So if you reverse the two (go from 7am to Midnight) you would get a larger trend? By way of example, my particular hobby horse is Arctic sea ice. Rather, they use what are called minimum-maximum thermometers that record both maximum and minimum temperatures between resets of the instrument. over 5 F, then 3 F, and then 2 F, and after each successive flattening, Midnight readings are irrelevant. If everyone else is reporting highs of 82 on July 15, but Joe is reporting 28, Joe is likely wrong. their procedures at the time that I initially wrote my code (summer 2002). TOBS = Time of Observation bias. 78 instances of 7 occurrences CRS solves that, so perhaps excising pre CRS records is a period, it went back and counted how often that temperature occurred in The time of observation was determined at each station within a climate division during January of the years 1931, 1941, 1951, 1965, 1975, and 1984 for the states of California, Colorado, Illinois, Indiana, New York, North Carolina, and Washington. JerryB has 190 sites with hourly data. NC, the MIN of the previous 24 hours temps. bothers some observers. Thanks for that reference, Steven! Discrete measurements are points on a grid. I respectfully disagree that it is correct to incorporate 25 measurements into the high/low of a 24 hour day. be unacceptable among some practioners of “climate change science”. 8am 0.36 -0.31 0.03 0.01 -0.13 -0.22 -0.15 0.03 -0.30 -0.06 -0.18 -0.10 -0.18 0.04 13.48 13.41 Then took the 6.5 year average of the daily averages. of observation will change the bias. It’s different than that. Thanks for that, Victor. Now I’m itching to play with a scatterplot of measurements in 3-D space. But in either case, one cannot simply connect the end of the previous trend line to the beginning of the new one. (This doesn’t stop CDIAC from publishing fictitious annual averages for 2001-2005, however!). Here I will focus in detail on the Time of Observation adjustment, which is responsible for the majority of the change in U.S. temperatures vis-à-vis raw data. You have 1221 stations. 1: 20 It doesnt effect the mean when you have 1500 monthly data points. I’m saying This migt be different for different stations. A new time of observation is simply the start of a new trend line. 20 instances of 9 occurrences down, or down, then up, by at least some particular number of degrees. No individual moment is in two adjacent days, hours, minutes or seconds. Impact of adjustments on U.S. temperatures relative to the 1900-1910 period, following the … USHCN TOB adjustments. Do we really need to align the different stations to be recording the exact same 24 hour sequences? Even if the exteriors of the sensors were cleaned, would inaccessible soil buildup in the interior not also cause warming? You notice that since the start of the period, the yearly average of the min has grown .5 You notice the yearly max has shrunk .5, If a site is measured at the same time throughout its history.. you will get a trend figure. CRN12 describes the physical being of the site. #128. Windy days cut the effect. Jerry’s method gives an average January temperature of anywhere from 155 to 165 degrees, depending on the order and sequence of the daily temperatures. period.”. behaviors established in the guideline. Free the code is my watchword no matter what the outcome. If there are just a few days missing, it doesn’t hurt to interpolate them from adjacent days and data from adjacent stations. For example, if yesterday’s AT OBSN temperature was 95, today’s maximum must be at least as high as 95, even if the maximum this calendar day was only 86. 6:00 51.11 An image of a common minimum-maximum thermometer is shown in Figure 3. Now, do I think that it would be a good idea to revisit TOBS? Change the TOBS to 7AM at year 4.5. Once this has been correctly implemented, any given time of observation will show no trend compared to any other time of observation…assuming changes in time of observation are treated as beginning a new, unrelated, series. 2 1 50 50 25 Let me explain why. THEN. every discussion degenerates into ” The ice is melting” and “fuel from dog poo and wood chips”. 3: 30. moment, at the end of the first time period is identical to the That may not be quite right, but I think I’m heading somewhere useful. 7am -0.10 -0.37 -0.09 -0.26 -0.31 -0.42 -0.48 -0.14 -0.42 -0.16 -0.13 -0.34 -0.21 -0.16 13.32 13.26 In temperate latitudes there is a symmetrical seasonal effect in TOB. I think that’s why I called it an RC type discussion, they seem to go around in circles a lot there with nobody understanding they’re not really having a discussion on the same topic! This definition appears rarely and is found in the following Acronym Finder categories: Organizations, NGOs, schools, universities, etc. (Talk about AGW! contact info for you. time to get some real work done and come back later. Thus, an additional incremental uncertainty of about 0.3 Deg. At high latitudes, 1000 km can mean midnight at one station and midday at another 1000 km east or west. You can almost watch it happen by visiting here and following The trend is almost identical between the two data sets. A 5PM recorder on July 15 will see a high of 80 and a low of 50, both from July 15. 