State of the Climate September 2009

  1. 2nd warmest September on record! (after 2005)
    El Nino is weak, but expected to strengthen.

    So, this makes 2 months in a row with 2nd warmest temperature on record designation.
    August 2009 was also the 2nd warmest (but behind 1998 instead of 2005).
    What's significant about all of this, is that it is occurring while solar activity is at a 90 year minimum.
  2. jcsd
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  3. Wagmc;

    It's not just ground based measurements.

    Current satellite data is also showing near record temperatures for September.

    Check out the latest from the NCDC:

    UAH data for the lower troposphere was the 2nd warmest September on record showing a trend of 0.13C/decade of warming.

    RSS data for the lower troposphere was also the 2nd warmest September on record showing a trend of 0.18C/decade of warming.

    I think most everyone realizes that El Nino during 1998 was exceptionally strong.
    Now, with only a mild El Nino, global temperatures are near establishing record highs.
  4. mheslep

    mheslep 3,466
    Gold Member

    It's not reasonable to say this '2nd warmest September' is 'showing' that trend. The trend you cite is from an average over several decades not from the single point of this September, nor is it blown away if, say, November returns to November 1950 temperatures.

    Stating 'near establishing record highs' is also consistent with a plateau in warming for the last decade. To illustrate: for arguments sake assume warming has halted and global temperatures continue to hover at this level for 50 years. Then within the 0.2C natural variability, it is almost certain we would continue to hear call outs of the 2nd, 3rd, 4th warmest land or ocean surface, month or season, and even the occasional record. And we would continue to hear the temperatures are 'above the 20th century average' (NCDC refrain) for the entire 50 years, even though temperatures rose none at all over that time.
  5. The trend values are quoted directly from the NCDC (National Climate Data Center).

    They stated the UAH/RSS warming trend of the lower troposphere for Sept 2009 was +0.13/0.18 C/decade.

    Interestingly, using the Jan-Sept 2009 UAH/RSS data for the lower troposphere, they state the trend is +0.12/0.16 C/decade.

    So, the longer term trend is not as much warming as what just the last month would suggest.

    Anyhow, the point is that using satellite data, the NCDC is finding a distinct warming trend. The RSS data is consistent with surface temperature measurements, while the UAH data shows smaller value by between 0.04 to 0.05 C/decade. Offhand, I don't know why the 2 satellite systems differ so much, but they are both showing a warming trend.
  6. They are not different satellite systems, they are different analyses. The satellites do not measure temperature directly. The different teams use different algorithms to extrapolate the temperature anomaly.
  7. mheslep

    mheslep 3,466
    Gold Member

    Yes, over 30 years, from '79 to '09, as of September.

    Over different time periods the trend of course varies. For shorter time periods closer to the present, the warming trend vanishes. For instance, thanks to sylas, we have this linear regression handy on the surface station data, 1974 to 2008:
    Last edited: Oct 21, 2009
  8. The NCDC is probably using all the satellite data when calculating the trend data.

    Using the data for Septembers, they come up with a long term trend of +0.13/0.18 C/decade of warming.

    Using the data for January-September periods, they come up with a long term trend of +0.12/0.16 C/decade of warming.

    So, what this shows us, is that the Sept 2009 value is showing a slightly faster warming than using the Jan-Sept 2009 value. This makes sense because there was a weak La Nina in the early part of this year that has since transitioned to a weak El Nino.

    However, as stated earlier, it not clear why the 2 differant analysis of the data (RSS vs UAH) are at such a wide variance to each other. UAH is showing less warming than RSS.
    RSS is more in line with surface measurements, but it remains to be seen how close surface temperatures should track the lower troposphere.

    My thoughts are that ower troposphere temperatures should track surface temperatures fairly closely.
  9. sylas

    sylas 1,745
    Science Advisor

    They are using datasets produced by Remote Sensing Systems (RSS) and University of Alabama Huntsville (UAH). Both datasets are in turn based on exactly the same raw data, which is from a series of satellites. No one satellite gives a continuous sequence of data over the whole period. Satellites have a limited lifetime.

