By Steve Goddard and Anthony Watts
Some of the excellent readers of the last piece we posted on WUWT gave me an idea, which we are following up on here. The exercise here is to compare GISS and satellite data (UAH and RSS) since the start of 2003, and then propose one possible source of divergence between the GISS and satellite data. The reason that the start of 2003 was chosen, is because satellite data shows a rapid decline in temperatures starting then, and GISS data does not. The only exception to the downward trend was an El Nino at the start of 2007, which caused a short but steep spike. Remembering back a couple of years, Dr. Hansen had in fact suggested that El Nino might turn into a “Super El Nino” which would cause 2007 to be the “hottest year ever.”
The last six years (2003-2008) show a steep temperature drop in the satellite record, which is not present in the GISS data. Prior to 2003, the three trends were all close enough to be considered reasonably consistent, but over the last six years is when a large divergence has become very apparent both visually and mathematically.
Since the beginning of 2003, RSS has been dropping at 3.60C/century, UAH has been dropping at 2.84C/century, and GISS has been dropping at 0.96C/century. All calculations are done in a Google Spreadsheet here:
The divergence between GISS and RSS is shown below. Since the start of 2003, GISS has been diverging from RSS at 2.64C/century, and GISS has been diverging from UAH at 1.87C/century. RSS has been diverging from UAH at minus 0.76C/century, indicating that RSS temperatures have been falling a little faster than UAH over the last six years, as can also be seen in the graph above.
Below is a 250km map of GISS trends from 2003-2008. One thing which stands out is that GISS has large areas with sparse or no coverage. Notably in Africa, Antarctica, Greenland, Canada, Brazil, and a few other places.
Click for larger image
Many of the GISS holes seem to be in blue regions on the map. Here is a post and video of the GHCN station loss over the past several years globally, created by WUWT contributor John Goetz:
Here are two images showing the difference between GISS global coverage in 1978 and 2008:
Click for a larger image
Click for a larger image
There is a tremendous amount of station dropout in 30 years. Dropout is worst in the high northern latitudes, most all of Canada, and about half of Africa. Of particular note is the red band at the southernmost latitude, which “seems” to indicate a continuous coverage there. Of course we know that is not true, given the paucity of stations in the Antarctic interior. Read more here.
By contrast, while it doesn’t hit both poles (neither does GISS) UAH has much broader global coverage as seen below. Could this be part of the explanation for the divergence between GISS and satellite data? What do the readers think?
![[Image]](https://i0.wp.com/discover.itsc.uah.edu/amsutemps/browse/AMSU_A_15.latest.a_04.png?resize=520%2C278&quality=75)
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![[Image]](https://i0.wp.com/discover.itsc.uah.edu/amsutemps/browse/AMSU_A_15.latest.d_04.png?quality=75)
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How different would the GISS graph appear, if it showed a -3.6C/century cooling trend over the last six years? For reference, the steep GISS warming trend from 1980 to 2002 was about 0.4 degrees.
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[snip – no more posts from you until you apologize for the last one on the other thread. – Anthony]
How does the divergence look when you compare latitude bands or by continents? That would allow you to look at station dropouts on a regional basis to see if that was correlated.
Since there is a weather station at the Amundsen-Scott base right at the South Pole, GISS should actually cover this pole. The northernmost and still operational weather station, on the other hand, is probably located at about 82N, quite far from the pole.
The Hadley/CRU temperature data set probably also diverges from GISS, since it show world mean temperatures dropping the last couples of years at almost the same rate as the satellite data sets.
REPLY: I had thought about Amundsen-Scott base, but the the red band seemed so large in area, compared to other stations, that it seemed unrealistic to treat it as a single station. Perhaps one station is being distorted in the map resentation. Mercator projection does that. – Anthony
There was this graph at Icecap. http://icecap.us/images/uploads/Stationdropout.jpg
What would it take to plot the temperature history prior to 1990 using only the post 1990 site data’?
Jim N
How is it that they have trend data for 2003-2008 for many areas that are blank in the 2008 map (e.g. northern Canada)?
Also be aware that the use of this type of map projection is quite misleading, making the polar regions look massively larger and more important than they really are.
DJ,
The spreadsheet linked in the article shows the standard deviation for the GISS minus RSS plot = 0.09. The trend line for the graph shows 1.6 standard deviations, across the six year period. Reasonably good statistical significance.
If you want to make any further calculations, please feel free to make your own copy the spreadsheet, and report back any findings you feel are important. That would be a constructive way to get involved in the conversation.
