Why New NOAA Temps are More Reliable

November 28, 2015

Figure 1
Figure 1: New and old homogenized global land/ocean records from Karl et al, 2015.

The current (#lamarlysenko) climate denial witch hunt being conducted by Lamar Smith and the House Science Committee was triggered by the publication of several new papers which have put to rest one of denial-dom’s favorite nonsense memes – that “temperatures have not been rising” for x years.

In particular, the paper by Thomas Karl and colleagues at NOAA has been a target, so it’s worth reviewing what the NOAA group wrote about.  Nutshell, they tapped into some more reliable data.

Kevin C at SkepticalScience:

Significant recent media and political attention has been focused on the new NOAA temperature record, which shows considerably more warming than their prior record during the period from 1998 to present. The main factor behind these changes is the correction in ocean temperatures to account for the transition from ship engine room intake measurement to buoy-based measurements and a calibration of differences across ships using nighttime marine air temperatures (NMAT). Here we seek to evaluate the changes to the NOAA ocean temperature record by constructing a new buoy-only sea surface temperature record. We find that a record using only buoys (and requiring no adjustments) is effectively identical in trend to the new NOAA record and significantly higher than the old one.

The changes to the prior NOAA global land/ocean temperature series are shown in Figure 1. There are some large changes in the 1930s that are interesting but have little impact on century-scale trends. The new NOAA record also increases temperatures in recent years, resulting a in a record where the period subsequent to 1998 has a trend identical to the period from 1950-1997 (and giving rise to the common claim that the paper was “busting” the recent slowdown in warming).

The paper that presented the revised record, Karl et al, didn’t actually do much that was new. Rather, they put together two previously published records: an update to the NOAA sea surface temperature record (called ERSST) from version 3 to version 4, and the incorporation of a new land record from the International Surface Temperature Initiative (ISTI) that makes use of around 32,000 land stations rather than the 7,000 or so GHCN-Monthly stations previously utilized. The new land record is quite similar to that produced by Berkeley Earth, though it has relatively little impact on the temperature trend vis-à-vis the old land record, particularly during the recent 1998-present period.

The slowdown-busting nature of the Karl et al paper relies almost entirely on the update from ERSST v3b to v4. During the post 1998 period, this is primarily due to a revised treatment of buoys and ship engine room intake (ERI) measurements and an improved calibration of differences across ships. During the past few decades the number of automated SST measurement buoys has expanded rapidly from effectively zero before 1980 to over 70 percent of all SST measurements today as shown in the figure below. Buoys are appealing measurement platforms, as they are not restricted to shipping routes and often have fully automated reporting via satellite uplink.

Figure 2
Figure 2: Share of SST observations by instrument type from Kennedy et al 2011. Note that this figure ends in 2006; since then buoys have continued to grow in observation share.

NOAA argues that the transition to buoys introduced a spurious cooling bias into the record. ERIs tend to warm the water a bit before measuring it (ship engine rooms being rather hot), whereas buoys do not. They identify a bias of around 0.1 C between buoys and ERIs and remove it by adjusting buoy records up to match ERI records in ERSST v4, as well as use NMAT readings to calibrate the differences across ships. These adjustments had not been done in the prior ERSST v3b. As an aside, the decision to adjust buoys up to ERIs or ERIs down to buoys should nominally be trend neutral. Indeed, in their work on HadSST3 Kennedy and colleagues explicitly tested this, and found “no appreciable difference” on trends.

However, there is a rather straightforward way for us to test if the adjustments done in ERSST v4 are proper or not: compare their adjusted record to a record made only from buoys. The buoy records are from purpose built instruments which are largely standardized, resulting in much more homogeneous record [details]. On the other hand, the buoy record is short, and has limited coverage in the early 90’s.

The buoy-only record is prepared by calculating daily averages for each buoy. Buoys which show a large daily temperature variation are rejected: in deep water the daily temperature range is only a few tenths of a degree, but in very shallow water it can be substantial which presents problems when some data are missing. Next, the daily data are placed into 550 x550km equal area grid cells based on the location of the buoy for that day, and monthly averages are determined for each cell.

The resulting coverage is still limited and so produces a biased estimate of global sea surface temperature. To produce a useful comparison to ERSST, we therefore reduce the coverage of the ERSST datasets to match the buoy dataset (now using a fine 1 degree grid for all the data) and then calculate anomalies for all the datasets using a 2001-2010 baseline. The area weighted mean temperature is then calculated for each record. While this doesn’t provide a very good estimate of global SST, it does allow a strict like-with-like comparison against ERSST over the regions where the buoys have coverage. The percent of global ocean covered by buoy measurements varies from around 40% in the mid 1990s to around 70% in recent years.

