'Hurricane Sandy: The next climate wake-up call?'

[skierinvermont]

Enviro Canada posts weekly not daily - week ending 11/5 started 10/29 - the day Sandy touched down.

That said the hurricane certainly hooked before that date, and the conditions that caused it to back to the west were in place before then. If the Greenland block had not been in place Sandy would have ended by steaming east so your point is well taken.

To show that Sandy was normal event all that's required is to show the frequency of October hurricanes that have veered west in the past. If this happened with some regularity, then regardless of landfall Sandy was a normal event that could be expected with or without AGW influence. The higher sea levels are a given, but if the atmospheric conditions are being influenced by AGW we should expect more of the same in the future.

Salbers

I think the Battery records are being averaged since 1856? while global sea level rise at 3 mm is quite recent. Would the global rise drop if shown as a linear trend since that time?

Terry

There are many storms that have turned west near that latitude.

Storm #3 1901

storm #4 1903

storm 5 1913

storm 7 1923

storm 4 1928

storm 7 1932

storms 5 and 7 1961

storm 4 1962

[LocoAko]

Interview with Dr. Francis from Rutgers:

http://citizensclimatelobby.org/content/q-role-global-warming-plays-extreme-weather-such-hurricane-sandy

Q & A on Role Global Warming Plays With Extreme Weather Such as Hurricane Sandy

Oct. 26, 2012 -- As residents in mid-Atlantic states and New England brace for Hurricane Sandy, many may wonder what role global warming is playing with this "Frankenstorm." Here to explain the linkage is a Q & A with climate scientist Dr. Jennifer Francis, research professor at the Institute of Marine and Coastal Sciences, Rutgers University.

Is global warming extending the hurricane season and also the range of these storms?

Warm ocean temperature is one of the main ingredients necessary for tropical storms to form and survive, so the fact that the oceans in general are warming and that sea-surface temperatures are now at an all-time record high off northeast N. America suggests that any late-forming storms that move up this way, like Sandy, should be able to survive longer and track farther northward.

The warming of the Arctic brought record-setting ice loss this year. How is that ice loss and the warmer Arctic affecting our weather?

Our research suggests that the fact that the Arctic is warming twice as fast as the rest of the globe is having two effects on the jet stream that play into weather patterns all around the northern hemisphere. One is to reduce the temperature difference between the Arctic and areas farther south, which tends to weaken the west-to-east winds in the jet stream. A weaker flow tends to make the jet stream take larger north-south excursions, just like a river tends to meander more as it flows across a shallow-sloped coastal plain. The other effect is to stretch the northward peaks of waves in the jets stream farther north, which enhances the size of the waves and consequently the chances of blocking patterns, like we're seeing now in the conditions steering Sandy. Both of these effects of Arctic warming tend to make the jet stream wavier, and as those waves get larger, they tend to move more slowly, which means the weather associated with them also moves more slowly...leading to increased chances of the types of extreme weather associated with "stuck" weather patterns.

If global average temperatures are getting warmer, why are we seeing snow storms in October?

For the reasons explained above, the larger waves in the jet stream bring warm air farther north as well as cold air farther south, where it can interact with moisture to create snowstorms earlier in the season (e.g., Halloween storm of 2011) and farther south (e.g., snow in Morocco last winter).

Did the warmer Arctic create the "blocking high" that prevented Sandy from moving out into the Atlantic?

We can't say for sure that the warmer Arctic created the block, as blocking patterns occur naturally, but it may have played a role in making it stronger or extending the ridge of high pressure farther northward or keeping it in place longer than it would have when the Arctic had more ice only a few decades ago.

Has the weakened jet stream increased the chances that winter storms and tropical storms would collide?

To my knowledge there is no research that has suggested this to be true, but considering the possible lengthening of the tropical cyclone season owing to warmer oceans, the ability of tropical storms to travel farther northward before they encounter cold water, and the larger southward dips in the jet stream owing to a warmer Arctic, then it's conceivable that the situation we're seeing unfold this week may become more likely as global warming continues unabated.

CONTACTS: Dr. Francis can be reached at [email protected].

For other questions about Citizens Climate Lobby, contact [email protected].

[TerryM]

There are many storms that have turned west near that latitude.

Storm #3 1901

storm #4 1903

storm 5 1913

storm 7 1923

storm 4 1928

storm 7 1932

storms 5 and 7 1961

storm 4 1962

Skier

The criteria was October hurricanes that veered west, you know - like Sandy.

