UAH August Global Temperature, still in a holding pattern

AMSU Channel 5 global image

Up slightly from .489 last month to .511 a change of .022 degrees C

August 2010 UAH Global Temperature Update: +0.51 deg. C

By Dr. Roy Spencer

While the global-average lower tropospheric temperature remained high, +0.51 deg. C in August, 2010, monitoring of the daily Aqua Ch.5 data at the Discover web site suggests that the cooling of global average sea surface temperatures that started several months ago is now causing the troposphere to cool as well. I will probably provide an update of that plot tomorrow.

Plot and recent data below:

UAH_LT_1979_thru_Aug_10

YR MON GLOBE NH SH TROPICS

2009 1 0.251 0.472 0.030 -0.068

2009 2 0.247 0.565 -0.071 -0.045

2009 3 0.191 0.324 0.058 -0.159

2009 4 0.162 0.315 0.008 0.012

2009 5 0.139 0.161 0.118 -0.059

2009 6 0.041 -0.021 0.103 0.105

2009 7 0.429 0.190 0.668 0.506

2009 8 0.242 0.236 0.248 0.406

2009 9 0.505 0.597 0.413 0.594

2009 10 0.362 0.332 0.393 0.383

2009 11 0.498 0.453 0.543 0.479

2009 12 0.284 0.358 0.211 0.506

2010 1 0.648 0.860 0.436 0.681

2010 2 0.603 0.720 0.486 0.791

2010 3 0.653 0.850 0.455 0.726

2010 4 0.501 0.799 0.203 0.633

2010 5 0.534 0.775 0.292 0.708

2010 6 0.436 0.550 0.323 0.476

2010 7 0.489 0.635 0.342 0.420

2010 8 0.511 0.672 0.349 0.362

As of Julian Day 243 (end of August), the race for warmest year in the 32-year satellite period of record is still too close to call with 1998 continuing its lead by only 0.06 C:

YEAR GL

1998 +0.61

2010 +0.55

As a reminder, six months ago we changed to Version 5.3 of our dataset, which accounts for the mismatch between the average seasonal cycle produced by the older MSU and the newer AMSU instruments. This affects the value of the individual monthly departures, but does not affect the year to year variations, and thus the overall trend remains the same as in Version 5.2. ALSO…we have added the NOAA-18 AMSU to the data processing in v5.3, which provides data since June of 2005. The local observation time of NOAA-18 (now close to 2 p.m., ascending node) is similar to that of NASA’s Aqua satellite (about 1:30 p.m.). The temperature anomalies listed above have changed somewhat as a result of adding NOAA-18.

[NOTE: These satellite measurements are not calibrated to surface thermometer data in any way, but instead use on-board redundant precision platinum resistance thermometers (PRTs) carried on the satellite radiometers. The PRT’s are individually calibrated in a laboratory before being installed in the instruments.]

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September 2, 2010 4:23 pm

What’s the typical lag time between the strong las nina we are seeing developing & reflection of that in the atmospheric temps?

tallbloke
September 2, 2010 4:26 pm

My thanks to Roy Spencer for his untiring work on updating and fully explaining the UAH record.
I agree with him that the Tropospheric temperature will soon be following SST’s down the slope. I predicted an anomaly as cool as Jan 2008 by Feb 2011 some 8 months ago. I still stand by that.

September 2, 2010 4:38 pm

And for those interested, I posted the preliminary August SST anomaly data:
http://bobtisdale.blogspot.com/2010/08/preliminary-august-2010-sst-anomaly.html

Graeme
September 2, 2010 4:55 pm

I the atmosphere follows the sea surface temps – will we see another harsh NH winter this December?

