The scoop on satellite temperature data

There’s a story at the Telegraph UK from Christopher Booker where he states “…the latest US satellite figures showing temperatures having fallen since 1998, declining in 2007 to a 1983 level…”

Wanting to make sure that there was some data to reference this claim for my readers, I’ve presented some graphs of satellite microwave sounder data below.

MSU data are produced by Remote Sensing Systems and sponsored by the NOAA Climate and Global Change Program. Data are available at www.remss.com

Below are the trend graphs for the data since 1979. Note that these graphs are multi channel, which represent different microwave sounder wavelength channels from the spacecraft. These channels represent different measured levels of the atmosphere.

Channel. TLT – Lower Troposphere

Channel TLT Trend Comparison 

Channel TMT – Middle Troposphere

Channel TMT Trend Comparison

Channel TTS – Troposphere and Stratosphere combined

Channel TTS Trend Comparison

Channel TLS – Lower Stratosphere

Channel TLS Trend Comparison

Above: Global, monthly time series of brightness temperature anomaly for channels TLT, TMT, TTS, and TLS.

All matter emits microwave radiation that varies with its temperature, among other factors. Microwave sensors on weather satellites can take more than 60,000 temperature measurements of oxygen in the atmosphere, from the surface to about 10 km (6 mi) altitude.

NOAA and it’s affiliated researchers have compiled almost three decades of data showing how atmospheric temperature has behaved over the entire globe.  At UAH (University of Alabama, Huntsville) where Dr. John Christy and Dr. Roy Spencer have been keeping watch on this trend for some time as well, they have tabular data online should you care to plot it. Here is an ongoing history of the data. You can see some of their other work here.

For Channel TLT (Lower Troposphere) and Channel TMT (Middle Troposphere), the anomaly time series is dominated by ENSO events and slow tropospheric warming. The three primary El Niños during the past 20 years are clearly evident as peaks in the time series occurring during 1982-83, 1987-88, and 1997-98, with the most recent one being the largest. Channel TLS (Lower Stratosphere) is dominated by stratospheric cooling, punctuated by dramatic warming events caused by the eruptions of El Chichón (1982) and Mt Pinatubo (1991). Channel TTS (Troposphere + Stratosphere combined) shows a mixture of both effects.

Temperatures in the lower troposphere (for non weather geeks, that is the portion of the atmosphere where we live) have shown a series of ups and downs since 1979, mostly in a ±0.4oC band, with negligible trends over that period. This contrasts with the near surface temperature record that shows a warming during the same period of time. The graph below is from Wikipedia.

The last 25 years of temperature variation

Note in the TLT graph above, the strong 1997-98 El Niño event caused significant lower tropospheric warming in late 1997, and record warmth in February 1998 as evidenced by the spikes shown in the TLT, TMT, and TTS graphs above.

Satellite measurements of the lower stratosphere (TLS) reveal two marked warm periods (as much as 1.5oC warmer), caused by sulfuric acid aerosols deposited in this layer by the eruptions of El Chichón in 1982 and Pinatubo in 1991.

These two warm periods are concurrent with a strong cooling trend over the 19-year period that has been attributed to ozone depletion in the lower stratosphere. In 1997, record low stratospheric temperatures were recorded.

On the TLT graph, for the years 1998 to present, there appears to be a slight downward trend in lower stratospheric temperature, and this is what I believe Christopher Booker is referencing in his article in the Telegraph.  Note that there have been other downward trends in the nearly 30 year measurement history, but the overall trend in the TLT, TMT, and TTS channels has been positive, so a short downward trend doesn’t necessarily prove anything. The TLS channel shows a negative trend, and along with the ozone depletion factor, indicates that we aren’t getting much heat transport from the troposphere into the stratosphere.

The real question is whether this small downturn in the tropospheric temperature trend is a short term anomaly, or something indicative of a longer term event. Only time will tell.

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11 thoughts on “The scoop on satellite temperature data

  1. Wowsers, Rev!
    Is this data semi-raw, with adjustments for orbital decay and the like? Or has it been through the usual hash-mill?
    So the lower trop doesn’t jibe with the surface data, eh? Veeeery interesting!
    Seems to me that THERE’S your delta. Does the dif match up with what you’d expect from the microsite biases? Or must needs you continue in madarin mode until the rest of the surface data comes in?
    Also, Note how that 5-year trend makes adjusted (bah!) temps look like it just keeps heading up from 1998. Ain’t no trendline here! Yeah, the multi-year averaging has its uses, but the main purpose seems to me to be to convey a statistical lie regarding the trend over the last decade.
    I assume you’ve seen how a bell-curve gets grossly distorted if expressued using multi-point averaging, and how it perverts the trend.

