Correlation of extreme hurricanes, AGW, and solar cycles

[WolfStock1]

Prompted by Hurricane Melissa  - what's the correlation of extreme hurricanes and AGW, and solar cycles?

When looking strictly at Cat 5's - they  definitely seem to be getting more frequent over time, but also seem to correlate heavily with the solar cycles; specifically being more frequent during peaks of solar cycles, with perhaps some lag (more frequent on the "back side").

Here's list of Cat 5's by year:

https://en.wikipedia.org/wiki/List_of_Category_5_Atlantic_hurricanes

Haven't charted yet, but there definitely seems to be strong correlation with the peak and/or back side of the peak of solar cycles; specifically cat 5 frequency peaking:

https://en.wikipedia.org/wiki/Solar_cycle

Haven't charted the correlation (maybe someone else has) but it definitely seems to be there; looking at the list of Cat 5's at least.   The correlation seems to be strongest in recent years:

1924
1928  - solar cycle 16 peak
1932  - solar cycle 16 backside
1932
1933
1933
1935
1938  - solar cycle 17 peak backside
1944  - off-cycle
1953  - off-cycle
1955
1961  - solar cycle 19 peak backside
1961
1966
1967
1969  - solar cycle 20 peak
1971
1977
1979  - solar cycle 21 peak
1980
1988
1989  - solar cycle 22 peak
1992
1998
2003  - solar cycle 23 peak backside
2004
2005
2005
2005
2005
2007
2007
2016  - solar cycle 24 peak backside
2017
2017
2018
2019
2022
2024
2024
2025  - solar cycle 25 peak
2025
2025
 

Odd thing is that a google search mentions *anti-correlation* of hurricane activity and solar cycles - but that's not what I see here, at least looking at the Cat 5's.   Perhaps during peak periods there are less overall hurricanes, but more Cat 5's (?).

[ATDoel]

I posted a link to the study in the other thread, here it is.  Effects of Solar Variability on Tropical Cyclone Activity - Nayak - 2024 - Earth and Space Science - Wiley Online Library

To me the most obvious trend here is the increasing number of Cat 5s, regardless of solar activity.  We've had 11 in the last 10 years, 17 in the last 20.  There's no other 20 year period that even comes close to that.  That has nothing to do with the solar cycles.

[Typhoon Tip]

Perhaps during peak periods there are less overall hurricanes, but more Cat 5's (?)"  

that was gonna be my knee jerk guess, yeah.  In other words,  occurrence counts of TCs ( in general) per year may be well correlated, but category 5s may require a broader set of favorable parameters. 

Not that anyone asked but ... I've wondered in the past if these upper tier TC frequencies are more endemic to this particular micro geological span of time.  They will tend to become less when/if the atmospheric thermodynamic rest state catches up to the oceanic heat phenomenon - if/when that happens.   TC mechanics require a thermodynamic initial state, from the quasi oceanic-atmospheric coupling at the bottom to the way the curve is all the way up to 100 mb.  If the bulk troposphere sounding was to modulate associated with CC, that may have an impact on the vitality of these storm engines - later generations... But for now, we have hotter than normal OHC underneath a TC viable sounding and that's a powderkeg  

[Roger Smith]

The anti-correlation idea may have come from 2004-05 which does not fit the theory. 

I noted in the hurricane Melissa discussion that 1780, a very bad year in the Caribbean, was also two years after a large solar peak in 1778, and the Long Island express (1938) while not a cat-5 was a year after a solar peak. 

Rather active years that came before a solar peak would include 1916, 1936, 1944 and 1998, as well as 2020. 

1887 is closer to a solar minimum like 2004 and 2005. 

1893 was a very active tropical year and there was a solar peak in 1893-94. 

The least active season in recent times, 1910, came at a solar minimum. 

I would include Andrew on the basis of the 1989 cycle peaking rather broadly from 1988 to 1991, the "1989" designation is only barely valid, and in fact also the 1968 peak had a very well defined secondary peak in 1972 (Agnes). 

Perhaps if there is a correlation, it is not because the solar conditions induce stronger hurricanes to form, but because some mechanism in the solar system peaks at that time and is responsible for these two different effects. Clearly it is not a necessary condition given the number of counter-examples. But it seems relatively robust over about twenty solar cycles, before 1780 we probably don't have enough data to form any conclusions. 

[FPizz]

1 hour ago, Roger Smith said:

The anti-correlation idea may have come from 2004-05 which does not fit the theory. 

I noted in the hurricane Melissa discussion that 1780, a very bad year in the Caribbean, was also two years after a large solar peak in 1778, and the Long Island express (1938) while not a cat-5 was a year after a solar peak. 