Figure 3
Figure 3: ERSST v3b, v4, and Buoy-Only SST anomalies and trends from 1995 through the end of 2014. The trend periods shown are the full record (1995-2014) and the “hiatus” period (1998-2014). 2015 is excluded as the year is incomplete, and the period prior to 1995 is excluded due to limited buoy coverage. The anomaly graph is baselined to 1995-2005 to show the time-evolution of differences.

As shown in Figure 3, a buoy-only record is quite similar to the ERSST v4 but shows statistically significantly more warming than ERSST v3b during the period from 1995 through the end of 2014 (p < 0.05 trend in the differences). This suggests that ERSST v3b suffered a cooling bias when blending buoy and ship records that is properly corrected in ERSST v4, at least for the areas where both ship and buoy records are available. Because the buoy record is relatively homogenous and requires no adjustments, it provides a good check in the validity of the combined ship-buoy series when normalized for spatial coverage.

In addition to the buoy-only dataset, we can also examine data from ARGO floats (which are not included in our buoy dataset). The ARGO floats have fairly good spatial coverage over the period since 2005. They are primarily intended to measure deep ocean temperatures, but also measure sea surface temperatures during their ascent from the depths to the surface. NOAA provides another sea surface dataset called OISST, which includes data from ships, buoys, and satellites. There are two versions of OISST: a daily version which is newer and includes adjustments to account for the transition from ships to buoys, and a weekly version which does not include this correction. Figure 4 shows how both the ARGO record and daily OISST record compare to ERSST v3b, v4, and our new buoy-only record when spatial coverage is normalized across all records.

Figure 4
Figure 4: ERSST v3b, v4, and buoy-only, ARGO, and OISST SST anomalies from 1995 through the end of 2014. The anomalies shown are relative to a 1995-2005 period; the ARGO record is too short for this baseline and instead is matched to the buoy-only record during the period of overlap.

Over the period from 2005 to 2014, ARGO buoys show statistically significantly more warming than ERSST v3b (p < 0.05 using an ARMA[1,1] model), but indistinguishable from ERSST v4 or the buoy-only record. Similarly, OISST has the highest trend of all series over the 1995-2014 period. The trends of all series over these two periods are shown in Figure 5.

Figure 5
Figure 5: ERSST v3b, v4, and buoy-only, ARGO, and OISST SST trends from 1995-2014 and 2005-2014. The latter period is chosen to compare ARGO to other records, as the ARGO record does not have sufficient coverage prior to 2005. Confidence intervals are calculated using an ARMA[1,1] model to account for autocorrelation. Note: the confidence intervals indicate the uncertainty in the trends, which is dominated by interannual variability. The uncertainty in the trend in the differences is much lower, leading to a statistically significant difference between the buoys and ERSSTv3b.

The ship records are important because they form the foundation for a long sea surface temperature record, but they require careful calibration. The differences between HadSST3 and ERSSTv4 suggest that the finer details of the ship record are not yet settled, and as a result care is required especially when considering short term trends. However the buoy data, ARGO floats, and daily OISST record all support the NOAA claim that ERSSTv3b suffered a significant cool bias over recent years arising from inhomogeneities in the ship record and the increasing use of buoys.

Code for downloading and processing the data for this analysis is available here: http://www.ysbl.york.ac.uk/~cowtan/data/buoy.zip. While the code and data are only 18 MB, the (optional) raw buoy data are approximately 44 GB. Gridded 1×1 files are also provided for buoy, ERSSTv3b, and ERSSTv4 data.




24 Responses to “Why New NOAA Temps are More Reliable”

  1. I know that I’ve posted/tweeted this a bunch of times before, but (at least for those who haven’t seen this yet), here’s a message-board post of mine that tells a simple story about one aspect of data-homogenization (corrections for station-moves): http://forums.sandiegouniontribune.com/showpost.php?p=5337377&postcount=222

    Take-home points:

    Even simple-minded processing of unadjusted aka raw land-station temperature data produces results that line up pretty closely to the fancy-pants NASA results that were computed from *adjusted* land-station data.

    Much of the bias seen in my raw vs. the adjusted NASA results can be attributed to corrections for station moves (corrections present in the adjusted that NASA uses, but not the raw data that I used).

    If the NOAA and NASA folks were looking to exaggerate warming, they sure went to an awful lot of trouble to get darned-little additional warming.

