Are there any ACC reasons advanced for the dearth of hurricanes this year?

See here for a sort of typical pre-season warning about how Anthropogenic Climate Change will be visiting destruction Real Soon Now.

Please: I don’t want a debate about ACC. I’ll get crushed for my perennial, undereducated, unsupported skepticism of any and all fervently cherished Great Causes, including ACC.

I am just wondering if there are any explanations derived from anthropogenic root causes for the light season. I’ve been reading about the sinking air, Sahara winds, and so on, but I’m not clear if those factors are independent of ACC, or thought to be part of it, or what.

What’s the Straight Dope on any putative relationship between hurricanes this season and ACC?

I’ve noticed that the NOAA has been over-estimating the number of hurricanes for several years now. Inevitably, they quietly revise the numbers downward later in the season, when it becomes clear that the annual prediction of Tons of Really Bad Hurricanes isn’t playing out. So whatever mistakes they’re making, it would seem they have yet to learn from them.

Same answer as with all ACC/GW/GCC issues:

Climate change is a prediction/observation of statistical averages over long time periods. These changes are currently much smaller than the normal variation in weather patterns. Hence, climate change models predict things in long-term statistical terms; any given year may or may not follow those predictions, since normal variations can drown them out-and in the case of things like El Nino, do so for many years at a time.

This is the same answer for why “it’s cold today, therefore Global Warming is a hoax!” isn’t an actual argument–and more generally, why anecdotes (individual experiences) are worthless as predictors of any system with significant randomness in it. Your grandmother who lived to be 138 years old while chain-smoking 13 packs a day doesn’t mean that smoking doesn’t cause cancer.

Mostly what TimeWinder said, but…

The link between climate change and increased hurricane intensity is one of the few things that’s actually had its certainty downgraded in the new IPCC report. There’s also a recent study out that suggests that climate change may make Atlantic hurricanes less likely to make landfall in the US, although that wouldn’t really mean anything with them not being generated at all. The hurricane intensity thing could very well turn out to be something they’re wrong about, although undoubtedly rising sea levels will make damage from the hurricanes that do hit coastal areas worse.

Here’s an article that seems to have a pretty good handle on it: Here Comes the Story of No Hurricanes – Mother Jones

The best guess at the moment for the blissfully quiet 2013 Atlantic Hurricane Season seems to be the position of the Azores-Bermuda High and significantly reduced humid air in a drought over Brazil:

From this article which you may find helpful.

Bit of confirmation bias. They do have a slight tendency to overestimate, but certainly not consistently over the last several years.

The local Houston Chronicle science reporter is naturally expected to do a fair amount of reporting on hurricanes, and he did an analysis of NOAA accuracy a couple years back. Bottom line: they’re pretty good and, while they have a slight tendency to overestimate, it’s not systematic nor does it happen with any consistent regularity (especially the last few years).

FWIW, he will probably also do an end of hurricane season wrap up at some point, which will likely touch on the accuracy of predictions and interesting climate events for this year and how they influenced hurricane formation.

As for the linking of ACC to a single season - you basically can’t, which the SciGuy also brings up whenever this comes up. Lots of things are one-off events and the weather over a single year can vary too much. But looking over a decade or more can begin to give longer term trends.

I think I get that, but there doesn’t seem to be as much hesitation linking any given severe storm (Sandy; Katrina…) to ACC.

Without shifting to GD, I’ve noticed that it’s sort of a confirmation bias for ACC when severe weather shows up (note my original cite in the OP as an example), but a shift to “remember; we’re talking climate and not weather” when quiet weather comes along.

So I was wondering if there are any ACC reasons advanced for the quiet season the way there are ACC reasons advanced for a more severe season…I’m trying to sort out if the explanations (the Azores-Bermuda High, e.g.) advanced for the quiet season have themselves been tied back to ACC underpinnings.

Yeah, and those are wrong, too. I can’t find the posts now, but I, at least have had posts clearly stating you can’t link individual storms that way. The SciGuy also says this.

That said, total ACE (accumulated cyclone energy) rather than number of storms, average water temperatures, and such things can be measured over the course of decades and have been. And yes, those things are showing an upward trend. So, while you can’t link any individual storm or even an individual hurricane season to climate change, you can link a series of 4 or 5 years to climate change after the fact.

Also, such explanations during the season (always remembering that hurricane season isn’t over yet) are simply inviting these unscientific sorts of links. We can look back in 2020 or 2030 and state 2013 was either an anomaly or the beginning of a new trend or whatever.

I’d think not, if only because the last dozen years or so have been extraordinarily active in terms of numbers of named storms, with 10 of the top 15 years of named storms being after 2000.

2013 was probably more of a return to normal than anything else. 2006, 2009 and 2002 were all somewhat similar to 2013 in terms of storms and hurricanes, as were most years in the 1990s and 1970s.

There’s the added complication that this sunspot cycle - since 2008 - has been the quietest since 1900. The peak has been continuously re-estimated downward. Before the end of the last cycle, this was going to be one of the biggest on record. Now, it’s not even half the previous 11 year cycle.