Rather active years that came before a solar peak would include 1916, 1936, 1944 and 1998, as well as 2020. 

1887 is closer to a solar minimum like 2004 and 2005. 

1893 was a very active tropical year and there was a solar peak in 1893-94. 

The least active season in recent times, 1910, came at a solar minimum. 

I would include Andrew on the basis of the 1989 cycle peaking rather broadly from 1988 to 1991, the "1989" designation is only barely valid, and in fact also the 1968 peak had a very well defined secondary peak in 1972 (Agnes). 

Perhaps if there is a correlation, it is not because the solar conditions induce stronger hurricanes to form, but because some mechanism in the solar system peaks at that time and is responsible for these two different effects. Clearly it is not a necessary condition given the number of counter-examples. But it seems relatively robust over about twenty solar cycles, before 1780 we probably don't have enough data to form any conclusions. 

Does this include the rest of the world or only the Atlantic?  A lot more storms to study i would assume.

[tacoman25]

3 hours ago, ATDoel said:

I posted a link to the study in the other thread, here it is.  Effects of Solar Variability on Tropical Cyclone Activity - Nayak - 2024 - Earth and Space Science - Wiley Online Library

To me the most obvious trend here is the increasing number of Cat 5s, regardless of solar activity.  We've had 11 in the last 10 years, 17 in the last 20.  There's no other 20 year period that even comes close to that.  That has nothing to do with the solar cycles.

Does this account for closer monitoring of storms especially those well offshore in recent decades, though?

[Roger Smith]

1 hour ago, FPizz said:

Does this include the rest of the world or only the Atlantic?  A lot more storms to study i would assume.

True, my comments were only for the N Atlantic seasons. 

[Roger Smith]

Another interval not fitting too well would be 1953-54 with numerous major hurricanes (even if not cat 5) at a solar minimum. By 1955 it was early stages of an eventual very large solar maximum. 

[FPizz]

2 minutes ago, Roger Smith said:

True, my comments were only for the N Atlantic seasons. 

It would be interesting to see if the rest of the globe follows that.  Would be so interesting if say the Pacific had more cat 5s with low solar.  Im sure there is some study somewhere for the world.

[donsutherland1]

2 hours ago, FPizz said:

Does this include the rest of the world or only the Atlantic?  A lot more storms to study i would assume.

All basins.

[FPizz]

2 hours ago, donsutherland1 said:

All basins.

Oh ok.  He only mentioned the Atlantic. 

[WolfStock1]

7 hours ago, ATDoel said:

I posted a link to the study in the other thread, here it is.  Effects of Solar Variability on Tropical Cyclone Activity - Nayak - 2024 - Earth and Space Science - Wiley Online Library

To me the most obvious trend here is the increasing number of Cat 5s, regardless of solar activity.  We've had 11 in the last 10 years, 17 in the last 20.  There's no other 20 year period that even comes close to that.  That has nothing to do with the solar cycles.

 

I don't think it's an either/or thing.    We can have both correlation with solar cycles AND increases due to AGW.

Some people try to explain away general increase by saying there isn't really a general increase - what you're seeing is solar cycles.   But if you believe there is a general increase you shouldn't just throw the baby out with the bath water and assert that therefore there *isn't* correlation with solar cycles.    Based on what appears to be cyclical nature of bursts of Cat 5's it seems to me it's clear there is some there.    (That jives with the paper actually; though the timing appears to be different to me.)

[chubbs]

Global Cat 5 in satellite era of good detection. ( Jeff Master's blog article on Melissa)

https://yaleclimateconnections.org/2025/10/jamaica-braces-for-cat-5-hurricane-melissa-earths-strongest-storm-of-2025/

 

[ATDoel]

15 hours ago, Roger Smith said:

The anti-correlation idea may have come from 2004-05 which does not fit the theory. 

I noted in the hurricane Melissa discussion that 1780, a very bad year in the Caribbean, was also two years after a large solar peak in 1778, and the Long Island express (1938) while not a cat-5 was a year after a solar peak. 

Rather active years that came before a solar peak would include 1916, 1936, 1944 and 1998, as well as 2020. 

1887 is closer to a solar minimum like 2004 and 2005. 

1893 was a very active tropical year and there was a solar peak in 1893-94. 

The least active season in recent times, 1910, came at a solar minimum. 

I would include Andrew on the basis of the 1989 cycle peaking rather broadly from 1988 to 1991, the "1989" designation is only barely valid, and in fact also the 1968 peak had a very well defined secondary peak in 1972 (Agnes). 

