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Did GISS discover 30% more land in the Northern Hemisphere?

Posted By Joanne Nova On July 16, 2010 @ 7:54 pm In Global Warming | Comments Disabled

:-o UPDATED with GLOBAL values! The questions get bigger.  (See below) July 18th.

Frank Lansner has been a busy man, and he’s asking some very thought provoking questions.

The Northern Hemisphere has a ratio of 40% land to 60% oceans, and the Hadley Met Centre seems to use a similar ratio (NH HadCrut Series: 58% ocean, 42% land). But  Frank Lansner wondered why, when he graphed the GISS land-data-set alongside the combined-sea-surface-temperatures (CSST), GISS comes up with an “averaged” line that runs much closer to the land data set and not the sea surface set. If it were weighted 60:40 (ocean:land) the combined Northern Hemisphere line ought to run slightly closer to the ocean based temperatures.

So Lansner mixed the land and sea temperatures in different ratios and graphed them and an odd thing occurred. Perhaps there is some good reason for it, but the GISS NH average line is currently running close to a mix that could be almost 70% land, and only 30% ocean. Back in 1985 the NH Average was closer to the sea temps as would be expected. In fact as late as 1995, the NH line still ran at around 40% land area. But somewhere post 1995 – 1999 for some reason (see the update at the bottom for some good suggestions) the average tracks closer to the 70% line. According to Frank, this effect does not occur with the HadCrut average.

GISS temperatures compared with land ocean ratios

GISS temperatures compared with different ratios of land: ocean data values. See below for a description of the CSST (Combined Sea Surface Temperature).

Frank is looking for feedback and suggestions, and wondering if there could be any other explanation. So am I. The effect is clear also in this graph. The land-based datasets are the brown ones near the top. The blue ones in the middle are GISS and then below that Hadley, then finally the black line is the satellite measured average for land and sea, and the combined sea surface temperatures. It’s interesting how closely the satellite set compares with the sea surface data.

Land and Sea data sets

Comparing land and sea and “average” combinations.

Lansner points out that the key difference between the brown lines at the top and the blue-black lines underneath is that Urban Heat Island only affects the lines at the top (i.e. there is no urban heat island over the oceans, and not too much “urbanity” near the satellites either). Lansner further split up the satellite measurements into satellite-land versus satellite-ocean and what’s especially interesting is how the satellite-land values agree better with the ocean measures after 2001 than they do with the surface-land thermometers. Are we eyeballing the effects of UHI and siting problems in the thermometers on the land, and are GISS somehow inadvertantly amplifying these artificial effects with weighting, homogenisation, gridding or averaging proceedures that rely more on these land measurements than on the independently consistent satelites and sea surface measures?

Urban Heat Island Effect on Surface measurements?

Urban Heat Island Effect on Surface measurements?

As would be expected the land temperatures are more volatile than the sea, and the two might split for a while, but then return to each other, as you’d expect. You can see here that the green line (which is the difference between the land and sea temps) returns to zero every 10 or 11 years or so. (Is any one else thinking about sun spot cycles?)

Land temperatures and sea temperature variation

Land temperatures and sea temperature variation

Combined Sea Surface Temperature (CSST)

Frank combined the Northern Hemisphere sea surface records from 1960 onwards where they all agree fairly well. Prior to that there were wildly different recordings that make SST’s less easy to combine meaningfully, though some inconsistencies show up after 1990. The CSST curve is a smoothed graph calculated as an average of the above series of smoothed and 5 yr averaged data. (This graph is Fig 25 in Part II)

Graph: Sea surface temperatures combined for the northern hemisphere

Sea surface temperatures combined for the northern hemisphere

Comparing Hansen’s graphs over time

Frank Lansner got started on this line of reasoning by working back through the 1945-1975 decline that he had written on in March 2010. In Part II of his new post he compares changes and adjustments Hansen graphs over time in more detail and combines them into one (see below). The decline that was well known from 1945 – 1975 still becomes less of a decline as the newer analyses are published. But the latest version of NASA´s compilations of NH temperatures today are not calculated the same way the original GISS-product from land stations on continents and islands was described earlier.

As Frank says: “For some reason, the methods of using ocean data has been changed from surface air data to water temperatures measured 2 m under sea surface. So, now the NH temperatures are build on sources: GHCN 1880-06/2010 + SST: 1880-11/1981 HadISST1, 12/1981-06/2010 Reynolds v2″

The color of cold?

