date: Thu, 26 Feb 2004 11:56:46 -0000 from: "Rob Wilson" subject: Fw: When Jones Meets MSU to: Hi Keith, I am on this climate sceptics e-mail group that you might have heard of. Please don't groan. I am only signed on so that I can sit on the fence and see both sides of the argument. The e-mail below just came through and it is very interesting. I have already read about the difference between ground-based temperature data and the MSU satellite lower troposphere temperature data in the literature, but never really thought about it. However, having read this e-mail, I can't help think that IF there is a 'significant' problem with the ground-based data-set, that they suggest, it would partly explain the divergence problems between TR data and temperature data. Any comments? I did not send this e-mail to Phil as I do not know how testy he is on the subject. All the best Rob ----- Original Message ----- From: [1]Willis Eschenbach To: [2]climatesceptics@yahoogroups.com Sent: Thursday, February 26, 2004 10:20 AM Subject: [Climate Sceptics] When Jones Meets MSU A work in progress, offered for your comments and criticisms. w. ______________________________________________________________________________________ There has been a lot of talk, investigation, and speculation about the differences between the Jones (HadCRUT2 combined land and ocean) ground-based temperature data and the MSU satellite lower troposphere temperature data. So I thought I'd look at them to see what I could find. I looked at the 20 year period from 1979 to 1998. Unfortunately, what I found was that the Jones dataset is full of holes. Of the 2,592 cells (5 degrees x 5 degrees covering the world) of the dataset, a full 60% of them are missing one month or more of data. Given this, I don't know how we can really compare the net change in global temperatures of the two sets -- the Jones dataset is trying to give a change in the global temperature using only 40% of the globe. Given that, here's the general picture. [cid:005501c3fc5f$9bee3c40$a7671f3e@Desktop] Fig. 1 - Comparison of satellite, GHCN, and balloon anomalies. From this, we can see that the MSU and balloon data agree closely, while the ground station data are quite different. Having looked at the general trends, here is my first comparison of average temperatures for 1979-1998 of the two datasets, a scatterplot of the two temperatures. I only used cells for which there were full Jones data for the entire period. [cid:005601c3fc5f$9bee3c40$a7671f3e@Desktop] Fig. 2 - Scatterplot of the Jones and MSU full datasets, with linear trend line There were several surprises in this for me. The first was that the MSU temperatures are colder than the Jones temperatures, but not as much colder as I might have expected. The second was the width of the scatter of the data. I had expected a much closer correspondence between the Jones and the MSU data. In some places, for the same MSU temperature the Jones temperatures are as much as 12 degrees apart. The biggest surprise, though, was that a 1 degree difference in MSU temperature does not correspond to a 1 degree difference in Jones temperature, as I had expected. A 1 degree difference in MSU temperature corresponds to a 1.22 degree difference in Jones temperature. Since the linear trend does not reveal the true relationship between the datasets, I took a Gaussian average of the scatterplot. To do this, I converted from Cartesian to Polar coordinates (x,y to r,theta). Then I sorted the data by r, and took the gaussian average of the theta values. Finally, I converted back to Cartesian coordinates. This procedure is necessary to avoid distortion of the gaussian average, especially at the hottest and coldest ends of the data. [cid:005701c3fc5f$9bee3c40$a7671f3e@Desktop] Fig. 3 - Scatterplot of the Jones and MSU data with Gaussian average (red) As you can see, the Gaussian average does not follow the trend line. What can we deduce from its wanderings? First, the temperate regions of the planet, where most of the people live, is where the Jones data is higher than the trend line. This supports the idea that local and urban warming have exaggerated the Jones temperature in these regions. Next, at the top end of the temperatures, the Gaussian average goes steeply upward. Since this means that we are getting much higher Jones temperatures than we would expect, this supports the idea that temperatures in hot city areas and areas like canyons in deserts are giving very high Jones temperatures. Here is a closeup of that region: [cid:005801c3fc5f$9bee3c40$a7671f3e@Desktop] Fig. 3 - Scatterplot of the high temperature end of the Jones and MSU datasets You can see that how the Gaussian average is rising very steeply in the hottest parts of the world. DISCUSSION 1) The wide scatter of data is most likely due to differences in the Jones data, as the MSU data is internally more consistent. There are no areas of the world for which the MSU are very different from the surrounding area, but there are in the Jones data. The MSU data "flows" from area to area while the Jones temperature has discontinuities, especially over the oceans as can be seen below. I have used the baseline average datasets for both the MSU and Jones data (although it is not clear to me how the Jones average dataset was constructed given that 60% of the cells have missing data). [cid:005901c3fc5f$9bee3c40$a7671f3e@Desktop] [cid:005a01c3fc5f$9bee3c40$a7671f3e@Desktop] You can see that the MSU dataset is cooler, going down to -71 degrees and peaking out at about +9 degrees. It is also much more even, as we would expect given that it is not subject to local heating as is the ground record. 2) The signature of urban and local warming can be seen in two ways. One is that the temperatures in the areas above freezing (273 degrees K), where trees, houses and roads are more prevalent, are higher than the trend; on the other hand, at temperatures below freezing they are lower than the trend. Here is Jones temperature vs. deviation from the trendline: [cid:005b01c3fc5f$9bee3c40$a7671f3e@Desktop] The other is that the data are "clumped" along the upper edge of the range, with few outliers, and the bottom of the range has a number of outliers. As there are few local conditions which lower local temperature and many conditions which raise it (trees, windbreaks, buildings, paving, etc.), this suggests that many of the Jones temperatures are reading higher than they should. 3. Given the slope of the trendline, we would expect that temperature changes in the Jones dataset should be larger than those in the MSU dataset. This seems to be the case -- for the 21 year period shown in Figure 1, the annual Jones delta t / annual MSU delta t is 1.25 +/- 0.56 (1 std. dev.). However, this does not explain the rise in the Jones temperature compared to the MSU temperature over the 1980 - 2001 period. ______________________________________________________________________________________ Yahoo! Groups Links * To visit your group on the web, go to: [3]http://groups.yahoo.com/group/climatesceptics/ * To unsubscribe from this group, send an email to: [4]climatesceptics-unsubscribe@yahoogroups.com * Your use of Yahoo! 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