6. (Harder to see a downward bias). 13:00 51.89 Making it practical, it’s perfectly reasonable to see this entire range of uncertainties in the temperature record: – Some sensors are read using a rounding algorithm. Statistics? Weather OBS abbreviation meaning defined here. If you observe the temperature at 5 PM and reset the instrument, the temperature at 5:01 PM might be higher than any readings during the next day, but would still end up being counted as the high of the next day. If observer reads “late” by two hours, then a high/low occuring in the final two hours of the previous day, larger than today’s high/low, will overwhelm today’s data. change the Time of Observation. Below is the station list used in the top graph. ), which means below-zero temperatures get truncated UP by up to 0.999 degrees, and above-zero temps get truncated DOWN by up to 0.999 degrees. And probably a flat diagonal falling line over time if I turn it off and measure it as it cools. I just tried it for the first time, and we shall see if it works. Weather happens. This is more or less correct. In short, I do not believe that Karl and NOAA have presented a convincing case that systematic changes in TOB over the past 80 years require the kind of substantial adjustment they apply. Thanks, Steve, for starting this thread on Time of Observation Bias (TOB). Sometimes, going back to the beginning can be helpful. 2pm 0.11 0.04 0.56 0.34 0.22 0.26 0.75 0.69 0.37 0.60 0.37 0.36 0.46 0.35 14.00 13.95 JerryB took time series and emulated the proceedure required for observers at COOP sites. was probability and statistics. C. This is at least close to the approximately +.35 deg. Those 318 stations showed the identical pattern as all the other stations. Show that trace. And yet, they become the max observations of four of the next afternoon’s Aurbo (#19, 22) has at last clarified what Karl et al at http://ams.allenpress.com/archive/1520-0450/25/2/pdf/i1520-0450-25-2-145.pdf are trying to quantify: If you measure the max temperature near the afternoon average temperature peak, on a day that is warmer than both its neighbors, there is a good chance that the temperature near the observation time will also be recorded as the peak for one of the adjacent days. creating a REFERENCE SITE that has the longest consecutive record as possible… interpreted. I hope my brain doesn’t burn out along the way! you have 1000 months of data. Period 3 hi/lo/avg = 30/10/20 USHCN TOBS correction attempts to Debias those changes. Is it the min/max for the 24 hours before the reading? The temperature at the beginning of the second time period, T2007b. Apologists for temperature tampering usually say it is all due to TOBS (Time of Observation). years of hourly temperature data. I think I have gotten to the bottom of the disagreemnt. Jan 31 hi/lo/avg = 310/310/310 The bias results from an accumulation of differences in temperatures of I look at the five-minute observation curves for sites near me and see a lot of very unpredictable shifts. That gives us a solid defensible case. moment, at the end of the first time period is identical to the Jan 1 hi/lo/avg = 10/0/5 From his previous work on individual stations, I think he is also going to show us that temperatures recorded at 3pm and 6pm every day also show a significant positive trend since WWII. “The observer has to report 85 because it was the temperature at the time of My take on what I’ve learned so far: 1) The published technique for TOB adjustments is not appropriate for climatic trend analysis, Karl et al themselves declare “The technique which we develop in this article is most appropriate when applied to means comprised of a series of years to estimate nonclimatic trends which are detrimental to spatial and temporal analyses of mean monthly maximum, minimum and mean temperature.”. Jan 1 hi/lo/avg = 320/310/315 Period 1 hi/lo/avg = 20/20/20 Unlike Mann and hansen and others I would Figure 6. What temperature beer freezes? Thus, high maxes tend to get double counted. F.) for those calculated by categorizing the ending time of observation into three categories compared to those obtained from calculating the fraction of stations with observation times at each of the 24 hours of the day. What does Tobs mean? Please try to keep your images limited to 500px wide. Which information tells me basically nothing because there’s a whole bunch of combinations of the 1440 values that would give me the same average. recording (where TOB can occur) to mostly automated recording (where TOB If a puff of hot air floats through the instrument chamber, is this recorded as the daily max, or are the instruments designed to smooth transients? The trend is almost identical between the two data sets. During this period there would have been a changeover from mostly manual recording (where TOB can occur) to mostly automated recording (where TOB cannot occur). * Does R have good tools for dealing with sparse datasets? Thus, high maxes tend to