Thank you very much
Well the thing that stands out like a sore thumb on the first GISS chart is the anomalous warming right across Russia. If that bright red spot on eastern Svalbard happens to be another Russian weather station reporting rather than a Norwegian one, I would be even more suspicious.
I hadn’t realised just how sparse GISS coverage is. Your graphic is truly GRAPHIC on this point. Why would anyone prefer it to HADCRUT. It’s time GISS either invested some serious money on increasing coverage or gave up.
The color scales are weighted to warming.
There are 5 colours of positive anomalies in the range 0.2 to 8.2, but only four colours of negative anomalies in the range -0.2 to -8.3. There is an extra white colour on the negative side which is the range -0.2 to -0.5.
So the world map is distorted towards the positive side.
Just how many of those white areas should in fact be blue?
Speaking as a person with only a high school stats background, I wonder – how many data sets are necessary to validate which (if any) temperature record is the outlyer?
For example in my world (aviation), we use GPS extensively, but only if we have data from 5 or more satellites. With that many discrete signals, the software in the GPS receiver looks at each set of sat data, and can accurately identify and discard a single bad signal. My question, then, is this – are 4 separate temperature records enough to identify one of them as spurious, to a high level of confidence?
One thing that strikes me as odd is that the GISS map from April has more gray area than the trend map (which must include April.)
Do the stations sometimes appear and disappear? If so, how can they be included in the trend data?
On a more serious note, I plotted RSS, GISS, and UAH average annual temperatures from 1979 to 2008 inclusive. The linear trends of the three indicate that RSS and GISS agree fairly well and that it is UAH that is not rising as fast. I was personally disipointed that I could not share the plot with you (I am not that computer savvey) but I used Excell on the raw monthly data (a spreadsheet I worked out last week).
I would imagine that woodfortrees can show nearly the same result. Here is the woodfortrees plot (with GISS offset -.24 so all three are about equal at near 1990)
http://www.woodfortrees.org/plot/uah/last:360/trend/plot/gistemp/last:360/trend/offset:-.24/plot/rss/last:360/trend
I am so happy you’ve done this, Anthony and Steve. I’ve been wondering about this but am mathematically challenged. Kudos to you both! Between the fudging of the figures and temperature station dropout, there’s a lot to answer for from Hansen et al.
Hansen seems to think Obama is a one term President since he believes Obama must make the necessary steps towards economic ruin within his first term. I think the President-elect needs to see this… and quickly before he does great harm to the country.
But you just told us that This 1980-2008 discrepancy between GISS and UAH is important, as it is nearly equal to the claimed warming trend since 1980. , now it is Prior to 2003, the three trends were all close enough to be considered reasonably consistent, but over the last six years is when a large divergence has become very apparent both visually and mathematically.
Extrapolating, will the next post be on how GISS has diverged from the satellite record since Christmas? 😉
Seriously, as I pointed out earlier, the satellite record is more sensitive to ENSO events,and this seems to me a more plausible explanation is that the chart is than any changes in coverage, to repeat myself there was a similar divergence of the opposite sign leading up to the 1998 El Nino, shown clearly in this here chart from a post by Eli that shows pretty conclusively how GISS-RSS delta peaked during the 1998 El Nino, so it seems more sensible approach to look to the recent La Nina as a leading cause of this, so far, short-lived divergence in the other direction.
Perhaps a regression analysis of the ENSO index vs the divergence would be instructive?
Bye for Now,
JP
Slightly more coherent version:
But you just told us that This 1980-2008 discrepancy between GISS and UAH is important, as it is nearly equal to the claimed warming trend since 1980. , now it is Prior to 2003, the three trends were all close enough to be considered reasonably consistent, but over the last six years is when a large divergence has become very apparent both visually and mathematically.
Extrapolating, will the next post be on how GISS has diverged from the satellite record since Christmas? 😉
Seriously, as I pointed out earlier, the satellite record is more sensitive to ENSO events,and it seems to me a more plausible explanation than any changes in coverage, to repeat myself there was a similar divergence of the opposite sign leading up to the 1998 El Nino, shown clearly in this chart chart from a post by Eli that shows pretty conclusively how GISS-RSS delta peaked during the 1998 El Nino, so it seems more sensible approach to look to the recent La Nina as a leading cause of this, so far, short-lived divergence in the other direction.
Perhaps a regression analysis of the ENSO index vs the divergence would be instructive?
