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DMI and GISS Arctic Temperatures: Hide the Increase?

Posted on 17 October 2010 by Peter Hogarth

SkS Note: Peter Hogarth has done us a great service by writing three level of rebuttals for the skeptic argument "DMI measurements show a cooling Arctic". This blog post is the Intermediate Version. However, if you want to ease yourself into the subject, you might want to kick off with the Basic Version first. Then if you're stout of heart, you might be ready to sink your teeth into the Advanced Version which features the trademark Hogarth detailed approach.

A recent WUWT article by Frank Lansner, August 5th 2010 has the heading “DMI polar data shows cooler Arctic temperature since 1958”. Peter Berenyi also posted a similar chart here on SkS (which sparked my interest). Frank Lansnser goes on to show data from Goddard Institute of Space Science (GISS) July polar views and compares this with graphics of Danish Meteorological Institute (DMI) data for July 2010 to cast doubt on the validity of the GISS gridded values in the Arctic region. This follows on from similar points made by Steve Goddard, and another article by Harold Ambler which tries to show how DMI is based on more data measurements than GISS, again providing a setting to raise questions about the reliability of GISS gridded values in the Arctic.

Similar claims that the DMI data shows Arctic “cooling” or highlights problems with other temperature data sets (eg from GISS, which mostly interpolates over the Arctic ice) appear on other websites. It appears that such sites regard the DMI data as a standard.

This post seeks to correct the public misunderstandings that these articles may cause, primarily about the claim of arctic “cooling” but also about comparisons between the DMI 2m Arctic absolute temperature time series and GISS temperature anomaly data from the Arctic region.

The Danish Meteorological Institute (DMI) Arctic temperature data is the output of the latest operational model as used for weather forecasting by the European Centre for Medium-Range Weather Forecasts (ECMWF). At present this output is an average of all model points at 2m height on a 0.5 degree grid over the most northerly part of the Arctic, above 80N. Because the number of land stations in the World Meteorological Organization (WMO) list above 80 degrees North is very small indeed (a handful), data inputs for the model must be supplemented by other sources for high resolution meteorological work. The models assimilate inputs from weather stations, drifting buoys, radiosondes, aircraft, vessels and since the 1970s, high coverage infra-red and microwave satellite based sensors. The models allow this high resolution satellite data to be used to interpolate between the sparse but very accurate observations from land stations, which form a network of absolute temperature value “tie points” - allowing calibration of the fine scale overall satellite derived relative changes.

DMI recommend that the 2m air temperature data should not be compared with overall Arctic temperature estimates from other data sets, which generally cover a wider area (usually above 65N) where more land station data is available.

We will now examine the claim of cooling “melt season” temperatures. Most of the area above 80N is (currently) still covered in permanent sea ice. In the Arctic Summer when the surface ice is melting, it is known that the air temperature close to the surface is limited by this ice melt temperature to just above zero degrees C, (Rigor 2000). This is why the Summer air temperatures have not varied much over the entire instrumental period. This maximum temperature “clipping” effect is clearly seen on all arctic data sets from Arctic buoy data to individual station data to satellite data.

Clearly high Arctic Summer surface temperatures just above zero are not really an indication of anything except proximity to a melting ice surface. To claim that the Arctic is cooling is misrepresenting the data.

It is also evident from these High Arctic data sets that the average temperatures in the Winter, Spring and Autumn periods have generally increased over the measurement period. It appears that the overall seasonal cycle is riding on a gradually warming average value, but peak positive excursions are being limited by the ice melt temperature in Summer.

It would be intuitive that such seasonal warming patterns would show up clearly in the overall DMI temperature anomaly trend, and this is the case. If we plot the entire daily DMI temperature data, and then a 365 day rolling average, we end with a positive trend of 0.383 degrees C per decade.

Figure 1: DMI daily temperature values, annual average and linear trend over the entire record period

Thus the reality is that the annual average Arctic surface temperature as indicated by DMI has risen at rates around twice the global average over the past 50 years, which is entirely consistent with other Arctic data sets, including the data from GISS. This annual temperature anomaly trend (red) gives clearer context to the Lansner chart (green).