  2. In 1983 there was a strong El Nino that would have warmed things but for the El Chichon volcano. If you take the cooling from the temperature record caused by volcanoes then you will get the correct temperature signal caused by changes in solar, ENSO, PDO and etc.

  3. Evan as far as I know, this data has been corrected for orbital decay, and has also gone through rigorous calibrations so that data from several different spacecraft with different instruments is merged into an essentially homogeneous data set.
    When you look at the truly raw data from the different spacecraft, spotting trends is very difficult. See this paper to get an idea of what I’m talking about:
    http://www.ncdc.noaa.gov/oa/climate/research/uah-msu.pdf

  4. Is this Christy and Spencer’s data?
    From the Introduction on the page you linked:
    …The scientists working on the microwave sounding data are Carl Mears and Frank Wentz at Remote Sensing Systems….
    Has Christy blessed these results? Or is there still disagreement amongst the warring parties scientists that analyze the data?

  5. James,
    I’ve made a couple of corrections to the text, to make sure the provenance of the data is clear. I don’t know if Christy has “blessed” these results or not, and I don’t want to get caught up in the middle of a war between two groups on the subject.
    My goal for this post was to provide some relevant data in time series form for those that came away from the Telegraph UK article with questions. Hopefully I haven’t created more than I’ve answered. 😉

  6. Thanks for the details, Anthony. I guess I started this, principally because I had not seen ANY data anywhere which fit the Booker/Telegraph description. And these graphs really do not either, if you consider both the “cooling since 1998” statement, which infers warming previous to 1998, and then the comparison back to 1983 temperature. He has to either have been looking at something else, or through a very distorted lens.
    However, based on the ever increasing stridence of the AGW group towards getting expensive legislation passed immediately, one wonders if they are seeing reversals in some of their temperaure trends more clearly then we have.

  7. I would hope that we might not discount any data. Just because the names Christy and Spencer have been mentioned shouldn’t be a reason to discount the data. ( some get tired of “he is a known skeptic” always being used to discount data while expecting to have the agw data taken at face value.
    Please don’t discount data on a name basis. Test the results and the data first and then if it is in error post your results and methods.
    My thoughts and Anthony you may remove the post if you desire.
    Bill

  8. If I remember correctly the models project a mid troposphere warming greater than lower and a stratosphere cooling. The latter appears to be happening, but not necessarily the former. If CO2 is increasing at a faster rate then wouldn’t you expect the curves of the troposphere data to at least be rising at the same rate or faster? Is there an explanation out there from the AGW proponents?

  9. Regardless of the perception of Christy and Spencer opinions on AGW, the past errors of theirs which have been corrected, etc, I don’t think anyone has had their work scrutinized as much as theirs.
    RSS’ analysis of the the raw satellite data has typically had a warmer trend than Christy and Spencer’s UAH results. Much of their difference had previously been resolved, but I think there are still small difference in their calibration algorithms when accounting for satellites going on and off-line.

  10. Thanks for the link, Rev.
    My head is still spinning. But at least I –seem–to gather that at least they weren’t conflating it with ground station data.
    Bottom line, so far: seems to be as flat as a pancake. With that nasty little recent down-tic. (Cycle 24 where aaaaaaare you? Poor Tom’s a-cold!)
    BTW, I got a bone to pick with you, Rev: You need to squeeze that surface temp graph a bit narrower. Your current slope doesn’t look nearly threatening enough. And play it safe: stick with the 5-year averaging. We want to avoid those ugly dips and we need to start our 1998-2007 trendline from a lower spot on the graph, don’t we? Get with the program! Your grant money [not] may be at issue!
    Kristen Byrnes–Presence noted. Sic the “minaccing” bums. (Not all liberals are against you.)

  11. Bill in Virgo, I am repeatedly struck by how every climate reconstruction shows a late 20th century downturn in temp (the divergence problem). Perhaps the proxies are right (obvious comment about the proxies teleconnection to future climate avoided. But I wouldn’t discount a temporal teleconnection paper from the usual source, in the not to distance future),

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