Bye for Now,
JP
Slightly more coherent version with working link. Blimey.
But you just told us that This 1980-2008 discrepancy between GISS and UAH is important, as it is nearly equal to the claimed warming trend since 1980. , now it is Prior to 2003, the three trends were all close enough to be considered reasonably consistent, but over the last six years is when a large divergence has become very apparent both visually and mathematically.
Extrapolating, will the next post be on how GISS has diverged from the satellite record since Christmas? 😉
Seriously, as I pointed out earlier, the satellite record is more sensitive to ENSO events,and it seems to me a more plausible explanation than any changes in coverage, to repeat myself there was a similar divergence of the opposite sign leading up to the 1998 El Nino, shown clearly in this chart from a post by Eli that shows pretty conclusively how GISS-RSS delta peaked during the 1998 El Nino, so it seems more sensible approach to look to the recent La Nina as a leading cause of this, so far, short-lived divergence in the other direction.
Perhaps a regression analysis of the ENSO index vs the divergence would be instructive?
Bye for Now,
JP
gary plyler (14:16:30) : “On a more serious note, I plotted RSS, GISS, and UAH average annual temperatures from 1979 to 2008 inclusive.”
Sorry, that manipulation doesn’t work for me. Straight line fits over a long interval remove information that clearly shows in unsmoothed data. The topic here is recent trends; using the 1979 ff data is an OT red herring.
“Below is a 250km map of GISS trends from 2003-2008. One thing which stands out is that GISS has large areas with sparse or no coverage. Notably in Africa, Antarctica, Greenland, Canada, Brazil, and a few other places.”
-No, one thing that stands out is the dismal coverage of oceans, more than two thirds of earths surface. Africa is bad but the ocean coverage is worse.
Gary,
It is interesting that RSS tracked GISS closely through 2002, and has started diverging over the last six years, as explained here. Do you have any ideas what might be causing that?
“It’s time GISS either invested some serious money on increasing coverage or gave up.”
GISS doesn’t set coverage criteria. They get their input data from NOAA. It would be up to NOAA to look into why so many stations are falling out of the network.
But you will notice that the stations fall out of the network in “steps” and there is no step change in the differences which means that the cause of the divergence is likely to be something other than the missing stations … such as their “adjustment” scheme.
Steven Goddard,
Do please try to figure out the basic and very obvious fact that the lower troposphere temperatures respond more to ENSO variations than does the surface composite, This was just as obvious in the opposite direction in 1998, Honestly, you could not give more sustained evidence of confirmation bias than you are doing. This is just entirely ridiculous and,frankly, reduces the ‘sceptic’ case to a matter of desperate data mining. Try to approach this with a scientific state of mind, rather than setting out to ‘prove’ your prejudices! Is it really the case that the ‘best science blog’ is running analyses of this kind, without the most basic suggestion of understanding what is being analysed?
REPLY: I grow rather tired of someone telling me what sort of analyses this blog should and should not do, particularly from someone who uses two different names. The idea of this blog is to explore things that interest me, the contributors, and the readers. This divergence interests us, and if it leads to a better understanding, then that is what we shall do. Often times people pointing out weaknesses or alternate ideas are the best way to learn, and I welcome pointing out mistakes or suggestions for other ways to analyse the data, sans the sort of snark you display.
Perhaps you are right, perhaps you are not, but, have you anything to illustrate your point about the GISS surface and ocean record being more sensitive to ENSO, other than an ad hominem taunt? If so, show it. Let’s discuss it and learn about it. – Anthony Watts
JP,
I don’t think the last six years have been marked by any particularly strong ENSO events, other than Dr. Hansen’s mention of the possibility of a “Super El Nino.” It is difficult to see how ENSO could be causing the divergence with RSS.
Now that Dr. Hansen has forecast that 2009 may be the “warmest year ever” due to his expectations of an El Nino, we will have to pay particularly close attention to the divergence in the coming months, as it is likely to get much larger.
Hmm. But wasn’t the drop in temperatures for 2007/early 2008 even greater for GISS than for UAH or RSS?
The radical departure does not come until mid-2008. Moreso than at any other point in the graph.
What is the reason for all of those stations dropping out?
Steven Talbot,
Suppose that we do get a strong El Nino as Dr. Hansen has forecast for this year. Using your “satellites are more sensitive to ENSO” theory, we should see a huge swing in the GISS minus RSS numbers from positive to negative (as in 1998.)
Keep your eye out for that!