Figure 2: DMI summer melt season temperatures and annual DMI temperature anomaly as well as five year running averages

The Goddard Institute of Space Science (GISS) global surface temperature anomaly time series is based on observations from publicly available observational data sets rather than models. Its primary usefulness is as an indicator of global or large scale regional temperature changes. The measurements used by GISS are gridded at either 1200km or 250km resolution, with appropriate weighting in grid cells containing both land and ocean. The SST data where available is used up to 100km from any coast, but data from any source is extended to a maximum radius of 1200km if no other measured data points are present within this range.

For the high Arctic, we have already noted that there are relatively few land stations, (a handful above 80N), and most of this area is currently still covered by permanent sea ice. A study using data from Polar drifting ice buoys showed that near surface air temperatures over the pack ice are relatively homogenous, with a CLS (correlation length scale) of 900-1000 km, see (Rigor 2000). Obviously SST can not be used in this region, as the sea surface is frozen. In open Ocean SST tracks variations in Air temperature, but this is not the case near the transitional and mobile ice “boundaries”. This is one reason why GISS does not currently use SST data in the seasonal ice region above 75N, even when this data is seasonally available (as is increasingly the case due to diminishing trends in ice extent and better coverage due to satellite data).

This means in the Arctic region, GISS data is relatively coarse grained, as individual grid cells above 80N may include station data interpolated out to as much as 1200km, and are likely to show the higher short term variability which is characteristic of data from individual Polar stations.

However, given all of the above, and the significant differences in horizontal resolution, and methodology, and the caveats and cautions from both DMI and GISS, how do annually averaged time series compare? The DMI data is the official data (not extracted from DMI graphics as Lansner and others have done).

Figure 3: Annual DMI and GISS Arctic temperature anomalies and trends

Here the annual average values for each year have been plotted for both the polar “zonal” GISS data (64-90N) and the DMI Arctic data, and the trends calculated for both data sets for the full DMI period. At this resolution the correlation is reasonable, and the 50 year gradients are statistically indistinguishable. These trend figures also match those from a recent comprehensive surface station based study of the Arctic which gives 0.364 degrees C/decade from 60-90N over this same period (Bekryaev 2010).

The Lansner article is thus misleading. On average relatively strong Arctic warming has occurred (rather than cooling) as indicated both by the GISS and DMI data. The GISS zonal Arctic temperature trends are consistent not only with the DMI Arctic trends but also the trends from other recent Arctic surface temperature studies (see the advanced version for more details).

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Comments 1 to 50 out of 140:

  1. Great article, but your trend line equations in Figure 3 are mislabeled or off by a factor of 10. They should either say yearly or the decimal point shifted right.
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  2. Very interesting Peter!

    I haven't had the time to look into this myself, but once again our friend Steven Goddard has shown a severe lack of skeptical thinking and maintained his unbelievable ability to cherry pick.
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  3. This article does show the weakness of the station data. 1200 km interpolation is not the best for analyzing the Arctic.

    Since 1979 the DMI and the satellite data are showing the same trends though. The strongest warming is taking place during the winter, but the summer is warming in the satellite data as well.

    The satellite trend is weak until 1997, but after 1998 the trend is clear. Of course 1998 is also the year the AMO went strongly into the warm phase and that makes distinguishing the cause of the warming very difficult.

    So I agree with the warming, just not the cause. It is too bad the DMI data does not extend back to 1930.
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  4. I recently emailed DMI with a query about summertime temperatures and got a reply a couple of weeks ago. Here are the relevant bits. My comments are in italics.

    I am curious about the temperature profiles for the Arctic, 80 degrees North from 1958 to present...

    I have read quite a few studies on Arctic summertime temperatures indicating that the temperature trend for the region has been significantly positive over the last few decades. The University of Alabama satellite record maintained by Roy Spencer and John Christy has a trend of 0.47C/decade since 1979. I realize that the circle of the Arctic your graph covers is a smaller area than many other assessments of Arctic temperatures...

    ...would you be amenable to providing a brief reply? I plan to disseminate it responsibly, unless you state otherwise.


