
Global Warming and Hurricanes, an Overview of Current Research Results - pron
https://www.gfdl.noaa.gov/global-warming-and-hurricanes/
======
sanxiyn
Scientific consensus, as published by IPCC AR5, is that there was no clear
change in floods, droughts, storms in the last century. People are often
surprised to find this because of sensational media reports, but that's what
we have.

[https://scienceofdoom.com/2017/02/12/impacts-v-climate-
chang...](https://scienceofdoom.com/2017/02/12/impacts-v-climate-change-is-
already-causing-worsening-storms-floods-and-droughts/) has detailed
discussion.

~~~
tzs
Here's a table of the number of category 4 or 5 Atlantic hurricanes broken
down by year range. Note that the first two rows are 50 year ranges, the next
two are 25 year ranges, and the last is 18 years, so the import columns are
the rate columns, which give the average number of storms per year of each
category during the corresponding year range:

    
    
       Years     Cat 4     Cat 5     4 or 5
                Num Rate  Num Rate  Num Rate
     1851-1900   13 0.26    0 0.00   13 0.26
     1901-1950   29 0.58    8 0.16   37 0.74
     1951-1975   22 0.88    7 0.28   29 1.16
     1976-2000   24 0.96    7 0.27   31 1.24
     2001-2017   21 1.2    10 0.59   31 1.82
    

Data taken from Wikipedia lists of category 4 and category 5 Atlantic
hurricanes:

[https://en.wikipedia.org/wiki/List_of_Category_4_Atlantic_hu...](https://en.wikipedia.org/wiki/List_of_Category_4_Atlantic_hurricanes)

[https://en.wikipedia.org/wiki/List_of_Category_5_Atlantic_hu...](https://en.wikipedia.org/wiki/List_of_Category_5_Atlantic_hurricanes)

~~~
leifaffles
How accurate and complete are measurements across these time periods?

Are more recent periods inherently going to have more hurricanes because we
now have the capability to detect more hurricanes? How has measurement changed
over the past 175 years?

------
marcus_holmes
So I read that as there's no measurable impact on hurricane activity yet. The
modelling indicates that they won't get more frequent, but will become more
intense in the future (stronger winds, more rainfall).

~~~
martingoodson
Look at figure 2. There is a 'measurable' increase in hurricane activity that
gets very severe in recent years. The problem is that the time series is very
noisy because records were patchy going back to 1880. Therefore statistical
tests cannot robustly distinguish signal from noise (if any).

The authors do cite a paper that analysed more recent records (from 1950
onwards) [1]. This paper (see figure 1a) demonstrates a very strong
statistical correlation between sea surface temperature and hurricane
activity. This supports a causal link between climate change and hurricane
activity.

[1]
[http://onlinelibrary.wiley.com/wol1/doi/10.1029/2007GC001844...](http://onlinelibrary.wiley.com/wol1/doi/10.1029/2007GC001844/full)

~~~
marcus_holmes
I summarised their conclusion (section E) in which they specifically state
there's no connection between warming and numbers of hurricanes.

what do you mean when you say "activity"?

~~~
jacquesm
That's a summary that leaves out some pretty crucial information. Here is the
total of section 'E' and it reads - to me at least - as if there is an effect,
but not _that particular_ effect:

"

In summary, neither our model projections for the 21st century nor our
analyses of trends in Atlantic hurricane and tropical storm counts over the
past 120+ yr support the notion that greenhouse gas-induced warming leads to
large increases in either tropical storm or overall hurricane numbers in the
Atlantic. One modeling study projects a large (~100%) increase in Atlantic
category 4-5 hurricanes over the 21st century, but we estimate that this
increase may not be detectable until the latter half of the century.

Therefore, we conclude that despite statistical correlations between SST and
Atlantic hurricane activity in recent decades, it is premature to conclude
that human activity–and particularly greenhouse warming–has already caused a
detectable change in Atlantic hurricane activity. (“Detectable” here means the
change is large enough to be distinguishable from the variability due to
natural causes.) However, human activity may have already caused some some
changes that are not yet detectable due to the small magnitude of the changes
or observation limitations, or are not yet confidently modeled (e.g., aerosol
effects on regional climate).

We also conclude that it is likely that climate warming will cause hurricanes
in the coming century to be more intense globally and to have higher rainfall
rates than present-day hurricanes. In our view, there are better than even
odds that the numbers of very intense (category 4 and 5) hurricanes will
increase by a substantial fraction in some basins, while it is likely that the
annual number of tropical storms globally will either decrease or remain
essentially unchanged. These assessment statements are intended to apply to
climate warming of the type projected for the 21st century by IPCC AR4
scenarios, such as A1B.

The relatively conservative confidence levels attached to these projections,
and the lack of a claim of detectable anthropogenic influence at this time
contrasts with the situation for other climate metrics, such as global mean
temperature. In the case of global mean surface temperature, the IPCC 5th
Assessment Report (2013) presents a strong body of scientific evidence that
most of the global warming observed over the past half century is very likely
due to human-caused greenhouse gas emissions."

Intensity and amount of rainfall would definitely qualify as elements in
determining activity. So of the two factors that make up activity only one of
those factors is now supported by the data and the jury is out on the other.