Did you actually follow the tracks of any of these? 1928's storm was over land and moved west somewhere over the Carolinas after a landfall in Florida. The best on your list is Ester in 1961. In mid September it actually did a loop in about the same area that Sandy had been in when it turned west.

Terry

[skierinvermont]

Skier

The criteria was October hurricanes that veered west, you know - like Sandy.

Did you actually follow the tracks of any of these? 1928's storm was over land and moved west somewhere over the Carolinas after a landfall in Florida. The best on your list is Ester in 1961. In mid September it actually did a loop in about the same area that Sandy had been in when it turned west.

Terry

None of them is a perfect match but they all had some turn to the west at a fairly high latitude. Some of the turns are not large, but Sandy's was not that large either.

[donsutherland1]

The chart shows how rare snow events this early in the season are, as opposed to the much more prevalent late November snows. I read a few reports that mentioned this as the earliest 4' event since records were kept.

Terry,

The 4.7" snowfall was the earliest 4" snowfall since modern recordkeeping began in 1869. However, if one goes back earlier, there was a 6"-8" snowfall in New York City on November 1-2, 1810.

[skierinvermont]

Terry,

The 4.7" snowfall was the earliest 4" snowfall since modern recordkeeping began in 1869. However, if one goes back earlier, there was a 6"-8" snowfall in New York City on November 1-2, 1810.

Attributing one early snow event to AGW, based on a sample size of one, was never justifiable. Especially given the long-term decrease in early snow events based on a larger sample size.

But this just emphasizes the point.

When I pointed out that snowfall in November as a whole was on a strong long-term decline, I was told without any justification that it was only snowfall in the final 3 weeks that AGW was decreasing, but that AGW would increase it in the first week as well (based on a sample size of one). Now we find out that snowfall in the first week is also on the decline.. from 7" in 1810 to 4.7" in 2012.

Of course a sample size of two is not much better than one.

[TerryM]

None of them is a perfect match but they all had some turn to the west at a fairly high latitude. Some of the turns are not large, but Sandy's was not that large either.

Both of the bolded are not true. Please check the tracks yourself. One of the storms makes landfall in Florida - hardly "a fairly high latitude", and Sandy's track was certainly contained a large turn westward.

The reason for restricting ourselves to to the earliest snow occurrences is that further into the season, when snow is much more liable to be experienced under normal conditions, the record gets muddied by unnecessary noise.

You've also mentioned small sample size, but what we actually have, since the inclusion of Don's information from 1810 is a sample size of 202, the fact that only 2 of these samples yielded positive results doesn't change the number of data points we have.

It could be inferred that since they noted snowfalls accurately in 1810, they were probably noting such events in large urban areas much earlier, and that since 1810 had been noted as an anomalous event the record probably stretches back further in that location - but at the moment at least that would be speculation.

LokoAko posted some quotes from Dr Francis that seem to concur with positions I've taken up thread.

She posits that a warmer North Atlantic allows storms to track further north. That the Jet Stream is being effected, as well as "stuck" weather patterns, and that October snowstorms are being experienced further south.

She finds that it's possible that ridging could be stronger, or last longer with the lessened Arctic Ice & even posits that tropical storms merging with winter storms may become more prevalent.

The only thing she didn't touch on was SLR on the east coast, but I think we've already discussed this adequately.

I'm quite willing to drop any other speculations made and concentrate on Dr Francis's points since I thing they combine to adequately demonstrate the growing danger to the east coast in the face of AGW.

Terry

[skierinvermont]

Both of the bolded are not true. Please check the tracks yourself. One of the storms makes landfall in Florida - hardly "a fairly high latitude", and Sandy's track was certainly contained a large turn westward.

The reason for restricting ourselves to to the earliest snow occurrences is that further into the season, when snow is much more liable to be experienced under normal conditions, the record gets muddied by unnecessary noise.

You've also mentioned small sample size, but what we actually have, since the inclusion of Don's information from 1810 is a sample size of 202, the fact that only 2 of these samples yielded positive results doesn't change the number of data points we have.

It could be inferred that since they noted snowfalls accurately in 1810, they were probably noting such events in large urban areas much earlier, and that since 1810 had been noted as an anomalous event the record probably stretches back further in that location - but at the moment at least that would be speculation.

LokoAko posted some quotes from Dr Francis that seem to concur with positions I've taken up thread.

