that the temperature records are good. NCDC provides placeholder values for temp, even when the data isn’t available, I trap these and remove them. This leaves me with a set of data as it is from NCDC, augmented with Rise, Fall, and Diff (Figure 3). The NCDC data also contains some station information, Latitude, Longitude, Altitude, Country, and State where appropriate. This allows me to aggregate temperature records by station location, as well as create a google map of the station in a aggregate set. When annual averages are generated, I average the daily values for a particular station, then average the annual values of the collections of stations in the area being examined.
This is where the temperature data would be homogenized. I feel that since temperatures are not linear spatially and the sample size changes so much over time, homogenizing temperature data is basically making up data that doesn’t exist. I understand some might say not doing this creates a bias where the data is over sampled, I feel making up data is worse than bias.
Figure 3 Annual average Min, Max, Rise, Fall and Diff Temperature for all Global Stations Google Map of Locations
After the preprocessing step there are some 109 million daily samples from 1940 to early 2011. A couple of things to note:
· Rise and Fall are almost identical to each other, and they are approximately 18F for the entire period.
· You can see the “AGW” warming signal in the Min/Max temperature records, yet Rise/Fall does not increase at the same pace.
· Diff is very small, and to make it more than a flat line, it is multiplied by a constant (in this case 365).
· Values are erratic for the earlier years that are under sampled.
· One would expect a positive trend in diff if there was a general loss of nightly cooling and there isn’t one.
The data divided up by Latitude (Figures 4-8):
Figure 4 Average temps for Stations > 66.5 Lat
Figure 5 Average temps for Stations >23 and <66.5 Lat: Google Maps for Eastern Stations, Western Stations
Figure 6 Average temps for Stations <23 and >-23 Lat
Figure 7 Average temps for Stations < -23 and > -66.5 Lat
Figure 8 Average temps for Stations < -66.5 Lat
Lastly I ran a report on the Continental US since it has a large number of stations, the graph is just of diff without a multiplier (Figure 9).
Figure 9 Diff for Continental US
I can also generate daily average reports, Here’s the daily average for stations North of 23 Lat 1950 to 2010 Diff * 100 (Figure 10).
Figure 10 Daily diff * 100 1950-2010 for > 23 Lat
When the ratio of Day to night increases, Diff is positive. When the ratio decreases Diff is negative. This is really a graph of temperature response to a change in incoming solar energy. I’ve read comments that said: “Boy it’d be nice to turn the Sun off for a while to measure the response”, will this is the next best thing to doing exactly that. The question I had from this graph, is what’s the slope of changing Diff as the day gets longer (Figure 11), and as the day get shorter (Figure 12)? So I created the following:
Figure 11 May to September cooling rate: Summer slope
Figure 12 November to March warming rate: Winter slope
If you plot out the slope of the daily temperature change for spring to fall and fall to spring you get this (Figure 13).
Figure 13 Slope of Spring to Fall and Fall to Spring temperature response as the length of day changes for >23 Lat
Unfortunately, there isn’t enough data to see if it truly is a ~60-70 year cycle, but it clearly shows that the slope for both the cooling and warming decreased, where the winter warming slope is both larger and changed more than the summer cooling slope. I would expect a Co2 signal to decrease the cooling slope, which we have, I wouldn’t expect it to decrease the warming slope as well.
What would affect both? A change in Orbit or tilt comes to mind, as does a change in Sea Surface Temps, but would SST’s change both? A change in cloud cover might change both.
What will be interesting to see is as we collect more data, does slope continue to go back up, detecting a natural cycle affecting cooling rates.
In any rate, the data shows Rise and Fall being very consistent over the entire data set, where diff seems to be negatively correlated to temperature increases, when it warms up, it cools a little more overnight. Which makes some sense, and if the heat that’s radiated into space is air warmed over warm ocean waters, which then moves over land, it makes even more sense.
