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

[TerryM]

My concern is if less sea ice mans more blocking in October and more Carribien activity in october, this setup may become more commonMaybe a storm backs into the Northeast coast once every 20 year instead of once every 300 years. We'll just have to wait another couple decades and see.

I'd assume that rather than just waiting for a storm to confirm the presence of increased blocking we could compare fall conditions in low extent years with high extent years. Actually I believe that's what Dr. Francis has done.

Terry

[bluewave]

Stu Ostro was able to create a great plot showing the rising 500 mb heights trend in October

culminating in the extreme blocking pattern this year and the track of Sandy.

That graph courtesy of NOAA’s Earth System Research Laboratory website is a plot of average 500 millibar heights in October at high latitudes (50°N to the pole). There is both an obvious upward trend since the 1970s and an extreme peak in October 2012, likely representing an influence of the warming climate upon the configuration of the atmosphere steering flow by "setting the table" and skewing the odds for if not outright causing Sandy’s unusual track, which led to the outcome.

Link

http://www.wunderground.com/blog/stuostro/show.html?entrynum=18

Track: Likely

Sandy's path heading northeast about halfway between North Carolina and Bermuda but then turning sharply left and making a perpendicular beeline to the New Jersey coast is unprecedented in the known historical record. That should beg the question, "What’s up with that? Did the fact that the climate is changing play a role?"

For that to be the case, there’d need to be a clear, logical meteorological connection, and there is.

Recent published research by Jennifer Francis and Stephen Vavrus identified specific connections between loss of Arctic sea ice (the minimum extent of which this year broke 2007's record low during the satellite era) and changes in general circulation patterns downstream including ridges of high pressure aloft.

And I’ve added Sandy to the >1000-slide compendium I’ve compiled of cases in the past few years in which strong ridges of high pressure aloft have played a role in extreme temperatures, precipitation, and storms, in the context of an overall trend of rising pressures aloft (actually heights such as that of the 500 millibar level) not just over the Arctic but in the larger scale.

Not only was the "blocking" ridge centered over southern Greenland exceptionally strong at the time of the storm, which in combination with an insanely "negatively-tilted" trough over the central-eastern United States forced Sandy to take that path, it occurred in the context of this:

[skierinvermont]

So if we see a 5 or 10% increase in blocking, you turn a storm with Sandy's approximate intensity and track from a 1 in 100 year event into a 1 in 95 year event. Of course you see a corresponding decrease in storms hitting Newfoundland and Nova Scotia.

[TerryM]

Bluewave - Thanks for introducing me to Stu's site - Bookmarked for lat night reading.

Skier - Why would you assume a 10% increase in blocking would produce such a small change?

Terry

[skierinvermont]

Bluewave - Thanks for introducing me to Stu's site - Bookmarked for lat night reading.

Skier - Why would you assume a 10% increase in blocking would produce such a small change?

Terry

If the mean AO and/or NAO shifted 10% higher, then the frequency of an AO or NAO below -1 necessary to cause retrograding of Atlantic storms would increase 10%.

Even in this new AGW world, the AO and NAO will still be positive 45% of the time and negative 55% of the time. If the frequency of a block strong enough to steer atlantic storms to the west increases 10%, then the frequency of storms taking such a track will increase 10%.

And as I mentioned you would see a corresponding decrease in storms striking Nova Scotia and Newfoundland.

[skierinvermont]

I just realized that bluewave posted an excellent paper in the other thread which perfectly demonstrates one of my arguments in this thread.

 

Warmer SSTs do not necessarily create greater convective instability if the atmosphere also warms simultaneously. The paper bluewave posted showed that the SST threshold for convective instability has steadily increased with global warming. 

 

That fact, combined with the fact that shear will likely increase with AGW, explain why the common-sense assumption that AGW will increase hurricanes is likely wrong. Convective instability does not necessarily increase unless SSTs warm faster than the atmosphere. Wind shear diminishes the ability for convection to organize into a TC.