    1) It would appear at a glance that summer time temperatures have increased little over the past few decades going by the DMI graph set. Do you hold this to be the case?

    From the link to WUWT, that you've attached below[*], it seems that a cooling temperature trend in the Arctic summer is present, throughout the past approximately 10 years. Where 'summer' is defined as the period where the +80N mean temperature is above 273K.

    However, I very much doubt that a simple conclusion can be drawn from that, as there are complicating aspects to that analysis, e.g.:

    1) The surface in the +80N area is more or less fully snow and ice covered all year, so the temperature is strongly controlled by the melting temperature of the surface. I.e. the +80N temperature is bound to be very close to the melt point of the surface snow and ice (273K) and the variability is therefore very small, less than 0.5K. I am sure you will find a much clearer warming trend in the same analysis applied to the winter period. The winter period is more crucial for the state of the Arctic sea ice, as this is the period where the ice is produced and the colder the winter the thicker and more robust the sea ice will become.

    2) The +80N temperature data after 2002 are based on the operational global deterministic models at ECMWF, at any given time. Before 2002 the ERA 40 reanalysis is used. I.e. the +80N temperatures are based on 4 different models, the model used for the ERA 40 data set and the operational models T511, T799 and T1279. The point is that there can be a temperature bias in one or more of the models, that can cause the lower temperature level since approximately 2002, where the shift between the ERA40 data and the operational model data occur in the WUWT-plot from the link below.


    2) Can you help me understand what appears to be a discrepancy with other reports on Arctic temperature trends?

    I do not think one can give a general comment on that - i.e. such discrepancies have to be discussed in a 'case by case' manner


    3) Are there any published studies done by DMI researchers on Arctic temperature trends - for reference?

    No - unfortunately, we have not had time to look deeper into this.


    * The WUWT link in my email was this one.

    http://wattsupwiththat.com/2010/08/05/dmi-polar-data-shows-cooler-arctic-temperature-since-1958/

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

    Looks like you've done a very good job, Peter. My correspondent was Gorm Dybkjær.
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  5. "peak positive excursions are being limited by the ice melt temperature in Summer."

    That's a key point, explaining the strange look of the seasonal buoy maps as well:



    Lots of red except in the summer, where one would have expected the most red.

    Can anyone with a shred of credibility see a cooling Arctic and a simultaneously melting Arctic?
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  6. kwinters79 at 13:17 PM on 17 October, 2010

    Thanks, fixed that.
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  7. barry at 23:21 PM on 17 October, 2010

    Thanks for that. I've looked at the ERA-40 and the T511 model data in the approx eight month overlap period during 2002 and there is evidence of a small bias.
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  8. TIS - can you explain to me your proposed mechanism by which the positive phase of the AMO manages to increase winter temperatures please? No problem explaining this of course within mainstream climate theory. Also, what is your calculation for increased heat flux from AMO and how does this compare with the increased radiation flux from GHG?
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  9. The Inconvenient Skeptic at 22:27 PM on 17 October, 2010

    Atlantic Multidecadal Oscillation (AMO) is derived from detrended North Atlantic SST variation. So your point is regional SST and Surface air temperatures correlate? We would intuitively expect some correlation, but what is driving the SST in this area upwards (as we see if we leave the trend in) and what is driving the multidecadal variations? SST in the North Atlantic appears to be driven by a combination of atmospheric forcing and possible meridional heat transport. What is the source of this underlying increasing thermal energy in both cases? You may consider the facts that the North Atlantic SST variability is strongest at the surface and is also strongest at higher latitudes.

    I will try to get time to dig out recent work in this area, but here is some more inconvenience for you, as it does not appear that AMO leads surface temperature. If anything the reverse looks likely, though I would be cautious here. The AMO is de-trended North Atlantic SST from NOAA ESRL and I have de-trended the HadCRUT3 surface temperatures also to allow comparison.

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  10. "In the Arctic Summer when the surface ice is melting, it is known that the air temperature close to the surface is limited by this ice melt temperature to just above zero degrees C, (Rigor 2000)."

    This basically has to do with the heat of fusion, right?

