Is Global Warming Making Atlantic Hurricanes Worse?

Updated on April 8, 2019
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MY ESOTERIC likes to think of himself as a bit of a polymath with degrees in Statistics, Accounting, Computer Science, & Operations Research

Hurricane Andrew - 8 -23-1992

Source

Atlantic Hurricanes

The Atlantic hurricane season lasts from June until November each year. The busiest months are August, September, and October. That said, I remember hurricanes happening in April, May, December, and January in years past.

The main driver of hurricanes is ocean temperature and low pressure areas. The warmer the ocean, the more frequent and powerful the storms can be. Other factors, principally the El Niño and La Niña effects in the Pacific Ocean, when present, can enhance or kill hurricanes. For a fuller explanation of how hurricanes form, read here.

This article is concerned with the ocean temperature aspect of hurricane formation. All date is sourced from here.

Heating the Oceans

As the global air temperature rises, due to global warming or any other reason that may cause global temperatures to increase, so does the water of the oceans beneath it rise. The mid-Atlantic Ocean, the Gulf of Mexico, and the Caribbean are no exceptions. As the water temperatures rise so does the probability they will spawn tropical storms and hurricanes. In addition to producing more storms, warmer and warmer water will produce stronger and stronger storms.

The question then is, is there evidence that Atlantic hurricanes are getting more frequent and worse. Yes there is as you will see in the next several sections.

There are two ways, along with several variations, to determine if the pattern of Atlantic hurricanes is indeed changing over time. One is to study variations over time to see if there is a trend. The other is to take statistics (mean, standard deviation,etc) at various points in time and then to test to see if they are different from each other. We will do both in this article.

Atlantic Hurricanes 1850 - 2018

We will start with method one, looking at the complete time series of hurricane data to see what we see. I don't plot each year because there is way too much variability. For example, in 1914 there was one tropical storm and no hurricanes; but in 2005, there were were 28 tropical storms, 8 minor hurricanes, and 7 major hurricanes; a total of 43, the most to-date.

So to avoid this confusing set of highs and lows, there are several techniques to "smooth" the data but still retain its essence. One of those is called "moving averages". What one does is take the average of the first so many data points and that becomes your first data. You then drop the first point, add the next point, and take a new average; the second data point. Do it again and again until you have gone through all of the data.

I this case, I chose to use a 20-year moving average because weather moves in slow cycles. And a 20 year period is long enough to smooth out yearly and seasonal variations.

The chart below depicts a 168 year period of Atlantic storms using the 20-year moving average method (which is why it starts in 1869, There are ten lines on it representing, from top to bottom:

  • Total Storms
  • Total Tropical Storms
  • Total Hurricanes
  • Total Minor Hurricanes (1, 2)
  • Total Major Hurricanes (3, 4, 5)

The dashed lines with each one is a linear trend line and the numbers represent the equation that best fits the trend and the "R-squared" value with tells you the goodness of fit or how much of the deviations are explained by the equation.

A Complete Look at Atlantic Storms Over a 168 Year Period

Source

Here is what this chart tells us.

Total Storms

This is the sum of the total tropical storms (not including tropical storms that later turned into hurricanes) and the total hurricanes. Even without the help of the trend line, it is easy to see that the total number of Atlantic storms is increasing over time. Specifically, there is, on average, 0.0679 additional storms each year. How good is that prediction? Look at the R-squared value of 0.77. Any value above 0.7 means, as a rule, the equation is valid. Taken together then, this is good evidence that number of storms is increasing over time due to global warming.

Total Tropical Storms

Now we look in more detail behind the increasing number of storms. Again we see a clear indication that storm activity is increasing, at least at the tropical storm level. Here, the number of tropical storms is increasing, on average, 0.0507 tropical storms per year. How confident are we? The 0.81 R-squared tells us we are very confident.

Total Hurricanes

Hurricanes are measured as Category 1, 2, 3, 4, and 5 right now. Each increase roughly represents an order of magnitude increase in the damage and devastation caused by these storms. In fact, they are thinking about adding a category 6 to the mix because storms are starting to get that violent. While still terrible, CAT 1 and 2 hurricanes are considered "minor" while 3, 4, and 5 are considered "major". This line represents all 5 categories.

In this case, we see that the total number of hurricanes is increasing at a rate of 0.0171 hurricanes per year. But how confident are we? Not as much at a 0.49 R-squared. But, there is a reason for that as we will see.

Total Minor Hurricanes

With Minor Hurricanes, things change. Part of the prediction from weather scientists is that the proportion of minor to major storms will change with the weight going to major storms. In other words, as the earth heats up, we will see more frequent and more violent hurricanes as time goes on. Indeed, that is what the data is starting to show.

