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Friday, April 8. 2016

Math models


A model is only as good as its power to predict.


Climate models appear to have no predictive capacity. Very short-term meteorological models have some use, but are often wrong. Economic models are famously wrong.  Ordinary common sense people like me anticipated, planned for, and profited modestly from the internet bubble and the housing bubble. Not the professional math geniuses.  Why not?


The Chinese ancients used math modeling to predict the future: The new astrology - By fetishising mathematical models, economists turned economics into a highly paid pseudoscience


It is dangerous to mistake models for reality.



Posted by The Barrister in Hot News & Misc. Short Subjects at 13:40 | Comments (16) | Trackbacks (0)

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The very shortest term meteorological models (less than 5 days) are the most accurate. Edward Lorenz famously proved that 5- day forecasts were about the upper limit of reliable forecasting, back in the early 60s... chaos math.

The lead article didn't mention the most infamous models of all, the climate models, which are being used to change Western democracies (for the worst) at every turn. It's gotten so bad, that US Senator Sheldon Whitehouse and a number of State attorneys general are calling for the prosecution of "climate deniers". Goodbye free speech. The entire climate fearosphere revolves on the axis of climate models, which are notoriously inaccurate, bearing little resemblance to real- world data, yet here we are.
#1 Alan Robertson on 2016-04-08 16:33 (Reply)
pimf- Should read: (for the worse,). All apologies.
#2 Alan Robertson on 2016-04-08 16:38 (Reply)
Economic models refuse to incorporate mass-people behavior (Asimov's Harry Seldon did it) even though retrospective analysis frequently attributes the "errors" of the model or prediction to people behaving in a mass-ignorant manner, it never gets added to the equation. The argument is always that the peoples will get themselves educated and make reasonable, rational decisions...

Climate modelers can't even reach a consensus to define the components of climate. (hides so she doesn't have to find sources for this argument) The geologic record allows us to see changing climate but transitional periods are just too large to break down and reconstruct as predictive, short term models. Or maybe they just aren't even trying this....
#3 ama on 2016-04-08 17:24 (Reply)
I don't recall where I found this quote, but it seems appropriate regarding models and forecasting:

In an autobiographical essay published 20 years ago, the left-leaning economist Kenneth Arrow recalled entering the Army as a statistician and weather specialist during World War II. “Some of my colleagues had the responsibility of preparing long-range weather forecasts, i.e., for the following month,” Arrow wrote.

“The statisticians among us subjected these forecasts to verification and found they differed in no way from chance.”

Alarmed, Arrow and his colleagues tried to bring this important discovery to the attention of the commanding officer. At last the word came down from a high-ranking aide.

“The Commanding General is well aware that the forecasts are no good,” the aide said haughtily. “However, he needs them for planning purposes.”
#4 Ralph Carbone on 2016-04-08 17:42 (Reply)
> A model is only as good as its power to predict.

I think you mean a scientific model. What we face so often these days are political models, which operates as follows: a political model is only as good as the power it transfers to those supporting the model.

There is no reason we should be surprised by this mode, it's what you get when you let politicians select what research gets funded.
#5 Rabble on 2016-04-09 02:33 (Reply)
QUOTE:
Math models

A common source of confusion is between global warming and climate change. Global warming refers to the Earth's mean average surface temperature, which is known to be increasing due to greenhouse gases. Global warming will inevitably cause changes to regional climates, but the climate system is chaotic, so prediction is fraught with difficulties.
#6 Zachriel on 2016-04-09 09:16 (Reply)
...which is known to be increasing due to greenhouse gases data manipulation.

FIFY
#6.1 BillH on 2016-04-09 09:48 (Reply)
BillH: ...which is known to be increasing due to greenhouse gases data manipulation.

Multiple, independent analyses of the raw data support a warming trend. See, for instance, Berkeley Earth.
http://berkeleyearth.org/summary-of-findings/
#6.1.1 Zachriel on 2016-04-09 09:52 (Reply)
au contraire mon frere That is exactly the point that models are inaccurate and the climate models are fraud. The so-called scientists have fudged the data, changed the data, cherry picked the data and tweaked the computer models to give a result that they want. If you pick the right starting year we have had at best 0.5 centigrade temperature increase in the last 100 years. If you carefully cherry pick you can make it appear we have had a greater temperature increase and conversely if you start the calculation from 1934 we have had about a 1 degree centigrade decrease in temperature.

The little ice age ended about 1850, it was inevitable that temperatures would rise slightly and they did. This began long before the first SUV or massive burning of fossil fuels. It is simply one of the continuing cycles of our climate. And thank god it happened. We have 7.2 billion people and we could not feed them if the climate was the same as in 1850. The warming cycle is so much friendlier to the flora and fauna than the cooling cycles are. Woe unto us when the cycle reverses and we return to global cooling. And it will. The AGW meme is a scam, an intentional fraud to extort money and power from a scientifically ignorant populace. It is a Marxist power grab on a massive scale.
#6.2 GoneWithTheWind on 2016-04-09 09:59 (Reply)
GoneWithTheWind: if you start the calculation from 1934 we have had about a 1 degree centigrade decrease in temperature.