    Anyway, regardless of the Arctic Summer temperature trend, the length of the melt season grew longer by an average of 6.4 days per decade from 1979 to 2007, according to NASA.
    http://www.nasa.gov/topics/earth/features/longer-melt-season.html
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  11. muoncounter, regarding,
    "Lots of red except in the summer, where one would have expected the most red. "

    You'll want to be careful not to confuse temperature anomaly with absolute temperature. If the baseline is -30 C, a plus 5 C anomaly is still colder than a +1 anomaly on a -1 C baseline.

    I would expect the Arctic to show a greater anomaly in the winter than the summer. The frozen Arctic Sea has a very high albedo; this means that less of the light in the visible spectrum and above will be converted to infrared in comparison to other, non-ice-covered parts of the world. CO2 acts on infrared (and a some microwave), not visible and UV. Albedo means nothing in the dark.

    You might also consider that an enhanced greenhouse effect results more in higher relative nighttime temperatures than in higher daytime temperatures, and the arctic winter is more or less one long night.
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  12. bgood2creation at 16:02 PM on 18 October, 2010

    Yes, latent heat is the reason the air temperatures reach a plateau just above melting point rather than rising further in Summer.

    Some more references on increasing melt season over the last thirty years: Markus 2009, Howell 2009, Rodrigues 2009.
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  13. Please excuse me for sounding stupid but isn't the sun the supplier of heat and co2 the catalyst or blanket that intensifies the suns rays? In the arctic winter there is no sun at all for six months.Is there a contradiction here? 6 months 0f 24 hr sunshine and its getting cooler year after year just when c02 should be having its biggest impact........ anyone.
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  14. Adrian smits:
    This post provides data that shows the Arctic is getting warmer as expected. You suggest that the Arctic is getting cooler. Can you provide a link to data or are you just trolling?
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  15. The DMI temperature graph shows pronounced summertime cooling in what should the time of year when c02 should have its greatest impact. All other things being equal. This last summer was one of the coolest since 1958. These guys in Denmark actually measure temperature all over the region up there as opposed to GISS who who extrapolate from 1200 miles away!You can find the graphs at WUWT.
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  16. adrian smits - Did you read the presentation by Peter Hogarth at the top of this thread? Continuous ice presence over the summer limits the rise of temps to just above zero degrees C, clipping temp rise. But the average yearly temperature is rising twice as fast as the rest of the globe - it just doesn't get as cold the rest of the year as it used to.

    To quote Peter: "Clearly high Arctic Summer surface temperatures just above zero are not really an indication of anything except proximity to a melting ice surface. To claim that the Arctic is cooling is misrepresenting the data.

    It is also evident from these High Arctic data sets that the average temperatures in the Winter, Spring and Autumn periods have generally increased over the measurement period. It appears that the overall seasonal cycle is riding on a gradually warming average value, but peak positive excursions are being limited by the ice melt temperature in Summer.


    The energy that would otherwise raise temps above zero is melting the ice. Higher average temperatures mean more ice is melting - the time spent clipped to zero increases, and the total amount of ice melted increases.

    WUWT is making (oh my - how atypical) a mountain of a trend out of a molehill of variation, ignoring the full data set. It's a pretty appalling misrepresentation of the data.
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  17. Regardless of what's happening to temperature in the Arctic summer we can safely forget about some kind of fundamental change in the mechanism of CO2 as a GHG because of the presence or absence of sunlight, Adrian. As a GHG CO2 doesn't really care if it's light or dark. Does somebody at WUWT actually suggest such a difference might be in play?

    Also, CO2 doesn't act as a GHG by intensifying the sun's rays. It's actually kind of a case of the opposite, with Earth's outgoing "rays" being lessened at certain wavelengths of IR. Further exploration of that is off-topic on this thread but see NOAA's FAQ on global warming to get started.
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  18. @adrian: did you read the article above? The reason why temperatures pretty much stay around 0 in the summer is due to melting ice.

    You seem to be under the impression that the CO2 heat trapping only happens during the day, but in fact it doesn't. If so, temperatures at night would plummet down below freezing every night!

    Furthermore, the greenhouse effect is a *global* phenomenon, not a local one. Heat is added to the global system, and as such it finds its way to all regions of the globe.

