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Post by magellan on May 6, 2009 2:47:03 GMT
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Post by walterdnes on May 6, 2009 3:44:58 GMT
An election-type analogy is that last month, I tried the equivalant of predicting an election the day before. This month, I waited for 25% of the results to come in (i.e. RSS) and adjusted the projections for the other 3 sites accordingly. This cut down the error on the UAH projection by 50%. I do wish UAH would switch over to a newer satellite.
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Post by neilhamp on May 6, 2009 7:54:11 GMT
Keep up the good work walterdnes I for one look forward to your posts each month
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Post by glc on May 6, 2009 9:18:20 GMT
That is a plausible explanation, glc...except that comparing AMSU daily temps to RSS, they don't seem to match February or March very well. And according to the AMSU data, it does look like April was cooler than March...which matches the UAH monthly data better. I'm not sure I follow what you mean. For a start April was warmer than March - it always is. Global temperatures tend to be higher in the NH summer because of the greater warming on land. Give me an example which illustrates your point. Especially when he points out UAH is picking up an extra 28 degrees of the globe and that Spencer is noting the differences exist primarily in that region (near the poles). It's more like 14 degrees. I'm fairly sure that it's only in the SH that RSS has a 70 deg cutoff. The difference between 84 deg and 70 deg represents about 3% of the total surface area of the earth, so it would take a sizeable change in temperature to have a significant affect in the global average. If the whole 70S-84S latitude band cooled by 1 degree this would only affect the global average by ~0.03 deg. It could account for some of the difference, though. But, remember, RSS v UAH is not the main issue. The real puzzler was the apparent discrepancy between UAH and the AMSU daily temperatures. When Roy Spencer wrote "Use the drop-down menu to pick ch5 (AMSU channel 5) which is the channel John Christy and I use to monitor mid-tropospheric temperatures." I made the mistake of thinking that the AMSU data is used to produce the UAH anomalies. It isn't. I'm happy, but I wonder what some of you would have made of things if GISS had done something similar.
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Post by glc on May 6, 2009 9:31:50 GMT
Magellan:
Re: your link to WUWT
If you'd asked me I could have told you that neither RSS and UAH were 'tuned' to surface data. Satellite measurements are totally independent of the surface temperature record. However, I'm a bit at a loss to explain how this is relevant to the subject under discussion.
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Post by magellan on May 6, 2009 12:28:12 GMT
Magellan: Re: your link to WUWT If you'd asked me I could have told you that neither RSS and UAH were 'tuned' to surface data. Satellite measurements are totally independent of the surface temperature record. However, I'm a bit at a loss to explain how this is relevant to the subject under discussion. UAH uses empirically derived calibration procedures. RSS uses climate models. They don't use the same methods for calibration. I'd say that's quite relevant.
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Post by glc on May 6, 2009 12:50:26 GMT
UAH uses empirically derived calibration procedures. RSS uses climate models. What!! Have you a source for this information. I think you're making it up. Why would RSS use a climate model?
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Post by duwayne on May 6, 2009 16:14:33 GMT
The April UAH anomaly seems quite reasonable to me. Month to month variations are largely due to ENSO with a lag time of about 3 to 4 months. The trend line for the UAH anomaly (see prior posts) for 2009 is 0.27C. When ENSO was neutral for 4 months, the average UAH anomaly turned out to be 0.27C as I had predicted months before. For these predictions, I use the seasonal (3 month) ONI numbers for measuring ENSO. I've found that Global Temperatures fluctuate at about 30% of the ONI numbers. So for March, if one uses the October-November-December seasonal ONI of -0.3 times 30% and then use that to adjust from trend (0.27-(0.3X.3) the predicted UAH anomaly is 0.18C versus 0.21C actual. For April, the predicted anomaly again using a 3 month lag time was 0.09C which matches the UAH number. In other instances the predictions have been off by quite a bit, maybe 0.1C or even a little more but I find if it's high for 1 or 2 months, it will then tend to be low by a similar amount for 1 or 2 months. I only spend about 5 minutes a week on the Global Warming stuff, so you can undoubtedly improve upon what I use. But as I've said here previously, it's the reason that I like to use the UAH anomalies for examining the underlying Global Temperature trends.
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Post by magellan on May 6, 2009 16:21:27 GMT
UAH uses empirically derived calibration procedures. RSS uses climate models.What!! Have you a source for this information. I think you're making it up. Why would RSS use a climate model? I've posted this several times, but it appears to have gone over some heads like a lead balloon. 1) It is discussed here: wattsupwiththat.com/2008/03/08/putting-a-myth-about-uah-and-rss-satellite-data-to-rest/2) Verified here: ams.allenpress.com/perlserv/?request=get-document&doi=10.1175%2F1520-0442(2003)016%3C3650%3AAROTMC%3E2.0.CO%3B23) Further verified here (I have the full article): www.agu.org/pubs/crossref/2008/2007JD008864.shtmlLimited time period running trends are created from various microwave sounding unit (MSU) difference time series between the University of Alabama in Huntsville and Remote Sensing System (RSS) group's lower troposphere (LT) and mid troposphere to lower stratosphere channels. This is accomplished in an effort to determine the causes of the greatest discrepancies between the two data sets. Results indicate the greatest discrepancies were over time periods where NOAA 11 through NOAA 15 adjustments were applied to the raw LT data over land. Discrepancies in the LT channel are shown to be dominated by differences in diurnal correction methods due to orbital drift; however, discrepancies from target parameter differences are also present. Comparison of MSU data with the reduced Radiosonde Atmospheric Temperature Products for Assessing Climate radiosonde data set indicates that RSS's method (use of climate model) of determining diurnal effects is likely overestimating the correction in the LT channel. Diurnal correction signatures still exist in the RSS LT time series and are likely affecting the long-term trend with a warm bias. Our findings enhance the importance of understanding temporal changes in the atmospheric temperature trend profile and their implications on current climate studies. Conceded by Tamino, after getting "educated", here: tamino.wordpress.com/2008/10/21/rss-and-uah/UPDATE
Note: Having compared RSS and UAH to the HadAT2 data set, I find that there’s more divergence between RSS and HadAT2 at the 1992 step than between USH and HadAT2. So I withdraw my opinion that the step change represents a reason to prefer RSS over UAH. Am I making it up?