She posits that a warmer North Atlantic allows storms to track further north. That the Jet Stream is being effected, as well as "stuck" weather patterns, and that October snowstorms are being experienced further south.

She finds that it's possible that ridging could be stronger, or last longer with the lessened Arctic Ice & even posits that tropical storms merging with winter storms may become more prevalent.

The only thing she didn't touch on was SLR on the east coast, but I think we've already discussed this adequately.

I'm quite willing to drop any other speculations made and concentrate on Dr Francis's points since I thing they combine to adequately demonstrate the growing danger to the east coast in the face of AGW.

Terry

What you label the sample size depends on how you set up the statistical analysis. If you are going to count every year since 1810 as a sample it doesn't change the fact that there isn't a statistically significant trend. 202 zeros followed by a one is not a statistically significant trend. And as Don pointed out it's actually a one followed by 201 zeros and then another one (# of snows >4" in first week of Nov). There is no trend at all (slope = zero) and if we do a trendline for # of inches of snow in first week of November, the trend is negative because it starts with 7" in 1810.

The data contradicts your assertion, and that of Dr Francis, that early season snow is increasing. Snowfall in the first week of November, and snowfall in November as a whole, is DECREASING. There is NO data to back the position. The hypothesis is nothing other than a knee-jerk reaction to a recent event. There is no peer-reviewed literature predicting an increase in early season snow (in fact the peer-reviewed literature says the opposite). The trends for the first week of November, and November as a whole, are negative, and in the latter case it is a STATISTICALLY SIGNIFICANT trend (probably the first statistically significant trend to be mentioned in this thread).

Regarding Hurricanes you are probably getting different results because you are using a different data source that has numbered the storms differently. Here are the storm tracks of some of the storms I mentioned:

[skierinvermont]

[TerryM]

The track show second to the bottom of your #308 post is I assume 1928 #4.

1928-4

Originating on September 6, 1928 in the Atlantic Ocean off the coast of Africa, Storm #4 tracked west across the ocean, northwest across the Lesser and Greater Antilles, and made landfall in Florida. The storm tracked north over the southeastern United States and entered the CHC Response Zone on September 19^th in Virginia. Storm #4 continued north where it impacted Canada near Niagara-on-the-Lake, in Ontario, on September 20^th, which is also the last track observation for this storm. Storm #4 was a major hurricane in the Caribbean, downgraded to a tropical storm over Georgia and finally a post tropical storm.

Could you explain how this meets any of the criteria we discussed? It made landfall in Florida on the first week of September after coming across the Atlantic on a normal track. It then made it's way northward as it lost power & finally made it all the way to Canada with 35 Knot winds. Where did the hard west hook occur? Was Greenland blocking even involved? How does it qualify as an October Hurricane? I don't think it ever made it north of 30 before landfall so how could it have "turned west near that latitude"

The chart's I've been using have lat & long marked - makes it much easier to ascertain positions and headings. - Simply reading the dates eliminates many of your candidates.

Here's a chart for Sandy (.png files suck)

http://www.atl.ec.gc.ca/weather/hurricane/bulletins/20121028055512.Sandy.png.en

As far as defending Dr. Francis's quotes, I think I posted a link to her paper back in the thread. It was peer reviewed as I recall in one of the more prestigious journals, but I'll see if she doesn't give references for storm frequencies.

Terry

[skierinvermont]

The track show second to the bottom of your #308 post is I assume 1928 #4.

1928-4

Originating on September 6, 1928 in the Atlantic Ocean off the coast of Africa, Storm #4 tracked west across the ocean, northwest across the Lesser and Greater Antilles, and made landfall in Florida. The storm tracked north over the southeastern United States and entered the CHC Response Zone on September 19^th in Virginia. Storm #4 continued north where it impacted Canada near Niagara-on-the-Lake, in Ontario, on September 20^th, which is also the last track observation for this storm. Storm #4 was a major hurricane in the Caribbean, downgraded to a tropical storm over Georgia and finally a post tropical storm.

Could you explain how this meets any of the criteria we discussed? It made landfall in Florida on the first week of September after coming across the Atlantic on a normal track. It then made it's way northward as it lost power & finally made it all the way to Canada with 35 Knot winds. Where did the hard west hook occur? Was Greenland blocking even involved? How does it qualify as an October Hurricane? I don't think it ever made it north of 30 before landfall so how could it have "turned west near that latitude"

The chart's I've been using have lat & long marked - makes it much easier to ascertain positions and headings. - Simply reading the dates eliminates many of your candidates.

