Update by Kip Hansen
Last week I wrote about UCAR/NCAR’s very interesting discussion on “What is the average global temperature now?”.
[Adding link to previous post mentioned.]
Part of that discussion revolved around the question of why current practitioners of Climate Science insist on using Temperature Anomalies — the difference between the current average temperature of a station, region, nation, or the globe and its long-term, 30-year base period, average — instead of simply showing us a graph of the Absolute Global Average Temperature in degrees Fahrenheit or Celsius or Kelvin.
Gavin Schmidt, Director of the NASA Goddard Institute for Space Studies (GISS) in New York, and co-founder of the award winning climate science blog RealClimate, has come to our rescue to help us sort this out.
In a recent blog essay at RealClimate titled “Observations, Reanalyses and the Elusive Absolute Global Mean Temperature”, Dr. Schmidt gives us the real answer to this difficult question:
“But think about what happens when we try and estimate the absolute global mean temperature for, say, 2016. The climatology for 1981-2010 is 287.4±0.5K, and the anomaly for 2016 is (from GISTEMP w.r.t. that baseline) 0.56±0.05ºC. So our estimate for the absolute value is (using the first rule shown above) is 287.96±0.502K, and then using the second [the first and second rules have to do with estimating the uncertainties – see Gavin’s post], that reduces to 288.0±0.5K [2016]. The same approach for 2015 gives 287.8±0.5K, and for 2014 it is 287.7±0.5K. All of which appear to be the same within the uncertainty. Thus we lose the ability to judge which year was the warmest if we only look at the absolute numbers.”
You see, as Dr. Schmidt carefully explains for us non-climate-scientists, if they use Absolute Temperatures the recent years are all the same — no way to say this year is the warmest ever — and, of course, that just won’t do — not in “RealClimate Science”.
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Author’s Comment Policy:
Same as always — and again, this is intended just as it sounds — a little tongue-in-cheek but serious as to the point being made.
Readers not sure why I make this point might read my more general earlier post: What Are They Really Counting?
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Very interesting.
Let’s see how your critique stands up to scrutiny.
hunter ==> Hardly a critique — I am just quoting Dr. Schimdt on the subject – read his whole post (always a good idea).
It would be informative for Steve Mosher to explain, in a non hostile way, what he thinks of this.
Hunter,
In three words or less, as is his usual drive-by ‘analysis’?
The question I have is: “Is the surface temperature meaningful in any way other than weather?” We live in the boundary layer at the surface, so surface temperature will effect us. I usually get that effect in Boston in february when I have to run the snowblower and in august when I have to run the air conditioner. Obviously, the length of the growing season matters. So yes, surface temperature does matter. The next question is one of the relation of the surface temperature to things like CO2. The earth is a dynamic process. The transport of enthalpy/entropy causes massive changes on a very short term basis. Stuff like CO2 and solar effects are gradual at most. Yes, all things being equal, a bit more CO2 will cause a bit more stored enthalpy over the long term, but only the long term.
A lot of the hysteria here is caused by a total lack of ability of our NEA edcratered (sic) public to frame temperature in a way that is meaningful in terms of physics. If you go up to the moron on the street and ask the question: “Yesterday it was 70 degrees F, today it is 71 degrees F. In percent, how much warmer is it today than yesterday.” You will get the answer of over 1% almost all the time. Truth be known, the correct answer is around 0.2% With that sort of massive framing error out of the block, trying to get any sort of rational action out of the populace at large is a lost effort.
Local temperatures are meaningful. Global average temperature is meaningless. It’s like determining if any car violated the speed limit by averaging the speeds of all the cars that passed the highway. Notice weather news don’t report global average temperatures. Who cares?
Local temperatures are only meaningful if you can explain why the temperature is a certain value. This requires factoring in the environment around that measurement.
A station next to a lake, the water temperature of that lake has a bearing on the temperature read by the station as does wind speeds and what the air is doing.