Perhaps if there is a correlation, it is not because the solar conditions induce stronger hurricanes to form, but because some mechanism in the solar system peaks at that time and is responsible for these two different effects. Clearly it is not a necessary condition given the number of counter-examples. But it seems relatively robust over about twenty solar cycles, before 1780 we probably don't have enough data to form any conclusions. 

There's a peer reviewed study that states there's an anti-correlation between the two.  We can scribble whatever we want on the back of a napkin but unless there's another peer reviewed study saying otherwise, there's an anti-correlation, no positive correlation.

[tacoman25]

2 hours ago, chubbs said:

Global Cat 5 in satellite era of good detection. ( Jeff Master's blog article on Melissa)

https://yaleclimateconnections.org/2025/10/jamaica-braces-for-cat-5-hurricane-melissa-earths-strongest-storm-of-2025/

 

This is one of those graphs where the trend line is heavily affected by the starting point. Start in 1987 or 1989 instead of 1982 (which fell during a period of suppressed activity, but there were definitely busier periods prior), and it's quite different.

[chubbs]

1 hour ago, tacoman25 said:

This is one of those graphs where the trend line is heavily affected by the starting point. Start in 1987 or 1989 instead of 1982 (which fell during a period of suppressed activity, but there were definitely busier periods prior), and it's quite different.

Here's a 1987 start.

 

[bluewave]

1 hour ago, tacoman25 said:

This is one of those graphs where the trend line is heavily affected by the starting point. Start in 1987 or 1989 instead of 1982 (which fell during a period of suppressed activity, but there were definitely busier periods prior), and it's quite different.

The starting point is when the climate began to warm more rapidly along with the oceans. So one of the predictions made years ago was that we would see an increase in the strongest of hurricanes but not necessarily the total number of storms. Has to do with dueling influences as the oceans reach all time record warmth. Stability can limit the total numbers but lead to the storms that do form being more intense.

First, we have seen a record concentration in Cat 5 hurricanes in the last decade due to the warmest SSTs ever observed in the Atlantic and other basins. Second, uneven warming of these basins also lead to stability issues at varying points in the season such as what used to be thought of as the peak from late August into early September.

So recently we have seen  an early burst of activity followed by a late August into early September lull and followed by unusually late season development. When we get these very warm SSTs at the higher latitudes during mid-summer it has lead to stability issues in the tropics. But later in the session these stability issues have been resolving leading to this record late season activity. 

[Roger Smith]

Since we only have annual counts from 1851 on, and some more anecdotal reports on seasonal severity before 1850, it occurs to me that any given 11-year cycle of any origin will correlate with the solar variability cycle which has never strayed far from a regular 11-year pulse since about 1837 (before that it also kept to that sort of frequency after the long downturn of the Maunder except for a speeding up to 9-10 years late in the 18th century followed by a slowdown to 12-13 years in the Dalton minimum). 

So just for the sake of exploring that solar-neutral 11-year concept, I arbitrarily used this progression and worked out average counts ... peak of cycle (for whatever reason) 1849, 1860, 1871, 1882, 1893, 1904, 1915, 1926, 1937, 1948, 1959, 1970, 1981, 1992, 2003, 2014, 2025. The average position of these years in the somewhat variable 10.5 year solar cycle is at peak year plus one, the specific displacements being +1, 0, +1, -1, 0, -1, -2, -2, 0, +1, +2, +2, +2, +3, +4, +1, 0?? at end. This reflects the fact that the solar cycles picked up in frequency in the later 20th century and have recently returned to a longer-period average closer to 11 years in this less active (so far) century. It should be mentioned that the 1905 peak for solar activity was in reality a flat-topped low-moderate peak from 1905-07 and also the 1968 peak was very indistinct between 1967 and 1972, so these "displacements" are more approximate.

And if one were to go back the peaks of this steady 11-year cycle are 1838, 1827, 1816, 1805, 1794, 1783, 1772, 1761, 1750, 1739, 1728, 1717, 1706 which also resembles the actual solar peaks except in the period before the Dalton minimum when again more intense cycles sped up (the actual peaks in this interval going back are 1837-38 (about equal), 1829-1830, 1816, 1801-04 (a weak flat-topped peak), 1787 (may have had a strong secondary around 1795), 1778, 1769, 1761, 1749-50, 1738, 1717, and 1705 (a weak peak coming out of the Maunder minimum). 

So here are the hurricane data re-arranged to fit this 11-year cycle; since the first year of data is 1851, the data start at year 1 of an 11-year cycle in which the modulation years are at year 10 (and the mean of solar maximum years at year 9). 

