# So with dual Super-hurricanes this year, is it conclusive that it's from global warming? **URL:** \ **Category:** Factual Questions\ **Created:** [September 7, 2017, 5:13pm UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745 "2017-09-07T17:13:37Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Okrahoma](https://avatars.discourse-cdn.com/v4/letter/o/90db22/32.png) [@Okrahoma](https://boards.straightdope.com/u/Okrahoma)\ **Post date:** [September 8, 2017, 12:37am UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/21 "2017-09-08T00:37:04Z")
> [@t-bonham@scc.net](#): > > I saw a list of the most severe Atlantic hurricanes in history recently. What impressed me was that 1/3 of them were in the last 15 years, with almost 1 per year in the last 3-4 years. That seemed to be compelling evidence. > **[List of the most intense tropical cyclones | North Atlantic Ocean](https://en.wikipedia.org/wiki/List_of_the_most_intense_tropical_cyclones#North_Atlantic_Ocean)** > > The most intense storm in the North Atlantic by lowest pressure was Hurricane Wilma. The strongest storm by 1-minute sustained winds was Hurricane Allen. > Storms which reached a minimum central pressure of 920 millibars (27.17 inHg) or less are listed. Storm information has been compiled back to 1851, though measurements were rarer until aircraft reconnaissance started in the 1940s, and inexact estimates were still predominant until dropsondes were implemented in the 1970s. 8 out of 25 in the last 15 years. And 3 of them in 2005. But if you look at the whole distribution there is no obvious pattern. The last 2 big ones are 2017 and 2010 - 7 year spread. But in the 7 years from 1992 to 1999 there were 4 big ones. Same in the 1985 to 1992 7 year spread - 4 big ones. So having 8 in 15 years is not something extraordinary. And I don’t know where you get “almost 1 per year in the last 3-4 years” with only 2 big ones from 2010 to now. ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [September 8, 2017, 12:46am UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/22 "2017-09-08T00:46:55Z")
[Trump here …NO!](https://www.vox.com/policy-and-politics/2017/6/1/15726472/trump-tweets-global-warming-paris-climate-agreement) [sup][sup]Note to mods: The GQ has been answered… this is a joke![/sup][/sup] ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [September 8, 2017, 1:23am UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/23 "2017-09-08T01:23:55Z")
> [@Lucas\_Jackson](#): > > [Trump here …NO!](https://www.vox.com/policy-and-politics/2017/6/1/15726472/trump-tweets-global-warming-paris-climate-agreement) > > [sup][sup]Note to mods: The GQ has been answered… this is a joke![/sup][/sup] **Moderator Note** Joke or not, it’s still a political jab. Keep it out of GQ. It has nothing to do with the question in the OP. Colibri General Questions Moderator ---
**Author:** ![Duckster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/duckster/32/1244_2.png) [@Duckster](https://boards.straightdope.com/u/Duckster)\ **Post date:** [September 8, 2017, 3:31am UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/24 "2017-09-08T03:31:22Z")
Global warming is a subset of climate change. The [jury is still out](https://www.gfdl.noaa.gov/global-warming-and-hurricanes/) on global warming effects on hurricanes. ---
**Author:** ![Gyrate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gyrate/32/3588_2.png) [@Gyrate](https://boards.straightdope.com/u/Gyrate)\ **Post date:** [September 8, 2017, 9:53am UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/25 "2017-09-08T09:53:01Z")
> [@SmartAlecCat](#): > > The records only go back until that year when the hall of records was mysteriously blown away. “ln Hertford, Hereford and Hampshire, hurricanes hardly ever hapoooohshhiiiii…” ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 8, 2017, 11:12am UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/26 "2017-09-08T11:12:11Z")
The jury might still be out on what global warming would theoretically be expected to do to hurricanes, but we’re getting close to the point where that doesn’t matter, because we’re finding out empirically what it does. Global warming is not something that will happen; it’s something that is happening right now, and has been for a century. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [September 8, 2017, 11:22am UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/27 "2017-09-08T11:22:57Z")
> [@Asuka](#): > > IIRC it was something akin to “We only call it a 500 year storm because we only have spotty records going back to 500 years, so we don’t know how often these things actually come up” No, that’s not how these things work. And we have [records](https://pubs.geoscienceworld.org/gsabulletin/article-abstract/115/9/1027/2030/records-of-prehistoric-hurricanes-on-the-south?redirectedFrom=fulltext) for [some](http://onlinelibrary.wiley.com/doi/10.1029/2006GC001463/full) [places](http://www.basinalliance.org/data/files/LiuFearn2000.pdf) going back much further than 500 years, all of which goes into the stats. ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [September 8, 2017, 11:52am UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/28 "2017-09-08T11:52:44Z")
