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#1463253 - 06/05/2018 18:56 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 434
Loc: Pinjarra Hills, Qld
I don't necessarily think 1960-90 is relevant, it is just a point of reference. My point is that selecting a reference period is as difficult as understanding the climate 'signals' because the signals are all probably occurring over different cycles, some driving some responding, and some we don't know what they are?
If the focus of this thread is short term I have less interest in signals longer than a decade or two. If the focus is climate drivers then it is a whole different ball game.
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#1463255 - 06/05/2018 19:10 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: Mike Hauber]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 434
Loc: Pinjarra Hills, Qld
Originally Posted By: Mike Hauber
Its a simple scientific fact that the rainfall for the recent wet season was below the average for the last 30 years.

There is nothing to stop someone from comparing the wet season to the average from 1930 to 1960 (which was drier so the recent season would be wetter than that average). But I'm not sure what relevance that comparison would have to anything.

Its not cherry picking to pick the last 30 years if the period 1930 to 1960 gives a different answer. Cherry picking applies if a similar period gives a different result. But picking the last 25 years, or the last 35 years. Or 30 years to 5 years ago or whatever is going to give almost the same result.


To be strictly correct the last 30 years would be 1987-2017 smile
Nonetheless I agree about same result of about 'normal'.
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Models are for estimating and gauges are for knowledge.

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#1463258 - 06/05/2018 19:25 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: Mike Hauber]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 2028
Loc: Wollongong, NSW, Aus
Originally Posted By: Mike Hauber
Its a simple scientific fact that the rainfall for the recent wet season was below the average for the last 30 years.

There is nothing to stop someone from comparing the wet season to the average from 1930 to 1960 (which was drier so the recent season would be wetter than that average). But I'm not sure what relevance that comparison would have to anything.

Its not cherry picking to pick the last 30 years if the period 1930 to 1960 gives a different answer. Cherry picking applies if a similar period gives a different result. But picking the last 25 years, or the last 35 years. Or 30 years to 5 years ago or whatever is going to give almost the same result.


However, it is cherry picking when you know that the last 30 years were drier than the previous 30 years, so you remove the signal thereby making it “drier”.

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#1463260 - 06/05/2018 19:38 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 434
Loc: Pinjarra Hills, Qld
Rather moot point about above/below 'average'. Same if the words are "wetter" or "drier" than average. Can confidently say though our last northern 'wet' season was not exceptionally far from the average either way for much of 'northern' Australia, no matter how one wants to define reference climatology.
_________________________
Models are for estimating and gauges are for knowledge.

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#1463270 - 06/05/2018 21:32 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: Kino]
Brett Guy Offline
Meteorological Motor Mouth

Registered: 05/10/2010
Posts: 5075
Loc: Bently Park, Cairns
Originally Posted By: Kino
Originally Posted By: Mike Hauber
Its a simple scientific fact that the rainfall for the recent wet season was below the average for the last 30 years.

There is nothing to stop someone from comparing the wet season to the average from 1930 to 1960 (which was drier so the recent season would be wetter than that average). But I'm not sure what relevance that comparison would have to anything.

Its not cherry picking to pick the last 30 years if the period 1930 to 1960 gives a different answer. Cherry picking applies if a similar period gives a different result. But picking the last 25 years, or the last 35 years. Or 30 years to 5 years ago or whatever is going to give almost the same result.


However, it is cherry picking when you know that the last 30 years were drier than the previous 30 years, so you remove the signal thereby making it “drier”.


Picking ANY 30 year period is cherry picking. We have over 100 years of data. The only thing that is not cherry picking(and therefore borderline dishonest) is using the entire dataset.

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#1463279 - 07/05/2018 08:36 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: Kino]
Mike Hauber Offline
Weatherzone Addict

Registered: 13/07/2007
Posts: 3059
Loc: Buderim
Originally Posted By: Kino


However, it is cherry picking when you know that the last 30 years were drier than the previous 30 years, so you remove the signal thereby making it “drier”.


The last 30 years were wetter than the previous 30 years. I think you should make an effort to understand such basic points to an argument before trying to tell other people they are wrong.

The claim is that last wet season was drier than the average of recent years. The rainfall for the previous 30 years is not relevant to such a claim. If I was trying to make some claim about some 'one true average' then there could be an argument, but I am not.

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#1463280 - 07/05/2018 08:40 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 2028
Loc: Wollongong, NSW, Aus
Oh, I fully understood the arguments, hence why I pointed out you were cherry picking, again.