Conclusion:
The world wide surface station measured average daily rising temp and falling temp is 17.465460F/17.465673F for the period of 1950 to 2010, not only is the falling temperatures slightly larger than rising temperatures, 17.4F is only 50%-70% of a typical clear sky temperature swing of 25F to 30F, which can be as large as +40F depending on location and humidity.
This shows conclusively that the average night time cooling is not limited by GHG because low humidity clear skies cool far more than the global average. Since recorded Min Max temperatures show no sign of a loss of cooling on a daily basis since at least 1950, even if CO2 has increased the amount of DLR, something else(most likely variablity of clouds) is controlling temperatures. This would seem to eliminate CO2 as the main cause of late 20th century warming.
As you stated, the earth’s Surface can cool by 20 or 30 F per night, that works out to 11 to 17 C per night. I previously did this calculation on the daily cooling of
the atmosphere:
mass atmosphere = 5* 10^18 kg=5*10^21gm
temp atmosphere 255K (effective radiating temp to space- underestimates heat content)
specific heat 1.01 joules/gm C
5* 10^21*1.01*255= 1.288 * 10^24 joules
radius earth = 6400km= 6.4*10^6 meters.
area earth = 4 pi r^2 =514,718,540,364,021.76
240 watts/sq meter = 240 joules/sec per square meter
60 sec/min*60 min/hr*24hr/day=86,400 secs per day
5.147* 10^14 sq meters*240 joules/sec/sq meter *8.64*10^4 secs/day= 1.067*10^22 joules per day radiated away
1.067*10^22/1.288*10^24 = 0.83%.
So the atmosphere as a whole cools by less than 1% over the course of a day. That figure makes sense when you figure that the earth’s surface temperature may change by 10 C or more overnight far more than average changes over a week, but weather patterns persist for several days, and that’s why meteorologists can predict daily highs out a week or so. That cooling is obviously mostly from the
earth’s surface and air near the surface ,leaving most of the atmosphere unchanged.
With an average temp of 287 K, that 0.83% would imply an average cooling of 2.4C overnight, way less than Mike Crows 11C min cooling at night.
Either the cooling of at higher latitudes is balanced by negligible cooling over much wider areas near the equator, or surface temps can fluctuate much more than atmospheric temps-quite likely since on a clear night a significant percentage of surface radiation can escape directly to space without being blocked by greenhouse gases.
@Bob, I’m inclined to not dismiss the physics of Co2 photon absorption/radiation. That said for whatever reason it doesn’t show up in the temperature record as a loss of cooling.
I’ve become interested in using an IR thermometer to measure the sky’s temp. On a 35F clear day it measured ~-40F. 35F has very little water vapor, so I think it’s getting close to measure GHG DLR. -40F is about 160w/sq m. So what I expect to see is a doubling will increase the -40, how that changes surface temps will depend on clouds and water vapor.
How does the Time of Observation (TOB) affect your calculations? As I understand it, sometimes the Tmax or Tmin does not occur at the times expected (i.e., off by a day from expectation, due to, say, a front coming through that makes all temperatures on one day higher or lower than all temps on the previous day). Is there a record of TOB associated with each station so that you could test whether it makes any difference?
Willis, great post and interesting analysis.
Why don’t you expect the supposed CO2 GHE to not affect the warming rate in the mornings? It should increase the warming rate if the GHE actually exists since it absorbs and reradiates LW energy back to the surface. According to the GHE theory, that would increase the rate of surface warming.
In fact, if the GHE really existed, then the rate of nighttime cooling, under identical conditions of wind, clouds and humidity, must increase as CO2 concentrations increase. You have demonstrated that there is no measurable change in either the nighttime cooling or daytime warming rates with respect to the increasing CO2 concentrations in Earth’s atmosphere.
Net heat transfer is from warm to cold. The rate of that heat transfer can be slowed or accelerated with an intervening material (low conductor such as a vacuum to high conductor such as a metal rod), but that will show up in the cooling rate of the warmer object. A colder object cannot heat a warmer object! That requires the introduction of additional energy into the “system”.