> [@Marvin\_the\_Martian](#): > > … You fit a probability distribution to this collection of data ; I am not sure what distribution is used for floods, but if you assume a normal distribution (unlikely since you can’t have a negative flood) … Most phenomena like that obey a [power-law distribution](https://en.wikipedia.org/wiki/Power_law#Power-law_probability_distributions). OP asks “Have the parameters of the power law for hurricane intensity changed?” Although power laws apply to a huge range of real-world statistics, it was in fact _flooding_ (along the Nile River) that, a century ago, led to the early understanding of such power laws. Power-law statistics (and specifically the old Nile River papers by Harold Hurst) led Benoit Mandelbrot to some of his conclusions. The famous 1998 collapse of a hedge fund led by Nobel Prize winners might be partly blamed on their use of normal distributions(\*) in their models rather than the power-law distributions which [are needed to describe fluctuations and risk in financial markets](https://books.google.co.th/books?id=2ciGAwAAQBAJ&pg=PA64&lpg=PA64). (\* - There are simplifying theorems that apply to normal distributions so these are often preferred in modeling. “The light’s better here.” :smack: ) ---
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [September 8, 2017, 12:46pm UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/29 "2017-09-08T12:46:43Z")
Think of it as the “frog in the pot” situation. Current fluctuation could be normal statistical variation, or it could be a sign of things to come. Like the frog in the slowly heating pot of water, we’ll only be sure when the statistics are incontrovertible. Also remember these things happen regularly. They only seem to impact our collective consciousness (i.e. become 24-hour news on CNN) when the storm takes aim at a well-populated area of the USA. The problem with these storms, as mentioned earlier, is not sea level. Compared to a 12-foot storm surge, a few cm (if that) of sea level rise is negligible. The biggest problem is the amount of rain - that causes flooding. In this whole thread, everyone discusses wind speed, etc. Nobody has mentioned comparative rainfall statistics. Yet we can point to various news stories over the years of rising sea surface temperatures… ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [September 8, 2017, 1:46pm UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/30 "2017-09-08T13:46:16Z")
It’s the wind speed that produces all the cool videos … ---
**Author:** ![Jackmannii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackmannii/32/311_2.png) [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)\ **Post date:** [September 8, 2017, 3:13pm UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/31 "2017-09-08T15:13:03Z")
One bad hurricane season does not make it “conclusive” that climate change is to blame, any more than having [a streak of 12 years without a major hurricane hitting the U.S.](http://dailycaller.com/2017/06/16/its-been-4253-days-since-the-last-major-hurricane-landed-in-the-us/) disproves climate change. Tempting as it is to assign definitive causes to isolated events, long-term trends are what count. As for severe seasons, one of the worst on record was [in 1780](https://en.wikipedia.org/wiki/1780_Atlantic_hurricane_season). ---
**Author:** ![Buck\_Godot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/buck_godot/32/6573_2.png) [@Buck\_Godot](https://boards.straightdope.com/u/Buck_Godot)\ **Post date:** [September 8, 2017, 4:00pm UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/32 "2017-09-08T16:00:38Z")
> [@Marvin\_the\_Martian](#): > > “500 year storm” is an estimate using statistics of the probability of an unlikely event occurring. I am not sure what figure of merit is used to characterize a storm’s “strength”, so let’s assume we are talking about a “500 year flood” (which is actually what is being discussed in Houston). > > See the Wikipedia page for [100-year flood](https://en.wikipedia.org/wiki/100-year_flood) for a more detailed explanation (100-year floods are used to determine who lives in a “flood plain” and will be obligated to purchase flood insurance by their lender). Basically you look at the historical record to collect the annual maximum flood level in a given location. You fit a probability distribution to this collection of data ; I am not sure what distribution is used for floods, but if you assume a normal distribution (unlikely since you can’t have a negative flood) calculating the mean and variance based on measured data is pretty straightforward. You now have a model giving you the probability of a particular