 

 

Here is the paper:

 

http://www.nature.com/ngeo/journal/v3/n12/abs/ngeo1008.html

 

 

Note they find that the convective threshold for SSTs has risen at about the same rate (.1C/decade) as actual SSTs have, implying no/little overall change in convective instability in the tropics.

 

 

In addition, we find a parallel upward trend of approximately 0.1 °C/decade over the past 30 years in both the convective threshold and tropical mean sea surface temperatures.

[blizzard1024]

If the mean AO and/or NAO shifted 10% higher, then the frequency of an AO or NAO below -1 necessary to cause retrograding of Atlantic storms would increase 10%.

Even in this new AGW world, the AO and NAO will still be positive 45% of the time and negative 55% of the time. If the frequency of a block strong enough to steer atlantic storms to the west increases 10%, then the frequency of storms taking such a track will increase 10%.

And as I mentioned you would see a corresponding decrease in storms striking Nova Scotia and Newfoundland.

What happened in the 1960s when the Earth was cooler, the AO and NAO were mostly negative and there was a lot of high latitude blocking? The whole argument

that the LIA and MWP was more regional and less globally hinges on persistent blocking and a negative AO and NAO.  As much as I love winter and snowstorms,

to say that AGW leads to more blocking is very premature. We don't have a long enough dataset. Even Gavin Schmitt has stated this. Back in the 1990s,

there were peer reviewed papers that stated that the NAO would be more positive with AGW. Here is one that I recall. You can find more in the late 1990s if you look. 

 

 Gillett, N. P., H. F. Graf, and T. J. Osborn (2003), Climate change and the North Atlantic Oscillation, in The North Atlantic Oscillation: Climatic Significance and Environmental Impact, Geophys. Monogr. Ser., vol. 134, edited by J. W. Hurrell et al., pp. 193–209, AGU, Washington, D. C., doi:10.1029/134GM09.

 

Here is the link to the abstract: http://www.agu.org/books/gm/v134/134GM09/134GM09.shtml

 

The NAO was more positive back then. Now it has become more negative. So AGW must be the cause of that too huh?  This is why many METs get skeptical. This stuff is complicated

and there are a lot of unknowns. To say that a storm like Sandy is more likely because of AGW is ludicrous. What about the great long island express hurricane of 1938? or Hurricane Hazel of 1954?/

They also had major hurricanes back in the LIA too. The only thing that is happening today is that society is more vulnerable to storms because of poor building practices (big homes on

the coast for example!).  The only thing that warming likely accounted for to make Sandy worse was the 7-8 inch sea level rise that made the storm surge worse from Sandy.  

[blizzard1024]

Of course you are correct, but this is a macro scale generalization of theory. What it implies is that the general circulation will become more efficient at dissipating thermal differences as the climate is actively warming. This physics has some predictive value. It helps explain the generation of order out of chaos, why there are galaxies, stars and planets and the eddies in planetary atmospheres we refer to as storms. Entropy production is a fundamental concept in physics. I am not saying that this is THE reason for Sandy, only that our weather should vary from what we consider normal as the world actively warms.

 

An AGW warming world means more warming occurs at the higher latitudes than at the tropics. Therefore baroclinicity declines and we see less storminess overall. This happens every year. In the summer, the storms are less frequent and weaker. They get stronger in the winter when the baroclinicity increases. Meteorology 101. 

[WeatherRusty]

An AGW warming world means more warming occurs at the higher latitudes than at the tropics. Therefore baroclinicity declines and we see less storminess overall. This happens every year. In the summer, the storms are less frequent and weaker. They get stronger in the winter when the baroclinicity increases. Meteorology 101.

Yes, what you are speaking of is the consequence of entropy production, or the smoothing out of potential differences. The Second Law of Thermodynamics. What I am speaking to is Maximum Entropy Production, which basically says that a system will take advantage of the fastest route to dissipation. A warmer system will dissipate whatever differences there are more quickly than a cooler one will. Entropy production goes up when the system is moving toward equilibrium. It ceases when it gets there. There is less entropy production in a stable non-equalibrium system. Chaotic motions transport about twice as much heat as steady-state circulations and standing eddies. In order to satisify both the Second Law and MEP the system produces chaotic flow.