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sol
New Member
Posts: 13
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Post by sol on May 6, 2009 18:18:33 GMT
Magellan, as my first post from being a long time lurker, I'll say that I think I just heard a pin drop. Can I get confirmation from anyone else of what I think I heard?
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Post by tacoman25 on May 6, 2009 18:57:26 GMT
That is a plausible explanation, glc...except that comparing AMSU daily temps to RSS, they don't seem to match February or March very well. And according to the AMSU data, it does look like April was cooler than March...which matches the UAH monthly data better. I'm not sure I follow what you mean. For a start April was warmer than March - it always is. Global temperatures tend to be higher in the NH summer because of the greater warming on land. Give me an example which illustrates your point. Of course April was warmer than March...I was referring to anomalies, which can roughly be ascertained by looking at how the daily AMSU data matches up to previous "averages". Even considering satellite drift, the daily data does not seem to match up well with RSS's monthly numbers.
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Post by kenfeldman on May 6, 2009 23:50:01 GMT
On the difference between the UAH and RSS temps, what is the margin of error on the measurements? The difference seems so small (about 0.1 degrees C) that it's probably within the margin of error.
For climate, the month to month measurements aren't really interesting. What's interesting is the long term trends.
RSS shows a warming trend of 0.155 degrees C per decade. UAH shows a warming trend of 0. 128 degrees C per decade.
Again, not a lot of difference between them, and not much difference between them and the surface temperature trends from Hadley, NOAA and NASA GISS. All show warming of between 0.1 and 0.2 degrees per decade now, which is in line with model projections of warming from AGW. If trends don't increase over the next few decades, you could discard the AGW hypothesis, but a few months of cool temperatures (or a few months of warm temperatures during the next El Nino for that matter) aren't really anything to get excited about.
As to trying to predict what the monthly anamolies will be a few days before they are reported, why make the effort? Is the couple of days between your prediction and the actual report important?
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Post by glc on May 7, 2009 0:37:01 GMT
RSS shows a warming trend of 0.155 degrees C per decade. UAH shows a warming trend of 0. 128 degrees C per decade. Roy Spencer states on his blog that RSS was cooler than UAH in the early days - hence a reason for the april discrepancy and difference in trend. If he's correct, recent trends should be similar. I've done this in a rush, so if someone could check it (I'm off to bed) I'd be grateful. Since Jan 1990, I get the following trends: RSS +0.18 deg per decade UAH +0.17 deg per decade Magellan: I've responded re: stratospheric influence on the other thread. And now I've just spotted this.... I've posted this several times, but it appears to have gone over some heads like a lead balloon. 1) It is discussed here: wattsupwiththat.com/2008/03/08/pu....e-data-to-rest/ What's discussed 'here'? Read the article - then tell me what you think it says.
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Post by glc on May 7, 2009 8:48:52 GMT
Magellan Re: your post(s) An earlier post of yours provides 3 links. I can't access the second of these, so perhaps you can summarise it's content. As for the first and third links - how are they related? Similarly the Tamino link. Can we start from the beginning and take one step at a time. In an earlier, earlier post you povided this link wattsupwiththat.com/2008/03/08/putting-a-myth-about-uah-and-rss-satellite-data-to-rest/ Now what is the point you are trying to make about it?
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Post by glc on May 7, 2009 10:12:21 GMT
UAH v RSS There appears to be an idea floating round that a significant difference exists between UAH and RSS datasets. This is total garbage. It's true there is a step change around 1992. Before 1992, RSS was cooler than UAH whereas since 1992 RSS has been warmer. It might be coincidence, but I wonder if the 'step' is related to the Pinatubo eruption in 1991. Whatever the reason, it almost certainly explains the difference in trends between UAH & RSS since 1979. I'm convinced that there is nothing that UAH & RSS are currently doing with respect to the various necessary data adjustments which is significantly altering the trend difference. To illustrate this, check out the UAH & RSS trends since 1992. www.woodfortrees.org/plot/uah/from:1992/to:2008/trend/plot/rss/from:1992/to:2008/trend I think that's what they call "parallel lines". Just to confirm the similarity in trends. Linear regression (since 1992) gives: UAH +0.22 deg per decade RSS +0.22 deg per decade And just for good measure the surface trends since 1992: GISS +0.24 deg per decade Hadley +0.20 deg per decade Can we now stop all the drivel about fiddling, fudging and other conspiracy nonsense. Magellan: don't let this distract from the WUWT article.
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