If you cannot explain and calculate the impact of those elements, then your reading is useless for causes
Water temperature of lake, wind speed, etc. are local effects. You measure the effects before you attribute causes. Are you saying global temperature is your Ultimate Cause?
I mean only meaningful to assess sensitivity if you know all the other factors, or as many as we can know, the actual measurement alone without the other data is useless for sensitivity studies
why? are you saying you could
not calculate calculate the
avg speed of all autos on the
road at a gi ven time, given
all their speeds?
In addition to make the uncertainty to appear smaller, there’s the added benefit that a one degree change all by itself may seem large (when compared to the baseline anomaly of zero) but a 1 degree change over a baseline value of 288 appears ridiculous.
David L.
Consider though that the ‘baseline anomaly of zero’ is itself arbitrarily set. Zero celsius is 273.15 K. We set it there for a good reason though – the range from ~273 – ~ 373 K is pretty much the zone we operate in as human beings. Water freezes and boils within that range. These are things that are important to us as a species; so that is why we arbitrarily set ‘zero’ to ~ 273 K for everyday use.
In terms of climate, the range is much closer. By most estimates, global average surface temperature during the entire Holocene period, over the past ~10,000 years, has varied by as little as +/- 0.5 C of ‘average’, meaning about 14C, +/- 0.5C (or 287 +/- 0.5 K). It’s been a very steady system.
Far from being ‘ridiculous’, a +1 C change in global average surface temperature, if indeed it has occurred in recent decades, could actually be a very big deal in the grand scheme of things.
DWR54 ==> The serious point of this post (and its predecessor) is that the Global Temperature change between years is really indiscernible — all the years are within the known margins of the original measurement error — which we know for most of the thermometer era to be at least +/-0.5°C, possibly as much as +/-2.0°C (certainly is this magnitude for the 1930s and before).
baselines are completely
arbitrary, provided the data are
good enough to establish a
baseline
Using anomalies it is also possible to state that this year is warmer than last year every single year. No matter that if the temperature went up say, 0.1 C for 30 years then it would be an unbelievable 3.0 C hotter. Nobody would be able to tell unless they make the direct comparison with previous absolute temperatures. Using anomalies makes it easy to avoid the difficulties of this compounding of errors, or lies (take your pick).
Additionally, it also helps to continuously change past years to lower temperature. With this technique you really can make temperatures continue up. Forever. Maybe it’s just coincidence that that is what seems to happen. Maybe not. But it is indeed very convenient for those who have staked their reputation on continuously rising temperatures.
There is, or will be, probably some physical location in the temperature record where the warming has ostensibly risen from below zero Celsius average to above zero, but there is still ice on the ground.
I have a little green paperback book entitled “How To Lie With Statistics.” Still available, lord knows how many reprints, mine from decades ago was in the 20 something reprint range. Problem is, it was designed to allow you to understand how statistics and things like the OP are used to lie and obfuscate, but today apparently most people, especially “climate scientists” use it as a how to manual.
u have to explain where the so-called lies
are, not just point to a book
on your bookshelf
I’m still scratching my head as to why the supposed genius Stephen Hawking thinks global warming is going to make Earth uninhabitable, but somehow the Mars enviroment is adaptable. WTF Einstein?
Sometimes, an exceptional ability in one intellectual area is accompanied by a deficiency in another area. Calculating idiot savants are an extreme example.
Schmidt, [ snipped by author — name-calling forbidden by WUWT Policy ]
I once thought I was wrong back in 1997, but later I found out I was mistaken.
I am confused about Gavin’s entire argument. One must compare apples to apples or oranges to oranges. He, instead, compares apples to oranges.
If one is going to compare absolutes, then one needs to compare absolutes. If one is going to compare averages (30 years in this case), then one must compare 30 year averages.
