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Whoops! I hit "send" before finishing. I wanted to add that this procedure I'm complaining about seems critical to their argument. They say, concerning their Fig. 2:
"The uncorrected hurricane count record (blue curve) shows a significant increase in Atlantic hurricanes since the early 1900s. However, when adjusted with the estimate of st…
Whoops! I hit "send" before finishing. I wanted to add that this procedure I'm complaining about seems critical to their argument. They say, concerning their Fig. 2:
"The uncorrected hurricane count record (blue curve) shows a significant increase in Atlantic hurricanes since the early 1900s. However, when adjusted with the estimate of storms remaining at sea and likely “missed” in the pre-satellite phase, there is no significant increase in Atlantic hurricanes since the end of the nineteenth century (red curve)."
In other words, the raw data goes against their argument. But they hand-wave it away with unspecified "adjustments" to make the data go with their argument. This seems like weak sauce to me.
Note: as our host has said repeatedly, that hurricanes are increasing does not, by itself, mean that we will suffer more losses from them. We could be better prepared to withstand them now than before, for example, or changing climate patterns could cause these more-frequent hurricanes to occur more often over the ocean. But this paper, from what I can see, does not make a strong argument against the view that hurricanes are increasing.
NOAA has a nice page (just updated) that goes into some detail on the adjustments for undercounts: https://www.gfdl.noaa.gov/global-warming-and-hurricanes/
I ask everyone to read it in full, but here is the relevant passage:
"This same general methodology has since been applied to Atlantic basin hurricanes (Vecchi and Knutson 2011) and major hurricanes (Vecchi et al. 2021). Atlantic basin hurricanes (Fig. 3, blue curve), show a weak rising trend since the late 1800s, but assuming there are no missing hurricanes in earlier years. After adjusting for a likely under-count of hurricanes in the pre-satellite era (Fig. 3, red curve) there is essentially no long-term trend in hurricane counts.
The evidence for an upward trend is even weaker if we look at U.S. landfalling hurricanes, which even show a slight negative trend beginning from 1900 or from the late 1800s (Figure 3, orange curve). U.S. landfalling hurricane frequency is much less common than basin-wide frequency, meaning that the U.S. landfalling hurricane record, while more reliable than the basin-wide record, suffers from degraded signal-to-noise characteristics for assessing trends. The U.S. landfalling hurricane series (which has no “missing” storm adjustments) is similar to the adjusted basin-wide Atlantic hurricane counts in terms of its lack of century-scale trend (Fig. 3).
Concerning Atlantic basin-wide major (Category 3-5) hurricanes, Vecchi et al. (2021) conclude that their counts also show little evidence of a long-term increase (since the 1880s) after accounting for changes in observing system capabilities; they also show that U.S. landfalling major hurricanes (with no adjustment) have no significant increasing trend since the late 1800s.
Figure 4 (from Vecchi et al. 2021) suggests that after adjusting for changes in observing capabilities (limited ship observations) in the pre-satellite era, there is no significant long-term trend (since the 1880s) in the proportion of hurricanes that become major hurricanes. The proportion of major hurricanes has increased in the Atlantic in recent decades (since 1980). This illustrates the challenge of finding significant long-term trends in hurricane intensity-related metrics if one extends the record back prior to the 1980s (e.g., to the late 1800s or early 1900s).
As far as Category 4-5 intensity storms, basin-wide unadjusted storm counts show a pronounced increase since the mid-1940s (Bender et al., 2010), but those authors cautioned that the data from such earlier decades needs to be carefully assessed for data inhomogeneity problems before such trends can be accepted as reliable."
Roger, thanks for the pointer.
I went to the NOAA webpage and clicked on the link in the sentence "After adjusting for a likely under-count of hurricanes in the pre-satellite era (Fig. 3, red curve) there is essentially no long-term trend in hurricane counts." This took me to a 2011 paper by Vecchi and Knutson, "Estimating Annual Numbers of Atlantic Hurricanes Missing from the HURDAT Database (1878–1965) Using Ship Track Density." This in turn uses data and methodology from an earlier, 2008 paper by the same guys, "On estimates of historical North Atlantic topical cyclone activity."
In that 2008 article, they use "ship observation positions" from ICOADS version 2.3.2a, which was released in 2005. On first glance, at least, the paper looks pretty good. But 2005 is pretty old, esp. because many, many historical records were not digitized by then. And sure enough, it turns out that ICOADS version 2.5, released in 2011 (https://rmets.onlinelibrary.wiley.com/doi/10.1002/joc.2103), trumpets how much more early historical data they were able to add, especially from then-newly digitized British records. The added data in 2.5 include
"the RECovery of Logbooks And International Marine data (RECLAIM; Wilkinson et al., 2010), Climatological database for the World's Oceans (CLIWOC) (García-Herrera et al., 2005), and Atmospheric Circulation Reconstruction over the Earth initiative (ACRE; http://www.met-acre.org/) are all multinational efforts that have augmented ICOADS with seventeenth to twentieth century data and metadata. For example, in recent joint projects, the UK Met Office and NOAA Climate Data Modernization Program (CDMP) (Dupigny-Giroux et al., 2007) have provided digitized and quality-checked data from logbooks (e.g. Brohan et al., 2008) and historical publications held in UK archives."
