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[bluewave]

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[TerryM]

Bluewave

I was surprised that the SH was effected more than the north, perhaps my fixation on Arctic ice.

I assume when they say "increased storm activity accompanied by a decrease in storm numbers over the

past thirty years.", this would indicate that we're experiencing more damaging storms, even though the number of milder ones is decreasing.

Will the northward expansion of the sub-tropical northern jet stream have an effect on the southern states, or will the effect be more widespread.

Terry

[donsutherland1]

Bluewave

I was surprised that the SH was effected more than the north, perhaps my fixation on Arctic ice.

I assume when they say "increased storm activity accompanied by a decrease in storm numbers over the

past thirty years.", this would indicate that we're experiencing more damaging storms, even though the number of milder ones is decreasing.

Will the northward expansion of the sub-tropical northern jet stream have an effect on the southern states, or will the effect be more widespread.

Terry

I haven't read the paper yet, but look forward to doing so later today. Perhaps the dynamics driving the poleward shift differ. In the Arctic, the warming might be the principal driver? In the Antarctic, the strengthening circulation due to ozone depletion might the the main driver?

[CoastalWx]

To me, it would have been more beneficial to observe the change in jetstreams over 60 years and even longer, instead of 30 years to capture our decadal cycles. I'm not sure how conclusive the study is because of that time constraint.

[ORH_wxman]

To me, it would have been more beneficial to observe the change in jetstreams over 60 years and even longer, instead of 30 years to capture our decadal cycles. I'm not sure how conclusive the study is because of that time constraint.

I agree. I am pretty sure that we have shifted the PJ northward in time as we warm...however, we think that decadal oscillations can mask or enhance a trend and starting at the beginning of one cycle and ending right as the other one is beginning might create a trend that is not representative of a longer term trend. (i.e. the PJ likely shifted southward in the 1940s-1970s timeframe as the globe cooled after it had shifted northward in the 1900-1940 time frame).

[tacoman25]

I haven't read the paper yet, but look forward to doing so later today. Perhaps the dynamics driving the poleward shift differ. In the Arctic, the warming might be the principal driver? In the Antarctic, the strengthening circulation due to ozone depletion might the the main driver?

And, as others have pointed out, natural fluctuations may also play a significant role over a 30 year time frame. Man-made factors are not the only drivers of climate shifts, especially over such short time spans.

[TerryM]

And, as others have pointed out, natural fluctuations may also play a significant role over a 30 year time frame. Man-made factors are not the only drivers of climate shifts, especially over such short time spans.

The paper disagrees as far as the jet stream displacement and blames AGW.

Terry

[Sundog]

What natural cycles would be responsible for driving the jet streams into higher latitudes? Are any of the reponsible cycles in their warm phase at the moment? And how long before they flip to a "colder" phase?

[tacoman25]

The paper disagrees as far as the jet stream displacement and blames AGW.

Terry

I, and others, are not saying AGW didn't play a role. The point is that over a 30 year period, it's easy for natural climate fluctuations to also have a signficant impact on such trends. Did you read the other posts above mine relating to this?

To simply apply to the AGW blanket to every short term climate trend, as often seems to be the case even by professional scientists, is too simplistic imo. There is still so little known about the natural fluctuations in our climate system, but we do know now that especially over a 2-3 decade period, they can have a substantial impact and cause some pretty noticable changes.

[tacoman25]

What natural cycles would be responsible for driving the jet streams into higher latitudes? Are any of the reponsible cycles in their warm phase at the moment? And how long before they flip to a "colder" phase?

Well, we know that the AO/NAO goes through periods where it is more negative, which I believe would cause the jet stream to sink further south due to high latitude blocking. The late 1970s-80s was a period with more high latitude blocking than the 1990s-mid 2000s. Then we have seen high latitude blocking return to a greater degree since 2008-09.

[ORH_wxman]

What natural cycles would be responsible for driving the jet streams into higher latitudes? Are any of the reponsible cycles in their warm phase at the moment? And how long before they flip to a "colder" phase?

Oceanic decadal cycles would help cause this if the shift northward is due to warming. Esp if amplification is occurring at the higher latitudes. The temp gradient between high latitudes and lower latitudes is what drives the PJ.

The colder phases of the AMO/PDO likely helped cause a significant cooling globally between the 1940s and 1970s with the arctic region being especially affected where it cooled 9 times faster than the global temperatures. This study does not cover that period which is where it would be interesting to see the results. Recently, the arctic in the 1990s and 2000s has warmed 7 to 8 times faster than the globe. While there is almost certainly an anthropogenic component to the warming, there is also likely a natural component as well.

If one was to claim no natural component to the temperature variation on a decadal scale, then they would have to explain the cooling period in the mid-20th centruy despite dramically increasing GHG concentration...and soon might have to explain a significant flat lining of current global temps if it keeps up another few years.

[TerryM]

"If one was to claim no natural component to the temperature variation on a decadal scale,"

But of course you're aware that no one has claimed any such thing.