 

<<< COUNTS in YEARS of 11-YEAR CYCLE (N Altantic basin) >>>

Cycle starts __YR 01 _YR 02 _YR 03 _ YR 04 _YR 05 _YR 06 _YR 07 _YR 08 _YR 09 _YR 10 _YR 11 __ Cycle ends

1851 ________ 6 3 1 __ 5 5 1 __ 8 4 2 __ 5 3 1 __ 5 4 1 __ 6 4 2 __ 4 3 0 __ 6 6 0 __ 8 7 1 __ 7 6 1 __ 8 6 0 __ 1861

1862 ________ 6 3 0 _ 9 5 0 __5 3 0 __ 7 3 0 __7 6 1 __ 9 7 1 ___ 4 3 0 _ 10 7 1 __ 11 10 2 _ 8 6 2 __ 5 4 0 __ 1872

1873 ________ 5 3 2 _ 7 4 0 __6 5 1 ___ 5 4 2 __8 3 1 _ 12 10 2__ 8 6 2 _ 11 9 2 __ 7 4 0 __ 6 4 2 __ 4 3 2 __ 1883

1884 ________ 4 4 1 _ 8 6 0 _12 10 4__19 11 2 _ 9 6 2 __ 9 6 0 __ 4 2 1 _ 10 7 1 __ 9 5 0 __12 10 5 __7 5 4 ___ 1894

1895 ________ 6 2 0 _ 7 6 2 _ 6 3 0 __ 11 5 1 __10 5 2 __7 3 2 __13 6 0 __ 5 3 0 _ 10 7 1 __ 6 4 0 ___5 1 1 ___ 1905

1906 ________ 11 6 3 _ 5 0 0 _10 6 1 _ 12 6 4 _ 5 3 1 __ 6 3 0 ___ 7 4 1 __ 6 3 0 __ 1 0 0 __ 6 5 3 _ 15 10 5 __ 1916   

1917 ________ 4 2 2 __ 6 4 1 _ 5 2 1 __ 5 4 0 _ 7 5 2 __ 5 3 1 ___ 9 4 1 __ 11 5 2 __ 4 1 0 __11 8 6 __ 8 4 1 ___ 1927

1928 ________ 6 4 1 __ 5 3 1 _ 3 2 2 __13 3 1 _ 15 6 4 _20 11 6 __13 7 1 __ 8 5 3 __17 7 1 __11 4 1 __ 9 4 2 ___ 1938

1939 ________ 6 3 1 __ 9 6 0 _ 6 4 3 _ 11 4 1 _ 10 5 2 _ 14 8 3 __11 5 2 __ 7 3 0 __10 5 2 __10 6 4 __16 7 3 ___ 1949   

1950 ________16 11 6__12 8 3__11 5 2 __14 7 3_ 16 7 3 _ 13 9 4 __12 4 1 __ 8 3 2 _ 12 7 3 __14 7 2 __ 8 4 2 ___ 1960    

1961 ________ 12 8 5 _ 7 4 0 _ 10 7 3 _ 13 7 5 _ 10 4 1 _ 15 7 3 _ 15 6 1 __ 8 5 0 _ 18 12 3__14 7 2 _ 13 6 1 ___ 1971   

1972 ________ 7 3 0 __ 8 4 1 _ 11 4 2 __ 9 6 3 _ 10 6 2 __ 6 5 1 _ 12 5 2 __ 9 6 2 _ 11 9 2 __12 7 3 __ 6 2 1 ___ 1982

1983 ________ 4 3 1 _ 13 5 1 _ 11 7 3 __ 6 4 0 __ 7 3 1 __12 5 3 __11 7 2 __14 8 1 __ 8 4 2 __ 7 4 1 __ 8 4 1 ___ 1993  

1994 ________ 7 3 0 _ 19 11 5 _13 9 6 __8 3 1 __14 10 3 _12 8 5 _ 15 8 3 _ 15 9 4 _12 4 2 _ 16 7 3 _ 15 9 6 ___ 2004

2005 _______28 15 7_ 10 5 2 _15 6 2 _16 8 5 __ 9 3 2 __19 12 5 _19 7 4 _ 19 10 2_ 14 2 0 _ 8 6 2 _ 11 4 2 ___ 2015 

2016 _______ 15 7 4 _ 17 10 6 _15 8 2_ 18 6 3 _30 14 7_ 21 7 4 _14 8 2 _ 20 7 3 _ 18 11 5 _ 13 5 4_ (2026)

=================

means _____ 8 5 2 __ 9 5 1 __ 8 5 2 __11  5 2 __ 11 6 2 _ 12 7 3 _ 11 6 1 __ 10 6 1 __ 11 6 2 _ 10 6 3 _ 9 5 2