For minor hurricanes, we actually see the number of is possibly decreasing. They are decreasing at a rate of -0.0005 storms per year. Unfortunately, with a R-squared of 0.0012, you can't take that prediction to the bank. With an R-squared that low, the best estimate is simply the average of storms over that period which is 3.56 minor hurricanes per year.

Major Hurricanes

Where minor hurricanes don't tell you much, major hurricanes speaks volumes. Here we see that the number of major hurricanes is increasing at a rate of 0..0176 major hurricanes a year. And, we are extremely confident that is true because the R-squared is a whopping 0.91!

Now we can see why total hurricanes has a low R-squared because it represents the combination of those from both the minor and major hurricane data. We can also see it is the increasing number of major hurricanes that is driving the overall increase in hurricanes. That is not good for people but good evidence that global warming is driving more and more devastation.

The chart below is a clearer picture of what we just discussed.

Just Hurricanes Over the Last 168 Years

Source

Testing Statistical Means For Global Warming

I said there were two methods of testing the hypothesis that Atlantic Storms are increasing due to global warming. We just covered the first, and the picture was clear. Now let's look at the second.

In this case, I am going to divide up the data into two large groups of about equal years - 1850 - 1934 and 1935 - 2018. Then we will calculate the mean and standard deviation of each group. With that, we will test to see if the means of each group are NOT EQUAL, meaning there is something going on. On the other hand, if they are EQUAL,or the second mean is smaller than the first then there is no support for global warming based on increasing Atlantic storm activity. We will consider each of our five demographics.

Total Storms

Group 1 (85) Mean - 12.08 Storms per Year

Group 1 (85) SD - 5.6

Group 2 (84) Mean - 18.4 Storms per Year

Group 2 (84) SD - 6.56

On the face of it, it certainly looks like those means are different with Group 2 being much bigger - but are they statistically? Using a standard statistical test between two means, the t-test, we find that the probability that those two means are different is greater than 0.9999. Said another way, there is a 99% chance (at a confidence level of 95%) that the number of storms in Group 2 (1935 - 2018) is larger than Group 1 (1850 - 1935); a very strong indicator of global warming.

Total Tropical Storms

Let's do the same thing for tropical storms.

Group 1 (85) Mean - 7.26 Storms per Year

Group 1 (85) SD - 3.64

Group 2 (84) Mean - 11.89 Storms per Year

Group 2 (84) SD - 4.04

Again, on the face of it, it certainly looks like those means are different with Group 2 being much bigger . Still using the t-test, we find that the probability that those two means are different is greater than 0.9999. Said another way, there is a 99% chance (at a confidence level of 95%) that the number of storms in Group 2 (1935 - 2018) is larger than Group 1 (1850 - 1935); a very strong indicator of global warming.

Total Hurricanes

Let's do the same thing for tropical storms.

Group 1 (85) Mean - 4.82 Storms per Year

Group 1 (85) SD - 2.36

Group 2 (84) Mean - 6.51 Storms per Year

Group 2 (84) SD - 2.87

Again, on the face of it, it certainly looks like those means are different with Group 2 being much bigger . Still using the t-test, we find that the probability that those two means are different is greater than 0.9999. Said another way, there is a 99% chance (at a confidence level of 95%) that the number of storms in Group 2 (1935 - 2018) is larger than Group 1 (1850 - 1935); a very strong indicator of global warming.

Minor Hurricanes

Let's do the same thing for tropical storms.

Group 1 (85) Mean - 3.47 Storms per Year

Group 1 (85) SD - 1.97

Group 2 (84) Mean - 3.65 Storms per Year

Group 2 (84) SD - 1.75

Again, on the face of it, it does not look like those means are different with Group 2 being much bigger . Still using the t-test, we find that the probability that those two means are different is only 0.4699. Said another way, there is a 47% chance (at a confidence level of 95%) that the number of storms in Group 2 (1935 - 2018) is larger than Group 1 (1850 - 1935); not an indicator of global warming at all. This is similar to the result we found in the first analysis for minor hurricanes.

Major Hurricanes

Let's do the same thing for tropical storms.

Group 1 (85) Mean - 1.35 Storms per Year

Group 1 (85) SD - 1.39

Group 2 (84) Mean - 2.86 Storms per Year

Group 2 (84) SD - 2.01

Again, on the face of it, it certainly looks like those means are different with Group 2 being much bigger . Still using the t-test, we find that the probability that those two means are different is greater than 0.9999. Said another way, there is a 99% chance (at a confidence level of 95%) that the number of storms in Group 2 (1935 - 2018) is larger than Group 1 (1850 - 1935); a very strong indicator of global warming.

