Dr. Roger Pielke Sr. reports that there’s a new paper out with a fun title, based on that famous for Robert A. Heinlein quote : Climate is what you expect, weather is what you get.Posted on 06/30/2012 6:51:59 AM PDT by Ernest_at_the_Beach
Dr. Roger Pielke Sr. reports that there’s a new paper out with a fun title, based on that famous for Robert A. Heinlein quote : Climate is what you expect, weather is what you get.
“The Climate Is Not What You Expect” By S. Lovejoy and D. Schertzer 2012
The abstract reads: (emphasis added by Pielke)
Prevailing definitions of climate are not much different from “the climate is what you expect, the weather is what you get”. Using a variety of sources including reanalyses and paleo data, and aided by notions and analysis techniques from Nonlinear Geophysics, we argue that this dictum is fundamentally wrong. In addition to the weather and climate, there is a qualitatively distinct intermediate regime extending over a factor of ≈ 1000 in scale.
For example, mean temperature fluctuations increase up to about 5 K at 10 days (the lifetime of planetary structures), then decrease to about 0.2 K at 30 years, and then increase again to about 5 K at glacial-interglacial scales. Both deterministic GCM’s with fixed forcings (“control runs”) and stochastic turbulence-based models reproduce the first two regimes, but not the third. The middle regime is thus a kind of low frequency “macroweather” not “high frequency climate”. Regimes whose fluctuations increase with scale appear unstable whereas regimes where they decrease appear stable. If we average macroweather states over periods ≈ 30 years, the results thus have low variability. In this sense, macroweather is what you expect.
We can use the critical duration of ≈ 30 years to define (fluctuating) “climate states”. As we move to even lower frequencies, these states increasingly fluctuate – appearing unstable so that the climate is not what you expect. The same methodology allows us to categorize climate forcings according to whether their fluctuations decrease or increase with scale and this has important implications for GCM’s and for climate change and climate predictions.
The conclusion reads:
Contrary to [Bryson, 1997], we have argued that the climate is not accurately viewed as the statistics of fundamentally fast weather dynamics that are constrained by quasi fixed boundary conditions. The empirically substantiated picture is rather one of unstable (high frequency) weather processes tending – at scales beyond 10 days or so and primarily due to the quenching of spatial degrees of freedom – to quasi stable (intermediate frequency, low variability) macroweather processes. Climate processes only emerge from macroweather at even lower frequencies, and this thanks to new slow internal climate processes coupled with external forcings. Their synergy yields fluctuations that on average again grow with scale and become dominant typically on time scales of 10 – 30 years up to ≈ 100 kyrs.
Looked at another way, if the climate really was what you expected, then – since one expects averages – predicting the climate would be a relatively simple matter. On the contrary, we have argued that from the stochastic point of view – and notwithstanding the vastly different time scales – that predicting natural climate change is very much like predicting the weather. This is because the climate at any time or place is the consequence of climate changes that are (qualitatively and quantitatively) unexpected in very much the same way that the weather is unexpected.
Pielke writes:
There are a series of informative comments on this paper by Judy Curry, Philip Richens, Shaun Lovejoy and others on the weblog All Models are Wrong post
In the insightful comment by Shaun Lovejoy on that weblog, he does write on one issue that I disagree with. Shaun writes
“….deterministic models (GCM’s) reproduce only weather and macroweather statistics (they do this quite well)”.
I agree on weather, but not on macroweather. Macroweather prediction has shown little, if any skill ; e.g. see the papers listed in my post
Kevin Trenberth Was Correct – “We Do Not Have Reliable Or Regional Predictions Of Climate”
Read Dr. Pielke’ whole post here.
**********************************EXCERPT***************************************ferdberple says:
For example, mean temperature fluctuations increase up to about 5 K at 10 days (the lifetime of planetary structures), then decrease to about 0.2 K at 30 years, and then increase again to about 5 K at glacial-interglacial scales.
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In other words, climate does not have a constant standard deviation. This is very important, because it means that the law of large numbers does not apply to climate. You cannot rule out natural variability increasing as time scales increase past 30 years, contrary to the law of large numbers.
Which means that 99.99% of the statistical methods applied to study climate will return incorrect results, because most statistical methods assume a constant deviation.
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Shaun Lovejoy’s comment on Roger’s site is rather good:
In reference to Roger’s disagreement with
deterministic models (GCM’s) reproduce only weather and macroweather statistics (they do this quite well)”
Shaun seems to be saying that GCMs can produce the statistics of “macroweather” quite well, not that they can actually predict or postdict the actual climate at all.
So there we have it – use GCMs for creating a dummy climate for a fantasy game – that’s fine – but don’t apply the results to any real-world problems or you’ll be screwed.
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Joachim Seifert says:
You expect and get the climate knowing the MACRO-climate drivers….
If you don’t know/guess/model/simulate around….you get nothing but
surprise weather… that is the misery of our times…
but it soon will end….JS
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Gunga Din says:
The myth is that there even is a “normal”, or, to rephrase, that there is something that the climate is “supposed to be”.
Drudge has a headline up:
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STORMS WREAK HAVOC...
Line of thunderstorms 100 miles long...
Winds exceed 70 mph...
Millions without power after record-setting heat...
More storms gathering...
Home country.....
And it is July almost.....
I recall many HOT July 4th hot times in Kansas....
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Demetris Koutsoyiannis says:
I am glad to see Shaun’s and Daniel’s paper and I congratulate them–particularly for the catchy title. You may also see an older version of negation of the same dictum in my paper “Hurst-Kolmogorov dynamics and uncertainty” (see http://itia.ntua.gr/1001/ for the 2011 paper – page 492 or pages 23-24 of the preprint; see also http://itia.ntua.gr/944/ for the 2010 predecessor presentation, slide 45).
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Philip Bradley says:
Seems rather trivial to me.
Temperature fluctuations increasing to 10 days is a function of the size and speed of movement of the mid-latitude high pressure systems. Winds are from the north on one side and the south on the other side.
As for predicting macroweather. Here in the southern hemisphere on the western side of Australia, the 10 day forecasts are pretty good. When Pielke says macroweather forecasts aren’t good, I suspect he is referring to the more chaotic NH weather systems.
I feel sorry for so many that have to go through this.
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