Here's a chart for Sandy (.png files suck)

http://www.atl.ec.gc...12.Sandy.png.en

As far as defending Dr. Francis's quotes, I think I posted a link to her paper back in the thread. It was peer reviewed as I recall in one of the more prestigious journals, but I'll see if she doesn't give references for storm frequencies.

Terry

The track bends westward over land while it is still a TC. It doesn't matter whether it is over land or water, the steering mechanisms are the same as long as a LLC persists.

I don't know how many of these tracks bent west because of blocking, but I would bet that is the reason for most of them.

[LocoAko]

The track show second to the bottom of your #308 post is I assume 1928 #4.

1928-4

Originating on September 6, 1928 in the Atlantic Ocean off the coast of Africa, Storm #4 tracked west across the ocean, northwest across the Lesser and Greater Antilles, and made landfall in Florida. The storm tracked north over the southeastern United States and entered the CHC Response Zone on September 19^th in Virginia. Storm #4 continued north where it impacted Canada near Niagara-on-the-Lake, in Ontario, on September 20^th, which is also the last track observation for this storm. Storm #4 was a major hurricane in the Caribbean, downgraded to a tropical storm over Georgia and finally a post tropical storm.

Could you explain how this meets any of the criteria we discussed? It made landfall in Florida on the first week of September after coming across the Atlantic on a normal track. It then made it's way northward as it lost power & finally made it all the way to Canada with 35 Knot winds. Where did the hard west hook occur? Was Greenland blocking even involved? How does it qualify as an October Hurricane? I don't think it ever made it north of 30 before landfall so how could it have "turned west near that latitude"

The chart's I've been using have lat & long marked - makes it much easier to ascertain positions and headings. - Simply reading the dates eliminates many of your candidates.

Here's a chart for Sandy (.png files suck)

http://www.atl.ec.gc...12.Sandy.png.en

As far as defending Dr. Francis's quotes, I think I posted a link to her paper back in the thread. It was peer reviewed as I recall in one of the more prestigious journals, but I'll see if she doesn't give references for storm frequencies.

Terry

FWIW, I don't remember her specifically talking about increased storms in November, etc. She just made a very convincing argument for less progressive patterns/more blocking as well as increased trough/ridge amplitude. This would create stronger storms, more persistent patterns, etc. as we know, and I completely go with what she says. Her theory is well understood (Rossby theory) and she has the data to prove her suspicions (the weakening jet speed, etc). I just didn't see a point specifically about early season snowstorms (which IMO fit into the broader context of her point).

[skierinvermont]

FWIW, I don't remember her specifically talking about increased storms in November, etc. She just made a very convincing argument for less progressive patterns/more blocking as well as increased trough/ridge amplitude. This would create stronger storms, more persistent patterns, etc. as we know, and I completely go with what she says. Her theory is well understood (Rossby theory) and she has the data to prove her suspicions (the weakening jet speed, etc). I just didn't see a point specifically about early season snowstorms (which IMO fit into the broader context of her point).

Yes increased blocking makes sense, but warming temperatures are the stronger factor for early season snows, which is what the data shows as well (statistically significant declining November snowfall for NYC).

[TerryM]

FWIW, I don't remember her specifically talking about increased storms in November, etc. She just made a very convincing argument for less progressive patterns/more blocking as well as increased trough/ridge amplitude. This would create stronger storms, more persistent patterns, etc. as we know, and I completely go with what she says. Her theory is well understood (Rossby theory) and she has the data to prove her suspicions (the weakening jet speed, etc). I just didn't see a point specifically about early season snowstorms (which IMO fit into the broader context of her point).

From the above interview with Dr. Francis

If global average temperatures are getting warmer, why are we seeing snow storms in October?

For the reasons explained above, the larger waves in the jet stream bring warm air farther north as well as cold air farther south, where it can interact with moisture to create snowstorms earlier in the season (e.g., Halloween storm of 2011) and farther south (e.g., snow in Morocco last winter).

Do you mean that she hasn't addressed this connection, or that we are reading too much into her comments.

Terry

[LocoAko]

From the above interview with Dr. Francis

If global average temperatures are getting warmer, why are we seeing snow storms in October?