The absolute temperature Gavin cites for a baseline is 287.4 to 287.5±0.5°K. 2016 came in at 288.0±0.5°K. So, the hottest year on record 2016 (in the middle of an El Nino) was at the high end of the error range (due to a rounding error) or just 0.1°C outside the error range. Hardly impressive, in my opinion, especially given diurnal temperature fluctuations which are generally at least two orders of magnitude higher than the minute increase (or possible increase) in absolute temperature which occurred.
As stated, if one is going to compare averages, one must compare averages. I do not know how one compares a year (the weather of an El Nino year like 2016 for example) to a climate data set of 30 years. Gavin uses 1981-2010 for his 30 year average.
The 1981-2010 anomaly was 0.56±0.05°C according to Gavin. The 1987-2016 anomaly is 0.54°C (I guess ±0.05°C). Not only is 1987-2016 climate data set inside the error ratio, but it is actually 0.02°C less than the baseline average he uses.
So Gavin argues one cannot use absolutes because “we lose the ability to judge which year was the warmest”, but using the absolute actually makes 2016 the hottest year, albeit just in/outside the margin of error. But this argument would have actually shown an increase in absolute temperature. He instead compares a year to a 30 year average to the hottest year 2016, but when looking at the 30 year average up to 2016, that average is less than the average he uses.
In my opinion, Gavin would have been better at using 287.1°K as his absolute temperature from the NOAA NCEI average of 13.9°C he cites. The problem is this 0.9°K/C temperature increase is still minuscule to:
A) Diurnal temperature fluctuations which are often about 10°C (or more in drier areas),
B) Temperature fluctuations due to uncontrollable variables, like cloud cover (water vapor), El Nino’s/La Nina’s, Milankovitch cycles, etc which produce much more error (fluctuations) into the overall climate system,
C) The 287-288°K/C overall temperature of the Earth of which 0.9°K/C is only 0.3% of a change in overall temperature.
While I agree it has probably gotten warmer (maybe 0.9°C/K) over the last century (plus), this temperature increase is very minuscule in the grand scheme of things and is generally inside of margins of error of instruments used to measure temperature over this same period or may be caused from human error looking at a thermometer (short guy versus tall guy) as noted in above comments.
Undercover ==> “I am confused about Gavin’s entire argument. ” You are not alone…..
The use of anomalies rather than absolutes has a number of justifiable reasons…and then I have seen some hilarious ones, like claiming that anomalies are used because climate change is an anomaly.
In any case, the failure of absolute temperature to discriminate from one year to the next certainly calls into question how “robust” any claims of any such year being warmer than another may be based on the anomalies.
wrong mj — they calculate absolute temps.
see manabe and wetherald’s papers going back
to 1967. or see
http://climexp.knmi.nl/CMIP5/Tglobal/
http://climexp.knmi.nl/CMIP5/Tglobal/global_tas_Amon_GISS-E2-R_rcp26_ave.dat
http://climexp.knmi.nl/CMIP5/Tglobal/global_tas_Amon_GISS-E2-R_rcp60_r1i1p1.dat
http://climexp.knmi.nl/CMIP5/Tglobal/global_tas_Amon_GISS-E2-R_rcp60_r1i1p2.dat
http://climexp.knmi.nl/CMIP5/Tglobal/global_tas_Amon_GISS-E2-R_rcp60_r1i1p3.dat
I understand that Global climate models do not work in absolute temperature, only anomalies. So output runs have to be base-lined.
How a GCM can be accurate working in anomalies and not absolute temperatures is beyond me. What about phase changes from solid Liquid Vapour and what about snow cover?
wrong. ur wrong
see the links i
posted just
abo ve
Very interesting, list of the highest temperatures recorded in each state. Only one state’s highest temperature is in this century. There were five in the 1880s and 1890s.
https://en.wikipedia.org/wiki/U.S._state_temperature_extremes
My error, I was looking at both Highest and Lowest. There are no High Temps in this century in any state, but there was one in the 1898 in Oregon.
Ahem… Current policy generation in action. Speak now.
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