(1928-pres) 11 6 3 __11 6 2__ 10 6 3 _ 12 5 2 _ 13 6 3 _ 15 8 4 _ 14 6 2 _ 12 6 2 _ 13 7 2 _ 12 6 2 _ 11 5 2

ANALYSIS

This independent 11-year cycle seems very close to random to me, if we say the long term mean is 10 6 2, most years in the cycle are within 1 in all aspects of the count, and if we say the more recent (1928 to present) average is 12 7 2, there is a bit of a peak in the years generally aligned with solar minima (years 5-7 in this cycle), a trend that seems to be increasing slightly but not in a very significant way. So this supports the contention that N Atlantic tropical activity peaks slightly every eleven years and whether by coincidence (an independent cause and effect from solar) or by virtue of the general overlap and a solar cause and effect, this peak occurs near sunspot minimum. 

I also counted the years with three or more major hurricanes, the frequency there is

5  3  5 4 4 8 2 3 3 7 4

This shows more of a 5.5 year cycle with peaks at solar minimum and solar maximum. I will reformulate the table above to coincide exactly with solar peaks but I don't think it is going to show a different outcome. 

...  

       

 

[Roger Smith]

Here is that same table reformulated so that sunspot maximum years are always in year 10 of the table. This leads to row entries of different lengths. My protocol was to begin each row 9 years before the sunspot peak year and either add extra years or remove years as required. The extra years are placed in otherwise blank YR 6 and YR 7 of a 13-year collection that represents 11 years in most cases.

 

<<< COUNTS in YEARS of 11-YEAR CYCLE (N Altantic basin) >>>

Cycle starts __YR 01 _YR 02 _YR 03 _ YR 04 _YR 05 _ _YR 08 _YR 09 _YR 10 _YR 11 _YR 12 _YR 13__ Cycle ends

1851 ________ 6 3 1 __ 5 5 1 __ 8 4 2 __ 5 3 1 __ 5 4 1 __  6 4 2 __ 4 3 0 __ 6 6 0 __ 8 7 1 __7 6 1 __ 8 6 0 __ 1861

1862 ________6 3 0 _ 9 5 0 __5 3 0 __ 7 3 0 __7 6 1 __  9 7 1 ___ 4 3 0 _ 10 7 1 __ 11 10 2 _ 8 6 2 _5 4 0 __ 1871

1873 ________ 5 3 2 _ 7 4 0 __6 5 1 ___5 4 2 __8 3 1 _ 12 10 2__ 8 6 2 _ 11 9 2 __ 7 4 0 __ 6 4 2 __ 4 3 2 __ 1883

1884 ________ 4 4 1 _ 8 6 0 _12 10 4__19 11 2 _ 9 6 2 __ 9 6 0 __ 4 2 1 _ 10 7 1 __ 9 5 0 __12 10 5 __7 5 4 __ 1894

1895 ________ 6 2 0 _ 7 6 2 _ 6 3 0 __ 11 5 1 __10 5 2 __7 3 2 __13 6 0 __ 5 3 0 _ 10 7 1 __ 6 4 0 ___5 1 1 ___ 1905

1906 ________ 11 6 3 _ 5 0 0 _10 6 1 _ 12 6 4 _ 5 3 1 __ 6 3 0 ___ 7 4 1 __ 6 3 0 __ 1 0 0 __ 6 5 3 _ 15 10 5 __ 1916   

1917 ________ 4 2 2 __ 6 4 1 _ 5 2 1 __ 5 4 0 _ 7 5 2 __ 5 3 1 ___ 9 4 1 __ 11 5 2 __ 4 1 0 __11 8 6 __ 8 4 1 ___ 1927

1928 ________ 6 4 1 __ 5 3 1 _ 3 2 2 __13 3 1 _ 15 6 4 _20 11 6 __13 7 1 __ 8 5 3 __17 7 1 __11 4 1 __ 9 4 2 ___ 1938

1939 ________ 6 3 1 __ 9 6 0 _ 6 4 3 _ 11 4 1 _ 10 5 2 _ 14 8 3 __11 5 2 __ 7 3 0 __10 5 2 __10 6 4 __16 7 3 ___ 1949   

1950 ________16 11 6__12 8 3__11 5 2 __14 7 3_ 16 7 3 _ 13 9 4 __12 4 1 __ 8 3 2 _ 12 7 3 __14 7 2 __ 8 4 2 ___ 1960    