For the reasons explained above, the larger waves in the jet stream bring warm air farther north as well as cold air farther south, where it can interact with moisture to create snowstorms earlier in the season (e.g., Halloween storm of 2011) and farther south (e.g., snow in Morocco last winter).

Do you mean that she hasn't addressed this connection, or that we are reading too much into her comments.

Terry

Hm... I suppose the latter. I see your point. I just meant (and I apologize if the distinction isn't too clear... I'm a bit rambly today) that with increased amplitudes and slower progression of patterns, extremes of both types will be clear (ie: the complete lack of snow last winter could be attributed, too, as a symptom of this), rather than explicitly stating that this slowdown/amplification will result in "more snow", period. ie: in this context, a decreasing trend of early-season snowfall with notable extreme exceptions seems to make sense...

[skierinvermont]

Hm... I suppose the latter. I see your point. I just meant (and I apologize if the distinction isn't too clear... I'm a bit rambly today) that with increased amplitudes and slower progression of patterns, extremes of both types will be clear (ie: the complete lack of snow last winter could be attributed, too, as a symptom of this), rather than explicitly stating that this slowdown/amplification will result in "more snow", period. ie: in this context, a decreasing trend of early-season snowfall with notable extreme exceptions seems to make sense...

If warming did not also cause extreme blockiness the decline in early snowfall would be even more severe. So in a sense you could say that AGW was a "cause" of early snow by promoting blocking.

However, since the net effect is to reduce the occurrence of early snow events, I believe it would be more accurate to simply say that AGW increases blocking and leave it at that. The effect on early season snow is a net negative.

[tacoman25]

FWIW, I don't remember her specifically talking about increased storms in November, etc. She just made a very convincing argument for less progressive patterns/more blocking as well as increased trough/ridge amplitude. This would create stronger storms, more persistent patterns, etc. as we know, and I completely go with what she says. Her theory is well understood (Rossby theory) and she has the data to prove her suspicions (the weakening jet speed, etc). I just didn't see a point specifically about early season snowstorms (which IMO fit into the broader context of her point).

At one point did this trend begin though?

[tacoman25]

If warming did not also cause extreme blockiness the decline in early snowfall would be even more severe. So in a sense you could say that AGW was a "cause" of early snow by promoting blocking.

However, since the net effect is to reduce the occurrence of early snow events, I believe it would be more accurate to simply say that AGW increases blocking and leave it at that.

I am very suspicious of this theory, partially because I don't recall it being widely accepted or promoted until after we began to see more impressive blocking periods in recent years. Anytime you have Monday morning quarterbacking in science, that doesn't bode well for the scientific process.

[Ground Scouring]

FWIW, I don't remember her specifically talking about increased storms in November, etc. She just made a very convincing argument for less progressive patterns/more blocking as well as increased trough/ridge amplitude. This would create stronger storms, more persistent patterns, etc. as we know, and I completely go with what she says. Her theory is well understood (Rossby theory) and she has the data to prove her suspicions (the weakening jet speed, etc). I just didn't see a point specifically about early season snowstorms (which IMO fit into the broader context of her point).

The bolded might also equate to increased low-level wind shear and stability (due to warmer mid-level temperatures and suppressed anticyclonic flow) in the Atlantic tropics, thereby meaning more years like 2012 with weaker storms and fewer U.S. landfalls. The persistent Plains ridge and Hudson vortex over the past few summer seasons might be prime examples of seasonal persistence due to increased amplification.

[stellarfun]

I think one ought also look at the frequency of intense N. Atlantic cyclones over the years, as to whether there is a frequency trend. Here is a list of four circa 950 mb cyclones in the N. Atlantic over one month's time in 2011.

Storm dates / Lowest pressure

Oct 25-28, 951 mb

Nov 5-7, 946 mb

Nov 18-20, 952 mb

Nov 20-27, 940 mb

From:

http://www.vos.noaa.gov/MWL/201208/MWL_0812.pdf

I fear, unlike the British, we simply aren't sufficiently non-plussed about such storms.

A BBC television forecast of a forthcoming 909 mb low. The cautionary note is 'be careful when driving'. (The actual low was 914 mb.)

[LocoAko]

At one point did this trend begin though?

Im mobile so I cant rewatch the videos or the paper but IIRC she stated it began in the mid 80s coinciding with the start of the more notable Arctic melting.

[LocoAko]

I am very suspicious of this theory, partially because I don't recall it being widely accepted or promoted until after we began to see more impressive blocking periods in recent years. Anytime you have Monday morning quarterbacking in science, that doesn't bode well for the scientific process.