Bill
@John West,
Incoming solar is mostly in the .5-1u range, the nearest Co2 band is a little over 4u and a small absorption at about 3.5u. Solar IR should pass through Co2 untouched.
So anything that would equally minimize the rate of heating and cooling while making plants flourish should be a good thing, right?
Viva la CO2! (May the Warmistas keep their criminal dirty hands off it.)
@Lance Wallace, No there’s no TOB info in the data. I approached this from the point of view that Non Weather related biases would be all similar for a single station, and the weather related ones would be random and not very common. If you look at the daily graph you can really see “Weather”.
Radiation is “line-of-sight” and “speed of light” so you would expect that any “slowing down” of energy lost to space will be through slower processes such as rates of convection, evaporation, condensation, and freezing. The daily minimum temperature is usually the dew point (or frost point) temperature, which is a measure of the amount of water vapor in the atmosphere. I’ve been doing energy and mass balances using data for the Southpole where days are a year long and it is the dryest place on earth. I find that water vapor at these very low level is statistically more significant than any CO2 effect. At the Southpole in the night time, there is a strong inversion ( air is warmer than the ice surface). The CO2 is being delivered to the surface from the upper atmosphere. In this situation, most of the radiation from CO2 will be lost to space rather than to the surface. Thus, one might expect CO2 to enhance energy lost to space. The CO2 is getting it’s energy through collisions with air molecules, not from radiation from the surface.
@MiCro
Wouldn’t agree with “untouched” but yes perhaps I should’ve said itty bitty tiny tiney, kinda like the itty bitty tiny tiney additional absorption CO2 offers above that of H2O anyway.
http://home.earthlink.net/~apptechy/OpticalMeasure/Solar_Spectrum%5B1%5D.png
A fundamental finding, backed by a huge volume of data, processed in a way that not only minimizes arbitrary choices of the author, but also cancels out the numerous “adjustments” and “enhancements” of the NCDC. Congratulations.
@John West 🙂 Fair enough!
@R Taylor, That was what I trying to accomplish. I spend a lot of time doing astrophotography, and experienced the large drop in temp after the Sun set. I also work with databases, and have experience with simulators, the whole topic is a nice fit.
Nice work Mike!
Simple approach with solid database. A great way to look for a signature.
What may be the next step in this work?
Kelvin Vaughan,
You might want to look at what Sleepalot and I discussed in these comments. We looked at the comparison of a Brazilian rain forest station and a N. African Desert station.
link 1
link 2
link 3
Actually the whole discussion: Some thoughts on radiative transfer and GHG’s, is worth reading again.
My take home from all this is as Mike Crow is pointing out it is a TIME function. Water (and CO2 maybe?) changes the rate of warming during the day and cooling during the night so the net effect is to LOWER day time temperatures and RAISE night time temperatures. The one set of data I looked at (see comments above) showed that water vapor had the net effect of overall cooling not warming but I did not do an exhaustive study as John Christy did.
However theoretically an increase in water vapor in the atmosphere should result in a net decrease in temperature since it is absorbing incoming sunlight and sending some of it back into space when it re-radiates.
The physics that applies to CO2 and earthshine also applies to H2O and sunshine. Therefore if H2O is causing a net warming then CO2 should cause a net cooling.
I don’t know how many readers have there own temperature recording stations, but mine show a very similar pattern as found in the article, this is just one small station within the CET area but my T/max and T/min follow the same general trend of overall temperatures, when they increase so do T/max and T/min and vice versa. As you know CET has been dropping rapidly recently, along with my own T/max and T/min, in fact T/min has dropped more than T/max recently. If T/min is the one affected by C02 then this part of the world doesn’t know about it. It would be interesting if any other independent recorders out there confirm these findings I think there is a lot of useful information to be gained from one off sites. They my not conform to the best sites around, but they do pick up useful trends. Mine may be in this category but it does closely follow CET.
