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State of the Climate

  1. Sep 16, 2009 #1

    Xnn

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    http://www.ncdc.noaa.gov/sotc/?report=global

    In summary, the climate is returning to record high temperatures.
     
  2. jcsd
  3. Sep 16, 2009 #2
    RSS seems to have other ideas:

    http://www.remss.com/data/msu/monthly_time_series/RSS_Monthly_MSU_AMSU_Channel_TLT_Anomalies_Land_and_Ocean_v03_2.txt [Broken]

    Last row august 2009, first column, anomaly in between -70 and +82.5:

    0.270 degrees, giving this plot:

    sc_Rss_compare_TS_channel_tlt_v03_2.png

    Source: http://www.ssmi.com/msu/msu_data_description.html#figures
     
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  4. Sep 16, 2009 #3

    sylas

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    Actually, they are not measuring the same thing. You are quoting TLT figures; which means temperatures in the lower troposphere. You should expect correlations, but it's still not the same as the surface anomaly. In particular, the 1998 peak seems to show up particularly strongly in the troposphere.

    It's all a part of the whole picture, but it's not a case of other ideas so much as another aspect of the climate system.

    Cheers -- sylas
     
  5. Sep 16, 2009 #4
    UAH actually has data going back to August 1998 and you can plot out CH04 (near surface layer). As near as I can tell August 1998 and August 2009 are almost the same. I wouldn't draw any conclusions from this one way or the other, except as tending to support the idea that we are going into another El-Nino. Of course, since I'm a lukewarmer, it doesn't exclude some warming either.

    Generally speaking, I find it poor procedure to extrapolate based on a sample size of one.

    http://discover.itsc.uah.edu/amsutemps/amsutemps.html" [Broken]


    Select CH04 and 1998 and 2009 and click redraw.
     
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  6. Sep 16, 2009 #5

    sylas

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    Can you clarify what you mean by "sample size of one"? I'm not sure what you mean by this. These data are timeseries, for which is what you use to try and find trends.

    This data from UAH looks very similar to what Xnn is reporting. 2009 is about the same as 1998, as Xnn has quoted from the NCDC analysis; and, if you go on to look at September, the UAH data is showing 2009 pulling well away from 1998. You can select just 1998 and 2009 for plotting with the page you've cited, which makes the comparison easier.

    This is a satellite measure, using microwave sounding. There are significant uncertainties associated with this data, and the differences between RSS and UAH products is all to do with how the raw data is processed. There are particular difficulties with calibrating and combining satellite data, and the uncertainties are generally a bit larger than what you can obtain with surface data.

    The data on the page you have cited is from one satellite: NOAA-15, launched in May 1998. It appears to be from channel 4 of the AMSU-A unit (Ref: AMSU-A instrument guide at NASA). This should be primarily a surface temperature, but note that the instrument is simply looking at brightness at a particular frequency -- 52.8 GHz, with a bandwidth of 0.4 GHz.

    I find it a bit curious that they are using a single channel in this way, but the references with the page are not easy to check. They appear to cite wikipedia for describing the AMSU units.

    Note that comparisons between 1998 and 2009 with this satellite may include drift effects. There's a fair bit of work done by the researchers at UAH and RSS to identify and correct for these effects; but it requires using several satellites. So even though the microwave sounding data does appear to back up what Xnn is reporting from the NCDC surface analysis, I'd be cautious with this plot of the NOAA-15 satellite only.

    Cheers
     
    Last edited: Sep 16, 2009
  7. Sep 18, 2009 #6
    I was referring to the original press release that started to the thread. I find it annoying when people say that month X is the Y hottest or coldest in our records and other people seem to think that proves or disproves something. As you say, the time series data is what is important. Monthly and even yearly results are just data points.
     
  8. Sep 18, 2009 #7

    sylas

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    OK, I understand what you mean... and I agree. A new warmest month, by itself, doesn't mean a whole lot; and I don't think anyone is drawing major conclusions from a single new high.