George E. Smith
September 2, 2010 4:59 pm

Dr Roy,
When you comment on your pocket PRTs, some people think you are trying to slip some Pyramid Inch scale by us somehow.
Can’ty ou simply tell them that those surface thermometers aren’t any better than your PRTs anyway !
Anyway, I believe you; and for me, that’s what counts.
I’m still not sure that I understand just exactly what your SSTs are actually reading as far as how thick is whatever surface layer that is being registered. So how does that SST read from above again ?
George

Gary Pearse
September 2, 2010 6:40 pm

It is always delightful to see real unadulterated data on climate, whether the trend is up or down. Political climatologists are so wrong about the vast majority of skeptics. When someone mixes up an elixir for profit (however defined) and tells you to trust it, it will cure all your ailments. Who do you think will be the buyers/sellers and who will be the skeptics? The unquestioning buyers/sellers are the gullible, wishful thinkers and those whose ends are served, like, for example, the elixir salesperson. In the elixir case, who could reasonably vilify one from Missouri? Why would the Missouran be obliged to prove that the elixir is inefficaceous? Why is elixir also called snake oil? Thank God for Missouri.It has at last begun to truly open up a prematurely and hurriedly closed debate. Interestingly, except for a desperate flurry of drive-by, the-end-is-nigh papers without time for data, models and codes, like the explosion of a 4th of July rocket at the end of its flight, there is an unmistakable end of a manic (I resisted the pun) crazy era. Roy’s satellite will chart our way back from the last vestiges of the Little Ice Age and a century of alternating hot and cold scary debates will be over. At some point not impossibly far away an Ice Age awaits.

September 2, 2010 7:01 pm

When comparing the different hemisphere’s temperature records it is obvious that the majority of movement is controlled by the northern hemisphere. While it has been colder than average in the south, it will take the northern hemisphere polar region which is poised to play its winter jet stream game, before global temperatures start to dive.

Feet2theFire
September 2, 2010 7:09 pm

Doc, I have to ask about that global image accompanying this post. It shows S America way ABOVE average? Where is all the SNOW and freezing temps well into Brazil? And record lows in the Amazon? Frozen cattle in Paraguay?
Did August go by really quickly? Am I remembering July?

Neil
September 2, 2010 7:26 pm

I’m confused… how on Earth are we determining global average temperature to an accuracy of 0.01 of a degree?

Editor
September 2, 2010 8:19 pm

Calibration against/with the surface temperature record.
When the satellite was first launched, Hansen’s GISS record was just about the only record available, and it was considered accurate. Therefore, the satellite output was developed based on what was thought to be the earth’s surface temperature.
Now, several “un-corrupted” (er, un-corrected) rural records from long-term global thermometers are available, and most differ greatly from Hansen’s adulterated values from 1990-2010. Will you re-calibrate the troposphere-surface correlation based on valid world-wide surface records, or let it stand with the original relationship?

Steward
September 2, 2010 8:46 pm

Just technically off the chart, it should crash now, as El Nino has ended.

September 2, 2010 8:50 pm

Best keep an eye out here for an idea of whether we dive or thrive in the future.
http://bigthink.com/blogs/eruptions/
Lots of raised alert levels coming in and at some big ones, capable of pluming a lot of reflective SO2 and H2S into the stratosphere. Hope they hold off a about a year or so.

Graeme W
September 2, 2010 10:21 pm

RACookPE1978, Dr Spencer clearly stated in his post that the satellite figures are not calibrated against surface temperature records:

[NOTE: These satellite measurements are not calibrated to surface thermometer data in any way, but instead use on-board redundant precision platinum resistance thermometers (PRTs) carried on the satellite radiometers. The PRT’s are individually calibrated in a laboratory before being installed in the instruments.]

He puts this on almost all of his posts because of the misconception that you’ve stated.

Jordan
September 2, 2010 11:34 pm

The partial coverage of the globe in that image is unsatisfactory.
Is there a reason why you don’t have two images to show the global picture?
I’d like to see Europe (especially the Moscow area) and an image of the SH winter too.
Two images please. Thanks.
REPLY: Never look a gift horse in the mouth. We graciously take what Dr. Spencer provides without complaint. In this case I think he was trying to illustrate the El Niño area effect in the troposphere. – Anthony

tallbloke
September 3, 2010 12:09 am

Jeff L says:
September 2, 2010 at 4:23 pm (Edit)
What’s the typical lag time between the strong las nina we are seeing developing & reflection of that in the atmospheric temps?