One would assume that someone with a red tag would be able to refrain from red herrings when building straw men.

Terry

[tacoman25]

"If one was to claim no natural component to the temperature variation on a decadal scale,"

But of course you're aware that no one has claimed any such thing.

One would assume that someone with a red tag would be able to refrain from red herrings when building straw men.

Terry

You are completely ignoring his overall point and just focusing on one statement.

Taken in context, that statement was following up on the valid point that this study does not cover a full spectrum of the natural cycles that we know influence temperature trends, among other aspects of the global/hemispheric climates. We cannot ignore the fact that over 30 year time periods the climate naturally sees temperature and atmospheric circulation changes, and so to take a study like this and basically attribute the findings to AGW without considering other factors would be a mistake. Will's post, as well as mine, were just reminders of this. What's the big deal?

Btw, "straw man" is the most overrused, over-generalized term used on here. It feels like it's nothing more than a default response most of the time, and a bit of a copout.

[ORH_wxman]

"If one was to claim no natural component to the temperature variation on a decadal scale,"

But of course you're aware that no one has claimed any such thing.

One would assume that someone with a red tag would be able to refrain from red herrings when building straw men.

Terry

That's not true. Don actually posted a peer reviewed study a few months ago which said that nearly all of the recent warming since around 1980 has been anthropogenic which contradicted an earlier study I posted. I cannot remember who the author was, so perhaps someone else would be able to remember. There was also a study posted that said the 1940s-1970s cooling was mostly due to aerosols which also flies in the face of using ocean cycles as a source of that 30 year cooling. Several unnamed posters in here have also suggested that natural ocean cycles play little to no role in decadal variability in temperature.

I am disappointed you decided to take the personal route on this.

[TerryM]

That's not true. Don actually posted a peer reviewed study a few months ago which said that nearly all of the recent warming since around 1980 has been anthropogenic which contradicted an earlier study I posted. I cannot remember who the author was, so perhaps someone else would be able to remember. There was also a study posted that said the 1940s-1970s cooling was mostly due to aerosols which also flies in the face of using ocean cycles as a source of that 30 year cooling. Several unnamed posters in here have also suggested that natural ocean cycles play little to no role in decadal variability in temperature.

I am disappointed you decided to take the personal route on this.

You said:

"If one was to claim no natural component to the temperature variation on a decadal scale,"

Nearly isn't the same a none and neither is mostly. You know this. I'm disappointed that anyone with high school diploma would think that anyone else would allow such a statement to stand.

You overstated your case in order to make a point, and by trying to justify it you're simply digging the hole deeper. If some idiot, perhaps in the thralls of alcoholic dementia, did at some time claim that there was no natural component to temperature variation on any time scale, I'd be the first to direct him to a detox facility - but wouldn't in any way try to prop him up as a straw man so susceptible to almost any variable gust.

I recognize that all the facts are accumulating on our side of the ledger, and the temptation to alter them, dismiss them or belittle them has to be growing as fast as the growth of open waters under the Arctic Sun. Just don't expect that obvious misrepresentations will go unchallenged.

Terry

[tacoman25]

I recognize that all the facts are accumulating on our side of the ledger, and the temptation to alter them, dismiss them or belittle them has to be growing as fast as the growth of open waters under the Arctic Sun. Just don't expect that obvious misrepresentations will go unchallenged.

Terry

Statements like this represent a real problem. This shouldn't be an "us vs. them" discussion - reality is not that simple. There are plenty of shades of gray. And that isn't an attitude open to learning and seeing new points of view. None of us have this all figured out.

What is the point of discussion if this is going to be your approach?

[ORH_wxman]

You said:

"If one was to claim no natural component to the temperature variation on a decadal scale,"

Nearly isn't the same a none and neither is mostly. You know this. I'm disappointed that anyone with high school diploma would think that anyone else would allow such a statement to stand.

You overstated your case in order to make a point, and by trying to justify it you're simply digging the hole deeper. If some idiot, perhaps in the thralls of alcoholic dementia, did at some time claim that there was no natural component to temperature variation on any time scale, I'd be the first to direct him to a detox facility - but wouldn't in any way try to prop him up as a straw man so susceptible to almost any variable gust.

I recognize that all the facts are accumulating on our side of the ledger, and the temptation to alter them, dismiss them or belittle them has to be growing as fast as the growth of open waters under the Arctic Sun. Just don't expect that obvious misrepresentations will go unchallenged.

Terry

The fact you are obsessing this deeply over semantics in an otherwise perfectly sound post is pretty telling.

Either discuss the science or not. But don't start blaming "strawmans" and building semantical cases. The premise of the point I made was that using a 30 year timescale is dangerous to determine trends of anthropogenic forcing. The study posted in this thread talks of such anthropogenical forcing, so my response was in context to that.

[ORH_wxman]

Statements like this represent a real problem. This shouldn't be an "us vs. them" discussion - reality is not that simple. There are plenty of shades of gray. And that isn't an attitude open to learning and seeing new points of view. None of us have this all figured out.