I don't see why this should cause suspicion. Itd be one thing if she was cherry picking strong storms and posthumously trying to find meaning, but if you read the paper, the reanalysis data clearly indicates what she claims: trough/ridge amplification and a slowed progression. Im not sure what is wrong with investigating something once it begins? She moted a trend, examined the data, and found evidence that matched theory. You seem reluctant to accept the results merely because it wasnt predicted ahead of time (whicj for all I know it may have been) versus discovered in observations which is perfectly valid science... forgive me if I am misunderstanding you.

[LocoAko]

I am very suspicious of this theory, partially because I don't recall it being widely accepted or promoted until after we began to see more impressive blocking periods in recent years. Anytime you have Monday morning quarterbacking in science, that doesn't bode well for the scientific process.

I was a bit rambly before and mobile so my response wasn't that adequate, so I'll try again.

... the theory is based on observations, so of course it makes sense that it didn't appear as an area of study/theory until it began happening. I'm not sure what your problem with this is? She isn't constantly modifying her theory to make big storms seem more likely. The data shows more blocking/slower progression/increased amplification. We know what the result of that is going to be. She just found a few examples of storms that seemed to have been possibly fueled by this. I'm really not sure why you're constructing a problem when there is none.

[ORH_wxman]

I was a bit rambly before and mobile so my response wasn't that adequate, so I'll try again.

... the theory is based on observations, so of course it makes sense that it didn't appear as an area of study/theory until it began happening. I'm not sure what your problem with this is? She isn't constantly modifying her theory to make big storms seem more likely. The data shows more blocking/slower progression/increased amplification. We know what the result of that is going to be. She just found a few examples of storms that seemed to have been possibly fueled by this. I'm really not sure why you're constructing a problem when there is none.

Do you have a link to the paper? I'm interested in reading it.

[LocoAko]

Do you have a link to the paper? I'm interested in reading it.

Here ya go.

http://marine.rutger...L051000_pub.pdf

Here are her other resources, including videos of the presentations she's given recently on it: http://marine.rutger...pubs_10-05.html

Edit: This may also be of interest (though I have not read it) - http://marine.rutgers.edu/~francis/pres/Francis_2009GL037274.pdf

[ORH_wxman]

Here ya go.

http://marine.rutger...L051000_pub.pdf

Here are her other resources, including videos of the presentations she's given recently on it: http://marine.rutger...pubs_10-05.html

Edit: This may also be of interest (though I have not read it) - http://marine.rutger...009GL037274.pdf

Thanks. Just read the first one and it is a good read. Haven't read the 2nd yet except the intro.

The only bothersome part about the papers is that they start in 1979. When discussing extreme blocking patterns as they relate to AGW factors such as arctic sea ice, it would be nice to have a longer period that includes the 1950s/1960s which also experienced extreme blocking. Unfortunately our sea ice data doesn't go back that far.

[nzucker]

The thing that doesn't make sense is that we didn't have much blocking at all in the 80s and 90s. Don't have time to read the paper this moment but it sounds as if we're cherrypicking the last few years to make this case. The 80s and 90s were largely +AO/+NAO years, and that +AO is actually blamed by some for the start of the decline in the Arctic.

[Dsnowx53]

Yes increased blocking makes sense, but warming temperatures are the stronger factor for early season snows, which is what the data shows as well (statistically significant declining November snowfall for NYC).

Maybe much further down the road, yes, but I think in the relative shorter term, the increased blocking will do much more to enhance snowfall than the warmer temps would do to negate it. Especially considering all you need for snow is well-timed cold, and not necessarily a below average temperature anomaly for an entire early-season month.

[Dsnowx53]

The thing that doesn't make sense is that we didn't have much blocking at all in the 80s and 90s. Don't have time to read the paper this moment but it sounds as if we're cherrypicking the last few years to make this case. The 80s and 90s were largely +AO/+NAO years, and that +AO is actually blamed by some for the start of the decline in the Arctic.

I'm certainly not an expert on this, but perhaps there is a lag between the warming of the poles and an actual sustained change in the blocking patterns.

The blocking has become much more prevalent in the last ten years or so, especially in the month of October. This composite is pretty staggering.

[Dsnowx53]

Interview with Dr. Francis from Rutgers:

http://citizensclima...hurricane-sandy

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Hard to argue against this, IMO.