flood level being reached in a one year period. To find the 100-year flood you would calculate from the fitted distribution the flood level which corresponds to a 1% probability (1/100). To find the 500-year, calculate the flood level which has a 0.2% probability. > > Since the data used to estimate the probability distribution is limited, there is considerable uncertainty in the calculations to the point where the “500 year” level basically comes down to “a shitload more water than we ever though we’d see”. Its a bit harder than that even. Based on what your saying, the 500 year flood means that there is a 0.2% chance of Houston getting hit by that kind of flood in a given year, but there is also a 0.2% chance of Miami getting hit by a 500 year flood and a 0.2% chance of Atlanta getting hit by a 500 year flood and a 0.2% chance of Charleston getting hit by a 500 year flood etc… So depending on average size of these floods and the overall area of the US that is susceptible to Hurricanes it may be that even under normal conditions we should expect a 500 year flood somewhere in the US as often as every decade or two. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [September 8, 2017, 5:25pm UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/33 "2017-09-08T17:25:30Z")
> [@Buck\_Godot](#): > > Its a bit harder than that even. Based on what your saying, the 500 year flood means that there is a 0.2% chance of Houston getting hit by that kind of flood in a given year, but there is also a 0.2% chance of Miami getting hit by a 500 year flood and a 0.2% chance of Atlanta getting hit by a 500 year flood and a 0.2% chance of Charleston getting hit by a 500 year flood etc… So depending on average size of these floods and the overall area of the US that is susceptible to Hurricanes it may be that even under normal conditions we should expect a 500 year flood somewhere in the US as often as every decade or two. That’s what the probabilities say … Consider this, there’s a 0.0004% probability that Houston gets _two_ 500-year floods in any given year … half the season’s over so there’s only a 0.0002% chance of Houston getting nailed _this_ year again … awesome … ---
**Author:** ![Marvin\_the\_Martian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/marvin_the_martian/32/2898_2.png) [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)\ **Post date:** [September 8, 2017, 5:34pm UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/34 "2017-09-08T17:34:32Z")
> [@Buck\_Godot](#): > > Its a bit harder than that even. Based on what your saying, the 500 year flood means that there is a 0.2% chance of Houston getting hit by that kind of flood in a given year, but there is also a 0.2% chance of Miami getting hit by a 500 year flood and a 0.2% chance of Atlanta getting hit by a 500 year flood and a 0.2% chance of Charleston getting hit by a 500 year flood etc… So depending on average size of these floods and the overall area of the US that is susceptible to Hurricanes it may be that even under normal conditions we should expect a 500 year flood somewhere in the US as often as every decade or two. You are assuming that the probability of location A getting a 500-year flood is uncorrelated with location B getting a 500-year flood. This is probably true for widely separated locations, but as the locations get closer (or on the same lake/river/oceanfront) this is less and less true. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [September 8, 2017, 6:21pm UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/35 "2017-09-08T18:21:13Z")
> [@Marvin\_the\_Martian](#): > > You are assuming that the probability of location A getting a 500-year flood is uncorrelated with location B getting a 500-year flood. This is probably true for widely separated locations, but as the locations get closer (or on the same lake/river/oceanfront) this is less and less true. That’s a good assumption … if we use the data from location A to calculate the probability of a flood at location A … the data from location B isn’t used … any correlation between a flood at location A and location B is strictly due to the _cause_ of the flood event … something the statistical arts doesn’t account for in this context … the 500 year flood probability is from _all_ causes … ---
