Update: The gross divergence in October data reported below between the various metrics is explained by an error, as reported at the bottom. The basic premise of the post, that real scientific work should go into challenging these measurement approaches and choosing the best data set, remains.
The October global temperature data highlights for me that it is time for scientists to quit wasting time screwing around with questions of whether global warming will cause more kidney stones, and address an absolutely fundamental question: Just what is the freaking temperature?
Currently we are approaching the prospect of spending hundreds of billions of dollars, or more, to combat global warming, and we don’t even know its magnitude or real trend, because the major temperature indices we possess are giving very different readings. To oversimplify a bit, there are two competing methodologies that are giving two different answers. NASA’s GISS uses a melding of surface thermometer readings around the world to create a global temperature anomaly. And the UAH uses satellites to measure temperatures of the lower or near-surface troposhere. Each thinks it has the better methodology (with, oddly, NASA fighting against the space technology). But they are giving us different answers.
For October, the GISS metric is showing the hottest October on record, nearly 0.8C hotter than it was 40 years ago in 1978 (from here).
However, the satellites are showing no such thing, showing a much cooler October, and a far smaller warming trend over the last 40 years (from here)
So which is right? Well, the situation is not helped by the fact that the GISS metric is run by James Hansen, considered by skeptics to be a leading alarmist, and the UAH is run by John Christy, considered by alarmists to be an arch-skeptic. The media generally uses the GISS data, so expect stories in the next day or so trumpeting “Hottest October Ever,” which the Obama administration will wave around as justification for massive economic interventions. But by satellite it will only be the 10th or so hottest in the last 30, and probably cooler than most other readings this century.
It is really a very frustrating situation. It is as if two groups in the 17th century had two very different sets of observations of planetary motions that resulted in two different theories of gravity,
Its amazing to me the scientific community doesn’t try to take this on. If the NOAA wanted to do something useful other than just creating disaster pr0n, it could actually have a conference on the topic and even some critical reviews of each approach. Why not have Christy and Hansen take turns in front of the group and defend their approaches like a doctoral thesis? Nothing can replace surface temperature measurement before 1978, because we do not have satellite data before then. But even so, discussion of earlier periods is important given issues with NOAA and GISS manual adjustments to the data.
Though I favor the UAH satellite data (and prefer a UAH – Hadley CRUT3 splice for a longer time history), I’ll try to present as neutrally as possible the pros and cons of each approach.
GISS Surface Temperature Record
+ Measures actual surface temperatures
+ Uses technologies that are time-tested and generally well-understood
+ Can provide a 100+ year history
– Subject to surface biases, including urban heat bias. Arguments rage as to the size and correctability of these biases
– Coverage can range from dense to extremely spotty, with as little as 20KM and as much as 1000KM between measurement sites
– Changing technologies and techniques, both at sea and on land, have introduced step-change biases
– Diversity of locations, management, and technology makes it hard to correct for individual biases
– Manual adjustments to the data to correct errors and biases are often as large or larger than the magnitude of the signal (ie global warming) trying to be measured. Further, this adjustment process has historically been shrouded in secrecy and not subject to much peer review
– Most daily averages based on average of high and low temperature, not actual integrated average
UAH Satellite Temperature Record
+ Not subject to surface biases or location biases
+ Good global coverage
+ Single technology and measurement point such that discovered biases or errors are easier to correct
– Only 40 years of history
– Still building confidence in the technology
– Coverage of individual locations not continuous – dependent on satellite passes.
– Not measuring the actual surface temperature, but the lower troposphere (debate continues as to whether these are effectively the same).
– Single point of failure – system not robust to the failure of a single instrument.
– I am not sure how much the UAH algorithms have been reviewed and tested by outsiders.
Update: Well, this is interesting. Apparently the reason October was so different between the two metrics was because one of the two sources made a mistake that substantially altered reported temperatures. And the loser is … the GISS, which apparently used the wrong Russian data for October, artificially inflating temperatures. So long “hottest October ever,” though don’t hold your breath for the front-page media retraction.
Um… 2008 – 1978… I’m pretty sure that’s 30 years. Am I missing something?