    Feel free to serve this to Uncle Wingnut and Auntie Teabag along with their turkey leftovers today.

    • Kevin Cowtan Says:

      I for one hadn’t seen that, and it is very interesting. Are you aware of any papers on this specifically? If not, it may compliment something I’m working on.

      • No papers that I’m aware of — it’s just an informal “back of the envelope” experiment I tried after reading somewhere that a number of temperature stations were moved from city centers to outlying airports during the 40’s and 50’s.

        I computed results via a very simplistic baselining/gridding/averaging routine — I used big 20 deg x 20deg grid-cells (at the Equator). I adjusted grid-cell longitude dimensions (going N/S from the Equator) to keep the grid-cells as constant in area as possible. Didn’t even bother checking for empty grid-cells to interpolate to.

        Like I said, a simple “first cut” analysis exercise. But the results show that the global-warming signal is so strong/robust that it doesn’t take very intelligent processing to bring it out.

        There are lots of “airport” temperature stations with records going back to the early 1900’s (or even earlier); those stations were obviously moved at some point in their history. In addition, I recall reading that other stations were moved to water treatment stations; those aren’t captured in the GHCN monthly metadata.

        I’m not sure how much effort it would take to compile a more complete list of “moved” stations (I haven’t seriously investigated it) — but if that could be done, it would be interesting to see what the results would look like if all those “moved” stations were excluded from the processing (and using the full-up NASA or NOAA algorithm as opposed to my simple “first cut” approach).

    • andrewfez Says:

      Didn’t Peter or Dana blog about a study a few years ago that showed no pause in warming if the northern latitudes were averaged differently, to account for the lack of stations up there? Or am I remembering that wrong; my memory ain’t what it used to be.

  2. “new papers which have put to rest one of denial-dom’s favorite nonsense memes – that “temperatures have not been rising” for x years.”

    Heck, that is also nonsense! The corrections are too small to put anything (even non-existing) to rest. This is just perpetuation of statistical stupidity, fighting stupid with stupid. Heck, no wonder there’s so much stupid out there.

  3. Kevin Cowtan Says:

    Just for the record, Zeke Hausfather wrote most of the article and did the argo and oisst comparisons, hence he should be listed as first author.

  4. omnologos Says:

    1. it’s too long an explanation

    2. the longer it is, the more complex it will look

    3. the more complex it will look, the more people will have to rely on the experts doing and saying the right thing

    4. the more people will have to rely on the experts doing and saying the right thing, the more important for the experts to be extremely open and sincere in their dealing with the public.

    5. if the temps are more reliable now, they were less reliable before. who knows what else is less reliable now, and still people will be asked to change their lives

    6. if the trend appears only after experts look for it, the trend is too small to be noticeable

    7. if Cowtan gets involved, everybody who knows anything about the hiatus will remember his previous effort at removing it

    Thanks for posting this Peter, I have seldom seen a better collection of hints that the alarmists have it all politically very, very wrong. Go get those emails to Congress, ASAP…nothing can be more important than the climate change apocalypse.

    • dumboldguy Says:

      The village idiot once again proves his mastery of fractured logic.


      • omnologos Says:

        Ah yes I forgot, as the world heats up time should be wasted in cretin comments devoid of all contents. If anyone gets worried about climate change, all it takes is to look at what you do and the worries evaporate

        • dumboldguy Says:

          Yes, exactly my point. You waste our time with “cretin comments devoid of all content(s) (sic)”. Go away and stop crapping up the thread.

    • Check out http://forums.sandiegouniontribune.com/showpost.php?p=5337377&postcount=222

      I wrote that piece specifically for non-technical folks.

      It shows (1) that the NOAA adjustments for land-station data have only a small impact on global-average temperature results, and (2), much of the small bias observed between the unadjusted-data trend and the NASA adjusted-data trend can be attributed to the movement of temperature stations from city centers to outlying airports.

      It shows quite clearly that the global-warming signal shows up strongly even in adjusted data, and adjustments are required to compensate for the fact that many of the stations in the temperature data-set had been moved during their history.

      I wrote that piece in language that high-school students should have no trouble understanding.

      I certainly hope that it isn’t too long or complex for you.

    • Lionel Smith Says:

      “1. it’s too long an explanation”

      You got that right for what followed was, you must have anticipated your own prolixity.

    • greenman3610 Says:

      Here’s the rationale for “long explanations”.
      My readers tend to be thought leaders, journalists, scientists, academics, and others.
      The way this works is, I give sufficient background here so that intelligent, but not necessarily specialist, readers can then knowledgeably explain and disseminate.
      You are invited to better understand broad outlines of the scientific discussion so as to contribute to the social and political discussion in your community.

