Return to Website

Number Watch Web Forum

This forum is about wrong numbers in science, politics and the media. It respects good science and good English.

Number Watch Web Forum
Start a New Topic 
YouTube Video (Referenced in January 2011 edition of NW)

Near the end, they show a comparison of "model" prediction to "real" data.

I have to call BS on the model depiction.

There is no way their models are able to create definition that tight. I know that we can get Petabytes of data stored now, but to get the granularity they represent on that picture is still not feasible. Geometries of grid size make the data storage issue really challenging. The iteration length (how much time happens between each iteration in the model) is based on the size of the grid and how long it will take a piece of air to move from one side to another. A 100km X 100km grid means an interval of 1 hour (potentially). A 10km X 10km grid means an interval of < 6 minutes. Approximate calculations for the map shown in the story. US is approximately 30 centimeters. 5000km / 30 = 166 km/cm. A millimeter would be about 16km. (I don't think they are down to 10km cells though).

Hmmm. Maybe I am wrong on this. The image on the screen can be deceptive. I use to fret that may pie crusts looked nothing like the ones they made on television. I could never get my dough so homogenous. If I did, the crust would be really tough. I finally realized that the image onscreen was both color shifted and color blended by the process of transmission. Pixels get averaged.

I still think there is a bunch of misdirection going on.

Re: YouTube Video (Referenced in January 2011 edition of NW)

You're referring to the bit around 35 minutes in where the simulation and real data for movement of clouds was being compared on a giant split-screen. A lot of the BS was coming from Paul Nurse who was applauding and expressing delight at the comparison, but I didn't think the comparison being shown on the screen actually looked that good. Nurse is a geneticist and cell biologist, and probably has no experience of running or validating computer models. Also I suspect that a weather model might be being used rather than a climate model. Weather forecasting with computer models supposedly works reasonably well for a period of up to about 4 days from a given starting condition.

The only AGW sceptic blogger who seemed to notice that the comparison was a bit deficient was Lubos Motl in this blog post:


"In another scene, they show two animated scenes - the observed and computer-modeled global cloudiness. The details obviously disagree - and the cloudiness in the regions often differs by a factor of two which corresponds to a several degrees of error in the temperature if the discrepancy in cloudiness is kept for a long time. But they produce lots of bogus statements that the agreement is stunning. Are you just blind, Mr Nurse?"

To properly assess the performance of the computer model you would have to look at predictions of temperatures and precipitation in the various regions rather than noting that moving cloud patterns look vaguely similar.

Re: YouTube Video (Referenced in January 2011 edition of NW)

I too was unimpressed by the computer model comparison segment. Just because they have been able to achieve a qualitative similarity in cloud formation appearance definitely does not mean that they have faithfully reproduced the physics involved.

I was also unimpressed with Professor Phil Jones' complaints of coordinated 'harassment' by sceptics. Jones may well have been inundated with FOI requests, but I do not think it was a case of coordinated harassment but rather a case of earnest, but misguided, blog readers all reading the stories of a few prominent sceptic bloggers detailing their own FOI requests for Jones' data. This provided an excuse for Jones to drag his feet still further in responding to the very first request, owing to a coordinated campaign of 'harassment' because he had too many to deal with. This is a red herring because with the internet, once you satisfy the first request, you have essentially satisfied all of them.