“spending hundreds of billions of dollars, or more, to combat global warming, and we don’t even know its magnitude or real trend,”
If they figured out the magnitude and trend, then there’d be something to judge the success of their pogroms, err, I mean, programs, against. Can’t have that, now, can we? It would just be a distraction from what the programs are all about.
and you wonder what was programmed into the Super Computers for Hansen’s long range forcasts!
These guys need to realize that Climate forcasting has to take into account of ALL parameters! Not the ones associated with what they think it might be. People, it’s all Theory, period! No proof!
Very interesting. Differences of this magnitude are not likely to be random. If I were a climate scientist I would insist that the discrepancies be resolved very quickly, before the scientific credibility of climate science is destroyed beyond its current low levels.
In your cons for GISS you forgot to mention the way Hansen fills in missing data. This meanst that the anomaly for every month in the entire record can change willy-nilly at any given time.
So although, in this release, October 2008 is the hottest October ever, by next month it could be the coldest.
For instance, when the figures for August 2008 were released in early September, the anomaly was 0.39. This was revised to 0.50 when September’s figures were released and is now back to 0.39.
So, how warm was August 2008? And when can we finally trust the figure?
“NASA’s GISS uses a melding of surface thermometer readings around the world to create a global temperature anomaly” – and it also uses satellite measurements for the oceans.
“NASA fighting against the space technology” – um, no. No-one is ‘fighting against’ space technology, especially not NASA.
“But they are giving us different answers.” – for individual months, yes. In terms of what they are telling us about climate change over the past thirty years, they are giving us exactly the same answer.
As they say in the news biz, there’s a “developing story” wrt to the GISS October numbers in the comments section of this post.
http://wattsupwiththat.com/2008/11/10/giss-releases-october-2008-data/
If true, looks like an honest mistake, but one wonders if they’d have checked a little more carefully if unusual cooling was shown in the monthly number.
The GIGO nature of surface data is indisputable.
Hansen is the leading partisan working as an academic, and controls the surface data.
My bet is that Hansen & co. are seeking a diversion from the record pace of Arctic ice growth.
GISS has used SEPTEMBER averages for October…. The October anomaly is wrong…. It’s Septembers numbers.
Scientists need to be more accountable for their mistakes and support of political policies….. Peoples livelihoods get wiped out by legislation based on this kind of bad information/science…. Where there is one mistake such as this, there is probably a whole culture of bias behind it. To produce an outlier such as this and not recognize it for what it is…. Is to be ideologically blinkered.
Jennifer | November 10, 2008 at 04:14 PM
“In terms of what they are telling us about climate change over the past thirty years, they are giving us exactly the same answer.”
So +0.8 is exaclly the same as +0.4 ?
You seem to be a robotic zelaot.
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The GISS increase isn’t either exaclly the same as a steady October mean temperature?
Actually GISS has the last 30 years about a +0.1 degrees offset compared with both satellite data (and partly compared with Had CRUT). This makes as much GISS offset as Patrick and McKintrick a year ago suggested in the study here:
http://www.spectator.org/dsp_article.asp?art_id=12492
http://www.uoguelph.ca/~rmckitri/research/jgr07/M&M.JGRDec07.pdf
Can Hansen make +2 degrees C, according to the models, if the temperature falls with 1 degrees C? Some progressives may hope: “Yes he can!”, and fear media don’t care.
(When will Hansen retire? Not before Kyoto decision next year I guess.)
I understand that GISS uses satellite data for its estimates of sea surface temperatures. I note that oceans generally have missing data in the GISS October 2008 Graph (http://data.giss.nasa.gov/cgi-bin/gistemp/do_nmap.py?year_last=2008). Since oceans cover 70% of the earth, one could wonder about the impact on GISS by missing the ocean data. Also, even more intriguing for me, GISS seems to have data on oceans when there is an island in the area! How far into the ocean does GISS assume the island temperature to be representative of SSTs — thereby wiping out the need for satellite information? It is well known that the quality control for surface thermometers used by GISS is horrible. In the past, I saw much similarity in GISS, RSS, HadCrut and UAH temperature trends in the last 29 years. Now I am noticing a definite divergence between GISS and satellite data. (Going back farther than 29 years, GISS has always been suspect because of its adjustments. It has often been reported that HadCrut does not release its methodology, so that undermines its credibility if one had to rely on it alone.)