Three to five months.

tallbloke
September 3, 2010 12:19 am

Graeme says:
September 2, 2010 at 4:55 pm
I the atmosphere follows the sea surface temps – will we see another harsh NH winter this December?

Cold but fine is my prediction. Depends on your definition of ‘harsh’ I suppose. In low lying England, ‘harsh’ is “Can’t get my car out of the drive.” In Himalayan Nepal it’s “My cattle have frozen to death.”

SS
September 3, 2010 12:28 am

Seems as though temps won’t go down until global ssts do. But thouse lag the Nino 3.4 ssts by a bit. Guess we’ll see when cooling begans.

John Finn
September 3, 2010 1:09 am

Gary Pearse says:
September 2, 2010 at 6:40 pm
It is always delightful to see real unadulterated data on climate, whether the trend is up or down.

I assume this is intended to be a dig at GISS (or Hadley). Tell you what when the GISS/Hadley August anomalies are released I predict they will be relatively lower than the UAH anomaly- as they have been throughout 2010 . By “relatively” I mean relative to a common base period (i.e. 1979-1998).
If , however, you are referring to “adjustments” then be aware that the UAH satellite record was adjusted earlier this year which resulted in Jan, Feb & Mar anomalies being lowered by ~0.1 deg each. Adjustments are part and parcel of data maintenance.

John Trigge
September 3, 2010 1:09 am

Why is a 20 year period (79 – 98) taken for the ‘average’ with which to compare against when many of the ‘climate scientists’ apparently think some randomly selected 30 year period is the holy grail of references?
There is 30 years of satellite data available, why not use it?

September 3, 2010 1:21 am

Geoff Sharp says: September 2, 2010 at 7:01 pm
When comparing the different hemisphere’s temperature records it is obvious that the majority of movement is controlled by the northern hemisphere.
You are right there,
http://www.vukcevic.talktalk.net/UAH.htm
but it would be helpful to know why is it so, is it a long term or just a temporary imbalance.

John Finn
September 3, 2010 1:25 am

tallbloke says:
September 3, 2010 at 12:09 am

Jeff L says:
September 2, 2010 at 4:23 pm (Edit)
What’s the typical lag time between the strong las nina we are seeing developing & reflection of that in the atmospheric temps?


Three to five months.
Indeed. Though you might find that when the UAH anomalies remain high while GISS/Hadley surface anomalies fall (e.g. during a developing La Nina) it’s because of the ‘lag’, but when the GISS/Hadley anomalies increase while UAH remains steady (e.g. during a developing El Nino) it’s because the data is being fiddled.

September 3, 2010 1:46 am

It will be interesting to see what the next month brings as falling SST and NH land mass start to cool the atmosphere. Like many here, I fear this winter will be very cold again here in Sunny Sussex. Last winter I was snowed in for 5 days – not a typical south coast event!

Gareth
September 3, 2010 2:35 am

What would happen to the graph if the anomaly period was 1979-2009?

BillD
September 3, 2010 3:17 am

I was talking with a student from Japan and she confirmed that the anomomously hot summer in her homeland is causing quite a stir there. Evidently it’s been the hottest summer since the record keeping started in 1898. I’m not sure how well the Japanese take UHI into account.