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#1463310 - 07/05/2018 14:32 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Delta-T Offline
Cloud Gazer

Registered: 21/01/2011
Posts: 37
Loc: Peachester
Seems to me this thread I misnamed. "Enso, IOD, PDO ,SAM etc" are emergent effects of climate not the cause. Ie they do not 'drive' the climate, the climate drives them. There are many climate drivers - Milankovitch cycles, plate techtonics etc.

Up-thread it was suggeted that "solar" input is the main climate driver. But that is very ambiguous. If the inference is that dumping 1367 watts per sqm on the earth's surface 'drives' the climate then it is true. But if "solar" means 'variation' in solar irradience then that is just silly given that the climate is being driven to a warming trend while irradience is going in the opposite direction.

A better title might be Short term climate cycles (Enso, IOD, PDO ,SAM etc)

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#1463313 - 07/05/2018 14:43 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 2028
Loc: Wollongong, NSW, Aus
Good point. That seems far more appropriate.

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#1463327 - 07/05/2018 17:09 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: Kino]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7422
Loc: Adelaide Hills.
Originally Posted By: Kino
Originally Posted By: Seira
I'm done with BS talk in this and similar threads...either be reasonable about things and invite discussion, or lose it!


Since when are you the arbiter? Aren’t you the one always demanding scientific analysis? What Petros said is 100% scientific - cherry picking isn’t scientific.

To clarify, it was not an arbitrating post, and it was and is my choice.

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#1463333 - 07/05/2018 18:26 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: Mike Hauber]
Petros Offline
Meteorological Motor Mouth

Registered: 30/12/2002
Posts: 6925
Loc: Maffra, Central Gippsland, Vi...
Originally Posted By: Mike Hauber
Its a simple scientific fact that the rainfall for the recent wet season was below the average for the last 30 years.

There is nothing to stop someone from comparing the wet season to the average from 1930 to 1960 (which was drier so the recent season would be wetter than that average). But I'm not sure what relevance that comparison would have to anything.

Its not cherry picking to pick the last 30 years if the period 1930 to 1960 gives a different answer. Cherry picking applies if a similar period gives a different result. But picking the last 25 years, or the last 35 years. Or 30 years to 5 years ago or whatever is going to give almost the same result.


Fully agree Mike, hence why I fully endorse your post about past 30 years rainfall (or any other period you or anyone cares to select when making a point.

It was the period selected by others (1960 to 90? forgot!) that is used as an "average" that I think was politically, not scientifically, selected. Just me saying, and agenda free.

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#1463337 - 07/05/2018 19:11 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: Delta-T]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 434
Loc: Pinjarra Hills, Qld
Originally Posted By: Delta-T
.... "Enso, IOD, PDO ,SAM etc" are emergent effects of climate not the cause.
.....

A better title might be Short term climate cycles (Enso, IOD, PDO ,SAM etc)


I support that.

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#1463365 - 08/05/2018 07:54 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: Petros]
retired weather man Offline
Weatherzone Addict

Registered: 01/07/2007
Posts: 4501
Loc: Wynnum
Originally Posted By: Petros
Originally Posted By: Mike Hauber
Its a simple scientific fact that the rainfall for the recent wet season was below the average for the last 30 years.

There is nothing to stop someone from comparing the wet season to the average from 1930 to 1960 (which was drier so the recent season would be wetter than that average). But I'm not sure what relevance that comparison would have to anything.

Its not cherry picking to pick the last 30 years if the period 1930 to 1960 gives a different answer. Cherry picking applies if a similar period gives a different result. But picking the last 25 years, or the last 35 years. Or 30 years to 5 years ago or whatever is going to give almost the same result.


Fully agree Mike, hence why I fully endorse your post about past 30 years rainfall (or any other period you or anyone cares to select when making a point.

It was the period selected by others (1960 to 90? forgot!) that is used as an "average" that I think was politically, not scientifically, selected. Just me saying, and agenda free.


I replied to this last time this argument surfaced - WMO ( World Meteorological Organization ) sets the world wide standard
called The Standard 30 Years, from which all member countries use for their averages. When I joined the Bureau the years used were 1930 to 1960. These Standard Years are advanced every couple of decades when the figures for the next proposed 30 year standard are thoroughly checked before publishing as the latest standard.


Edited by retired weather man (08/05/2018 07:54)
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#1463367 - 08/05/2018 08:00 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: Brett Guy]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 434
Loc: Pinjarra Hills, Qld
Originally Posted By: Brett Guy


We have over 100 years of data.