Glad we agree. The globe has warmed. It is projected to continue warming. Last year was a record warm year, breaking the previous record from the year previous.

GoneWithTheWind: The little ice age ended about 1850, it was inevitable that temperatures would rise slightly and they did.

That's right. However, natural causes do not explain the extent of the warming trend, but greenhouse warming does.
http://berkeleyearth.org/wp-content/uploads/2015/02/annual-with-forcing-small.png

There is also positive evidence of greenhouse warming, that is, not only is the surface warming, but the stratosphere has cooled.
http://www.metoffice.gov.uk/hadobs/hadat/images/update_images/global_upper_air.png

The danger isn't current warming, but that warming is expected to continue.
#6.2.1 Zachriel on 2016-04-09 10:37 (Reply)
We do agree that there has been warming and I believe we both know it is a result of the natural climate cycles and not CO2 or human actions. The difference is for you AGW is both a religion and a political tool to facilitate converting Democracy to Socialism. The problem with the religion of AGW is their commandments do not include "Thou shalt not lie". But more like the Islamic religion in the AGW religion lying is allowed and encouraged if it furthers your goals.

Your statement "The danger isn't current warming, but that warming is expected to continue." really says it all. It is both an acknowledgement that so far the warming hasn't been significant AND that all the potential scary stuff is simply a prediction based on computer models which provably do not work.

The very real fear is the return of the next global cooling cycle. That will be a disaster of biblical proportions. Ponder the maunder.
#6.2.1.1 GoneWithTheWind on 2016-04-09 15:29 (Reply)
GoneWithTheWind: We do agree that there has been warming and I believe we both know it is a result of the natural climate cycles and not CO2 or human actions.

As already pointed out, natural causes do not explain the extent of the warming trend, but greenhouse warming does.
http://berkeleyearth.org/wp-content/uploads/2015/02/annual-with-forcing-small.png

GoneWithTheWind: The very real fear is the return of the next global cooling cycle.

Anthropogenic global warming is overwhelming the natural cycle. See Feulner & Rahmstorf, On the effect of a new grand minimum of solar activity on the future climate on Earth, Geophysical Research Letters 2010: "a moderate temperature offset of no more than −0.3°C in the year 2100 relative to a scenario with solar activity similar to recent decades. This temperature decrease is much smaller than the warming expected from anthropogenic greenhouse gas emissions by the end of the century"
#6.2.1.1.1 Zachriel on 2016-04-10 08:44 (Reply)
GoneWithTheWind: The so-called scientists have fudged the data, changed the data, cherry picked the data and tweaked the computer models to give a result that they want.

Berkeley Earth works with the raw data.
#6.2.2 Zachriel on 2016-04-09 10:40 (Reply)
Atmosphere math: in 3 dimensions, flows tend to shorter and shorter scales, so no resolution is adequate for representing the flow. But you need the short flows because they act as a sort of ersatz viscosity back on large scale flows. So you can't compute the atmosphere.

But wait! In two dimensions, flows don't tend to shorter scales. In fact, something called vorticity is conserved, and is sometimes itself used to compute what the atmosphere will do.

The difference is that a vortex can't kink in two dimensions, but it can and does in three dimensions.

Since weather is mostly large scale two dimensional flows, weather computations are good until something kinks, which is a couple of days or so. Then it fails.
#7 rhhardin (Link) on 2016-04-10 12:01 (Reply)
"natural causes do not explain the extent of the warming trend"

And yet the warming trend is far less than the previous natural and cyclical warming trend (Medieval warming). And in fact the current warming trend is very moderate and benign. It is unlikely that we could sustain 7.2 billion people on earth without this beneficial climate.

"Anthropogenic global warming is overwhelming the natural cycle"

Except for the last 23 years where there has been zero global warming. AGW is so overwhelming that it has stopped. The consensus has fallen apart and a majority of scientists now believe there is no AGW and/or that the real fear is the inevitable global cooling cycle that is eminent.

The simple truth is there was never any AGW and the warmie/Marxist simply used this natural cyclical event as a huge fraud to extort money and power from free people in democratic countries with the intent of destroying the world's economy and making it ripe for a Marxist/socialist revolution. The warmies have admitted it, their secret emails have confirmed it and their actions prove it.
#8 GoneWithTheWind on 2016-04-11 10:16 (Reply)
GoneWithTheWind: And yet the warming trend is far less than the previous natural and cyclical warming trend (Medieval warming).

While there have been very warm periods in Earth's history, the current warming is already warmer than at any period in the last thousand years, and probably longer. Keep in mind that warming is expected to continue.

GoneWithTheWind: Except for the last 23 years where there has been zero global warming.

Last year set an instrumental record for surface temperature, which broke the record set just the year before.
#8.1 Zachriel on 2016-04-11 15:01 (Reply)

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