    It is an expectation of conventional climate science that we are going to have new records for the global average temperatures showing up regularly over the next few decades, and probably beyond unless something unexpected happens. But that's really a secondary consequence of the longer term underlying trend; and we knew about the trend before this new warm month came along. What is perhaps more interesting... because it is harder to predict... is the shorter term ENSO cycle ... La Nina and El Nino. It seems we are moving into the next El Nino, and that this is projected to continue to mature. That's bad news here in Australia; we watch this cycle closely because it tends to bring drought.

    Cheers -- sylas
     
  9. Sep 18, 2009 #8
    Aren't you guys already in a drought?
     
  10. Sep 18, 2009 #9

    sylas

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    Exactly. There was a bit of rain a while ago, but if it sets in again strongly we are in trouble.

    There's a fair bit more background information at Drought, at Australian Bureau of Meteorology.
     
    Last edited: Sep 18, 2009
  11. Sep 18, 2009 #10

    Evo

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    Staff: Mentor

    State of the Climate
    National Oceanic and Atmospheric Administration
    National Climatic Data Center

    http://www.ncdc.noaa.gov/sotc/index.php

    Some parts of the world are getting colder, the US, for example. This is important to take into consideration when people come up with crazy ideas to drop temperatures.
     
    Last edited: Sep 18, 2009
  12. Sep 19, 2009 #11

    vanesch

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    Yes, but from the same link:

    As others said, all this, by itself, doesn't mean much, as it is anecdotical. Individual changes are well within the variability of the weather.

    What matters are long-term trends. Whether, statistically, yearly results are systematically more and more present in the higher percentiles. Also, any projected change doesn't mean an uniform warming ; for instance, if ever the gulf stream alters, Western Europe might get much colder.
    We'd need 100 years extra of data taking to be sure :tongue:
     
  13. Sep 19, 2009 #12

    Astronuc

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    We received about 18.2 inches (46 cm) of rain since June 1 through Aug 15 - about 6 inches more than normal, according to the local newspaper. The amount of rain this summer is the highest it's been since 20.8 inches fell from June 1 to Aug. 31 in 1975, said Jessica Rennells, a climatologist at the center.

    The apparent cause: The jet stream shifted

    A local wildlife pathologist mentioned that the sea surface temperatures near NY were higher than normal or some long term average, so the combination of cool air and warm ocean gave as more rain than normal for this period. But - we didn't have flooding, since the rain was distributed over a longer period.

    Last year we had relatively dry weather. And the year before that, we were under drought conditions.
     
  14. Sep 19, 2009 #13

    Evo

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    There is undeniably an overall upward trend with periods of drops, more noticeable in certain parts of the world. Right now I am enjoying the colder weather in the US the last 4 years, although it's been hurting the crops, especially the wheat here in the US heartland.

    When the NCDC claimed that ocean surface temperatures have increased, isn't this due, in part, to them dropping the satellite data and changing the data that they use for their measurements? How much of a change is there really, and based on what? Aren't they comparing data based on the new way they measure against the old way they measured? I'm asking seriously, I just read a bit and don't know how they can make such a change without saying, ok, from now on, this is the data we'll use, so we're starting over. Weren't most of the earlier ocean temperature readings based on satelite?

    Here is an explanation of how great using the satellite data is
    http://cfpub.epa.gov/eroe/index.cfm?fuseaction=detail.viewMeta&ch=50&lShowInd=0&subtop=315&lv=list.listByChapter&r=203629 [Broken]

    But the NCDC decided to throw it out in July 2009 because it was showing a decrease in global temperatures.

    http://www.ncdc.noaa.gov/oa/climate/research/sst/papers/merged-product-v3.pdf [Broken]
     
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  15. Sep 20, 2009 #14
    Evo,

    They removed it from the extended data set.

    It is still part of the monthly and yearly analysis.
     
  16. Sep 20, 2009 #15

    Xnn

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    They are saying that the new analysis is an improvement since it excludes some historically under sampled areas that were responsible for excessive dampening of global temperatures. In other words, there are some areas of the world that had sparse historical data that was of questionable value.