John Marshall
September 3, 2010 3:49 am

August 2010 in the UK was cooler and very much wetter that the so called ‘normal’. With SH temperatures at near record lows then I find it difficult to believe that globally August 2010 has been one of the warmest. Also the DMI has shown that north of 80N has been at near record low temperatures. So somewhere in the NH it has really been hot but I do not know where?

brokenhockeystick
September 3, 2010 4:04 am

“[NOTE: These satellite measurements are not calibrated to surface thermometer data in any way, but instead use on-board redundant precision platinum resistance thermometers (PRTs) carried on the satellite radiometers. The PRT’s are individually calibrated in a laboratory before being installed in the instruments.] ”
Measurement equipment wherever I have worked is always recalibrated once a year on average to take account of sensor drift. What recalibration is done on the satellite sensors to ensure no deviation up/down from actual in the readings.
I also agree with Neil, there is something very wrong with quoting average global temperatures to within +/- 0.01°C. How accurate can this measurement possibly be with the instrumentation, sampling intervals etc? Surely there should always be a statement of the uncertainty whenever the temperatures are quoted?

John Finn
September 3, 2010 4:57 am

Gareth says:
September 3, 2010 at 2:35 am
What would happen to the graph if the anomaly period was 1979-2009?

Apart from the fact that each point on the graph would be ~0.07 deg lower – absolutely nothing. The shape of the graph and the trend would remain exactly the same. The same could be said if you subtracted 10 deg C from each monthly anomaly value. The numbers would be different but the trend would remain the same.
RACookPE1978 says:
September 2, 2010 at 8:19 pm
Calibration against/with the surface temperature record.
When the satellite was first launched, Hansen’s GISS record was just about the only record available, and it was considered accurate. Therefore, the satellite output was developed based on what was thought to be the earth’s surface temperature.

Yet another old favourite that refuses to die – despite Roy Spencer’s own statements.
Now, several “un-corrupted” (er, un-corrected) rural records from long-term global thermometers are available, and most differ greatly from Hansen’s adulterated values from 1990-2010.
Do they – which ones?

September 3, 2010 5:52 am

It will be fascinating to see where we at after the next 3 months of above average land surface temperatures that I have forecast !

DR
September 3, 2010 6:23 am

John Finn,
Have you considered satellites have a more complete spatial coverage of the globe and therefore is a more accurate representation of temperature fluctuations?

Pascvaks
September 3, 2010 6:46 am

Sorry but I don’t see any correlation between 2009 and 2010. Something is askew me thinks. From where I’m sitting on this here planet, there hasn’t been any real, significant change and, yet, for some strange reason the on-board redundant precision platinum resistance thermometers (PRTs) carried on the satellite radiometers have shown a wierd temperature increase for all of 2010. I know we don’t need another conspiracy theory, we do have more than enough already, but -I’m sorry- something just doesn’t look right for the NH data column. It’s like the Russians or the Chinese or Soros or Fat Albert or Mann or Jones or someone is lazing the satelite, and have been all year.
Down where I stand, at the bottom of the global pyramid, in the mud and the blood and the beer, I smell a rat. Professor, something’s rotten in Denmark!

Phil.
September 3, 2010 7:30 am

John Marshall says:
September 3, 2010 at 3:49 am
August 2010 in the UK was cooler and very much wetter that the so called ‘normal’. With SH temperatures at near record lows then I find it difficult to believe that globally August 2010 has been one of the warmest. Also the DMI has shown that north of 80N has been at near record low temperatures. So somewhere in the NH it has really been hot but I do not know where?

Try the NE USA, where I am we had our first 90ºF+ day in April and that has continued all summer, currently interrupted by Hurricane Earl but we’ll be back there next week. Coverage of the US Open Tennis in NY showed on-court temperatures above 105ºF and players having problems with the heat. Japan has had its hottest summer on record I believe.

John Finn
September 3, 2010 7:31 am

DR says:
September 3, 2010 at 6:23 am
John Finn,
Have you considered satellites have a more complete spatial coverage of the globe and therefore is a more accurate representation of temperature fluctuations?

I’m not sure which of my posts you are referring to, but I have no problem accepting the satellite accuracy just as I have no problem accepting the land surface records. The land surface mesurements use easily enough samples to produce a sufficiently accurate estimate of the overall trend. Since ~1990 the trends of all 4 main datasets have been remarkably similar. Before 1990 there is some disagreement between UAH and the other 3.