~~~
Brakenshire
I think his initial comment is a fair summary of that section:

> So I read that as there's no measurable impact on hurricane activity yet.
> The modelling indicates that they won't get more frequent, but will become
> more intense in the future (stronger winds, more rainfall).

~~~
jacquesm
> The modelling indicates that they won't get more frequent

Is simply incorrect.

"One modeling study projects a large (~100%) increase in Atlantic category 4-5
hurricanes over the 21st century, but we estimate that this increase may not
be detectable until the latter half of the century."

Isn't saying they will not get more frequent, it is saying they _may_ get much
more frequent but that it will take a long time before we will be able to
detect this reliably.

Which is logical given the limited number of data points.

~~~
vitus
That's not quite an accurate rebuttal. That modeling study projects a large
increase in _severe_ hurricanes, not in hurricanes overall.

My understanding is that the models suggest that hurricanes will get more
severe, in a fashion that outpaces any downward trend in quantity.

"In the Bender et al. 2010 study, we estimate that the effect of increasing
category 4-5 storms outweighs the reduction in overall hurricane numbers such
that we project (very roughly) a 30% increase in potential damage in the
Atlantic basin by 2100."

~~~
jacquesm
Right you are, but the main point stands.

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lstroud
Am I misreading this or is it saying something like: Our models suggest we
should be seeing an increase in qty or severity of storms. However, to this
point the historical evidence does not agree with the models. That said, since
effect should increase over time, we'll probably see it down the road. Either
that, or we will need new models. :)

~~~
gizmo686
Close. The problem is not so much that the historical evidence disagrees with
the models, but rather that it is consistent with both the models, and the
null hypothesis. A major reason for this cited by the article is the low
quality of historical records makes it difficult to use historical evidence. A
related problem is that the trends observed in the historical record could be
noise.

Similarly, the historical record does not provide enough evidence to conclude
that are models are wrong.

As an extreme example, suppose our entire historical record was "September 10,
1900: sunny skys in Florida. September 10, 2017: Category 5 hurricane in
Florida".

This is simply not enough information to draw any conclusion.

------
drallison
I find myself wondering whether the information published in this article is
reliable or not, given the current Administration's bias and hostility against
science ([http://thehill.com/policy/energy-
environment/349877-climate-...](http://thehill.com/policy/energy-
environment/349877-climate-skeptics-on-the-rise-in-trumps-epa)). I cannot just
take the data, arguments, and conclusions and assume they have been reviewed
and vetted by a panel of experts prior to publication. It is a sad day....

~~~
_red
Its disingenuous to imply that there is not an incredible amount of money
_pushing_ for "Climate Change" scenarios. The entire construct is to create
carbon credit exchange (ie. Chicago Climate Exchange) which JP Morgan
estimated to be potential $1.5T a year market.

Pretending that its honorable scientist on one side and medieval science-
haters on the other is a childlike simplification.

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xg15
I'm assuming the "% change in PDI" means "% change relative to some fixed
point in time" and not "% change relative to previous data point" in that
diagram.

But then what does the sharp downturn if annual PDI at the "present" point in
time mean? Does that mean that this year's season is actually _weaker_ than
last year's?

------
Gravityloss
Related:

More on Bayesian approaches to detection and attribution

[http://julesandjames.blogspot.fi/2017/09/more-on-bayesian-
ap...](http://julesandjames.blogspot.fi/2017/09/more-on-bayesian-approaches-
to.html?m=1)