    Anyhow, with both the old and new versions, yearly rankings of global temperatures are just about the same. 2005 is still the warmest year with 1998 being second warmest. In addition, the 10 warmest years (out of 127) still occurred in the last 12 years.

    The new analysis actually results in most of the warmest years cooling off by about 0.01C. 2005, 1998 and 2002 being cooler by about 0.01C compared to the older version of software while 2003 stays the same.

    The biggest differences I can see is 2003, which by staying the same has moved up from being the 4th warmest to being the 3rd warmest and 1999 which moved from 9th warmest to 10th warmest since it's temperature was reduced by 0.03C.
     
  17. Sep 21, 2009 #16

    Evo

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    No, it's not.
     
  18. Sep 21, 2009 #17
    You may be right that they have removed all the satellite data. But not in July 2009, but in October 2008.

    However you are misinterpreting their motive.

    Satellites have a cool bias due to clouds and aerosols. When there is not enough buoy and ship data available the bias can not be adjusted. Including the satellite data creates a cold bias that is not reflective of the actual SST when in situ data is sparse.

    http://www.ncdc.noaa.gov/oa/climate/research/sst/papers/SEA.temps08.pdf [Broken]
     
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  19. Sep 21, 2009 #18

    sylas

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    Yes, it is.... although we're going to need more than a simple yes it is not it isn't to sort out what is going on.

    Skyhunter is correct in saying "it is still part of the monthly and global analysis". But note it is only used in a part of the analysis; and has been removed from other parts.

    Evo is describing correctly a change made in July 2009 (not October 2008) which means satellite data is not used for sorting out the long term trends, described in the opening sections of the regular state of the climate reports.

    Everyone agrees that the satellite data is removed from the ERSST data set. They now use version ERSST.v3b, with no input from the satellites. There are, however, other datasets considered within the whole analysis and satellite temperature measurements still have an important role.

    Different instruments have different associated issues. Satellite data is very good for looking at regional differences and short term variation, but it has significant problems with long term trends, because of the nature of satellites. They tend to decay slightly in orbit and in behaviour of instruments, and there's no way to get up there and fix them. The best you can do is calibrate, and identify and remove the biases. The original renewed dataset ERSST.v3 did use bias adjusted satellite data, but it was later removed in ERSST.v3b because the tiny residual biases that were apparently a problem for some users. (Added in edit. As Skyhunter notes above; satellites also can pick up spurious signals from the atmosphere.)

    The descriptions given by Evo for why the data was removed are true enough, but could easily be misunderstood. She said:

    The explanation for how great satellite data is omits to mention the problems with satellite data. The description of why it is omitted is incomplete. It gives the misleading impression that the data was removed simply because it showed a result they didn't like.

    That would, of course, be totally unacceptable as a reason for removing satellite data.

    Satellite data is known to have a bias, which is understood and measured and accounted for when it is used in a dataset. What is used (when it is used) is called a "bias adjusted" satellite record. The real reason that the data was removed is a tiny residual bias; and the additional inaccuracy was a problem for some users. As Xnn has noted, the effect is very small. But it is an inaccuracy and a source of bias from non-temperature related artifacts of the satellite data.

    The data set ERSST.

    A formal description of the new version of this data set is given in
    • Smith et. al. http://www.ncdc.noaa.gov/oa/climate/research/sst/papers/Merged.Recon.v8.pdf [Broken], in J. Climate, 21, pp 2283-2296, doi:10.1175/2007JCLI2100.1
    This paper describes the situation prior to October 2008, in which the bias adjusted satellite data was a part of the data set ERSST.v3. Figure 4 of the paper shows the small residual bias that results from this. Then, in October 2008, the satellite data was removed altogether, as described in the brief note cited previously: Summary of Recent Changes in the Land-Ocean Temperature Analyses. It indicates that the dataset version ERSST.v3b has this satellite data omitted, and explains why this was done.

    Added in edit: In July 2009 the regular monthly analysis switched from version 2 to version 3b of ERSST.