Conclusion - Global Warming is Real

It should now be obvious, even to the deepest skeptic who doesn't have an agenda that, at least based on increased activity of Atlantic storms, that global warming isn't real. All you have to do is believe that:

  1. Atlantic storms are related to water temperature
  2. That the warmer the water, everything else being equal, you get more storms
  3. That the warmer the water, everything else being equal, you get more violent storms
  4. That the warmer the air, the warmer the surface water
  5. That all scientists agree to the above

If you believe those things, then the data shows that Atlantic storms are increasing in number and ferocity and therefore it is global warming that is driving it.

Questions & Answers

    © 2019 Scott Belford

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      • My Esoteric profile imageAUTHOR

        Scott Belford 

        2 months ago from Keystone Heights, FL

        Thanks for the comment Doc. Doesn't look like Open Mind is very open minded about Joe Biden, lol. I did like the page on links.

      • Doc Snow profile image

        Doc Snow 

        2 months ago from Camden, South Carolina

        Enjoyed your statistical examination. Scott, if you're not already aware of it, you might enjoy Tamino's blog "Open Mind":

        https://tamino.wordpress.com/

        "Tamino" is the blogging 'handle' of a professional statistician who is also highly concerned about climate change.

        On the matter of the relatively stable number of total hurricanes, the expert consensus seems to be that that's what we expect to see as warming continues. Apparently, in addition to warming oceanic waters fueling hurricanes, the warming also tends to increase wind shear in the atmosphere--and vertical wind shear inhibits hurricane formation, as discussed here:

        https://en.wikipedia.org/wiki/Wind_shear#Effects_o...

        If a hurricane survives the effects of wind shear and becomes well-organized, then the main variable is often the water temperature. So we have competing effects driving this trend of increasing mean hurricane strength.

      • bradmasterOCcal profile image

        Brad 

        4 months ago

        Meanwhile, China, the Paris Protocol’s champion and the world’s most notorious polluter, produced the largest increase of carbon in the atmosphere in 2017. Coupled with India, China’s carbon contributions accounted for nearly half of the total surge in 2017 global carbon emissions.

        Just because the U.S. is one of only a few nations not in the Paris agreement does not suddenly make it a good deal. The accord was not a binding treaty, but only a collection of pledges based on the honor system (agreed to by nations with inconsistent records). Since the agreement lacked an enforcement clause, it could not hold countries accountable or penalize them if they failed to meet their obligations. But most of the participating countries’ commitments were far from inspiring, anyway.

        The Manhattan Institute’s Oren Cass, an expert on energy policy, called the Paris Accord something “between a farce and a fraud.” One hundred and ninety-seven nations gathered together to agree to combat climate change, but some participants were much more ambitious than others. Some countries agreed to do what they already planned to do, if not less.

        Cass explained that China pledged to “reach peak emission by about 2030.” Well, the United States government had already completed a study to guess when Chinese emissions would peak; their guess was about 2030.

        India did not pledge to lower their emissions at all, but merely pledged to “reduce the emissions intensity.”

        Numerous countries promised to remain on their current emission trajectories. Bravo! Obama applauded their efforts and happily accepted their half-hearted pledges. But then he committed the U.S. to meet disproportionately large, economy-crippling targets. Obama’s pledge stipulated that the U.S. would reduce emissions by nearly a quarter. Using the National Energy Modeling System 2015, a computer model created by the U.S. Department of Energy, the Heritage Foundation projected that the Paris Accord would cost the U.S. nearly 400,000 jobs and the national economy $2.5 trillion by 2035.

        Not to mention, Obama kindly donated $3 billion from the unlimited U.S. bank account over four years to the Green Climate Fund, which uses developed nations’ money to help developing countries reduce their carbon dioxide emissions. If the patterns of history hold, the money probably will not go to its intended purposes and will instead be funneled to the ruling elites of the impoverished nations. As the saying goes, “Foreign aid is taking money from poor people in rich countries and giving it to rich people in poor countries.” If the U.S. remained in the agreement, it’s likely future administrations would turn the Green Climate Fund into another U.S. foreign aid black hole.

        Parting ways with an unnecessary, unfairly expensive international agreement did not end U.S. free-market innovation or investment in new energy technologies, which caused this year’s large decrease in carbon emissions depicted by the AEI graph. Leaving does not mean losing sight of the future.