[blizzard1024]

Yes, what you are speaking of is the consequence of entropy production, or the smoothing out of potential differences. The Second Law of Thermodynamics. What I am speaking to is Maximum Entropy Production, which basically says that a system will take advantage of the fastest route to dissipation. A warmer system will dissipate whatever differences there are more quickly than a cooler one will. Entropy production goes up when the system is moving toward equilibrium. It ceases when it gets there. There is less entropy production in a stable non-equalibrium system. Chaotic motions transport about twice as much heat as steady-state circulations and standing eddies. In order to satisify both the Second Law and MEP the system produces chaotic flow.

That is interesting. Maybe you would get smaller waves that are higher in amplitude with more vertical motions, and hence more intense precipitation and wind. Instead of wave 4 pattern circulating the pole maybe you would have more waves that are more intense, instead of few larger scale waves that are not as intense. Not sure here. Certainly by definition, baroclincity is driven by temperature gradients, but if the static stability is low you would get shorter wavelength more intense waves. However, if the upper troposphere warms as much as or more than the surface then this might not hold either. This is an interesting fluid dynamic mental exercise. 

[TerryM]

Another link to low Arctic sea ice and Sandy.

http://climatecrocks.com/2013/10/30/arctic-ice-loss-a-factor-in-weather-extremes-new-study/

Terry

[Ginx snewx]

What happened in the 1960s when the Earth was cooler, the AO and NAO were mostly negative and there was a lot of high latitude blocking? The whole argument

that the LIA and MWP was more regional and less globally hinges on persistent blocking and a negative AO and NAO.  As much as I love winter and snowstorms,

to say that AGW leads to more blocking is very premature. We don't have a long enough dataset. Even Gavin Schmitt has stated this. Back in the 1990s,

there were peer reviewed papers that stated that the NAO would be more positive with AGW. Here is one that I recall. You can find more in the late 1990s if you look. 

 

 Gillett, N. P., H. F. Graf, and T. J. Osborn (2003), Climate change and the North Atlantic Oscillation, in The North Atlantic Oscillation: Climatic Significance and Environmental Impact, Geophys. Monogr. Ser., vol. 134, edited by J. W. Hurrell et al., pp. 193–209, AGU, Washington, D. C., doi:10.1029/134GM09.

 

Here is the link to the abstract: http://www.agu.org/books/gm/v134/134GM09/134GM09.shtml

 

The NAO was more positive back then. Now it has become more negative. So AGW must be the cause of that too huh?  This is why many METs get skeptical. This stuff is complicated

and there are a lot of unknowns. To say that a storm like Sandy is more likely because of AGW is ludicrous. What about the great long island express hurricane of 1938? or Hurricane Hazel of 1954?/

They also had major hurricanes back in the LIA too. The only thing that is happening today is that society is more vulnerable to storms because of poor building practices (big homes on

the coast for example!).  The only thing that warming likely accounted for to make Sandy worse was the 7-8 inch sea level rise that made the storm surge worse from Sandy.  

Thank you, my gosh the lengths people go to link GW are insane. I suppose the fact the spring tide and the timing of the storm at max tide are GW related. Same storm, max low tide and this discussion doesn't happen.

[Jonger]

Thank you, my gosh the lengths people go to link GW are insane. I suppose the fact the spring tide and the timing of the storm at max tide are GW related. Same storm, max low tide and this discussion doesn't happen.

 

No possible way to debate or discuss this either, they can just point to the 120ppm of CO2 we pumped into the atmosphere and say EVERYTHING is AGW influenced. Whether co2 is responsible for 25% of 75% of the warming, they can still use that logic and it works. Dr. Masters has a running tally of world wide weather costs, he doesn't attempt to figure population and infrastructure expansion into the equation.