    Hence, whereever ERSST is used in the analysis, satellite data has now been removed.

    The NCDC monthly and yearly analysis

    For reference, here is the State of the Climate Global Analysis for July 2009, which is the first to use ERSST.v3b.

    Much of the information in the analysis is based on the surface measurements, which are more reliable for trends from year to year; and in this case the satellite data is not used. If it had been used the differences would have been tiny in terms of degrees, and would have resulted in some changes in the rank of years or months that are so similar that this changes the ranking. (In my opinion, the ranking data is not very useful. It has popular appeal, but that's all.)

    Other parts of the analysis that do use the satellite data for sea surface temperature measurements are the ENSO SST analysis. This does not use the ERSST dataset, but the OISST data... standing for "optimum interpolated". This does use bias adjusted satellite data.

    It's not hard to guess why -- but for completeness note that this paragraph is my own supposition and not referenced to the NCDC. ENSO analysis is about the all important southern oscillation and the La Nina El Nino cycles. For this, you really want to have high resolution data over the whole ocean. The trends from year to year are not actually all that significant, and so the small biases from satellite data don't matter much. What matters are the differences between one part of the ocean and the other... and this is where satellite data excels. (Added in edit. On reflection, Skyhunter reminds me of the other satellite problem; mixture of surface and atmospheric signals, and this bias still needs to be removed. And it is; as best they can manage.)

    In any case, the OISST analysis is described here: http://www.ncdc.noaa.gov/oa/climate/research/sst/oi-daily.php [Broken]. The acronyms AMSR and AVHRR are for satellite instruments, and NOAA-17 and METOP-A are satellites.


    Cheers -- sylas

    ------------------------

    Added in edit: Skyhunter and I replied at the same time, so here's a postscript on his response:

    The removal was in July 2009, and it did remove all the satellite data from the ERSST data. Yes indeed... the satellite data was removed from ERSST in October 2008. Even so, satellite data is still being used in the state of the climate monthly reports, where the OISST data is used.

    Yes, Evo's description of the reasons was misleading. Satellite data is not removed just because they didn't like the result.

    In fact, removing the satellite data had a negligible effect on the global trend.

    The cold bias of the satellite record is a well known artifact of the instruments used, which give a small spurious non-temperature related bias. You have mentioned aerosol effects and clouds, which I did not mention. Satellites can only look down through the atmosphere, and the radiometers pick up microwave soundings at different frequencies. From this it is possible to extract a surface signal, but it is inevitably mixed with signals from within the atmosphere. When the satellite data is used, the bias is removed by an extra level of processing. So there's very little real difference in trend by omitting it altogether.

    That is, it is simply incorrect to say that it is thrown out because it shows a decrease in global temperature.

    The fact is, global temperatures are continuing to rise, unless you are really really selective about picking start and end points to get a misleading short term variation. And even that is not going to work any more, given that the short term cycles are reversing again. Rankings for individual years or months, or looking at short term variation, are all statistically invalid as a way of revealing the trend in temperature for global climate. Whether for a rise or a fall.
     
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  20. Sep 22, 2009 #19
    The satellite data was removed from ERSST version 3 in October/November 2008. The transition from version 2 to version 3 however did not occur until July 2009.
     
  21. Sep 22, 2009 #20

    sylas

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    Yes, quite right. Thank you! My text above mixes up the dates somewhat. I shall edit in a correction.

    The original ERSST version 3 still used satellite data, as described in the reference Smith et al (2008); and then in October/November 2008 version 3b was provided, in which there was no input from satellite data; and then in July 2009 version 3b replaced version 2 in the regular published analysis.

    The OISST product is a different data product for sea surface temperatures, with some slightly different processing and different resolutions. It is compared with ERSST in Smith et al (2008). OISST still uses satellite data, and it is still used within the monthly regular analysis, for the ENSO reports. OISST is not used for reporting global monthly temperature anomalies and rankings.

    Cheers -- sylas
     
    Last edited: Sep 22, 2009
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