    Instead of focussing on slightly dropping surface temps in summer, you should ask yourself why temperatures during the rest of the year have dramatically increased.

    "These guys in Denmark actually measure temperature all over the region up there"

    Yes, and they agree the Arctic has been warming up, as I indicated above.
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  19. Your still not answering my question gentlemen.The above article describes why there may not be much movement in the arctic in the summer time but it fails to explain why its cooling down since 1958 in the summer when c02 should be having its greatest impact. Even a marginal up trend should be occurring during the summer with 24 hr sunlight........What am I missing here?
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  20. Adrian, before we spend more time on this, can you just confirm that you understand increased atmospheric CO2 won't behave differently depending on whether it's summer or winter, or light or dark for that matter?
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  21. I must say that WUWT's treatment of this makes it hard to stay on topic. Strange blending also leads to such jokes as "Again, the years 2008-2010 is not really supporting any downward trend, although the entire period 1978-2009 shows decline using a banal flat trend."

    "Oh, Muffy, your trend is so banal, my dear. You should see my stylist at the WUWT salon."
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  22. Adrian Smits @ 19 - The above article describes why there may not be much movement in the arctic in the summer time but it fails to explain why its cooling down since 1958 in the summer when c02 should be having its greatest impact.

    Guess that depends on how one defines "greatest impact". There is indeed a great impact on the Arctic sea ice volume.



    And extent:

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  23. Adrian: Fill a pot with ice cubes. Add water. Put a thermometer on top of the ice and water. Put the pot on the stove. Turn the stove on. Watch the thermometer.

    So long as the ice remains the surface temperature reading will be right about 0 C. All the heat being generated by the stove goes into melting the ice. Exactly the same thing is happening in the Arctic. Until that ice is gone the temperature will stay right around 0 C. In the Arctic it gets a bit warmer (1 C) because wind and currents can move the ice around and cause areas of open water, but those are minor weather fluctuations with no statistically significant trend. This can be clearly seen in Figure 2 above... the red annual trend in the DMI data is clearly increasing while the green summer trend is nearly flat. The enhanced greenhouse effect is present year round, but in the summer the extra energy it causes has not yet melted away the ice in the small area covered by the DMI data.

    Do the ice in the pot experiment. It should help you understand that anyone claiming that lack of warming over an ice covered ocean contradicts AGW is lying to you. So long as satellites show that area covered by ice the temperature CAN'T go up... but that doesn't mean there isn't more heat - any more than the lack of temperature increase at the water surface of the pot means that the stove isn't generating heat.

    It should also be pointed out that the DMI results are "extrapolated" just like the GISS results... just from a smaller/more geographically concentrated set of measurements.
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  24. Hi John and company :-)
    Simple question: When everyone (?) can see, that its rather risky business for GISS to guess what temperatures are in the ice sheet near the North pole just using land temperatures over 1000 km away - why do GISS do this? Why dont they mark the ice sheet covered area GREY and stop wild guessing?

    K.R. Frank Lansner
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  25. - And im sooo sorry for my Danglish, but maybe you guts has the format to figure out the message anyway?
    K.R. Frank Lansner
    ...My name has been spelled wrong 2 times in this skepticalscience writing, I think I can cope :-)
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  26. Why dont they mark the ice sheet covered area GREY and stop wild guessing?

    If you're calculating a global mean temperature anomaly, and you leave the high-latitude Arctic out of your analysis, you're effectively assuming that the Arctic has the same temperature anomaly as the rest of the globe.

    Which seems like a more reasonable estimate for the temperature anomaly at the North Pole: a weighted average of temperature anomalies at other Arctic sites, or the average temperature anomaly for the whole rest of the world, the vast majority of which is outside the Arctic?