Gareth
September 3, 2010 7:44 am

John Finn said: “Apart from the fact that each point on the graph would be ~0.07 deg lower – absolutely nothing. The shape of the graph and the trend would remain exactly the same. The same could be said if you subtracted 10 deg C from each monthly anomaly value. The numbers would be different but the trend would remain the same.”
The current temperature would appear less anomalous. Something similar to this is done by the Met Office when they announce every year that the global temperature is around 0.4 degrees C above the ‘long term average’ which only comes as far forward as around the same time as this. It is an entirely artificial ‘average’.
In this instance is the exclusion of one third of the data justifiable? I don’t think it is. Even with a natural upward trend the further away we are from the end of the basis period the worse things will look.

Phil.
September 3, 2010 7:55 am

DR says:
September 3, 2010 at 6:23 am
John Finn,
Have you considered satellites have a more complete spatial coverage of the globe and therefore is a more accurate representation of temperature fluctuations?

The satellite MSU don’t include data poleward of 82.5° North and 70° South, as well as areas with land or ice elevations above 3000 meters.

Mr Lynn
September 3, 2010 8:25 am

Pascvaks says:
September 3, 2010 at 6:46 am
. . . Down where I stand, at the bottom of the global pyramid, in the mud and the blood and the beer, I smell a rat. Professor, something’s rotten in Denmark!

Somewhere Shel Silverstein (who wrote “The Boy Named Sue” for Johnny Cash) is smiling. Not to mention Will Shakespeare.
/Mr Lynn

Richard M
September 3, 2010 8:46 am

We are seeing some impact from the recent change in the UAH algorithm. While it lowered temps by .1C 6 months ago, we are now seeing the flip side … an increase of about .1C from where it would have been before the change.
As for GISS. They are still out of sorts with the other 3 records. That has been identified as due to their handling of the Arctic. They are clearly wrong.
In addition, GISS also modified historic temps downward. This creates a greater trend. I find this and the lack of better UHI analysis to be the biggest problems with GISS.
It appears the UAH temps have starting falling fast. There was a prolonged bump over July and the first half of August that needs some explanation relative to the oncoming La Niña. I have a feeling it was due to additional warmth over the rest of the oceans. Climate is complex and we can’t look a single area and expect to know what will happen.
BTW, I seem to see a little more skepticism in John Finn’s most recent posts. I would no longer classify him as an alarmist. More of a luke warmer.

Bill Illis
September 3, 2010 8:47 am

The Big Blue Blob is now 13,000 kms long and it says things are about to change.
http://www.osdpd.noaa.gov/data/sst/anomaly/2010/anomnight.9.2.2010.gif

Oldjim
September 3, 2010 8:59 am

@brokenhockeystick
This may help explain the system of calibration
http://www.drroyspencer.com/2010/01/how-the-uah-global-temperatures-are-produced/

Gail Combs
September 3, 2010 9:26 am

Bob Tisdale says:
September 2, 2010 at 4:38 pm
And for those interested, I posted the preliminary August SST anomaly data:
http://bobtisdale.blogspot.com/2010/08/preliminary-august-2010-sst-anomaly.html
_________________________________________
Thanks Bob,
Given that the SST this year are cooler than the SST in 1998, that the oceans are 70% of the surface area and we had record cold in the southern hemisphere and parts of Russia, what is your guess about this year being the “hottest ever?”

Phil.
September 3, 2010 9:32 am

Richard M says:
September 3, 2010 at 8:46 am
We are seeing some impact from the recent change in the UAH algorithm. While it lowered temps by .1C 6 months ago, we are now seeing the flip side … an increase of about .1C from where it would have been before the change.
As for GISS. They are still out of sorts with the other 3 records. That has been identified as due to their handling inclusion of the Arctic. They are clearly wrong.