 

There is a new sub-division on the north side of Howell, MI... Probably 100 homes worth an average of $250k each, assuming a tornado hits that sub-division, that's going to rake in about $25M in damages in 2013, but last year it would have knocked over a few trees and resulted in nothing. The same logic applies on a larger scale.

[Ginx snewx]

No possible way to debate or discuss this either, they can just point to the 120ppm of CO2 we pumped into the atmosphere and say EVERYTHING is AGW influenced. Whether co2 is responsible for 25% of 75% of the warming, they can still use that logic and it works. Dr. Masters has a running tally of world wide weather costs, he doesn't attempt to figure population and infrastructure expansion into the equation.

 

There is a new sub-division on the north side of Howell, MI... Probably 100 homes worth an average of $250k each, assuming a tornado hits that sub-division, that's going to rake in about $25M in damages in 2013, but last year it would have knocked over a few trees and resulted in nothing. The same logic applies on a larger scale.

Basic math, more people more buildings, more infrastructure, more exposure to elements. How much damage did the 1615 hurricane cause in NE? The same storm today would be benchmark for damages in the country. Incredible Dr Masters is relating weather costs to GW. Just incredible.

[skierinvermont]

Thank you, my gosh the lengths people go to link GW are insane. I suppose the fact the spring tide and the timing of the storm at max tide are GW related. Same storm, max low tide and this discussion doesn't happen.

 

 

No possible way to debate or discuss this either, they can just point to the 120ppm of CO2 we pumped into the atmosphere and say EVERYTHING is AGW influenced. Whether co2 is responsible for 25% of 75% of the warming, they can still use that logic and it works. Dr. Masters has a running tally of world wide weather costs, he doesn't attempt to figure population and infrastructure expansion into the equation.

 

There is a new sub-division on the north side of Howell, MI... Probably 100 homes worth an average of $250k each, assuming a tornado hits that sub-division, that's going to rake in about $25M in damages in 2013, but last year it would have knocked over a few trees and resulted in nothing. The same logic applies on a larger scale.

 

 

Basic math, more people more buildings, more infrastructure, more exposure to elements. How much damage did the 1615 hurricane cause in NE? The same storm today would be benchmark for damages in the country. Incredible Dr Masters is relating weather costs to GW. Just incredible.

 

Ginxy, while I am no fan of the media hype around trying to link all severe weather events to AGW, there is legitimate serious scientific work suggesting a possible link between AGW and a more -NAO. A -NAO was one causal factor contributing to the Sandy landfall. So it is possible that AGW may contribute to an increased frequency of fall Northeast hurricane landfalls. It is important to note however, that overall hurricane frequency and intensity are projected to change little with AGW (although the flooding rains that accompany them are projected to increase with reasonable confidence). So an increase in the northeast would be a regional phenomenon of little global significance. But it may help inform infrastructure planning in the future if future studies conclude with some confidence that northeast hurricane frequency will increase. 

 

There are also dozens of studies that calculate the cost of weather disasters, or particular kinds of weather disasters, that adjust for inflation, population growth, wealth growth and infrastructure changes. Other methods include simply counting the number of weather events that meet certain criteria (ie Class 3 hurricane, or 6"+ of rain in a 24hr period, etc.). There is some evidence globally of increased frequency of extreme events.

 

 

In addition Jonger's post is extremely misleading. Masters does appear to keep a tally of billion dollar disasters in the U.S. on his blog. But he does not explicitly blame this on climate change and he issues this disclaimer:

 

Although damages due to weather-related disasters are increasing, we cannot yet say climate change is to partially to blame. There are too many other complicating factors such as increases in wealth and population that may be responsible for the rise in damages, and there is too much noise in the data to see the signal of climate change, as I explain in my January 2012 post, "Damage losses and climate change". We are better off looking at the atmosphere itself to find evidence of climate change, and there are plenty of examples of that--such as the record loss of Arctic sea ice this summer.