      • bradmasterOCcal profile image

        Brad 

        4 months ago

        Scott

        This is the reason why you and the rest of anti Trumpers are whining about global warming

        --------------------------------

        Under the Paris Agreement, each country must determine, plan, and regularly report on the contribution that it undertakes to mitigate global warming.[6] No mechanism forces[7] a country to set a specific target by a specific date,[8] but each target should go beyond previously set targets. In June 2017, U.S. President Donald Trump announced his intention to withdraw his country from the agreement.

        --------------------------------------------------

        Scott this is the reason, you want this global warming to become a voting issue against president Trump.

        -------------------------------------------------

        Under the agreement, the earliest effective date of withdrawal for the U.S. is November 2020, shortly before the end of President Trump's current term. In practice, changes in United States policy that are contrary to the Paris Agreement have already been put in place.[9][10]

      • bradmasterOCcal profile image

        Brad 

        4 months ago

        Scott

        Once again, what is the solution to your alleged problem? It isn't the Paris Accord.

      • My Esoteric profile imageAUTHOR

        Scott Belford 

        4 months ago from Keystone Heights, FL

        Jay - also notice the increase in Arctic temperature increase in the last 10,000 years (red lines) also coincides with the increase in CO2 (yellow lines) and the decrease in ice (grey)

        And, if you look at the red lines on the first chart in this link, you will see the increase in Arctic temperatures further than 50,000 years ago were much shorter in duration, when linked solely to the cycles, than they are now with increased CO2 added.

      • My Esoteric profile imageAUTHOR

        Scott Belford 

        4 months ago from Keystone Heights, FL

        Actually I have Jay, recently. According to the latest research, they are a major contributing factor to the many variations of the past several hundred thousand years. The difference here is that during all that time, the levels of CO2, and other greenhouse gases, have stayed within normal bounds.

        That is no longer the case as we are in uncharted territory with the level of CO2 in the atmosphere. You can tell that from the chart in your link. Look at how CO2 has exploded in recent years. You have to look close because of the time scale, but that yellow line shoots straight up at year 0.

      • bradmasterOCcal profile image

        Brad 

        4 months ago

        Scott

        I have read it, and I asked you and you tell me to read the Paris Accord.

        How do you think that the Paris accord is going to change climate control or global warming?

        Try giving an answer instead of a comment to a question.

        Basically, if you don't know how something works, don't try to fix it.

      • Jay C OBrien profile image

        Jay C OBrien 

        4 months ago from Houston, TX USA

        I like your approach.

        Have you considered the Milankovitch Cycles? We conclude that within 15000 years the earth would naturally be returning to a new ice age lasting 100,000 years. The earth then enters another long period of high eccentricity lasting a further 400,000 years. Future Interglacials will last only ~10,000 years, before the cycle repeats.

        https://principia-scientific.org/next-ice-age-due/

      • My Esoteric profile imageAUTHOR

        Scott Belford 

        4 months ago from Keystone Heights, FL

        Brad, read the Paris Climate Accord Agreement and that will give you a start. Or, read the many annual climate reports, that will help you as well.

      • bradmasterOCcal profile image

        Brad 

        4 months ago

        Scott

        Assuming that you are right, now what is the solution and how would it work?

      • My Esoteric profile imageAUTHOR

        Scott Belford 

        4 months ago from Keystone Heights, FL

        Thanks Mike. I have heard of this Luntz propagandist.

      • peoplepower73 profile image

        Mike Russo 

        4 months ago from Placentia California

        Scott: Excellent article and I can tell it was right in your wheel house of statistical analysis. I'm sure glad you used the term global warming instead of climate change. Global warming is so much more descriptive of how encompassing the effect really is.

        Frank Luntz, a conservative propagandist created a guide for republican's to "say this not that." He advocated use of vocabulary crafted to produce a desired effect; including use of the term death tax instead of estate tax, and climate change instead of global warming.

      • My Esoteric profile imageAUTHOR

        Scott Belford 

        4 months ago from Keystone Heights, FL

        Thanks, HS and so true about the climate-deniers.

      • profile image

        Howard Schneider 

        4 months ago from Parsippany, New Jersey

        You are absolutely right, Scott. The scientific statistics and analysis makes it abundantly clear that global warming and the resulting climate change is not only real but an existential threat to this planet. The Republicans and their corporate benefactors use the Trumpian method of continually espousing that this is false creating doubts in people who do not follow it and are uninterested in trying. There is so much money to be made by business by investing in alternative energy sources but unbelievably they continue this cover up. We are all paying the consequences of these lies and our children will pay a much steeper price. Excellent hub. You will probably be consistently attacked by the Trumpian hubbers but you are clearly correct.

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