Note: clearly satellites can see urban heat, as demonstrated by this recent paper unveiled at the 2010 AGU meeting by NASA. See: Satellites Image the Urban Heat Islands in the Northeast. It can also be demonstrated that the UHI biases the thermometers upwards. As cities grow, so does the increased bias. In that paper NASA says:
The compact city of Providence, R.I., for example, has surface temperatures that are about 12.2 °C (21.9 °F) warmer than the surrounding countryside…
So when you see images like this one above, where the satellites can clearly see the UHI, wouldn’t it make sense to then just look at the biggest low pass filter heat sink on the planet, the oceans, to see what the difference might be? After all, we don’t have urban heat islands in the oceans. Frank Lansner thinks it is worth exploring in this guest post. – Anthony
UAH reveals Urban Heat
Guest post by Frank Lansner
How UAH (University of Alabama, Huntsville) satellite temperature data supports Urban Heat (UHI) as a real and significant factor when estimating global temperatures.
Northern Hemisphere temperatures in recent years:
Fig1. UAH global temperatures trend equals global sea surface temperatures: The black temperature graph – average RSS+UAH satellite NH (Land + Sea) – has a smaller warming trend than the other (brown) land data series – but in fact resembles the cooler Sea Surface Temperature trend. (The blue graph “CSST” is an average of the rather similar SST´s: MOHSST6, HADSST1, HASSST2, ERSST.v3b, HADISST1and Kaplan SST 98.)
The satellite data represents both land and ocean temperatures – and yet they resemble only the SST´s. Why ?
Satellite temperatures and SST do have one thing in common: They are for sure without the UHI warming error from the cities and airports – they are excluding UHI:
Fig2. Now we split the UAH data up in a land fraction and an ocean fraction. Both still seems to yield considerably lower temperature trends than the land data (brown) measured from mostly cities and airports on the ground.
So UAH land temperatures have colder temperature trend than the ground based land temperatures. Are the land-data deviations due to general issues with the satellite data then? Perhaps the satellite data happens to show colder trends for some “known” reasons etc?
Not likely: There is a good resemblance between the UAH ocean temperature trends and then the directly measured ocean data, SST (“CSST”). This shows that satellite data (and thus also satellite land data) are indeed useful and likely to be correct.
So, unless the satellites always starts to fail just when flying over land, the deviation between land data measured on the ground (mostly from cities and airports) vs. satellite land data is likely to originate mostly from the ground based land measurements. This “extra heat trend” seen in the ground based land temperature data may be explained by UHI + possibly faulty adjustments of data and siting problems.
– One more result might also support the correctness of UAH data:
Systems will always seek equilibrium.
On fig 2 we see a pattern of gabs between the UAH land and ocean data. However, after the gabs the UAH land and ocean data these data unite again and thus despite the temporary deviations, they still seem to produce a common trend.
Is it surprising that the temperatures over land and sea will seek equilibrium? Or would it rather be surprising if they did not? What force should maintain a still bigger difference in temperatures between land and see trends?
Fig 3. Lets focus on the temporary gabs between satellite land and ocean temperatures. The green curve represents a de-trended version, just the difference between the land and ocean temperature data from satellite. From fig 3 it appears to some degree that land and sea temperatures align or reaches equilibrium mostly when temperature do not change fast.
Lets take a look at the same phenomenon in the decades just before the satellite age – I use original temperature data published en around 1974-84 for this:
Fig 4. On this illustration we have confirmed, that the land-AIR temperatures are fastest to reach a temperature change “100%”, then the Marine-AIR temperatures comes soon after “80%” and finally the sea water surface temperatures reaches the new temperature level. Again it seems, that after a given time ocean temeperatures and land temperatures tends to find equilibrium. The bac-to-equilibrium-between-land-and-sea-surface-temperatures seems to happen whithin few years, escpecially if general warming/cooling pauses or reverses.
With a reasonable argumentation that also the Land fraction of satellite data is a good indicator of land temperatures, lets look at the “extra heat” seen in the ground based land temperature measurements (mostly from cities and airports). How much “extra heat” do the ground based land data contain?
Fig5. The extra heat in CRUTEM3 land data compared to UAH on NH is 0,103 K per decade.
Fig6. On global scale, the extra heat in CRUTEM3 land data compared to UAH on NH is 0,088 K per decade. (0,23K over 26 years from 1981 to 2007).
If the extra heat in data measured on land is applied to a period 1900-2010 – just to get a rough idea of the possible impact – using 35-40% land area as hadcrut does – we get global extra heat of +0,34 to +0,39 K added to the overall warming of the Earth related to the extra heat occurring when measuring from cities, Airports etc.
0,34-0,39 K is roughly half the supposed global warming 1900 – 2010 , but in this context we cannot claim to have quantitative precision, obviously. But the rough estimate of 0,34-0,39 K suggests that the impact of “extra heat” that cannot be detected by satellites plays an important role when trying to estimate global temperature trends.
The problem of “extra heat” in land temperatures (likely to be UHI and more) is escalated by GISS because they extrapolate the ground based land temperature measurements over the oceans in stead of using real ocean data:
Fig7. In the case of Hadcrut temperature series they use around 35-40% land data when calculating global data, but GISS have a temperature product using roughly twice this fraction for land area as fig 7 shows.