 

He points out the exact same data issues (wealth, population growth, etc.) that you and Jonger just pointed out. Jonger has inaccurately described the contents of Masters' blog. While it might be fun to bash on alarmists, let's try to accurately portray their statements first. Unsurprisingly, we find that Masters (and climate scientists which Masters is not) are capable of the same 'basic math' you and Jonger just performed. 

[SN_Lover]

Sandy was not unprecedented.  The only difference between this storm and other storms in the past is the increase in assets. Since we are more globally connected and own more stuff, the effects were felt in our pockets more than previous comparable storms. Climate Change is happening, but i don't think it should be linked to just one storm. 

[Jonger]

Thank you, my gosh the lengths people go to link GW are insane. I suppose the fact the spring tide and the timing of the storm at max tide are GW related. Same storm, max low tide and this discussion doesn't happen.

 

 

No possible way to debate or discuss this either, they can just point to the 120ppm of CO2 we pumped into the atmosphere and say EVERYTHING is AGW influenced. Whether co2 is responsible for 25% of 75% of the warming, they can still use that logic and it works. Dr. Masters has a running tally of world wide weather costs, he doesn't attempt to figure population and infrastructure expansion into the equation.

 

There is a new sub-division on the north side of Howell, MI... Probably 100 homes worth an average of $250k each, assuming a tornado hits that sub-division, that's going to rake in about $25M in damages in 2013, but last year it would have knocked over a few trees and resulted in nothing. The same logic applies on a larger scale.

 

 

Basic math, more people more buildings, more infrastructure, more exposure to elements. How much damage did the 1615 hurricane cause in NE? The same storm today would be benchmark for damages in the country. Incredible Dr Masters is relating weather costs to GW. Just incredible.

 

Ginxy, while I am no fan of the media hype around trying to link all severe weather events to AGW, there is legitimate serious scientific work suggesting a possible link between AGW and a more -NAO. A -NAO was one causal factor contributing to the Sandy landfall. So it is possible that AGW may contribute to an increased frequency of fall Northeast hurricane landfalls. It is important to note however, that overall hurricane frequency and intensity are projected to change little with AGW (although the flooding rains that accompany them are projected to increase with reasonable confidence). So an increase in the northeast would be a regional phenomenon of little global significance. But it may help inform infrastructure planning in the future if future studies conclude with some confidence that northeast hurricane frequency will increase. 

 

There are also dozens of studies that calculate the cost of weather disasters, or particular kinds of weather disasters, that adjust for inflation, population growth, wealth growth and infrastructure changes. Other methods include simply counting the number of weather events that meet certain criteria (ie Class 3 hurricane, or 6"+ of rain in a 24hr period, etc.). There is some evidence globally of increased frequency of extreme events.

 

 

In addition Jonger's post is extremely misleading. Masters does appear to keep a tally of billion dollar disasters in the U.S. on his blog. But he does not explicitly blame this on climate change and he issues this disclaimer:

 

Although damages due to weather-related disasters are increasing, we cannot yet say climate change is to partially to blame. There are too many other complicating factors such as increases in wealth and population that may be responsible for the rise in damages, and there is too much noise in the data to see the signal of climate change, as I explain in my January 2012 post, "Damage losses and climate change". We are better off looking at the atmosphere itself to find evidence of climate change, and there are plenty of examples of that--such as the record loss of Arctic sea ice this summer.

 

He points out the exact same data issues (wealth, population growth, etc.) that you and Jonger just pointed out. Jonger has inaccurately described the contents of Masters' blog. While it might be fun to bash on alarmists, let's try to accurately portray their statements first. Unsurprisingly, we find that Masters (and climate scientists which Masters is not) are capable of the same 'basic math' you and Jonger just performed. 

He posts this chart monthly and there is no disclaimer listed usually. You can't expect the average Joe to dig deeper into the site than that. He usually wraps this chart around a AGW story or two, you and I know his chart is another form of shock and awe AGW alarmism tactic.