Version 3.0, released in 2016, adds even more:
"Large, multinational efforts such as the Climatological Database for the World's Oceans (CLIWOC) (García-Herrera et al., 2005) provided data, concentrated during 1750–1850, when temporal and spatial coverage remain sparse. ... A new source of digitized data for R3.0, from English East India Company (EEIC) logbooks, improves coverage during this early period. These voyages were selected from the much larger quantity of non-instrumental 17th–19th century EEIC data also recorded (Farrington et al., 1999)..."
If one is to believe this description, it would seem that the ICOADS version relied upon by Vecchi and Knutsen was missing a lot of data from the UK--important because the UK was then the world's leading maritime power. Amazingly, they apparently didn't have much data from the East India Company, then the world's biggest shipping outfit. That's some serious undercounting Vecchi and Knutsen had to account for!
It seems odd to me that for hurricanes, a contentious and important subject, NOAA hasn't updated its analysis to include this new data, which might reduce its reliance on statistical adjustments that are always going to be uncertain.
Not a climatologist, but very familiar with Gulf of Mexico hurricane data and issues. Suggest two things that support papers “adjustment”:
1) look at hurricane landfall data and you won’t see an increase over last century, and
2) maps of shipping traffic (actual routes taken by ships) prior to 1960 or so very much avoided the middle Atlantic. They went north or down to the equator. No sane ship Captain was traveling hurricane alley before planes and satellites. That’s why they called it the Bermuda Triangle.
1) Agree on the hurricane landfall data, from what I know. See our host's figure from https://www.forbes.com/sites/rogerpielke/2020/01/09/tropical-cyclone-landfalls-around-the-world-over-the-past-50-years/?sh=63a2a2e53b00 But that's not what they were arguing--weirdly, they don't even mention landfalls. I was critiquing the argument they made, not a better, stronger argument made by other people.
2) Disagree about the shipping traffic. There was a ton of shipping traffic in hurricane alley, because that's where three of the colonial world's most important commodities were centered: sugar, tobacco, and slaves. Here's a map of Euro-Am shipping 1750-1800 to show what I mean: https://web.archive.org/web/20130304044344/http://spatialanalysis.co.uk/2012/03/mapped-british-shipping-1750-1800/ (data sources on the site)
You use terms such as "absolute crapload" and "tons of" to describe the number of ships prior to 1900. In my part of the world such terms are not regarded as accurate, or even informative.
I do not have actual statistics at hand, and cannot myself give numbers to the merchant fleet in historical terms. What I know is that the European Maritime Safety Authority quotes the current merchant fleet of ship above 500 GRT to be around 90.000 vessels. Given that in the 19th century an Atlantic crossing would take around 6 weeks, while today is about 6 days, the number of vessels at sea in any given place at any given time is in my view probably much higher than the period before 1900.
Yes, it is true that ships in general are bigger today. But they transport much more goods since we are many times more people in the world today with much higher consumption.
On another note, it is in my view beyond dispute that hurricanes were less well spotted in early days since captain would avoid sailing through adverse weather. Modern ships are much more capable of handling adverse weather than the sailing ships used before 1900.
To conclude, unless you can show actual figures on the number of ships and voyages prior to 1900 and after 1900 as a direct comparison you are left with a personal assertion which carries little weight. I am aware that my own assertion here carries little weight since I explicitly stated that I do not have figures on this. That at least leaves you and me on par.
I am sorry that my Internet comment does not meet your scholarly standards.
As I indicated, I am not an expert on this subject, but the little evidence I do know would suggest that a) there were more vessels in the Atlantic then than now; and b) that there were, in any case, enough ships on the ocean to make one wonder whether they really missed a lot of hurricanes (the original point).
An example to suggest why this might be the case:
The British merchant navy was (and maybe still is?) the biggest single national fleet. The UK government published a register of all UK commercial vessels in international trade from 1849-1977. Some of these lists have been digitized by Google Books and other entities. The 1858 version lists about 40,000 ships (https://books.google.co.uk/books?id=nOkNAAAAQAAJ&dq=MERCANTILE+NAVY+LIST&pg=PA1&hl=en#v=onepage&q&f=false). The 1948 edition shows fewer than 15,000 vessels--the number fell by almost two-thirds (https://collections.mun.ca/digital/collection/mha_mercant/id/38658/rec/198).
There is indeed greater tonnage crossing the seas now than before, as I said. But the kind of evidence I cited suggests it is carried in fewer, bigger ships. In any case--again--the point is that there was an absolute crapload of ships on the sea in the 19th century, and it seems odd to posit from the get-go, as these folks did, that they somehow missed tons of hurricanes.
International trade is not directly translatør to ocean going vessels. We know that today there are around 35.000 deep sea vessels that cross the oceans. Trading vessels above 500 GRT number around 90.000. In all there are probably more than 150.000 vessels trading somewhere.
Most ships used to trade along the coast and within regions. The trade between continents has most definitely increased during the 20th century. As I stated previously, it is not just a matter of the nummer of vessels but also the speed at which they travel. The amount of goods transported today is manyfold the trade before 1900, and even though ships are bigger they also do more trips.
In previous years, ships used to stay for weeks in ports and they spent more time crossing the sea. Today they cross the oceans faster and stay only days in port, thus the total number of vessels at sea at any given time and location is probably much higher than before 1900.
You are of course free to keep to your own anecdotes.
I am always dubious about supposedly (precisely? accurately?) ascertained data and comparisons over centuries when definition, instrumentation, data collection, transmission and record keeping changed from primitive to most sophisticated. Meteorologists call it homogenization https://community.wmo.int/climate-data-homogenization with plenty of more or less 'objective' criteria applied, hence pretty 'soft' i.e. practically non-repeatable, non-reproducible results.