    The raw data used is microwave brightness, in different frequencies, coming up from the Earth. One can estimate temperatures for different altitudes by appropriate weighting of the different microwave frequencies. It is also necessary to correct for satellite orbital decay, satellite drift for the time of day at which points are sampled, merging and calibration of data from different satellites, effects of cloud, and a lot more. This analysis is done by RSS and UAH, independently of each other, from the raw microwave brightness data. The NCDC then uses the RSS and UAH datasets, which are for temperatures, and calculates trends.

    An introduction to the microwave data and the temperature extraction processes is available at the RSS (remote sensing systems) website. See Description of MSU and AMSU Data Products. The differences between RSS and UAH (University of Alabama Huntsville) are entirely due to the mathematical procedures for homogenizing the raw data. It is not possible at this stage to identify plainly which one is correct, and so both are reported.
    The difference here has nothing to do with 2009 in particular, but rather with the difference between a trend for a single month from 1978-2009 and a trend for a period of Jan through Sept over this span of years. As climate changes, you do not only get increasing temperature; you can also get increasing or decreasing intensity of seasons; the difference between summer and winter. That is the cause of what you are seeing here.

    Cheers -- sylas
    Last edited: Oct 22, 2009
  10. Are you sure of this?
    Was it true in 2007 and 2008 and should we expect it in the future?
  11. sylas

    sylas 1,745
    Science Advisor

    I'm completely sure that this is not about 2009 in particular; but about the difference between the September trend and other trends, over the 31 years of the record. Mathematically, there is no question that you are indeed looking at the difference between the trend at different seasons. You can see the same thing using trends up to earlier years, like 2005. It's not exactly the same; the trends do alter a little bit which each new data point. But the September trend is strong and Feburary is weak.

    You are not looking at a 2009 figure, but at trends over 30 years; and the effect of adding the 2009 data point is small on those trends.

    Beyond that I make no further claims about the cause of seasonal differences. In fact, this is one of the major RSS UAH differences; one has a stronger seasonal effect than the other. This is an artifact of the analysis method, and at this point it is not clear which dataset has the artifact.

    Cheers -- sylas
  12. The moon lifts the ocean about a meter and moves about 1600 kilometers per hour. Does this tidal force leave a heat track,say, during a full moon?
  13. sylas

    sylas 1,745
    Science Advisor

    No. The energy dissipated by tides is a bit under 4 TeraWatts, which sounds large; but turns out to be less than 8 milliWatts per square meter of Earth's surface. Not enough for a heat track.

    The moon being full makes no difference; that's only about how the moon is lit by the Sun.
  14. The tides are higher during a full (or a new) moon. Of course it's still not significant.
  15. sylas

    sylas 1,745
    Science Advisor

    Ah... yes; because the Sun and the Moon are aligned so that their contributions to tides add. Thanks for the correction.
  16. I meant that the heat track would be more visable in the dark. A big tide of ten meters should produce about 1/100 of a degree. A rattlesnake can resovle the difference.
  17. sylas

    sylas 1,745
    Science Advisor

    It's not exactly a "track". There are attempts to identify where this energy is dissipated; but you can't do it by looking for tiny fractions of a degree over vast swathes of the ocean with much larger temperature differences already there for all kinds of reasons. Instead, you map the height of water and infer where the energy is being dissipated.

    See this report for an interesting study on the matter: TOPEX/Poseidon: Revealing Hidden Tidal Energy, at NASA. The associated reference is

    Here is a thumbnail image of the tidal energy dissipation zones inferred as part of this study; the NASA page has the higher resolution picture available.

    Felicitations -- sylas
    Last edited: Oct 26, 2009
  18. Question #2
    I am computing average atmospheric temperature, Tav, up to 11 km. My imaginary planet has three regions: desert, ocean, and temperate areas.

    Surface temperate = 30, adiabic lapse = 10, Tav = -13.4
    Surface temperate = 20, adiabic lapse = 5, Tav = -4.7
    Surface temperate = 15, adiabic lapse = 6.5, Tav = -15.9

    Does this jive with sattelite data?
    Thanks for the link, will read it.
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