    Incidentally, interpolation is a well defined mathematical process, and the GISS algorithm for doing this has been replicated nicely by others (e.g., Clear Climate Code). Let's reserve the term "wild guessing" for cases where people are ... actually guessing.
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  27. FLansner at 23:58 PM on 20 October, 2010

    Thank you for responding here. My sincere apologies for the typo on your name at the start of the article, I have corrected this. The "advanced" version does cover the question of the 1000km interpolation used by GISS in the high Arctic. This has been shown to be reasonable based on studies of the station data and NP and IABP drifting buoy data, temporary Ice Station/aircraft comparative studies, as well as the satellite data from AVHRR. The temperature anomalies are fairly homogenous over quite large distances in the ice covered Arctic. This is clearly not the case in the tropical regions where El Nino upwelling occurs, which is the example of land/ocean transition you use in your article to cast doubt on the use of interpolation. Obviously the tropical land/ocean and polar land ice/sea ice coastal regions are very different.

    DMI also suggest that transitions (bias) for example from ERA-40 to later higher resolution models could account for some of the Summer differences you have highlighted. These differences are clearly small compared with the average overall rising trend in the same DMI data.

    You may be interested in the more detailed comparison of GISS 12 month rolling average data gridded above 80N compared to DMI >80N rolling 365 day average data in the chart in the advanced version? The Arctic region presents challenges, and we should treat the data carefully, but as Ned says, we are far from wild guessing.
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  28. No Ned they are guessing because they use temperature measurements from 1000 km away on land that is not covered with ice.That's why the GISS temperature anomaly is so far out of whack with the DMI measurements.Besides CBDunkerson claims the temperature hardly changes at all in the summertime in the high arctic so why should they be extrapolating from so far away where the land does get clear of snow and warm up.CBDunkerson has explained the mechanics of of how things work up there reasonably well.but those mechanics where the same 50 years ago and with more and more open water in that region supposedly getting warmer and warmer why does DMI show average cooling that is fairly pronounced in the summertime over the last 50 years....still waiting. thank you.
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  29. #26 Ned at 00:31 AM on 21 October, 2010
    Which seems like a more reasonable estimate for the temperature anomaly at the North Pole: a weighted average of temperature anomalies at other Arctic sites, or the average temperature anomaly for the whole rest of the world, the vast majority of which is outside the Arctic?

    Neither one, of course. The proper thing to do is to measure it directly. As you can see arctic temperature trends are quite different above land, sea ice and open sea.



    As there are all kinds of buoys drifting in the ice, air temperature above the Arctic ocean is actually measured. Why is it so hard to incorporate these data into the surface datasets? Or at least to use them as controls to validate eerie interpolation algorithms? Informatics anyone?

    There is even a buoy with a webcam deployed each year right at the pole, with its own temperature record.
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  30. BP, that's basically non-responsive. If anything, the figure you paste in confirms my point nicely -- trends at or near the pole tend to be more similar to trends elsewhere in the high Arctic than to trends further south. Presumably, if your figures extended to the equator, there'd be no visible correlation at all there.

    Lansner specifically asked why GISS doesn't just leave the Arctic blank. I answered that question -- leaving any region "blank" when calculating a global mean temperature anomaly implicitly assumes that that region's anomaly is identical to the average of the rest of the globe.
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  31. adrian smits writes: No Ned they are guessing because they use temperature measurements from 1000 km away on land that is not covered with ice.That's why the GISS temperature anomaly is so far out of whack with the DMI measurements.

    Except they aren't "out of whack" at all. Did you even bother reading the article by Peter Hogarth at the top of this thread? The 50-year trend for DMI is +0.37C/decade and for GISS it's +0.35C/decade. Here's Figure 3 from Peter's post, in case you're having trouble finding it:


    Figure 3: Annual DMI and GISS Arctic temperature anomalies and trends

    So, if you like the DMI data, you ought to conclude that GISS does a good job of estimating Arctic surface temperature trends.
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  32. Has anyone really looked at Berenyi Peter's seasonal sat.trends figure 9? If you look at the scale white would seem to indicate some cooling above 80 degrees for summer fall and winter.I don't get it.What am I missing when I look at those maps? The middle of the white scale is -0.5. So I'm correct in assuming the arctic has been cooling for three seasons and not just the summer.....anyone?
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  33. Adrian #32: "What am I missing when I look at those maps?"

    The 'white' range is actually -0.5 to 0.5, rather than just -0.5 as you stated. A white area on the map could thus represent anything from mild cooling to mild warming.