Fig 8 until around 2008 this illustration of land vs ocean temperatures was online at the NASA/GISS website. As we have seen, satellite data indicates that land temperatures from ground has trend around twice the trend of land data from satellite data – and as almost twice the warming trend of SST, ocean data. This tendency is confirmed on fig 8. From 1880 to 2007 we have an ocean warming trend around 0,6K and for land its around 1,2 K – twice.
Again, we saw from 30 years of satellite temperatures that global satellite data matches ocean temperatures rather closely. If valid, then the fig 8 indicates a 0,6 K faulty extra heat, UHI etc from 1880 to 2007.
****
Article from which most graphics where taken:
Review and feedback of the above article by E.M.Smith, Musings from the Chiefio:
“The rewritten past”: http://chiefio.wordpress.com/2010/12/13/the-rewritten-past
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And Bob, please read the text from fig 7. It says:
“Fig7. In the case of Hadcrut temperature series they use around 35-40% land data when calculating global data, but GISS have a temperature product using roughly twice this fraction for land area as fig 7 shows.”
So i actually to begin with wrote “GISS have A temperature product using….”
I did not just write “GISS temperatures says…”, i was actually rather carefull even with this detail that you attack so much?!
Bob, is not Tsurf a GISS product?
?
The problem is, Bob, that is this level of “errors” is enough for you to drown the whole debate with your error claims, I think you could attack pretty much all other stories the same way.
Frank Lansner says: “And Bob, please read the text from fig 7. It says…”
Don’t change the subjecy. We are discussing what you wrote in the preceeding paragraph, Frank. You wrote, “The problem of “extra heat” in land temperatures (likely to be UHI and more) is escalated by GISS because they extrapolate the ground based land temperature measurements over the oceans in stead of using real ocean data…”
You wrote, “Bob, when I show a potential problem for land ground based data measurements, this is a problem for the official GISS online Tsurf product where land data are used for both land and ocean.”
But I just discussed with links to the GISS paper that the GISS dTs is obsolete: If their “current” analysis uses SST data, then the dataset you referred to in the post is “not current”, meaning it is outdated, or obsolete.
You asked, “Why do you think that GISS keep the Tsurf available online with fine maps and data updated every month?”
It is not used in their official proclamations about what year is warmest, so it does not concern me. Again, it is obsolete.
Hi Bob, I think our discussion ( mainly about the GISS dT/“tsurf” product ) is caused by the fact that GISS sends a mixed message to begin with.
Either,
1) The dT/Tsurf product has been ditched, 100% obsolete by NASA it self: Then it makes no sense to criticize that GISS uses it, but in stead sceptics could and should trumpet and celebrate that the crown juvel of Hansens scientific work through times has exactly been ditched by NASA.
Or
2) The dT/Tsurf product is just not the preferred product by GISS, but they still update and mae public the Tsurf Maps and data for the public and thus can and should be criticized for the problems the tsurf has.
Bob, if you are 100% correct, that dT is “obsolete” and I can quote you for this, it is one of the corner stones in Hansens work and scientific standings that is finally withdrawn. This is of course something that would deserve a nice sceptic headline if 100% true. But what would happen if we made an article at WUWT, for example saying “Hansens methodic used and promoted since 1981, 86 has been withdrawn and ditched by NASA” or similar? Then very fast, the counter argument would be: “Oh no, GISS still find it relevant to update the dT/Tsurf and they even bring it on the front page of GISStemp homepage, so they still find it scientifically relevant!”
So this semi-withdrawel of the dT by NASA – in my view has a purpose. They cant defend it, but cant really ditch it 100%.
The “note” you refer to goes:
“Note: LOTI provides a more realistic representation of the global mean trends than dTs below; it slightly underestimates warming or cooling trends, since the much larger heat capacity of water compared to air causes a slower and diminished reaction to changes; dTs on the other hand overestimates trends, since it disregards most of the dampening effects of the oceans that cover about two thirds of the earth’s surface.”
“The dT overestimates trends…” says NASA. ( What year did note start to sound like this??) I recently argued on WUWT that the very method of dT/Tsurf used over Artctic and Antarctic where indeed overestimating trends. I just compared to DMI/ERA-40 data 80-90N, and the error was obvious.
What happened?
Over at SCEPTICAL SCIENCE they went bananas!! They DEFENDED the dT as if this was a goldmine of correct methodic. So I guess, the message, that NASA now says that the dT method overestimates trends should have some more spotlight? And the fact that they still use the method over Arctic/Antarctic and on this ground claims huge Arctic warming… while admitting that the method overestimates? Hmm, it’s a story.. ?
K.R. Frank
Ps, i made a resme of this discussion here: http://hidethedecline.eu/pages/posts/discussion-of-the-article-uah-reveals-urban-heat-210.php – i can imagin you might have some say, and im ready to adjust if I have not refered correctly.
Actually, it was obsolete when shiny new.
Heh.
Frank Lansner says: “Bob, if you are 100% correct, that dT is “obsolete” and I can quote you for this, it is one of the corner stones in Hansens work and scientific standings that is finally withdrawn. This is of course something that would deserve a nice sceptic headline if 100% true.”
Not sure why it would. They don’t use it in their recent reports or press releases, so it’s non-news.