1961 ________ 12 8 5 _ 7 4 0 _ 10 7 3 _ 13 7 5 _ 10 4 1 _ 15 7 3 _ 15 6 1 __ 8 5 0 _ 18 12 3__14 7 2 _ 13 6 1 ___ 1971   

1972 ________ 7 3 0 __ 8 4 1 _ 11 4 2 __ 9 6 3 _ 10 6 2 __ 6 5 1 _ 12 5 2 __ 9 6 2 _ 11 9 2 __12 7 3 __ 6 2 1 ___ 1982

1983 ________ 4 3 1 _ 13 5 1 _ 11 7 3 __ 6 4 0 __ 7 3 1 __12 5 3 __11 7 2 __14 8 1 __ 8 4 2 __ 7 4 1 __ 8 4 1 ___ 1993  

1994 ________ 7 3 0 _ 19 11 5 _13 9 6 __8 3 1 __14 10 3 _12 8 5 _ 15 8 3 _ 15 9 4 _12 4 2 _ 16 7 3 _ 15 9 6 ___ 2004

2005 _______28 15 7_ 10 5 2 _15 6 2 _16 8 5 __ 9 3 2 __19 12 5 _19 7 4 _ 19 10 2_ 14 2 0 _ 8 6 2 _ 11 4 2 ___ 2015 

2016 _______ 15 7 4 _ 17 10 6 _15 8 2_ 18 6 3 _30 14 7_ 21 7 4 _14 8 2 _ 20 7 3 _ 18 11 5 _ 13 5 4_ (2026)

=================

The means are now aligned with the most recent cycle so that year 10 is always the peak solar year. No year is counted twice and where not obviously aligned it is averaged in with closest solar equivalents. Years 1 and 2 in this analysis are 2 and 3 years after solar peaks (year 11 is one year after). Years 3 to 9 are counted from before solar peaks only, any years not included are then averaged into best fits. 

means _____ 8 5 2 __ 9 5 1 __ 8 5 2 __ 9  5 2 __ 12 7 3 _ 11 6 2 __ 9 5 1 ___ 9 6 1 __ 12 6 2 _  9 5 2 _ 9 6 2

(1928-pres) 11 6 3 __13 7 2__ 11 6 3 _ 12 5 2 _ 14 7 3 _ 13 6 3 _ 12 6 2 _ 12 6 2 _ 14 7 2 _ 11 6 2 _ 13 6 2

While there are a few differences from the straight-line eleven year averages, these solar-oriented averages take on essentially the same pattern, like the solar maximum there seems to be a biennial second order frequency wave evident especially in the more active recent portion.

Overall, it could be argued that these frequency counts are within the ranges allowable by random variability, there is no huge forcing evident. 

I would invite anyone with a hypothesis to advance it, as to why Atlantic hurricane frequency appears to peak at two opposite portions of the 11-year solar cycle whether robustly forced by actual solar data, or passively forced by the mean. I am aware that at solar maximum, heat energy from the Sun is generally a bit higher (despite the cooler sunspots, the more active solar wind accounts for this), and perhaps at solar minimum there could be an argument for stability of subtropical highs which cannot hurt the count. 

One final look at the situation ... here are the more active years placed against a stylized solar cycle ... 

 

x x x x x xxxxxxxxxxxxxxxxxxxxxxxx[][]1988-89xxxxxxxxxxxxxxxxxxxxxxxxxxxxx x x x x

x x x x x xxxxxxxxxxxxxxxxx1936[][][]xxx[][][][]1969x1780 xxxxxxxxxxxxxxxxxxxxx x x x x x

x x x x x xxxxxxxxxxxxx1916[][]xxxxxx1893xx[][][][]1949xxxxxxxxxxxxxxxxxxxx x x x x x x x

x x x x x xxxxxxxxxx1846[][]xxxx2011-12xxxxxxxxxxx[][][]2004xxxxxxxxxxxxxxxxxxxxxx x x x x x x

x x x x x xxxxxxxxx[][][]xxxxxxxxxxxxxxxxxxxxxxxxxxxxx[][][][][]2005xxxxxxxxxx x x x x x x

x x x x xxxx1954[][][][]xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx[][][][][][]1887xxxxxx x x x x

x2020[][][]xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx[][][[][][][]xxxxxx1933

1878[]xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx[][][][][][][][]1995

 

I would contend what this shows is that high climbers are all over the mountain scattered at random. (2011-12 and 1893 are placed within the mountain profile to represent near peak but lower altitude peaks of solar activity. I added 1846 and 1780 which are recognized to be "big seasons" outside the framework of my analysis otherwise. 1900 would be about where 1878 is situated. 