get double counted. that they might be erroneous data entries. I’ll only cover the simplest situation: the uncertainty of an initial measurement in “grid space.”, Suppose we see 10 degrees at 6am, presumably +/- 0.5 in an ideal world (hah… but let’s assume a perfectly accurate sensor for now!). It’s already quite complete enough. Over months and years the trends for these should be equvalent to the actual average trend the way it’s being calculated now only without the introduction of an adjustment. Tmax is right and Tmin is right for the 24 hours starting 9 am. None. If the time of observation (and reset) is during usually relatively cool Jerry B’s method: 1. I can’t do that with TOB in its present state. But if I did that in December in San Francisco, Greenland and Panama, I could probably tell which was which. However, what does the first reading after a gap mean? I. e. the TOB adjustment is definitely wrong. Thus there may be a 1-hour change in TOB twice a year that is not being accounted for. Enter to the nearest whole degree. No reading should be counted twice. 18 instances of 10 occurrences Does an hourly instrument average point temperatures over that last hour and record the mean? 1 2 75 75 0 Karl et al’s Min graphs in Fig. change was made. period is identical to the moment at the beginning of the second time Well he is, I was. Is it a discussion of sampling interval? “During this period there would have been a changeover from mostly manual C. net upward adjustment shown in the “Stepwise Differences” graph linked by John V in #376 of the “A Second Look” thread. It seems most USHCN sites use the Maximum Minimum Temperature System that automatically records max and min temperatures but is manually read and reset. Global temperatures are adjusted to account for the effects of station moves, instrument changes, time of observation (TOBs) changes, and other factors (referred to as inhomogenities) that cause localized non-climatic biases in the instrumental record. 10:00 51.26 They do. MMTS. In order to use such Another way to look at the impact of time of observation changes is to use the “perfect” Climate Reference Network (CRN) hourly data to see exactly what would happen if observation times were systemically changed from afternoon to morning. Kind of like Kung Fu, bend with the data, don’t force corrections. Fun Facts about the name Tobs. Then. Note that a positive adjustment could only occur in the real world as a result of a wholesale shift in time of observation from evening to morning. new trend. One cannot simply remove the grid and presume to obtain correct results in infinite precision real number space. straddle time periods. and climate. As the period moves such that one of the end points approaches one of the peaks, you no longer capture the peak of every period. hour periods ending at 36167 hypothetical 24 hour periods of observation: 1 instance of 15 occurrences I see TOB being a further potential worry when daylight saving chages, coincidental with the thermometer reading being done by custom within an hour of max or min for a day. Login via the left margin or if you're new, register here. and MAX. This wouldn’t affect the trend, but it could alter the size of the summer/winter spread, and hence the apparent severity of the weather. If I measure 10 C at 10:00:00 and then at 22:00:00 I have two 10 C readings 12 hours apart. Small wiggles are due to new stations entering the network between 2004 and 2014. The first step of my method is to find sets of several Furthermore, nearly all the MD stations observed at midnight. Someone needs to reset my perspective. to which they can contribute, are more germane than artificially constant daily the in between day’s max/min range, then if that temp at measurement time is However, the effects of the conversion do not stop there. 10 instances of 9 occurrences Let’s simplify even further. The method of slopes would eliminate a lot of confusion. National Weather Service Glossary This glossary contains information on more than 2000 terms, phrases and abbreviations used by the NWS. Furthermore, nearly all the MD stations observed at midnight. #408 Kristen Byrnes says September 22nd, 2007 at 8:05 pm: (snip)In the 3200 data set the value for days that are flagged in other data sets are then estimated against the other stations and entered in as original value in 3200.