As of this writing, Tuesday, September 11, Hurricane Florence is threatening millions of folks from South Carolina to Delaware. It’s currently forecast to be near the threshold of the dreaded Category 5 by tomorrow afternoon. Current thinking is that its environment will become a bit less conducive as it nears the North Carolina coast on Thursday afternoon, but still hitting as a Major Hurricane (Category 3+). It’s also forecast to slow down or stall shortly thereafter, which means it will dump disastrous amounts of water in southeastern North Carolina. Isolated totals of over two feet may be common.
At the same time that it makes landfall, there is going to be the celebrity-studded “Global Climate Action Summit” in San Francisco, and no doubt Florence will be the poster girl.
There’s likely to be the usual hype about tropical cyclones (the generic term for hurricanes) getting worse because of global warming, even though their integrated energy and frequency, as published by Cato Adjunct Scholar Ryan Maue, show no warming-related trend whatsoever.
Maue’s Accumulated Cyclone Energy index shows no increase in global power or strength.
Here is the prevailing consensus opinion of the National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory (NOAA GFDL): “In the Atlantic, it is premature to conclude that human activities–and particularly greenhouse gas emissions that cause global warming–have already had a detectable impact on hurricane activity.”
We’ll also hear that associated rainfall is increasing along with oceanic heat content. Everything else being equal (dangerous words in science), that’s true. And if Florence does stall out, hey, we’ve got a climate change explanation for that, too! The jet stream is “weirding” because of atmospheric blocking induced by Arctic sea-ice depletion. This is a triple bank shot on the climate science billiards table. If that seems a stretch, it is, but climate models can be and are “parameterized” to give what the French Climatologist, Pierre Hourdin, recently called “an anticipated acceptable range” of results.
The fact is that hurricanes are temperamental beasts. On September 11, 1984, Hurricane Diana, also a Category 4, took aim at pretty much the same spot that Florence is forecast to landfall—Wilmington, North Carolina. And then—34 years ago—it stalled and turned a tight loop for a day, upwelling the cold water that lies beneath the surface, and it rapidly withered into a Category 1 before finally moving inland. (Some recent model runs for Florence have it looping over the exact same place.) The point is that what is forecast to happen on Thursday night—a major category 3+ landfall—darned near happened over three decades earlier… and exactly 30-years before that, in 1954, Hurricane Hazel made a destructive Category 4 landfall just south of the NC/SC border. The shape of the Carolina coastlines and barrier islands make the two states very susceptible to destructive hits. Fortunately, this proclivity toward taking direct hits from hurricanes has also taught the locals to adapt—many homes are on stilts, and there is a resilience built into their infrastructure that is lacking further north.
There’s long been a running research thread on how hurricanes may change in a warmer world. One thing that seems plausible is that the maximum potential power may shift a bit further north. What would that look like? Dozens of computers have cranked away thousands years of simulations and we have a mixture of results: but the consensus is that there will be slightly fewer but more intense hurricanes by the end of the 21st Century.
We actually have an example of how far north a Category 4 can land, on August 27, 1667 in the tidewater region of southeast Virginia. It prompted the publication of a pamphlet in London called “Strange News from Virginia, being a true relation of the great tempest in Virginia.” The late, great weather historian David Ludlum published an excerpt:
Having this opportunity, I cannot but acquaint you with the Relation of a very strange Tempest which hath been in these parts (with us called a Hurricane) which began on Aug. 27 and continued with such Violence that it overturned many houses, burying in the Ruines much Goods and many people, beating to the ground such as were in any ways employed in the fields, blowing many Cattle that were near the Sea or Rivers, into them, (!!-eds), whereby unknown numbers have perished, to the great affliction of all people, few escaped who have not suffered in their persons or estates, much Corn was blown away, and great quantities of Tobacco have been lost, to the great damage of many, and the utter undoing of others. Neither did it end here, but the Trees were torn up by their roots, and in many places the whole Woods blown down, so that they cannot go from plantation to plantation. The Sea (by the violence of the winds) swelled twelve Foot above its usual height, drowning the whole country before it, with many of the inhabitants, their Cattle and Goods, the rest being forced to save themselves in the Mountains nearest adjoining, where they were forced to remain many days in great want.
Ludlum also quotes from a letter from Thomas Ludwell to Virginia Governor Lord Berkeley about the great tempest:
This poore Country…is now reduced to a very miserable condition by a continual course of misfortune…on the 27th of August followed the most dreadful Harry Cane that ever the colony groaned under. It lasted 24 hours, began at North East and went around to Northerly till it came to South East when it ceased. It was accompanied by a most violent raine, but no thunder. The night of it was the most dismal time I ever knew or heard of, for the wind and rain raised so confused a noise, mixed with the continual cracks of falling houses…the waves were impetuously beaten against the shores and by that violence forced and as it were crowded the creeks, rivers and bays to that prodigious height that it hazarded the drownding of many people who lived not in sight of the rivers, yet were then forced to climb to the top of their houses to keep themselves above water…But then the morning came and the sun risen it would have comforted us after such a night, hat it not lighted to us the ruins of our plantations, of which I think not one escaped. The nearest computation is at least 10,000 house blown down.
It is too bad that there were no anemometers at the time, but the damage and storm surge are certainly consistent with a Category 4 storm. And this was in 1667, at the nadir of the Little Ice Age.