[TheClimateChanger]

I wish we had hurricane and tropical cyclone statistics from the last glacial maximum. It wouldn't surprise if there were years with few, if any, storms, at least in the North Atlantic. I just don't know how high the SSTs were for much of the region. Probably greatly suppressed where storms were capable of forming, how intense they could get, and also the length of the summer.

[GaWx]

42 minutes ago, Roger Smith said:

Here is that same table reformulated so that sunspot maximum years are always in year 10 of the table. This leads to row entries of different lengths. My protocol was to begin each row 9 years before the sunspot peak year and either add extra years or remove years as required. The extra years are placed in otherwise blank YR 6 and YR 7 of a 13-year collection that represents 11 years in most cases.

 

<<< COUNTS in YEARS of 11-YEAR CYCLE (N Altantic basin) >>>

Cycle starts __YR 01 _YR 02 _YR 03 _ YR 04 _YR 05 _ _YR 08 _YR 09 _YR 10 _YR 11 _YR 12 _YR 13__ Cycle ends

1851 ________ 6 3 1 __ 5 5 1 __ 8 4 2 __ 5 3 1 __ 5 4 1 __  6 4 2 __ 4 3 0 __ 6 6 0 __ 8 7 1 __7 6 1 __ 8 6 0 __ 1861

1862 ________6 3 0 _ 9 5 0 __5 3 0 __ 7 3 0 __7 6 1 __  9 7 1 ___ 4 3 0 _ 10 7 1 __ 11 10 2 _ 8 6 2 _5 4 0 __ 1871

1873 ________ 5 3 2 _ 7 4 0 __6 5 1 ___5 4 2 __8 3 1 _ 12 10 2__ 8 6 2 _ 11 9 2 __ 7 4 0 __ 6 4 2 __ 4 3 2 __ 1883

1884 ________ 4 4 1 _ 8 6 0 _12 10 4__19 11 2 _ 9 6 2 __ 9 6 0 __ 4 2 1 _ 10 7 1 __ 9 5 0 __12 10 5 __7 5 4 __ 1894

1895 ________ 6 2 0 _ 7 6 2 _ 6 3 0 __ 11 5 1 __10 5 2 __7 3 2 __13 6 0 __ 5 3 0 _ 10 7 1 __ 6 4 0 ___5 1 1 ___ 1905

1906 ________ 11 6 3 _ 5 0 0 _10 6 1 _ 12 6 4 _ 5 3 1 __ 6 3 0 ___ 7 4 1 __ 6 3 0 __ 1 0 0 __ 6 5 3 _ 15 10 5 __ 1916   

1917 ________ 4 2 2 __ 6 4 1 _ 5 2 1 __ 5 4 0 _ 7 5 2 __ 5 3 1 ___ 9 4 1 __ 11 5 2 __ 4 1 0 __11 8 6 __ 8 4 1 ___ 1927

1928 ________ 6 4 1 __ 5 3 1 _ 3 2 2 __13 3 1 _ 15 6 4 _20 11 6 __13 7 1 __ 8 5 3 __17 7 1 __11 4 1 __ 9 4 2 ___ 1938

1939 ________ 6 3 1 __ 9 6 0 _ 6 4 3 _ 11 4 1 _ 10 5 2 _ 14 8 3 __11 5 2 __ 7 3 0 __10 5 2 __10 6 4 __16 7 3 ___ 1949   

1950 ________16 11 6__12 8 3__11 5 2 __14 7 3_ 16 7 3 _ 13 9 4 __12 4 1 __ 8 3 2 _ 12 7 3 __14 7 2 __ 8 4 2 ___ 1960    

1961 ________ 12 8 5 _ 7 4 0 _ 10 7 3 _ 13 7 5 _ 10 4 1 _ 15 7 3 _ 15 6 1 __ 8 5 0 _ 18 12 3__14 7 2 _ 13 6 1 ___ 1971   

1972 ________ 7 3 0 __ 8 4 1 _ 11 4 2 __ 9 6 3 _ 10 6 2 __ 6 5 1 _ 12 5 2 __ 9 6 2 _ 11 9 2 __12 7 3 __ 6 2 1 ___ 1982

1983 ________ 4 3 1 _ 13 5 1 _ 11 7 3 __ 6 4 0 __ 7 3 1 __12 5 3 __11 7 2 __14 8 1 __ 8 4 2 __ 7 4 1 __ 8 4 1 ___ 1993  

1994 ________ 7 3 0 _ 19 11 5 _13 9 6 __8 3 1 __14 10 3 _12 8 5 _ 15 8 3 _ 15 9 4 _12 4 2 _ 16 7 3 _ 15 9 6 ___ 2004