Really, do you think that ignoring the Arctic as the satellites do is the correct way to go?
In addition, GISS also modified historic temps downward. This creates a greater trend. I find this and the lack of better UHI analysis to be the biggest problems with GISS.
Why, in the context of a comparison with the three other records?
It appears the UAH temps have starting falling fast.
At about the same rate as the record history so it stays around the record value (1998).
There was a prolonged bump over July and the first half of August that needs some explanation relative to the oncoming La Niña. I have a feeling it was due to additional warmth over the rest of the oceans.
The UAH temperature represents the atmosphere up to 10km whereas La Niña is an ocean surface phenomenon, it takes time for the higher troposphere to adapt.

September 3, 2010 10:28 am

Ulric Lyons says: September 3, 2010 at 5:52 am It will be fascinating to see where we at after the next 3 months of above average land surface temperatures that I have forecast !
Buddy, you sure have some big kahunas to be talking like that around here. Get my drift?
Vuk, maybe the fact that 2/3 of the volcanoes lie in the northern hemisphere and we have a bit better view of the north pole of the Sun than the south pole?

gary gulrud
September 3, 2010 10:41 am

Central MN seems to be on the La Nina pipeline courtesy of PDO jet-today is struggling to break into the 60’s with one day forecast above 70 over coming week.
Of course we could have an Indian Summer, but this sudden change from high 80’s and humid is a shock to the system.

gary gulrud
September 3, 2010 10:43 am

“Really, do you think that ignoring the Arctic as the satellites do is the correct way to go?”
So we should just make up numbers instead? AGW is dead, the chakra exorcised, adapt.

September 3, 2010 2:46 pm

Gail Combs says: “Given that the SST this year are cooler than the SST in 1998, that the oceans are 70% of the surface area and we had record cold in the southern hemisphere and parts of Russia, what is your guess about this year being the ‘hottest ever?'”
It depends on the combined dataset. GISS and NCDC probably. Hadley not as likely. I started a post on the impacts of “make-believe data”, aka infilling. I put it aside for a few weeks to attend to other posts and I should be able to get back to it in a few weeks.

Editor
September 3, 2010 2:58 pm

Looking at the 12-month running means in 1998, the surface-based Hadley and GISS datasets turned downwards a few months before the satellite-based RSS and UAH datasets. See http://woodfortrees.org/plot/hadcrut3gl/from:1997/to:2000/mean:12/plot/gistemp/from:1997/to:2000/mean:12/plot/uah/from:1997/to:2000/mean:12/plot/rss/from:1997/to:2000/mean:12 Actually, RSS and UAH plateaued for a few months before dropping.
Since we’re also coming off a strong el Nino this year, a similar pattern is to be expected. See http://woodfortrees.org/plot/hadcrut3gl/from:2008/to:2011/mean:12/plot/gistemp/from:2008/to:2011/mean:12/plot/uah/from:2008/to:2011/mean:12/plot/rss/from:2008/to:2011/mean:12 As of June’s data, GISS had already started turning down and Hadley has plateaued. UAH and RSS are still rising. Here are their respective 12-month running means…
Month Hadley GISS UAH RSS
May 0.500 0.669 0.442 0.423
June 0.502 0.666 0.475 0.461
July 0.503 0.659 0.480 0.480
And UAH’s 12-month running mean ending in August is 0.502. So it appears that the satellite-data trend lags behind the surface-data trend this time around too. I expect Hadley to come in with August 2010 anomaly slightly lower than their August 2009 anomaly.

DR
September 3, 2010 3:31 pm

Phil said:

The satellite MSU don’t include data poleward of 82.5° North and 70° South, as well as areas with land or ice elevations above 3000 meters.

Yes Phil, I’m aware of that. Let’s try again. Example: What percentage of the African continent do surface stations cover? Satellite?
Apply that to all land masses. More questions after that 🙂

DR
September 3, 2010 5:02 pm

Phil said:

The satellite MSU don’t include data poleward of 82.5° North and 70° South, as well as areas with land or ice elevations above 3000 meters.