**Author:** ![Marvin\_the\_Martian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/marvin_the_martian/32/2898_2.png) [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)\ **Post date:** [September 8, 2017, 7:07pm UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/36 "2017-09-08T19:07:24Z")
> [@watchwolf49](#): > > That’s a good assumption … if we use the data from location A to calculate the probability of a flood at location A … the data from location B isn’t used … any correlation between a flood at location A and location B is strictly due to the _cause_ of the flood event … something the statistical arts doesn’t account for in this context … the 500 year flood probability is from _all_ causes … Yes, the statistical model is valid for a particular location (although in reality flood maps in areas with little or no data are generated using the statistics from hydrologically similar areas). My objection was the assertion that if the probability of a 500 year flood in location A is 0.2% (by definition) and the probability at location B is also 0.2% then the probability of a 500 year flood at _either_ location A or B is 0.4%, and if we add up enough locations then it is likely that we would have a 500-year flood _somewhere_ at frequent intervals. Adding probabilities like this is only valid if the events are independent (i.e., uncorrelated). Since many areas would share the same cause of the flood, the flood events are clearly correlated and adding the probabilities is incorrect. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [September 8, 2017, 7:59pm UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/37 "2017-09-08T19:59:00Z")
Right … if we divide up the world’s land mass into 500 equal-area chunks (a little bigger than Arizona) … _on average_, one of these chunks will experience a 500-year flood somewhere in its area every year … keep in mind, if a tiny tickle of water runs every 500 years in Central Antarctica, that’s a 500 year flood event … the statistical arts are useful, but there are some drawbacks … **Buck Godot** used as an example Houston and Miami … these two locations are far enough apart where just adding the probabilities is valid enough … as valid as can be had until we have 500 years of good scientifically accurate data … we’re just guessing at this point … ---
**Author:** ![Marvin\_the\_Martian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/marvin_the_martian/32/2898_2.png) [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)\ **Post date:** [September 8, 2017, 8:10pm UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/38 "2017-09-08T20:10:51Z")
> [@watchwolf49](#): > > Right … if we divide up the world’s land mass into 500 equal-area chunks (a little bigger than Arizona) … _on average_, one of these chunks will experience a 500-year flood somewhere in its area every year … keep in mind, if a tiny tickle of water runs every 500 years in Central Antarctica, that’s a 500 year flood event … the statistical arts are useful, but there are some drawbacks … This is actually the opposite of what I am saying…there is no way that the weather in all of those chunks is uncorrelated with every other chunk. El Nino, for example, affects weather over an enormous area. Flood probabilities in Miami and Houston are both going to be affected by water temperatures in the Atlantic. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [September 8, 2017, 8:29pm UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/39 "2017-09-08T20:29:49Z")
> [@Marvin\_the\_Martian](#): > > This is actually the opposite of what I am saying…there is no way that the weather in all of those chunks is uncorrelated with every other chunk. El Nino, for example, affects weather over an enormous area. Flood probabilities in Miami and Houston are both going to be affected by water temperatures in the Atlantic. When a butterfly flaps its wings in Australia, a tornado is eventually spawned in Nebraska … cause-and-effect … I get that … I just think you’re diving into a level of minutia that can’t be supported by the margin of errors we’re dealing with … a 500 year flood in Miami _or_ Houston is 0.4% give or take 0.2% … neither one of us has the data to dispute that error … ---
**Author:** ![Marvin\_the\_Martian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/marvin_the_martian/32/2898_2.png) [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)\ **Post date:** [September 8, 2017, 9:41pm UTC](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745/40 "2017-09-08T21:41:35Z")
> [@watchwolf49](#): > > When a butterfly flaps its wings in Australia, a tornado is eventually spawned in Nebraska … cause-and-effect … I get that … I just think you’re diving into a level of minutia that can’t be supported by the margin of errors we’re dealing with … a 500 year flood in Miami _or_ Houston is 0.4% give or take 0.2% … neither one of us has the data to dispute that error … What I am saying has nothing to do with the butterfly effect - I don’t know how you can read that from my posts, I am talking about very macro effects like ocean temperature which can impact weather over a very wide area, thereby introducing a correlation in the weather between locations within that area. Once there is correlation, you can’t calculate the probability of A or B by simple addition. That’s all that I am saying. [Previous page](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745.md?page=1) [Next page](https://boards.straightdope.com/t/so-with-dual-super-hurricanes-this-year-is-it-conclusive-that-its-from-global-warming/795745.md?page=3)