[Snow_Miser]

I was under the impression that a warmer world would result in a more positive NAO. That's what some proxies seem to suggest.

 

http://www.sciencemag.org/content/324/5923/78

 

[Jonger]

Please tell me that's not an NAO chart going back 800 years... That's gotta be a misprint.

[skierinvermont]

Please tell me that's not an NAO chart going back 800 years... That's gotta be a misprint.

 

I suggest reading the methodology before jumping to conclusions. I would think you might have learnt this after your OHC and other debacles..

 

There is significant evidence for sustained -NAO conditions during the LIA. Greenland was exceptionally warm and Europe was brutally cold. 

[skierinvermont]

I was under the impression that a warmer world would result in a more positive NAO. That's what some proxies seem to suggest.

 

http://www.sciencemag.org/content/324/5923/78

 

reconstruction nao.png

 

SL - the correlation between the NAO and global temperature over the past millennium is likely due to a 3rd variable linking the two; namely the sun. Low solar activity causes low global temperature. It also may effect the stratosphere in ways that lead to a -NAO. It likely wasn't global cooling causing the -NAO, but the sun which was causing both. 

[ORH_wxman]

Ginxy, while I am no fan of the media hype around trying to link all severe weather events to AGW, there is legitimate serious scientific work suggesting a possible link between AGW and a more -NAO. A -NAO was one causal factor contributing to the Sandy landfall. So it is possible that AGW may contribute to an increased frequency of fall Northeast hurricane landfalls. It is important to note however, that overall hurricane frequency and intensity are projected to change little with AGW (although the flooding rains that accompany them are projected to increase with reasonable confidence). So an increase in the northeast would be a regional phenomenon of little global significance. But it may help inform infrastructure planning in the future if future studies conclude with some confidence that northeast hurricane frequency will increase. 

 

There are also dozens of studies that calculate the cost of weather disasters, or particular kinds of weather disasters, that adjust for inflation, population growth, wealth growth and infrastructure changes. Other methods include simply counting the number of weather events that meet certain criteria (ie Class 3 hurricane, or 6"+ of rain in a 24hr period, etc.). There is some evidence globally of increased frequency of extreme events.

 

 

In addition Jonger's post is extremely misleading. Masters does appear to keep a tally of billion dollar disasters in the U.S. on his blog. But he does not explicitly blame this on climate change and he issues this disclaimer:

 

Although damages due to weather-related disasters are increasing, we cannot yet say climate change is to partially to blame. There are too many other complicating factors such as increases in wealth and population that may be responsible for the rise in damages, and there is too much noise in the data to see the signal of climate change, as I explain in my January 2012 post, "Damage losses and climate change". We are better off looking at the atmosphere itself to find evidence of climate change, and there are plenty of examples of that--such as the record loss of Arctic sea ice this summer.

 

He points out the exact same data issues (wealth, population growth, etc.) that you and Jonger just pointed out. Jonger has inaccurately described the contents of Masters' blog. While it might be fun to bash on alarmists, let's try to accurately portray their statements first. Unsurprisingly, we find that Masters (and climate scientists which Masters is not) are capable of the same 'basic math' you and Jonger just performed. 

 

This is really weak and based on one or two studies which is in complete contrast to earlier studies that said the NAO would tend to be more positive with AGW. In addition to those earlier studies, a recent study by Barnes et al specifically looked at these blocking type scenarios and determined that they would become less frequent with AGW.

 

So claiming the blocking pattern was influenced by AGW in any type of significant manner is AT BEST quite flimsy. And likely completely unfounded. The best attribution you can make for Sandy on AGW is higher sea level. To go further than that is exactly the type of marginal science you love to criticize on this forum. Yet, I don't see you picking that pieces.

[CoastalWx]

http://www.pnas.org/content/110/38/15211

[bluewave]

This is really weak and based on one or two studies which is in complete contrast to earlier studies that said the NAO would tend to be more positive with AGW. In addition to those earlier studies, a recent study by Barnes et al specifically looked at these blocking type scenarios and determined that they would become less frequent with AGW.