Lansner also finds this particular graph, which, rather like Sherwood 2008, uses an “unintuitive” scale.
The graphic below from Hansen and Lebedeff 1987,  shows the temperature trends from 1940-65. At a glance you might guess that things have become a little warmer. But the color of -0.5 to 0oC is a yellow, rather than a cool green, and it covers vast tracts of the world (most of Africa, Western Europe, North America, the North Atlantic, Siberia, and India). For the world to “look warmer”, it only needs to cool by less than half a degree. The “turning point” in the color scheme is at -0.5, not zero. This makes it look like cooling is only occurring in a few isolated spots.


Lansner points out in Part I that many of the reasons offered in papers for “adjustments” could just as easily change the data in either direction. The only way to know if the adjustments (which always seem to bring the observations of the world closer to the carbon-dioxide-powered-models) are legitimate would be for an independent team to go through all the data sets, all the reasons, and all the individual cases. It would be a large job. Does the free world really want to rely on unfunded volunteers to make sure that work gets done? Wouldn’t it be prudent to pay professional scientific auditors (no, not me) to go through the entire set with the aim of finding as many holes and flaws and inconsistencies as they can? Presumably, if it’s all unfaultable, expert and honest, they won’t find much that matters.

Lansner’s full original four part post is here and I know he would appreciate comments and feedback.  It’s quite ambitious, and it would be helpful if these lines of inquiry could be followed up. He’s done an extraordinary amount of work. If there were more funded positions for scientists who were interested in finding other causes of warming (non-greenhouse ones) these kinds of questions would have been posted years ago, and would not be left to volunteers to ask.

Thanks to DE, Cohenite, and George White for thoughts, and of course, thanks to Frank.

UPDATE 1: How land measurements take over the high seas…

Boballab #9 I think you will find that the reason has to do with the way GISS adjusts temperatures to make their gridded product. You will find that they use thermometer readings from land to adjust sea surface temperatures up to 1200km out to sea. An example of this is islands like Guam and Diego Garcia and the entire Arctic. Go to this link and turn off the SST data and use the 1200km “smooth”: http://data.giss.nasa.gov/gistemp/maps/

From that you will see that the Arctic is a bright red color, the Arctic’s water temperatures are being derived from Land measurements from around that ocean.

Now with the SST data still turned off turn the smooth down to the 250KM setting and you get a vastly different picture. There is almost no data for the Arctic anymore, it has turned gray. You will also see the vast gaps in terresterial coverage too.

Now do the reverse with the SST data turned on and the land data off. On both the 1200km and the 250km smooth the entire Arctic ocean has no data, none, zip, zilch, zero. No SST data is used for the entire Arctic Ocean or the waters around Antarctica.

Now combine the land and SST data in the GISS map maker program and you once again get that nice big red splotch across the Arctic.
This shows that the so called water temperatures for the Arctic is 100% derived from LAND measurements, and probably why Frank is getting the readings he is (since one entire oceans readings are nothing but extroplations from LAND data). The HADCrut3 product of the Hadely center and CRU does not extrapolate Arctic temperatures, they leave it blank, only GISS does this. Matter of fact Phil Jones commented on this in one of the Climategate emails and that is how GISS got 2005 so hot, by using land readings as Arctic SST readings, and treating the Arctic Ocean as Land

DB writes in comment #10 - The most likely reason for the overweighting of land temps in the northern hemisphere lies in the Arctic. Since sea surface temps are not available when the the Arctic Ocean is covered with ice, GISS extrapolates land temperature anomalies out over the ocean. This graph by Bob Tisdale shows the total overlap of GISS land only and land+sea for the Arctic: GISS follows this practice year-round which results in higher anomalies in the summer since the warming trend for Arctic SSTs is about an order of magnitude lower than the land.

UPDATE 2 The Global ratios beg even more questions.

Frank has created a global graph. Back in 1910, the global temperature was a lot more like the sea surface temperatures. But over time, land measurements became more and more important. In the last ten years the global surface average appears to be calculated from a weighting of over 65% land measurements even though globally, land only occupies 30% of all the surface.



Global GISS land sea weighted ratios

Global GISS land sea weighted ratios

To put this in perspective

Frank writes in his new post that this change alone could account for 0.17 OC rise over the last century!

If the 30% land fraction from the real world was used, GISS global 2007 would be 0.55K warmer than GISS global 1900.

With the still increasing GISS land fraction actually used, we have GISS global 2007 0.72K warmer than GISS global 1900.

The difference is 0.17K added by increasing land fraction over the 20th century instead of using 30% land constantly. But this calculation could be done in many ways. We know for a fact that the oceans cover 70% of the planet. So why not use 70% of data from SST?

Animated arrow thanks to WI Gifs & Animations

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