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Saturday, March 12, 2016

Uncertainty in uncertainty

I may seem to pick on Marcott et al. 2013, but that paper came out while I was playing with ocean paleo-reconstructions in the tropics.  Marcott used a number of tropical paleo reconstructions that I didn't use because they were too coarse (ultra low frequency) and had a unknown uncertainty in the samples.

The unknown uncertainty is "natural" averaging.  Most of the proxies are based on plankton of some sort and the biological temperature proxies would go through boom bust cycles.  You can have more depositing of a particular type of plankton during either.  So if you have a core sample say one inch thick that spans say 300 years, one particular good growth period would dominate the sample or one massive die off could.  The published accuracy of the sample is based on how well a lab can count something not how well biological life fits a normal distribution assumption.

At the time I was using the Oppo et al. 2009 and the Mohtadi et al. 2010 aka Anand on the legend was the low frequency reconstruction I didn't use.  There is a large difference between the two, especially near the end.  The lower frequency reconstructions have more uncertainty in dating which is pretty well know plus the natural averaging of the samples isn't known and the impact isn't discussed as far as I know.

Most of the criticisms of Marcott, Mann and other paleo re-constructors deal with just about everything other than the "effective" averaging produced "naturally" by the organisms and unintentionally by "novel" methods.

My curiosity might be misdirected, unfounded or irrelevant, especially since I am a Redneck and not a part of the "scientific" establishment, but since just about every higher resolution "cap" reconstruction diverges from lower resolution reconstructions, I am a tad stubborn about wanting a few answers.

It is a bit frustrating to me since in Redneckville such an obvious issue would dealt with something profound like, "What the F__ is going on!" but in climate scienceville some dweeb starts babbling about standard error when this is pretty much a non-standard situation :)

Technically, the error is only about a degree or about equal to the estimated amount of warming during the instrumental period and you can massage or polish all you like, but the result should always consider the absolute magnitude of the potential error if it is never specifically addressed.  In order to reduce the error you have to do more digging and less assuming.  It is very unlikely the error is "normally" distributed uniformly over the entire time frame of the reconstruction which is part of the assumptions made to get those unbelievably tight error margins in the published literature.

Inquiring Rednecks want to know what's the deal Lucille?

Friday, March 11, 2016

How to make history disappear as if by magic

Greg Goodman has a nice post on basic issues with Ordinary Least Squares regression analysis at Dr. Curry's place.  Someone asked about what impact it would paleo reconstructions of sea level.  While I don't have a specific sea level example I do have a sea surface temperature example.

The yellow curve is from the Mohtadi et al. 2010 paper reconstructing temperatures of the Indo-Pacific Warm Pool which has an sample rate of about 400 years and the blue curve is from Oppo et al. 2009 from the same area but it has a sample rate of about 50 years.  With more samples and higher resolution you get a clearer picture.  The Mohtadi reconstruction was one of many reconstructions used in the seriously flawed Marcott et al. paper of 2013.

If you regress Oppo with respect to Mohtadi you would have oranges on the x axis and apples on the y axis.  If you just average the two, the coarser Mohtadi would smooth out the information in the finer Oppo.  Either way you end up with a flatter than it should be past history and a sudden pop, either up or down when the influence of the coarse Mohtadi data ends.  If you pick coarse data or make higher resolution data coarse by inappropriate or "novel" averaging, you can make the details of the past disappear, as if by magic.  Even though Oppo et al. 2009 was available for Marcott and company it was not included in their "ground breaking" paper.

This is like the most basic of basics screw ups, so someone with a bit of knowledge would assume ignoring the obvious has to be deceptive instead of frigging stupid, if the mistake is made by a "professional" and published in a peer reviewed journal.  Unfortunately, since nearly everyone has access to canned statistic packages, stupidly using extremely powerful statistical tools is more likely than intentional deception.

With only the options of dishonest or stupid, tact becomes a bit of an issue.  Most engineers are not know for excessive amounts of tact, generally expect professionals to know what they are doing and have close to anal attention to detail, so they lean toward the dishonest accusation.  Hey!  It is an honest mistake and no one really likes being called stupid.

Back in the day, scientists had plenty of time to ponder prior to responding through snail mail or journals, so they were a lot more creative in parsing their insults.  Now a days, time is money and profanity is more socially acceptable.  Deal with it.

Thursday, March 10, 2016

Error Cascade

Judith Curry had a post on Error Cascade back in 2012.  There are tons of ways to screw up and one not so big screw up can lead to a progression of more screw ups that end in pretty spectacular failures.

There is some fairly new hysteria online about Arsenic in rice, water, apple juice and just about everything, since Arsenic is common if soils.  Some of the "Organic Gurus" primed the pump with Arsenic in poultry.  OMG!  Chicken farmers are feeding Arsenic to chickens then you eat them!!  Damn, that has to be bad, right?

I was bored and Googled a few things.  It appears the Arsenic deal started in Bangladesh in 1994.  Water wells had a higher than normal level so the WHO stepped in to set a few standards a limit Arsenic in water to about 50 ppb.  Since most places do not have as high a level, the WHO set somewhat arbitrarily a 10 ppb standard for every place else.  Once the drinking water standard was set and set pretty low, the US EPA requested research into field testing kits that were cheap and could read down to close to zero to include the 10 ppd water standard.

I haven't found out everything I want about the timing of Arsenic sample testing, but it appears that 5 ppb with any real accuracy is a pretty new development.  Consumer Reports got some on the new test kits and started testing whatever blew wind up their skirts and had a "block buster" discovery that some rice crop could have up to around 160 ppb Arsenic content.  This got the US "health food" guys going.

In the mean time, scientists with WHO recommended that Bangladeshi folks switch from deeper wells to shallow wells and surface water to reduce exposure to the killer Arsenic.  Surface water and shallow wells are not know to be great water sources in areas with poor sanitation, lots of people and lots of diseases.  So a MIT study found that the water source switch was killing more children that the Arsenic.

The FDA, concerned with the US food supply, basically took the position that there is no evidence that Arsenic in low ppb amounts is doing any harm.  The Arsenic in chicken haters pretty much forced the FDA to set limits on Arsenic in poultry even though that Arsenic was "organic" and posed a much lower health risk than Inorganic Arsenic.

All the time this was going on, "Organic Food" fans were developing pseudo-scientific remedies for Arsenic poisoning that has never been determine to really be a problem.  I stumbled on "Seattle Organic Restaurants" website and they recommended a "cleansing" using bananas and coconut milk to flush the deadly toxin from your pristine bodies.  Coconut milk and bananas can have as much or more Arsenic as some rices and both are an order of magnitude greater that the frigging chicken which has mainly organic arsenic to begin with :)

I am extremely grateful to Dr. Curry for enlightening me with error cascade because the terminology I was used to was "Cluster Fuck".

Throwing the Baby out with the Drinking Water: Unintended Consequences of Arsenic Mitigation Efforts in Bangladesh,

Update: More cascade potential fun.  Flint City has started replacing lead pipe run outs with new copper run outs to the meter.  Toronto, Canada did the same and noted that partial replacement, city to meter but no owner change out tended to make the lead situation worse.  Most northern cities do not like using PVC for run outs mainly because of union plumber concerns.  Using non-conductive PVC instead of copper would reduce at least part of the issues with partial replacement.  So catastrophe fans, things should get interesting.  Toronto's lead pipe replacement program questioned.