Considering in May you said MSU has no coverage at the poles, that’s an improvement.
Actually, after re-reading your post, UAH covers 85 North. Surely you wouldn’t suggest GISS has more real coverage than satellites?

Richard M
September 3, 2010 6:43 pm

Phil. says:
September 3, 2010 at 9:32 am
Really, do you think that ignoring the Arctic as the satellites do is the correct way to go?

I think ignoring is better than making it up. Deal with what you know. I guess you think the opposite.
“It appears the UAH temps have starting falling fast.”
At about the same rate as the record history so it stays around the record value (1998).

My comment was relative to the mid June through mid-August. Nothing else.
The UAH temperature represents the atmosphere up to 10km whereas La Niña is an ocean surface phenomenon, it takes time for the higher troposphere to adapt.
If you took the time to look at the near surface values you’d see the same delay in cooling that has occurred in the troposphere. So, it’s not completely due to lag time. In addition, it appeared a cooling trend started way back in May and then got short circuited. I don’t claim to know the answer, just wondering aloud.

Phil.
September 3, 2010 6:54 pm

DR says:
September 3, 2010 at 5:02 pm
Phil said:
The satellite MSU don’t include data poleward of 82.5° North and 70° South, as well as areas with land or ice elevations above 3000 meters.
Considering in May you said MSU has no coverage at the poles, that’s an improvement.

Well clearly it doesn’t.
Actually, after re-reading your post, UAH covers 85 North.
Try reading that again.
Surely you wouldn’t suggest GISS has more real coverage than satellites?
As I recall ~60 points is all that’s needed.

Graeme W
September 4, 2010 1:10 am

Anthony and/or Dr. Spencer, can I make a suggestion? The issue of calibration crops up from time to time, and Dr. Spencer made a detailed post on the subject here at WUWT:
http://wattsupwiththat.com/2010/01/12/how-the-uah-global-temperatures-are-produced/
Could either a link to the above post be placed somewhere permanent so it can be referenced whenever the question is raised, or included with all of Dr. Spencer’s posts on the satellite data? That way we’ll hopefully eliminate, or at least reduce, the incidence of these queries about calibration with land temperatures.
Only a suggestion — feel free to ignore it if it’s inappropriate….

Reply
: I put it on the resources page ~ ctm

barry
September 5, 2010 2:47 am

Why is a 20 year period (79 – 98) taken for the ‘average’ with which to compare against when many of the ‘climate scientists’ apparently think some randomly selected 30 year period is the holy grail of references?

The 20-year period was selected, I presume, because, there was not 30 years of data when anomalies were first being calculated against a baseline.
As has been pointed out above, it makes no difference what the baseline is. Keeping it the same makes it a much simpler matter to compare data. If you change the baseline, then every bit of data has to be changed, and the data is somewhat prominent in the blogosphere. It’s the same reason NSIDC stick with their baseline – it makes year-to-year comparisons awkward, especially when having to explain to interested public unfamiliar with base line and anomalies.
Can’t think of any good reason to change the baseline, up down or whatever. Just keeps things straightforward. Reminds me of the argument about imperial and metric. The length is the same, only the standard by which it is measured changes. I guess it would be like the MSM suddenly decding to use using metric scale when reporting in the US – they’d have to spend time explaining what it means in imperial terms anyway.

barry
September 5, 2010 2:58 am

As for GISS. They are still out of sorts with the other 3 records.

Depends what you’re looking at. For the entirety of the satellite record, UAH is the outlier and GISS is closer to the other 2 (RSS and HadCRUt).
http://www.woodfortrees.org/plot/gistemp/from:1979/trend/offset:-0.209/plot/rss/from:1979/trend/offset:0.024/plot/hadcrut3vgl/from:1979/trend/offset:-0.128/plot/uah/from:1979/trend
Not that the deviation is terribly significant. The biggest difference between the trends is 0.03C/decade. Storm in a tea-cup material.