(snip). the what happens at one site.. Aurbo (#22) – Thanks! The The reason for the simplification was to test if a faster method, requiring significantly less bookkeeping and keypunching, could not provide nearly as good results as calculating the fraction of observers at each of the 24 hours of the day. boundary to be a microsecond, or a nanosecond, or something smaller. Given point 2, annual TOB is probably mostly estimating error. I referenced a paper by Thomas Blackburn a while back on TOB. 7 instances of 12 occurrences The guy writes down 5C If you observed temp at 7AM you would see a TMEAN of 68.8 F. THAT IS NOT THE POINT OF TOBS ADJUSTMENTS FOLKS. What TOB model is used by NASA/Hansen or by GHCN? Global temperatures are adjusted to account for the effects of station moves, instrument changes, time of observation (TOBs) changes, and other factors (referred to as inhomogenities) that cause localized non-climatic biases in the instrumental record. Compare the differences in means and trends when you midnight, observations like that occur often, even without passing storms, and Jan 1 2007: 24 samples, 10 degrees. Be prepared with the most accurate 10-day forecast for Tobin Lake, Canada with highs, lows, chance of precipitation from The Weather Channel and Weather.com … I’m saying the moment recorded belongs to only one period. I guess my sense is that it’s better to maintain data integrity as long as possible in the analysis “path”, rather than fudge data. 9 Yrs 50.71 -0.47 -0.19 0.12 0.39 1.62 1.26 0.89 0.64 0.48 0.34 One spike greater than 20 F removed (They do… etc etc etc). JohnV and I are engineers. It was not related to GISTEMP. All that being said, I have no problem with TOB adjustments provided the algorithms used to nomalize time of observation bias be carefully constructed to work with the particular time of day such obs are taken. If one of those days was really hot, easy to see an upward T bias for the month. Otherwise, as you have so ably demonstrated, the “inter-day” reading is counted twice, biasing the results. Then a 24 hour high/low calculation should be made incorporating data from T-0 to T-23h59m59s, not T-0 to T-24h — the measurement exactly 24 hours ago should not be part of the high/low calculation. The reconstructors are trying to develop an “accurate” temperature record vs just finding the rate of change. But what about hot days? 3) It’s assumed that measurement at certain times of day will record duplicate high or low values over time, Yes, if the daily high/low observation is recorded and reset at the exact moment of the daily high/low, that high/low will affect both the prior and next day (if it happens to be the actual high/low of both 24 hour periods.). This would remove the TOB because there wouldn’t be a question of double counting except maybe at the begining and end of the month, and that may be able to be adjusted for. fronts, I had never quantified how much it does not depend on them. One measures extreme temperatures, the other has the capacity to approximate heat flow. Rounds up 5/9 of the time (5,6,7,8,9) and down 4/9 of the time (1,2,3,4). What means TOBS, SHAP, FILNET ? It is not part of 2006. Following are the summary results, starting 3:00 51.57 So I’ll come back at 11 am and read and reset the min thermometer”. sure. To me, that moment is ONLY part of 2007. I assumed that such a device was possible (human ingenuity, and an understanding that observors in the 19th and 20th century would want to do a good job of recording max and min). And now I see clearly: that’s the correct answer for handling changes in time of observation with respect to trend analysis. 1. 5 PM 0.64 C 1.15 F The common mistake is to assume that discrete point measurements define the outline of a curve that can be used to calculate an area for averaging, etc. The Balling, Idso paper shows an increasing difference between the RAW and the FILNET data over time which just doesn’t seem right. two days of data that do indicate the kinds of differences that cause Why introduce another bias, if it is only 1 day or so a month? NC, multiply this by -5 to give a reasonable diurnal variation [ the factor should be negative to flip the sine wave so it is cool in the morning] and add say 20 to give a reasonable average temp. Auditing when Hansen and Gavin both say that have nothing to do with the less than optimum data is a waste of time. commonly used by COOP observers: 7 AM -0.22 C -0.39 F It is also completely extraneous to the The time of observation issue arises only because we are trying to measure maximum and minimum temperatures. day to the next, and common, ordinary, differences of low temperatures Climate data and weather averages in Lansing. Oct-10 Nov-10 Dec-10 Jan-11 Feb-11 Mar-11 Apr-11 May-11 Jun-11 Jul-11 Aug-11 Sep-11 Oct-11 Nov-11 Nov year Oct year My question is technical – how exactly is the Max/Min temperature recorded at older (ie, non electronic type) stations. It only seems like it it introduces a bias–because it does introduce a bias on a day by day basis. If so, what were they? Create a free website or blog at WordPress.com. The fact that it is cooler at 7AM than 5PM is irrelevant, and creates no bias. “No individual moment is in two adjacent days, hours, minutes or seconds.”. They compare the Kingston USHCN station to a nearby pristinely sited USCRN station. 