What's Causing The Hurricanes? (yahoo.com)

An anonymous reader quotes AFP: Hurricane Irma, now taking aim at Florida, has stunned experts with its sheer size and strength, churning across the ocean with sustained Category 5 winds of 183 miles per hour (295 kilometers per hour) for more than 33 hours, making it the longest-lasting, top-intensity cyclone ever recorded. Meanwhile Jose, a Category 4 on the Saffir Simpson scale of 1 to 5, is fast on the heels of Irma, pummeling the Caribbean for the second time in the span of a few days. Many have wondered what is contributing to the power and frequency of these extreme storms. "Atlantic hurricane seasons over the years have been shaped by many complex factors," said Jim Kossin, a NOAA hurricane scientist at the University of Wisconsin. "Those include large scale ocean currents, air pollution -- which tends to cool the ocean down -- and climate change"...

Some think a surge in industrial pollution after World War II may have produced more pollutant particles that blocked the Sun's energy and exerted a cooling effect on the oceans. "The pollution reduced a lot of hurricane activity," said Gabriel Vecchi, professor of geosciences at Princeton University's Environmental Institute. Pollution began to wane in the 1980s due to regulations such as the Clean Air Act, allowing more of the Sun's rays to penetrate the ocean and provide warming fuel for storms. Vecchi said the "big debate" among scientists is over which plays a larger role -- variations in ocean currents or pollution cuts. There is evidence for both, but there isn't enough data to answer a key question...

The burning of fossil fuels, which spew greenhouse gases into the atmosphere and warm the Earth, can also be linked to a rise in extreme storms in recent years. Warmer ocean temperatures yield more moisture, more rainfall, and greater intensity storms. "It is not a coincidence that we're seeing more devastating hurricanes," climatologist Michael Mann of Penn State University told AFP in an email. "Over the past few years, as global sea surface temperatures have been the warmest on record, we've seen the strongest hurricanes -- as measured by peak sustained winds -- globally, in both Southern and Northern Hemisphere, in both Pacific and now, with Irma, the open Atlantic," he added. "The impacts of climate change are no longer subtle. We're seeing them play out in real time, and the past two weeks have been a sadly vivid example."

Comments

Hawker

[Hognoxious]

Hawker, later known as Hawker-Siddeley. Also responsible for typhoons and tempests.

Stolen from twitter

[SuperKendall]

Credit Twitter

2006: "Hurricanes are going to be worse and more frequent!"
2007:
2008:
2009:
2010:
2011:
2012:
2013:
2014:
2015:
2016:
2017: "Told you so!"

Re:Stolen from twitter

[hey!]

Note you're taking a very US-centric view here. Not all hurricanes are Atlantic hurricanes, and not all Atlantic hurricanes hit the US. And your memory of US hurricanes must be spotty, since you don't seem to recall Hurricane Sandy.

Let me fill in the some of blanks you've left.

2007: Dean and Felix were both extremely deadly Category 5 Atlantic Hurricanes that hit Mexico instead of the US.

2008: Gustav was a Category 4 storm in the Carribbean but dropped to Cat 2 by the time it hit Louisiana.

2009: Gustav is a powerful storm on the high end of category 4, but hits wind shear when it enters the Gulf of Mexico which weaken it to a category 1. Hurricane Paloma, the third strongest Atlantic hurricane on record, develops off Nicuragua and hits the Cayman Islands and Cuba; it weakens by the time it hits the US but it does drop 14 inches of rain.

2010: a grand total of 12 full-fledged Atlantic hurricanes form, the second highest number on record. As usually happens in bumper-crop years most of the hurricanes were relatively weak, but Earl, Ivan and Julia reached category 4. Both Ivan and Julia turned away from the US, and Earl succumbed to wind shear before striking the US.

2011: another extremely active year with 19 named tropical storms, most of them modest in intensity. Irene, was a category 3, but like most hurricanes that make landfall north of Cape Hatteras it had slowed to Category 1. Katia was a category 4 but moved up the Eastern Seaboard well offshore; Katia was similar Irene.