    Also, while there is alot of white, the Winter and Fall maps show areas of warming greater than 0.5 in the 80 degree area (innermost circle) and Spring shows alot. Only Summer is completely white and thus 'flat'. The other three seasons show warming. Thus the warming trend shown in the annual DMI data for that region and only the Summer data being flat... because of the ice cover.

    Looking at satellite images of the Arctic ocean it looks like the 80 N area has been almost completely ice covered even at the September minimum point every single year recorded. There simply haven't been any large / prolonged areas of open water in that zone to allow temperatures to start increasing.

    Yet.

    If ice volume continues to decline at the rate it has been that previously permanent ice cover in the 80 N circle is going to change in the next few years... and then we'll see increasing temperatures for that region just like most of the rest of the planet (i.e. pretty much everything except a similar small area around the opposite pole).
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  34. Should have also mentioned; those maps BP put up are 13 years out of date.
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  35. I see -1.0 on the left side of the white -0.5 in the middle and +0.5 on the right side of the white part of fig. 9 are my eyes playing tricks on me?
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  36. Adrian @35....no, it seems not. Weird. It is a poor quality image, so maybe the colours are not represented correctly.
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  37. If you go to the original site by clicking on the image it is possible to see that the -1.0 to -0.5 range is actually a very light grey rather than white.
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  38. Examining the image (having copied it into an image processing program from the original site), the -1.0 to +0.5 region is entirely white. There's an apparent contrast over the -0.5, but that's an optical illusion.

    Poor choice of image colors, in my opinion.
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  39. Huh, that's weird. In any case, a better copy of the image from the original source;

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  40. My apologies, I was incorrect in my last post. The figure as represented on the summary web site shows white from -1.0 to +0.5, but the originals from the paper show a light blue from -1.0 to -0.5, and white from -0.5 to +0.5. Looks like some color fidelity got lost when putting together the summary website.
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  41. BP, Adrian, Flansner,
    Where is the data from 30 years ago to compare the current bouys to? GISS has published an analysis of this data and have shown that their estimates are closer to reality than using the global average. HADCRU has published a paper stating that they underestimate the arctic temperature rise due to their use of the global average. Can you produce peer reviewed papers that support your claim that the GISS estimates are inferior to your proposals? Without data you are just suggesting you are smarter than GISS.

    The DMI data comes from a model, not actual measurements. Can you suggest why it is better than the GISS model? Provide data please, not just opinions. The data Peter shows here shows that the two analysis are similar. Perhaps the bias introduced by DMI changing models is the only problem.
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  42. Why is BP posting data that does not show the last 13 years of warming? Those years are when the Arctic warmed the most.
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  43. Berényi Péter at 01:53 AM on 21 October, 2010

    If you go to the "advanced" post linked at the beginning of this article, you'll see some actual buoy data. You can assume most published work on Arctic surface temperatures in the ten years since 2000 (such as Polyakov 2002) will reference this. GISS are of course well aware of the satellite and buoy data, and DMI incorporate buoy data. I cover this briefly.

    michael sweet at 06:34 AM on 21 October, 2010

    The "analysis" link is not connecting? Although the DMI data is from a model, the model is loaded with actual measurements, and quite a lot of them from satellites to get the high spatial resolution necessary for "weather forecasting".
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  44. Hi Peter Hogarth!
    Im very positively surpriced by your kind tone and welcome indeed. One could hope the climate debate was like this in general.

    I am answering questions on 3 blogs now on this issue, so i hope you can forgive im a little late, here.

    As I understand you, there are trouble for GISS projections in regions near pacific equator.
    Well... :-) Why do GISS then do this?

    But very important: What I showed in my original article was, that GISS projections for SST has problems all over the world.

    May i remind you this important graphic from the article:
    http://hidethedecline.eu/media/ArcticGISS/fig6big.jpg

    I have made many areas black so that only GISS projected SST are shown in the UPPER graphic. And then the corresponding HADLEY SST is shown in the lower graphis.

    The match in the whole world [SNIIIIP] aerm... is not good. Its not just the Arctis, its not just somewhere we see a terrible mismatch. Its everywhere.