 

So claiming the blocking pattern was influenced by AGW in any type of significant manner is AT BEST quite flimsy. And likely completely unfounded. The best attribution you can make for Sandy on AGW is higher sea level. To go further than that is exactly the type of marginal science you love to criticize on this forum. Yet, I don't see you picking that pieces.

 

That old assumption was most likely based on model errors. The newer studies are showing an increase

in blocking with warming.

 

 

Arctic sea ice was observed to be at a new record minimum in September 2012. Following this summer minimum, northern Eurasia and much of North America experienced severe winter weather during the winter of 2012/2013. A statistical model that used Eurasian snow cover as its main predictor successfully forecast the observed cold winter temperatures. We propose that the large melting of Arctic sea ice may be related to the rapid advance of snow cover, similar to the connection made in studies of past climates between low Arctic sea ice and enhanced continental snowfalls and glacial inception via ice sheet growth. Regressions between autumnal sea ice extent and Eurasian snow cover extent and Northern Hemisphere temperatures yield the characteristic "warm Arctic/cold continents" pattern. This pattern was observed during winter 2012/2013, and it is common among years with observed low autumn sea ice, rapid autumn snow cover advance, and a negative winter Arctic Oscillation. Dynamical models fail to capture this pattern, instead showing maximum warming over the Arctic Ocean and widespread winter warming over the adjacent continents. We suggest that the simulated widespread warming may be due to incorrect sea ice-atmosphere coupling, including an incorrect triggering of positive feedback between low sea ice and atmospheric convection, resulting in significant model errors that are evident in seasonal predictions and that potentially impact future climate change projections.

 

- See more at: http://www.tos.org/oceanography/archive/26-4_cohen.html#sthash.IDFLUfjG.dpuf

 

http://solberg.snr.missouri.edu/gcc/EarthSci1304014MokhovKOR.pdf

 

 

According to the observation data [3], the blocking lifetime in the atmosphere of the NH extratropical regions tends to increase under hemispheric warming. The data were obtained by comparison of blocking number–duration relations for the ten hottest and ten coldest years in NH in 1950–1990. As follows from [3], the noted variations in blocking conditions corre spond to increase in their formation and dissipation time by 15% at an increase in the NH nearsurface temperature by 1 K.

 

 

 

 

[bluewave]

http://www.pnas.org/content/110/38/15211

 

http://www.washingtonpost.com/blogs/capital-weather-gang/wp/2013/08/21/researcher-defends-work-linking-arctic-warming-and-extreme-weather/

Comments on Barnes 2013: Revisiting the evidence linking Arctic amplification to extreme weather in midlatitudes. GRL. by J.A Francis

 

I am pleased that Dr. Barnes, a respected and talented atmospheric dynamicist, has taken an interest in the topic of linkages between the rapidly changing Arctic and the large-scale circulation. The emerging influence of Arctic amplification (AA) on mid-latitude weather patterns is complex, and her expertise will help resolve some fundamental dynamical questions that are relevant to understanding mechanisms driving these linkages as the Arctic continues to warm faster than elsewhere.

What perplexes me, however, is that her intent in interpreting the new results in Barnes (2013) seems less than objective and is a direct attempt to disprove the work presented in Francis and Vavrus (2012; hereafter FV12). A very different interpretation of the results could be made. While her overarching conclusion is that the connections between AA and mid-latitude extreme weather are unfounded, I see a great deal of support for our results in her new work. For example:

Figure 2 presents time series of wave amplitudes (or extents) measured using two methods: one similar to ours and an alternative based on seasonal latitude differences. In all cases the trends are positive, suggesting an increase in amplitude during fall and summer, albeit only some of the trends are statistically significant. Because AA has emerged from the noise of natural variability only in the last 15 year or so, it is not surprising that its influence would not drive 30-year trends in a statistically significant way. Note that her new method does exhibit significant trends. This supports FV12.