What would it cost to develop and deploy a simple “surface temperature measurement pod” that could be deployed globally to report automatically via satelite temperature measurements made using an single, agreed-upon measurement technology and data processing protocol? Measurements could be downloaded to multiple ground sites to be made available to the public via the internet. True, both Hansen and Steve McIntyre would be out of a job, but at least the arguments over data capture, processing, etc. might end.
Accurate, consistent measurement would be valueable not only in determining what’s really going on, but in the off chance that skeptics loose the current debate, we could begin to measure the results of any climate reenginerring programs and hold the alarmists and politicians accountable for the havoc they may wreak.
Re: comparison of GISS data and MSU data
Actually the GISS data is not all surface data. According to Dr. Hanson’s 2005 paper, to get a temperature reading from all grids, computer generated temperatures are entered as the temperature for grids that do not have a weather station. This means that the temperature anomaly registered for some grids in areas like Russia, parts of Africa, the Antarctic and Arctic are highly suspect and probably have a warm bias. There is so evidence this practice was ever changes and the discrepancy between UK-Hadley data and GISS data seems to confirm this.
Magnus Andersson: with your question about 0.8 and 0.4, it’s almost like you think that drawing a line from the first point to the last would be a valid way to characterise a trend. Please clarify. And you will find, if you do the calculations, that there is no offset between GISS and satellite measurements when the anomalies are quoted relative to the same base period.
Suzanne Morstad:
You have a valid concern. In fact, one of the stations that GISS uses has been closed for 12 years, but the GISS algorithm calculates a value for it each month.
I am greatly intrigued by the question of to what degree GISS uses satellite data for oceans and to what degree its ocean data comes from surface stations on islands and the coasts. We know that for the Arctic Ocean, GISS uses surface stations that are heavily subject to micro issues such as nearby heat sources. On some islands and some coasts, UHI issues may also be a problem.
So far, no answer from RealClimate.
“it’s almost like you think that drawing a line from the first point to the last would be a valid way to characterise a trend. Please clarify.”
A trend is characterized by its magnitude as well as its direction, and an increase by 0.2 degrees C isn’t exactly an increase by 0.4 degrees C.
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“no offset between GISS and satellite measurements when the anomalies are quoted relative to the same base period”
If that is correct for any base period then the GISS record is identical to the satelite record, which is of cource not the case. If you’re right you have to prove that there is no difference for all time intervals.
One can visually see the difference of 0.2 degrees C in distance between 1980 and 2006 in e.g. this graph:
http://farm4.static.flickr.com/3160/3018086463_83af7e71c8_o.png
Magnus: still not clear what trends you are deriving and how. You can’t just draw a line from the first point in a time series to the last.
I am right about there being no offset between the datasets. You can verify this easily. Download the monthly anomalies for all the major temperature measures, choose any suitably long reference period you like, scale each dataset so that the mean anomaly in the reference period is zero, then plot them.
Urban Heat Island Effect.
Here is a comparison between urban and rural sites that are within 100 km of each other across the US. This covers 111 years of data.
http://www.youtube.com/watch?v=LcsvaCPYgcI
Jennifer:
I’m tired of your repeated annoying idea that I don’t know how a trend is calculated (or the math behind it) but I think this proves you’re wrong. Please show me your figures.
http://www.woodfortrees.org/plot/gistemp/from:1979/to:2007/trend/plot/uah/from:1979/to:2007/trend
Magnus: what is that graph supposed to show us? If it’s the offset you’re showing, well, obviously, if you measure the temperature anomaly relative to two different periods in your two datasets, there will be an offset. If it’s the slope you’re showing, well, you need to go one step further and calculate the errors on the derived trends. Are they statistically different? You might also wish to plot GISS vs. HadCRUT and GISS vs. RSS.
We skeptics are taking all this far too seriously. The power of words and suggestion are indeed very powerful. We must therefore be artful and playful and not use alarmist terminology to debunk……. “Gullible” Warming.