Thursday, May 05, 2011

Check Your Wallet

Remember bunnies when Eli, Skeptical Science, Jason Box, and Lucia were discussing how Frauenfelder, Knappenberg and Michaels were hiding the incline? Well it gets better. EveryRabett who looks at Figure 2

would say hmm, don't look like there is that much more melting going on at the end of the record than in ~ 1930, but Every Rabett would be very wrong. Take a closer look at the right end of the figure.

Now look at the legend, notice that the red line is a ten year trailing average. Now, some, not Eli to be sure, might conjecture, and this is only a conjecture, that while using a trailing average is a wonderfully fine thing if Some Bunny, not Chip Knappenberger to be sure, is looking at smoothing the data in the interior of the record, but, of course, Chip understands that if you are comparing the end of the data record to the middle, this, well, underweighs the end. The rising incline of the trailing average at the end is depressed with respect to the data. Some Bunny, of course, could change to a five year moving average, which would make the last point not the average of the melt between 1999 and 2009 but the average between 2003 and 2009, a significantly larger average melt. Of course, this effect would be even clearer if someone, not Eli to be sure, knew that the melt in 2010 was a record.

Eli eagerly awaits much fussing and fulminating from the unusual suspects about how dishonest it is to hide the incline. And convenient

13 comments:

Timothy Chase said...

Ten year *trailing* moving average, huh. Then there is the uncertainty envelope that is bound to be wider on the reconstructed data as opposed to the current with all the instrumentation we have nowadays -- and yet the top of the envelope for 1930 and 1960 is roughly at the same height as present. I wouldn't be surprised if their reconstructed ice melt extent index involves similar slight-of-hand.

jyyh said...

Use of *trailing* or *offset by period of averaging/2* dislocates the thick red line so it doesn't match the x-axis. They're really not into smoothing the ends of the dataset, nor representing the data in an easily accessible manner, however well the reconstruction is done.
statistical uncertainty introduced by smoothing the ends is *not the same* as the uncertainty in the original dataset of the GIS meltdown.
Tamino could perhaps do a crash course on this off the top of his head, I can't but I do remember the uncertainty introduced by smoothing the ends is a fixed amount, increasing by the decrease of the data points averaged. For extra clarity, this end could be marked by using a thick blue line just to indicate the calculation method is different.

Martin Vermeer said...

Oops.

How did I miss this... I'd hate to think what would have happened to Mike Mann, had he even half-thought of doing a thing like this.

Anonymous said...

Why am I not surprised....

ML

Anonymous said...

I'm sure McIntyre was just about to post on this.

arch

Anonymous said...

Commenter Chris at SkepticalScience demonstrates the huge difference using the correct averaging makes to the FKM data, he also included the 2010 data.

http://www.skepticalscience.com/news.php?n=713&p=4#50534

Took him two hours. Yet FKM have not been able to do this or figure it out since last September.

Horatio Algeranon said...

Horatio has found from his experiences climbing mountains that looking back down the trail is always better than looking up.

Makes everything seem less steep...

Neven said...

Also take note of Albatross's comments (#161 onwards) in the same SkS thread.

I think I'll ask Chip Knappenberger to write a letter to my 6-year old daughter 15 years from now to explain why he behaved and acted as he does now. It makes me sad and incredibly angry at the same time.

David B. Benson said...

It's not my wallet I'm worried about.

Anonymous said...

"Yet FKM have not been able to do this or figure it out since last September."
Give them a break. They've been busy.
http://www.skepticalscience.com/news.php?n=713&p=4#50470

Pete Dunkelberg

Anonymous said...

Pete @7/5/11 9:54 PM,

Yes they have been very busy, busy misinforming and spinning the science.....

Wiley Coyote said...

Dear Mr. Dr. Professor Rabbit,

I am sincerely grateful for the admonitions to guard the wallet, which from the standpoint of those of us unfortunate to have no pockets whatsoever, cannot be repeated frequently enough. The marsupials have much less of a problem with this. The warnings of impending fulminations from certain quarters is also much appreciated. Some of us find these so entertaining that even American Idol has lost considerable comparative lustre.

Speaking of entertainment, we have started a book club amongst the pack, as part of our group self edification program. We are somewhat lacking in actual books at the moment, having used our copy of The Honest Broker as tinder on a particularly damp and frosty night last month. Fortunately however, one of us has recently laid hands on a copy of an interesting looking paper titled "An enormous amorphous silica stock in boreal wetlands", by Struyf et al. We think this might well prove more informative and interesting in the long run anyway.

Sincerely,
Wiley

glacierchange said...

The use of the 10 year moving average helped them extend their warm period up through the exceptional warm year of 1961, when by any realistic measure the warmer period was over.