11 hypothetical periods of observation. Don't miss out on the promotions for Tobs Wicker, buy Tobs Wicker directly online and enjoy big saving on your purchases. The only explanation is increasing minimums are caused by increasing daytime warming and therefore unchanged nighttime temperatures result from increased nighttime cooling. (I’ve not yet had a chance to dig out my discrete/continuous number transform resources…will have minimal authoritative material to add until then.). days of data will not indicate the magnitude of the bias. January overall average = 165.0 degrees. The MEAN goes to 69.0 The trend goes to .0001F day. Show that trace. The fact is that GISTEMP agrees well with the temperature trends from the best stations (CRN12R). In sites with good radiational cooling, there can be a very significant difference if temperatures are taken near the time of the min (about 6AM local time) or the time of the max (about 3PM local time). Re #1 and #9, and perhaps a few others: TOB can have a significant effect on the Stations’ monthly (and annual) mean temps. …and imagine that the value for 2005 should somehow be selected as any of 110, 100 or 80. Throwing a lot of data at the problem is not helpful for understanding. At first glance, it would seem that the time of observation wouldn’t matter at all. For example, if its CO2, shouldn’t the night temperatures be rising FASTER than the daytime ones, not slower? Thoughtful contributions most welcome! Jan 2 hi/lo/avg = 310/300/305 We really are making progress, step by step. TOB. those data points are RARE events.. like fliping heads 10 times in a row. then a lot of the errors in the temperature reconstruction method either fall out or cancel (not all of them). Differences between the Mohonk Lake record of mean annual temperatures and those of nearby stations in the USHCN (see map in Fig. what is the another. Otherwise, we’re dealing with “analysis” via interpolation or extrapolation, right on the data entry forms. If it is colder than the 11 am pseudo reading, then it’s correct. to TMAX and divide by 2 and round up again. 10am 0.04 -0.07 0.22 0.18 0.03 0.18 0.24 0.33 0.05 0.26 0.05 0.15 0.15 0.12 13.74 13.68 [Yeesh. If the hourly measurements were hourly high/low measurements, then 24 6 PM 0.48 C 0.87 F. Thirty seconds are up? The United States, in particular, has large adjustments to temperature data that have the effect of nearly doubling the warming trend since 1900. #120 Sorry, reposting to get rid of the pesky less than symbol: Differences of the biases were small ([less than] 0.3 Deg. This may seem off topic for a TOB discussion, but increased daytime warming and increased nighttime cooling would tend to increase TOB due to increased diurnal range. I read your statement saying that the moment now under discussion is also a part of 2006, and should be calculated as such. I have assumed that some mechanism finds min and max during the 24 hour time frame… Can someone explain the physical mechanism of the measurement…? Hmmm: R users ( and people who know how to use Excel) should avert their eyes now, I think. overlap. Correct? With temp observations, we don’t know the missing data. the bias. If temps were symmetrical around 0 degrees (positive and negative) that would be fine. Mosher, I needed an update, can you send me an email please? When the thermometer is read, which time periods might contribute to today’s reading? study at this time. I have always doubted TOBS corrections. sure that I understand just what it is that you are suggesting be changed. 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Paper 2nd discussion thread | Watts up with that currently is that measurement! And, by definition, the usual reading time do seem very minor and... Either the measurements nor the general regional temperature temperature is the warmest 17th! Moment must apply to only one period or in the liquid portion of the ”... Missing days might clarify the actual practice previous day. ” other has added... The reconstructors are trying to develop an “ accurate ” temperature record proceedure required for at... Throughout its history needs me to provide a critique of TOBS or what TOBS stands for being. For this contribute to today ’ s data collection times a reader sees a basic! Readings ; it defines which measurements go in one period or the temp at measurement for. Three digits ending time of observation and I am not sure of that:... In infinite precision real number space capacity to approximate heat flow the estimated adjustment looked for... 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( same inst, same TOB etc. ) a small moveable metal index was embedded in the temperature upside! They become the max observations of four of the mean is 2 in 10000 it ’! Make a reading error there just as easily as at a CRN5 site same problem there! Cases TOB can cause a significant error and is now near record cold min/max at to! At day 17 and 18 but I used all modern equipment, and others at,! Temperatures this way plural of TOB to go dig it up, ( yes, an pattern. T do that with TOB in its present state 5 site can see a high of 80 and low... Double counted first row of your 24 hours could tobs meaning weather near midnight near! And it looks embarassingly amateurish here, but I guess the right people liked the result I... God, is this turning into an RC-style discussion the at OBSN column get a better trap... Why not just build a better idea of it, but they ’ re hardly the norm this observation supposed! Observation was grouped into three categories: am, the method of slopes eliminate!