      • omnologos Says:

        There is a misunderstanding here. It is not me that you need convince. My overall weight in any climate treaty or negotiation is around one part in seven billion.

        What I illustrated above is the way all this anti-hiatus effort will be looked at.

        Personally, if I were a climate alarmist, I would have said that the hiatus, if it exists, is not relevant to multidecadal climate change. If people want to study it, so be it, but of course that’s not “climate” they are studying because “climate” is “at least three decades”.

        Unfortunately there have been many words wasted on DEMONSTRATING there is no hiatus (in 63 ways or so). This smacks of bias and little awareness about what climate change is about, on the past of the alarmist squad. Things are now getting worse as more and more people realize how impervious climate scientists are to any request of background information and data, wasting time in pointless legalities when the world is on the edge of destruction.

        Just couple that behavior with the other usual culprits (jet-setting activists, focus on demonizing the opposition, refusal to open debate) plus today the Paris climate march ending up with demonstrators throwing candles at the police (the same candles left to remember the victims of the recent terror attacks): and you end up with climate activism screaming out and loud that there is no emergency.

        Because if there were an emergency, those most aware of it would just behave differently. And never ever try to “dispel” an irrelevant hiatus.

      • omnologos Says:

        “on the part” not “on the past”

  5. skylanetc Says:

    “1. it’s too long an explanation

    2. the longer it is, the more complex it will look”


    That’s a denier for you. If it isn’t in simplistic sound bites, omnologos is not going to bother actually reading it for comprehension.

  6. redskylite Says:

    I cannot understand what Omnologos nor Lamar Smith are rabbiting on about. If they think that NOAA and NASA are cooking the books, why does the Japanese Meteorological Agency’s stats also match the upwards rise. Even if they thing it is a conspiracy between scientists in the U.S and Japan, take a look at the Hong Kong observatory records. Yes that’s right they match on a rise too. Have a look at the Keeling curve, suspicious don’t you think. ? I think you are either just awkward b&ggers who like to argue or you have too much money invested in fossils. The temperature is going up its undeniable, and it is not likely to be a linear rise to 2 degrees Celsius.

    Ask the birds . . . or do you think they are alarmists also . . .?

    Messengers Of Climate Change: Birds Moving Towards Poles, Higher Grounds Due To Warming Habitats.


    • Tom Bates Says:

      Does it matter, Lamar committee simply asked for the internal emails which they have the right to do under the constitution and law as part of the oversight of congress. Perhaps you remember the recent story on that gas station in kabul which cost 42 million and our military said nobody knows why as their group was disbanded. Congress has the right to oversight unless you think all spending is sacred. Lamar may be curious as the RSS and UAH data show no warming for decades and it has not been adjusted while the antarctic gains ice as does Greenland. Perhaps he read the article in the Alaskan paper about trees under a melting glacier in Alaska about a thousands years old which shows it was warmer than or maybe that was a freak of nature. Or perhaps he looked at the October warmest claim and wondered how the mean in Barrow Alaska in 1902 was colder than in 2015. Or maybe he is just having a bad day.

      • Tom Bates Says:

        oops me bad not colder warmer in 1902. Personally I would just like to see the unadjusted temperatures compared to the adjusted and than some discussion of all adjustments along with how many stations were adjusted and how many stations are used each year. Since the temperatures are gridded, it would be helpful to know how many represent actual measurements and not plugs out of the total.

      • dumboldguy Says:

        OOOOPS, says TommyB the Confused Denier, as he first asks “does it matter”, maunders on briefly about gas stations in Kabul, states “….while the antarctic GAINS ice AS DOES Greenland”, and cherry picks data with “Barrow Alaska in 1902 was colder than in 2015” (OOOPS, he meant warmer)

        Lord love a duck, but where do these folks come from and why do they all have the same tired old list of horseshit “talking points” and irrelevancies that they always bring up.

        “Perhaps he read the article in the Alaskan paper about trees under a melting glacier in Alaska about a thousands years old which shows it was warmer than…”
        Warmer than WHAT, Tommy?

        Maybe Tommy is just having a bad day, or maybe he is a “freak of nature” re: his logic and communication skills, but anyone who bothers to answer his question at 11:17 am will be pissing into the wind.

  7. Tom Bates Says:

    so what is the unadjusted temperatures and how does that compare to the UAH and RSS data?

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