2005 _______28 15 7_ 10 5 2 _15 6 2 _16 8 5 __ 9 3 2 __19 12 5 _19 7 4 _ 19 10 2_ 14 2 0 _ 8 6 2 _ 11 4 2 ___ 2015 

2016 _______ 15 7 4 _ 17 10 6 _15 8 2_ 18 6 3 _30 14 7_ 21 7 4 _14 8 2 _ 20 7 3 _ 18 11 5 _ 13 5 4_ (2026)

=================

The means are now aligned with the most recent cycle so that year 10 is always the peak solar year. No year is counted twice and where not obviously aligned it is averaged in with closest solar equivalents. Years 1 and 2 in this analysis are 2 and 3 years after solar peaks (year 11 is one year after). Years 3 to 9 are counted from before solar peaks only, any years not included are then averaged into best fits. 

means _____ 8 5 2 __ 9 5 1 __ 8 5 2 __ 9  5 2 __ 12 7 3 _ 11 6 2 __ 9 5 1 ___ 9 6 1 __ 12 6 2 _  9 5 2 _ 9 6 2

(1928-pres) 11 6 3 __13 7 2__ 11 6 3 _ 12 5 2 _ 14 7 3 _ 13 6 3 _ 12 6 2 _ 12 6 2 _ 14 7 2 _ 11 6 2 _ 13 6 2

While there are a few differences from the straight-line eleven year averages, these solar-oriented averages take on essentially the same pattern, like the solar maximum there seems to be a biennial second order frequency wave evident especially in the more active recent portion.

Overall, it could be argued that these frequency counts are within the ranges allowable by random variability, there is no huge forcing evident. 

I would invite anyone with a hypothesis to advance it, as to why Atlantic hurricane frequency appears to peak at two opposite portions of the 11-year solar cycle whether robustly forced by actual solar data, or passively forced by the mean. I am aware that at solar maximum, heat energy from the Sun is generally a bit higher (despite the cooler sunspots, the more active solar wind accounts for this), and perhaps at solar minimum there could be an argument for stability of subtropical highs which cannot hurt the count. 

One final look at the situation ... here are the more active years placed against a stylized solar cycle ... 

 

x x x x x xxxxxxxxxxxxxxxxxxxxxxxx[][]1988-89xxxxxxxxxxxxxxxxxxxxxxxxxxxxx x x x x

x x x x x xxxxxxxxxxxxxxxxx1936[][][]xxx[][][][]1969x1780 xxxxxxxxxxxxxxxxxxxxx x x x x x

x x x x x xxxxxxxxxxxxx1916[][]xxxxxx1893xx[][][][]1949xxxxxxxxxxxxxxxxxxxx x x x x x x x

x x x x x xxxxxxxxxx1846[][]xxxx2011-12xxxxxxxxxxx[][][]2004xxxxxxxxxxxxxxxxxxxxxx x x x x x x

x x x x x xxxxxxxxx[][][]xxxxxxxxxxxxxxxxxxxxxxxxxxxxx[][][][][]2005xxxxxxxxxx x x x x x x

x x x x xxxx1954[][][][]xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx[][][][][][]1887xxxxxx x x x x

x2020[][][]xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx[][][[][][][]xxxxxx1933

1878[]xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx[][][][][][][][]1995

 

I would contend what this shows is that high climbers are all over the mountain scattered at random. (2011-12 and 1893 are placed within the mountain profile to represent near peak but lower altitude peaks of solar activity. I added 1846 and 1780 which are recognized to be "big seasons" outside the framework of my analysis otherwise. 1900 would be about where 1878 is situated. 

 Hey Roger,

  I’ve noticed what seemed like a (slight?) partial correlation between high sunspot months (say 130+) and low ACE with possibly a couple of weeks of lag. One hypothesis is that the increased solar energy heats up the upper atmosphere more than the lower, which if true could lower instability in the tropics.

[Roger Smith]

1 hour ago, TheClimateChanger said:

I wish we had hurricane and tropical cyclone statistics from the last glacial maximum. It wouldn't surprise if there were years with few, if any, storms, at least in the North Atlantic. I just don't know how high the SSTs were for much of the region. Probably greatly suppressed where storms were capable of forming, how intense they could get, and also the length of the summer.

Well as you probably know there are not often tropical storms in the South Atlantic Ocean, I believe there have only been two in modern times, and that is probably down to the water temperatures rarely exceeding 25 C there, as well as the size of the basin (but it's larger than the Arabian Sea which manages a few). The weather in the glacial maximum must have been quite extraordinary in general, maybe there were a few hurricanes but confined to the tropical latitudes.