My interpretation of the results in her Figure 3 is that in the ranges of 500 hPa heights that typically occur in mid-latitudes during summer (5.6 to 5.8 km) and autumn (5.5 to 5.7 km), the wave amplitudes are increasing from the early to the later part of the record. This, once again, supports FV12. She claims that because warming is shifting a particular height contour northward, it is incorrect to conclude that wave amplitudes are increasing. In fact, it is this northward shift – in particular the larger shift in high latitudes where warming is greatest – that we hypothesized would be a factor causing the waves to elongate.

Figure 4 presents measures of wave phase speed. While FV12 did not present wave speeds, we speculated that larger amplitude waves should have slower wave speeds. Her measure of phase speed for waves at 500 hPa slows with time, supporting our speculation. She then measures speeds at the 250 hPa level and finds no change in speed. This much higher level is near the tropopause, often above the jet stream, and can be affected by dynamics of the stratosphere. The stratosphere is cooling with increasing greenhouse gases, leading to very different dynamical changes. Why did she choose to analyze this level? My only guess is to deliberately cast doubt on FV12.

The mechanisms linking Arctic amplification with large-scale circulation patterns are clearly not simple and we still have much to learn. These new results provide additional insight into those linkages, but it appears that the interpretation of these results in Barnes (2013) was conducted with a particular intent. I welcome and appreciate Dr. Barnes’ contribution to the community’s efforts to understand the effects of AA on large-scale circulation changes, but perhaps a more balanced approach to interpreting the results could be applied going forward.

 

 

[skierinvermont]

This is really weak and based on one or two studies which is in complete contrast to earlier studies that said the NAO would tend to be more positive with AGW. In addition to those earlier studies, a recent study by Barnes et al specifically looked at these blocking type scenarios and determined that they would become less frequent with AGW.

 

So claiming the blocking pattern was influenced by AGW in any type of significant manner is AT BEST quite flimsy. And likely completely unfounded. The best attribution you can make for Sandy on AGW is higher sea level. To go further than that is exactly the type of marginal science you love to criticize on this forum. Yet, I don't see you picking that pieces.

 

There are multiple peer-reviewed studies supporting the conclusion. I would not call that "marginal science." As bluewave pointed out above, the previous model studies have been addressed. 

 

I did not say there was definitive evidence for the connection. 

[forkyfork]

Sandy was not unprecedented. The only difference between this storm and other storms in the past is the increase in assets. Since we are more globally connected and own more stuff, the effects were felt in our pockets more than previous comparable storms. Climate Change is happening, but i don't think it should be linked to just one storm.

can you show us a similar storm from the past to prove that?

[IsentropicLift]

can you show us a similar storm from the past to prove that?

Coming from people that lived through it, the 1944 hurricane brought higher storm surge to parts of the NJ coastline.

[Jonger]

Sandy was not unprecedented. The only difference between this storm and other storms in the past is the increase in assets. Since we are more globally connected and own more stuff, the effects were felt in our pockets more than previous comparable storms. Climate Change is happening, but i don't think it should be linked to just one storm. can you show us a similar storm from the past to prove that?

I'm guessing you have a secret stash of pre-1960's satellite images to know this is unprecedented? I mean, we have such detailed knowledge of fish storms from before satellites.

Fossil fuels created a paradox. The cheap energy gave us the ability to develope weather instruments and space travel, but then we blame them for the weather we can now see.

[bluewave]

I'm guessing you have a secret stash of pre-1960's satellite images to know this is unprecedented? I mean, we have such detailed knowledge of fish storms from before satellites. Fossil fuels created a paradox. The cheap energy gave us the ability to develope weather instruments and space travel, but then we blame them for the weather we can now see.

 

It was the first such track in the historic record. You don't need a satellite to tell you that.

 

http://www.ldeo.columbia.edu/~sobel/Papers/hall_sobel_grl_submitted.pdf