What is the point of discussion if this is going to be your approach?

He doesn't look at this from a scientific standpoint in the true sense of the word. He looks as it as an "us vs them" debate where anyone who isn't on board with the idea that we are causing catastrophic weather extremes (or will in the future) is "them".

Reality, as you said, is quite far from that. There are countless shades of just how much any one of us believes the level of climate sensivity and its effects on our weather.

[TerryM]

Well thank heaven my reasoning processes have been deciphered. The wife's been trying for decades.

I didn't bring up the strawman - merely referenced the elephant in the room. As far as a black of white view of the subject, I think if you flip back through my posts you'll discern a fairly wide range of shadings. When people resort to disinformation, cherry picking or logical fallacies to present their case, I do tend to see them as on the other side.

You might have noticed this difference in the past. Some of us rush to correct misinformation that we, or another arguing our point has made, others allow any distortion to pass if it might distract from the argument at hand. At least a few that minimize AGW share this trait, and I'm usually quick to praise them.

I think I've been corrected at least once by everyone who shares my view that we are in trouble, and I know I've responded in kind. If more of the minimizers developed this mind set, perhaps your biases would be less evident.

Terry

BTW - I'm an old man & it's time for my nap.

[Jonger]

That's not true. Don actually posted a peer reviewed study a few months ago which said that nearly all of the recent warming since around 1980 has been anthropogenic which contradicted an earlier study I posted. I cannot remember who the author was, so perhaps someone else would be able to remember. There was also a study posted that said the 1940s-1970s cooling was mostly due to aerosols which also flies in the face of using ocean cycles as a source of that 30 year cooling. Several unnamed posters in here have also suggested that natural ocean cycles play little to no role in decadal variability in temperature.

I am disappointed you decided to take the personal route on this.

The numbero uno of AGW cop-outs.

[WeatherRusty]

The numbero uno of AGW cop-outs.

Anthropogenic aerosol pollution carries with it a great deal of uncertainty regarding negative radiative forcing, but it is a real and significant factor nonetheless. PDO obviously plays a significant role in moderating global temperature also, assisting the ebb and flow of natural variability on the temperature trend by influencing average equatorial Pacific SSTs.

Nothing of this ignored, however uncertainty imposes rather wide bounds on impact attribution. It's not a cop-out.

[WeatherRusty]

Regardless of natural variability, the shifting of the average jet stream positions poleward due to AGW is the basis for expecting expanded drought conditions in the southwest U.S. as well as increased temperate zone precip poleward as the general circulation adjusts to a warming climate.

[Msalgado]

I haven't read the paper yet, but look forward to doing so later today. Perhaps the dynamics driving the poleward shift differ. In the Arctic, the warming might be the principal driver? In the Antarctic, the strengthening circulation due to ozone depletion might the the main driver?

The Southern hemisphere usually displays a much "cleaner" 3 celled model because the large areas of land mass aren't able to disrupt the pattern with localized heating and low pressure systems. The areas where you see low pressure develop (and in turn drive monsoon patterns) are in places you would otherwise see a subtropical high and this has an effect on jet stream placement (weaker subtropical highs would be less likely to drive the jet stream poleward - I believe)

Disclaimer that I have yet to read the study but on the surface of things I'm not surprised by the response difference in hemispheres because the SH displays a somewhat relatively simpler system.

[donsutherland1]

The Southern hemisphere usually displays a much "cleaner" 3 celled model because the large areas of land mass aren't able to disrupt the pattern with localized heating and low pressure systems. The areas where you see low pressure develop (and in turn drive monsoon patterns) are in places you would otherwise see a subtropical high and this has an effect on jet stream placement (weaker subtropical highs would be less likely to drive the jet stream poleward - I believe)

Disclaimer that I have yet to read the study but on the surface of things I'm not surprised by the response difference in hemispheres because the SH displays a somewhat relatively simpler system.

Thanks for this additional information, Msalgado. I agree with you about the difference among the hemispheres. I had initially thought that given the more dramatic amplification in the Arctic, the shift in the jet would have been greater there. I had not considered the factors you described for the Southern Hemisphere. Considering that information, it does make sense that even as there has been less amplification down there, the impact on the migration of the jet stream has still been somewhat larger than in the Northern Hemisphere.

[Mallow]

This is actually related to the work that one of my advisers (Dr. Sukyoung Lee) is doing. She is looking into what might cause the poleward shift of the jet, and since her paper is in peer review right now and thus has not yet been published, I'll just say that the fact that the Southern Hemisphere shows a stronger signal is actually no surprise to me, since one of the causes seems to be SH-specific.

[PottercountyWXobserver]

This is actually related to the work that one of my advisers (Dr. Sukyoung Lee) is doing. She is looking into what might cause the poleward shift of the jet, and since her paper is in peer review right now and thus has not yet been published, I'll just say that the fact that the Southern Hemisphere shows a stronger signal is actually no surprise to me, since one of the causes seems to be SH-specific.

ozone?