This is significant because the last few global coolings (the “Little Ice Age”) coincided with fewer sunspot cycles. the 1800’s, the 1400’s through the 1600’s. (when the Vikings died off in Greenland)

So it may be a case of the weather doing what it can in spite of human influences, not because of them. Heat is a big driver of hurricanes, and especially of massive precipitation that accompanies them. Travelling over hot water adds power to a hurricane. If the earth cools off, the tropical storms are less powerful. Never underestimate the ability of Mother Nature to overpower an piddling human efforts.

Just for clarification, you mean cooling coincides with fewer sunspots during a cycle, right? The length of the cycle’s not changing, just the total solar irradiance driven by faculae and sunspots present during the minima and maxima of the cycle?
So since the connection is between more sunspots, and a more warm troposphere, does that really give us a connection between seeing fewer sunspots this year, and a weak Atlantic basin hurricane formation season??
It seems like we’re reaching way out into left field unless there’s some work to corroborate a connection between sunspots and hurricane formation.

The short answer is, we know almost nothing.
Fewer sunspots in a cycle (i.e. Maunder minimum) coincides with time of colder over-all climate.
Heat, especially a hot surface layer of water, is what helps add to the power of a hurricane (and its precipitation levels).
We are unexpectedly in the quietest sunspot cycle in a century.
Whether this ha translated into the observed quiet times with hurricanes, or whether it’s statistical variation, who knows? If the Hudson freezes over like it did when George Washinton dragged his cannon across the ice from upper Manhattan to New Jersey - then we could confidently say we’re in a new cooling spell. If people can skate on the Thames in London, like they did in the 1600’s - then we can say we’re in a new cooling spell. Until then, all we can do is hope the climate does not get much hotter or much colder, but there’s not a lot we can do that comes with guarantees… Except that sometime in the next few thousand years, we may head into another 100,000 year cycle of serious glaciation.

Does it?


From pg. 205 in “The global signal of the 11-year solar cycle in the stratosphere: observations and models” in the Journal of Atmospheric and Solar-Terrestrial Physics 64 (2002) 203–210 (bolding mine) (PDF here: )
The short-term causality goes the other way - more sunspots, slightly warmer atmosphere.

Maybe you’re thinking of a connection with some other cycle? There are other cycles in sunspot activity besides the 11-year one. You may be thinking of the 88-year Gleissberg cycle or the 200+ year Suess cycle, but the problem in attempting to link 2013 sunspot abundance with 2013 hurricane formation using either of these cycles is the lag time involved:

From pg. 2842 in “Solar total irradiance and the global sea surface temperature record” in Journal of Geophysical Research, VOL. 96, NO. D2, pgs. 2835-2844. (PDF here: )

Examining Fig. 8 puts a kibosh on the idea that a longer-term cycle gives you temperature effects in 2013 of sunspot numbers in 2013.

If so, that would make sense intuitively with weak hurricane formation since
cooler atmosphere —> fewer hurricanes.

However, there are far too many other variables involved to rely on intuition.

In addition to the dry winds blowing off the Sahara, I heard that those winds also contained granules of sand, which inhibit the formation of tropical cyclones.

Sand would appear to actually help cyclone formation by seeding rain… intensifying the system.

Cyclone occur in the doldrums over warm water, where a rain storm forms into a cycle … the circle of wind generates more rain which powers the wind which generates rain…

A dry wind may remain too dry to form cyclones.

One very relevant criteria is that the cyclone can only form when its over water that is 27 C or higher…
which is just about the surface temperature of the Gulf and Sea… so it doesn’t take much change of the surface temperature to have a quiet season.

Cyclones occur, and are occurring everywhere. Tropical cyclones, however, are formed quite differently from frontal cyclones. The sea surface temps must be at least 80 degrees F (27 C) for a hurricane, but cooler waters can form lesser tropical cyclones, such as tropical depressions and tropical storms. They do not occur only in the doldrums. Many, in fact, originate in the Gulf of Mexico and the Caribbean Sea. I believe Super storm Sandy originated in the Caribbean. It was a hurricane until it lost its warm core. A tropical cyclone has a warm core, different from non-tropical, which have cold cores.

You can seed clouds and possibly produce rain, but that has nothing to do with a tropical cyclone. If sand gets into the core, that could disrupt the convection. Tropical cyclones derive their energy from convective instability and condensation of copious quantities of water. Hence, they lose their strength over land because they lack, primarily, the warm waters, but also, to some extent, convection. The “circle of wind” does not generate rain. The source is has I noted.

Tornadoes also have circles of wind, vortexes actually, and those vortexes actually arise from the ground where you have shearing winds (winds just above the ground in an opposite direction from the winds at the ground.) Convection causes those horizontal vortexes to rise, and that’s the beginning of a tornado. Wind shear disrupts a tropical storm.

In fact it was thought some time ago that seeding hurricanes would disrupt them. For some reason that idea was dropped.