What to make of THIS bizarre anomaly map?
UPDATE: 2 Feb 2009:
Well, if you can’t fix it, at least you can hide it. If you now try making an anomaly map of baseline vs. self you now get this message:
Surface Temperature Analysis: Maps
Anomalies for any period with respect to itself is 0 by definition – no map needed
Guess it is easier to sweep dirt under the rug rather than actually clean up the code…
What Have I Done?
I was exploring another example of The Bolivia Effect where an empty area became quite “hot” when the data were missing (Panama, posting soon) and that led to another couple of changed baselines that led to more ‘interesting red’ (1980 vs 1951-1980 baseline). I’m doing these examinations with a 250 km ‘spread’ as that tells me more about where the thermometers are located. The above graph, if done instead with a 1200 km spread or smoothing, has the white spread out to sea 1200 km with smaller infinite red blobs in the middles of the oceans.
I thought it would be ‘interesting’ to step through parts of the baseline bit by bit to find out where it was “hot” and “cold”. (Thinking of breaking it into decades…. still to be tried…) When I thought:
Well, you always need a baseline benchmark, even if you are ‘benchmarking the baseline’, so why not start with the “NULL” case of baseline equal to report period? It ought to be a simple all white land area with grey oceans for missing data.
Well, I was “A bit surprised” when I got a blood red ocean everywhere on the planet.
You can try it yourself at the NASA / GISS web site map making page.
In all fairness, the land does stay white (no anomaly against itself) and that’s a very good thing. But that Ocean!
ALL the ocean area with no data goes blood red and the scale shows it to be up to ‘9999’ degrees C of anomaly.
“Houston, I think you have a problem”…
Why Don’t I Look In The Code
Well, the code NASA GISS publishes and says is what they run, is not this code that they are running.
Yes, they are not publishing the real code. In the real code running on the GISS web page to make these anomaly maps, you can change the baseline and you can change the “spread” of each cell. (Thus the web page that lets you make these “what if” anomaly maps). In the code they publish, the “reach” of that spread is hard coded at 1200 km and the baseline period is hard coded at 1951-1980.
So I simply can not do any debugging on this issue, because the code that produces these maps is not available.
But what I can say is pretty simple:
If a map with no areas of unusual warmth (by definition with the baseline = report period) has this happen; something is wrong.
I’d further speculate that that something could easily be what causes The Bolivia Effect where areas that are lacking in current data get rosy red blobs. Just done on a spectacular scale.
Further, I’d speculate that this might go a long way toward explaining the perpetual bright red in the Arctic (where there are no thermometers so no thermometer data). This “anomaly map” includes the HadCRUT SST anomaly map for ocean temperatures. The striking thing about this one is that those two bands of red at each pole sure look a lot like the ‘persistent polar warming’ we’ve been told to be so worried about. One can only wonder if there is some “bleed through” of these hypothetical warm spots when the ‘null data’ cells are averaged in with the ‘real data cells’ when making non-edge case maps. But without the code, it can only be a wonder:
The default 1200 km present date map for comparison:
I’m surprised nobody ever tried this particular ‘limit case’ before. Then again, experienced software developers know to test the ‘limit cases’ even if they do seem bizarre, since that’s where the most bugs live. And this sure looks like a bug to me.
A very hot bug…
UPDATE: 1 Feb 2009: Added non-zero biased maps
Over on WUWT, where this thread has been picked up, there was a discussion in comments where the question was raised “does this only show up in NULL maps?”
The assertion was made that anything beyond about 5C was very unlikely to be a valid anomaly. So I’ve made a couple of more maps that I think show these effects bleeding into the non-NULL cases. These are both December 2009 (the default) vs 1998 baseline (a selected value) anomaly maps. One has a 250 km smoothing, the other 1200 km. I think these may show that “this bug has legs”:
So maybe someone up in Alaska can tell us if this year, after a 12 years of cooling from the 1998 peak, is really 12 C hotter than then…
And the more smoothed so muted 1200 km map:
Where the temperature range is reduced a bit, but the coverage is expanded greatly. Still, an 8 C ‘anomaly’ ought to have been noticed…
In looking at the 1998 ‘warmest year’ map it does look like it has a cool Arctic, so who knows. Maybe the ‘warmest year’ wasn’t as hot as the ‘warmers’ were claiming?
In thinking about the likely nature of this bug, one idea that came to mind is that it might be in the ‘display’ part of the code. Perhaps when there are no ‘anomalies’ to display, the graph drawing code does not bother to map some 9999 missing data flags to the normal default of ‘grey’? It’s all speculation. Well, other than the fact that the map as drawn full of red oceans at 9999 C is clearly a bug.