By the way look at the latest CET data http://www.metoffice.gov.uk/hadobs/hadcet cet_info_mean.html this shows the fifth month in a row with temperatures below average.
Regards
Keith Gordon
From my EE viewpoint:
My own suspicion is that the effect of CO2 at the densities we’re talking about may very well be a small phase change rather than an amplitude change. This would not show up if one only looks at min/max. It would only show up as a slight delay in the occurrence of the minimum temperature and/or the max temperature.
Of course since the effect would be dwarfed by normal daily variations it would be hard to isolate.
@JCrew, As I mentioned I want to start logging the IR temp of the sky. Other than that I’m not sure. I originally built it to process stations by Lat and Lon, I recently added by country. I did that to look for the large spike in the early 70’s (present in most of Northern Eurasia station readings). I’m also looking at trying to identify just clear sky deserts, which I think define the limits of cooling. But I’m doing the second because I didn’t want to be accused of cherry picking the data.
@fhhaynie, I think the min temp limit doesn’t have to be the dew point or frost line. I’ve watched it cool through both dew point and then frost line, and continue until the Sun comes up. But if you’ve noticed roads, exposed dirt, bricks don’t have frost, it’s because they’re still too warm, at the same time the cars and grass were covered. But I was impressed at the amount of heat that had to be lost to wring all of that water out of the air, and then freeze it.
Oh, one more thing I wanted to add to this thread. NCDC included almost the same set of station CRU uses (at least for the same years data). As you can see from the sample size, the early years are very under sampled, and therefore any homogenized temperature data is also based on is IMO suspect.
MiCro says:
@John West,
Incoming solar is mostly in the .5-1u range, the nearest Co2 band is a little over 4u and a small absorption at about 3.5u. Solar IR should pass through Co2 untouched.
Is “most of” the relevant factor here? If it’s 2W/m2 (for example) it is still important irrespective of this as a proportion of total radiance.
re 1972/3 spike.
Is this just an artefact of the number of stations? The station count jumps at that time too.
If not it is the most significant factor and needs to be focused on. My gut feel, even on first sight was that it’s a glitch, not climate.
However, there’s a clear event in CO2 around 73/74 so it’s worth looking closely to see whether it’s real.
http://climategrog.wordpress.com/?attachment_id=232
Well done Mike. You seem to be one of those “army of ones.”
And the truth goes marching on!!
MiCro says:
May 17, 2013 at 6:02 am
I’ve become interested in using an IR thermometer to measure the sky’s temp
You may be interested in the posts over at Tallblokes Talkshop by Tim Channon starting here
http://tallbloke.wordpress.com/2013/02/11/discussions-on-pyrgeometers-ir-measurement/
and then continuing with posts looking at the UK Chilbolton site.
Greg Goodman says:
May 17, 2013 at 7:55 am
re 1972/3 spike.
I don’t know if you noticed my comment on the spike, but it’s prevalent in the individual aggregate reports for Russia, Siberia, Mongolia, and China for that period. I’m not sure what it’s source is, it would be interesting to locate the source of the co2 spike to see if they’re in the same location.
bof
The idea seemed me good in the begining. But after fig 3 and the remark : “Diff is very small, and to make it more than a flat line, it is multiplied by a constant (in this case 365)”, I wondered.
(A)GW is all about 2K / century rise of temp, that is less 2/36500 K per night variation in cooling (or not). I really doubt that available data can show such minuscule trend : 0,00005 K/day.
Your methodology is ingenious and could work, but it doesn’t.
Nice try, thought.
GLEFAVE commented on An analysis of night time cooling based on NCDC station record data.
in response to geoarmstrong:
This basic thought lead to the slope analysis on the daily change in response to changes in the length of day. Which does show up, but it shows up in both the warming and cooling trends.
I did want to expose this work, to get the thoughts of others to see where it can lead.