    If such a match is good enough for a method to be used by NASA, its really incredible.

    K.R. Frank Lansner
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  45. Hi Frank (re #44),

    Could you please explain to us why then there is such excellent agreement between the surface temperature data and those from the satellite MSU data, not to mention the balloon data and OHC data? And note that the MSU satellite data are not calibrated against the surface temperatures. Your concerns have been addressed on this very site and elsewhere.

    The surface SAT records (GISTEMP, HadCRUT, JAMA, NOAA-NCDC), despite their known limitations, are robust.

    The Arctic is warming at twice the rate of the rest of the globe-- that has been determined from multiple, independent data sets, and is explained by a phenomenon called "polar amplification". It is no artifact.
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  46. Berényi Péter at 01:53 AM on 21 October, 2010

    The first data you cite is ocean flux buoy data (ocean temperature data) which is not quite relevant to surface temperature, but the second linked data set is recent and pertinent. The snippet of data in the link very nicely shows the Summer 0 degrees C clipping effect. I will try to get the complete high resolution time series updated (given time) as I have the earlier buoy data. If we look at slightly less up to date buoy data as in Polyakov 2002, where: “The datasets of monthly surface air temperature and sea level pressure used in this study contain data from land stations, Russian NP stations, and drifting buoys operated by the International Arctic Buoy Programme (IABP)”. We see again GISS correlates well over the buoy data period. Below I have plotted the Polyakov Arctic annual values with publicly available GISS annual Arctic zonal values. The buoy data is used from around 1950 onwards in Polyakov.

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  47. FLansner at 08:28 AM on 21 October, 2010

    As I understand it, GISS has access to relatively high spatial resolution land and ocean measurements over most of the globe, and they have no need to extrapolate unless station data is actually not available (as over much of the very high Arctic) or SST data and local air temperature are very different (as near the "boundaries" of the high Arctic sea ice).
    0 0
  48. Hi Albatross,
    The resemblance or lack of same between different sources of temperature data i have written a lot about:

    http://hidethedecline.eu/pages/posts/the-perplexing-temperature-data-published-1974-84-and-recent-temperature-data-180.php

    Here i would focus on PART 4, where for example this graphic appears:
    http://hidethedecline.eu/media/PERPLEX/fig78.jpg

    Here, notice how UAH OCEAN temperatures rather nicely follow the SST (called CSST, an average of different hadley and NOAA sources to SST). But the UAH LAND temperatures does not match the different sources of land temperatures, being GISS, GRUTEM3, Vinnikov and NCDC.

    The overall difference between UAH and the land based readings are not so easy to see when land and ocean are combined, but difference for land is clear. This indicates that something makes land temperatures (mostly taken from cities) are too hot, and this could be explained by UHI.

    But this general idea you have that all the different sources just shows the same is very wrong. Even the individual balloon sources dissagre (!) RATPAC has one story, ERA-40 another for example.

    But to get back to the Arctic area near the North pole 80-90N: We have only the choice between data measured in the area (DMI) or data projected from land far away. I think you need biiiig globalwarming glasses not to see what data source is most reliable.

    K.R. Frank Lansner
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  49. Hi Peter!

    Its true, GISS has mostly 2 "products", its only in one they use the projections. Non the less, these projections are seen not rarely when argumenting for global warming, for instance in this NASA graphic used to show that the Arctic is going crazy:
    http://hidethedecline.eu/media/arctic%20temperatures/nasa2005.jpg

    But to make the Arctic look Sooooo dark red as on the NASA site here, they used start year 1955. But as you see in comment 46 above, start year 1937 would have shown something else. And using DMI/ERA-40 data would have shown a more nuanced picture.
    If you say that both GISS and DMI is only so-so useful, then i think they should make the area grey.

    K.R. Frank
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  50. FLanser,

    Are surface temperature records reliable? (argument #6)
    The warming trend is the same in rural and urban areas, measured by thermometers and satellites.

    Does Urban Heat Island effect exaggerate global warming trends? (argument #21)
    Urban and rural regions show the same warming trend.
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