A comparison to the 118 years of data can be made for year to date or month to date rainfall such as this year to date:
http://www.bom.gov.au/water/landscape/#/...rate///2018/1/1

However that page on BoM website does not have an option for October to April rain total comparison.

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#1463382 - 08/05/2018 11:28 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: retired weather man]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 2028
Loc: Wollongong, NSW, Aus
Originally Posted By: retired weather man
I replied to this last time this argument surfaced - WMO ( World Meteorological Organization ) sets the world wide standard
called The Standard 30 Years, from which all member countries use for their averages. When I joined the Bureau the years used were 1930 to 1960. These Standard Years are advanced every couple of decades when the figures for the next proposed 30 year standard are thoroughly checked before publishing as the latest standard.


Is 30 years sufficient to determine any real trend? Given a planet with billions of years existence? It seems insignificant? Perhaps this is why any "drivers" are misunderstood, poorly modelled and reactive.

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#1463386 - 08/05/2018 12:28 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: Kino]
Mike Hauber Offline
Weatherzone Addict

Registered: 13/07/2007
Posts: 3059
Loc: Buderim
Originally Posted By: Kino


Is 30 years sufficient to determine any real trend?


Yes. Trend analysis follows statistical laws - can the observed trend be duplicated by random variations. These laws work the same regardless of whether the planet has been in existence for decades or billions of years.

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#1463405 - 08/05/2018 18:36 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: retired weather man]
Petros Offline
Meteorological Motor Mouth

Registered: 30/12/2002
Posts: 6925
Loc: Maffra, Central Gippsland, Vi...
Originally Posted By: retired weather man
Originally Posted By: Petros
Originally Posted By: Mike Hauber
Its a simple scientific fact that the rainfall for the recent wet season was below the average for the last 30 years.

There is nothing to stop someone from comparing the wet season to the average from 1930 to 1960 (which was drier so the recent season would be wetter than that average). But I'm not sure what relevance that comparison would have to anything.

Its not cherry picking to pick the last 30 years if the period 1930 to 1960 gives a different answer. Cherry picking applies if a similar period gives a different result. But picking the last 25 years, or the last 35 years. Or 30 years to 5 years ago or whatever is going to give almost the same result.


Fully agree Mike, hence why I fully endorse your post about past 30 years rainfall (or any other period you or anyone cares to select when making a point.

It was the period selected by others (1960 to 90? forgot!) that is used as an "average" that I think was politically, not scientifically, selected. Just me saying, and agenda free.


I replied to this last time this argument surfaced - WMO ( World Meteorological Organization ) sets the world wide standard
called The Standard 30 Years, from which all member countries use for their averages. When I joined the Bureau the years used were 1930 to 1960. These Standard Years are advanced every couple of decades when the figures for the next proposed 30 year standard are thoroughly checked before publishing as the latest standard.


Sorry RWM, didnt see the post about this when you made it.

If that's true (not questioning it), I must admit it's welcome news to me and leaves me simply wondering "when does the next 30 year increment sample become adopted"?

Like others, I cant get my head around why then or now, 30 years is a valid sample, assuming reasonable quality of rain records (typically high quality).

.....still learning, and love the topic.

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#1463408 - 08/05/2018 19:29 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 434
Loc: Pinjarra Hills, Qld

In my opinion if the focus of the thread is short term 'trends' in climate (whether that be cause or response) a thirty year sample would be adequate for expectations of many typical "climate scenarios". If such 'scenarios' could be defined, but are not, so it is vague.
For extremes of climate or longer term climate 'causes' or 'responses' thirty years is inadequate.

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#1463411 - 08/05/2018 20:10 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Locke Offline
Weatherzone Addict

Registered: 27/12/2007
Posts: 4446
Loc: Brisbane
Would "Natural Climate Cycles 2018" be a good, non-contentious, broad ranging title for the thread?

This covers discussion around forecasting and impacts of ENSO, IOD, PDO, AMO, AO, NAO, SAM and MJO just to name a few.

In the end though I guess the title doesn't matter as much if people understand what the thread is for and use it accordingly.
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This post and any other post by Locke is NOT an official forecast & should not be used as such. It's just my opinion & may or may not be backed by sound meteorological data. For official information, refer to Australian Bureau of Meteorology products.

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#1463412 - 08/05/2018 20:25 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: Locke]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7422
Loc: Adelaide Hills.
Originally Posted By: Locke
In the end though I guess the title doesn't matter as much if people understand what the thread is for and use it accordingly.

On that point I agree smile .

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