2012: the third super-active Atlantic hurricane season in a row, with twenty named storms, including Hurricane Sandy , aka "Superstorm Sandy". You do remember that one?

2013: An actual quiet year, with only two hurricanes which did not affect the US.

2014: Another below average year with only one hurricane.

2015: Thrid straight below average year -- again for Atlantic hurricanes. The most powerful was the Category 4 Joaquin, which hammered Bermuda and threatened the Eastern Seabord of the US. It turned north instead. It's also important to note that 2015 wa the year of Hurricane Patricia, which formed on the Pacific side of Mexico. Patricia was the second strongest storm ever recorded with peaked sustained winds of two hundred and fifteen miles per hour.

2016: An active hurricane year with fifteen storms, seven hurricanes, four of them major, including the Category 5 Matthew, the Category 4 Nicole, and the Category 3 Gaston and Otto.

Now to summarize:
(1) The Atlantic Basin is not the *world*. Often quiet Atlantic years are not quiet at all elsewhere.

(2) The US is not the entire Atlantic Basin.

(3) It takes more than atmospheric energy for a powerful hurricane to hit the US. Think of energy being like gravity, and the hurricane being like a pachinko ball. Most of the time, hurricanes don't fall into one of our slots. Most hurricanes that do hit the US weaken, not for want of energy but because of wind shear; Cape Verde hurricanes ride the tradewinds across the Atlantic but then nearly always weaken substantially if they turn north to the US.

Re:One active season and now everything is differe

[ColdWetDog]

A century isn't a particularly long period of time. So far, Irma has busted two (known) records but data for these have only been collected for a couple of decades.

The *big* issue is not what the hurricanes are doing, it is what mankind has managed to splop down right in front of said hurricanes - lots of people, lots of expensive infrastructure and a whole bunch of video cameras. Build it and they will come. And expect the federal government (or somebody with more money then they have) to bail them out from some bad investment choices.

Moral hazard. It's what's for dinner.

Global warming and Atlantic hurricanes

[Anonymous Coward]

The problem with linking global warming to Atlantic hurricanes is that hurricane activity isn't necessarily predicted to increase in the Atlantic from global warming. In the north Pacific, sea surface temperatures will warm and vertical wind shear is predicted to weaken. This favors an increase in hurricane activity in the north Pacific. While the water in the north Atlantic basin is predicted to get warmer due to global warming, vertical wind shear is expected to increase. It's not entirely clear which of these opposing factors will have the greater impact, so it's not certain that hurricane activity will increase in the north Atlantic.

There is a naturally occurring wave called the Madden Julian Oscillation (MJO) that can either enhance or suppress tropical convection. The phase of the MJO has likely helped to enhance Harvey, Irma, Jose, and perhaps even Katia. La Nina also enhances convection in the north Atlantic basin, generally results in a moister atmosphere, and weakens the vertical wind shear. All of these are favorable for hurricane activity. It's also the peak of the Atlantic hurricane season, when the waters are warm and vertical wind shear is still rather weak.

The main reason Harvey produced so much rain over Texas and Louisiana was that it sat over that area for several days. It's not that the rain rates were souch more extreme, but that it just sat over the same area. While rain rates might be enhanced a little due to global warming, the main reason Harvey was so extreme was because it was almost stationary for days. That is not a consequence of global warming, just an unusual weather event.

I also tend to view Irma and Jose as another unusual weather event, but not necessarily linked to global warming. It just doesn't match up with the predictions for the north Atlantic, and so I hesitate to blame global warming for those storms. It's possible that when the shear abates due to the weather, warmer water might result in stronger Atlantic hurricanes at those times. However, the overall increased shear will likely limit hurricane activity more at other times. One hypothesis is that global warming might result in fewer Atlantic hurricanes, but the storms that do occur will tend to be stronger. I understand the logic of that, but I'm just not convinced that Irma and Jose are significantly linked to global warming. There just isn't enough scientific evidence to support that link.

Coriolis effect

[Stoo]

No Coriolis effect, no spin, no hurricanes.
I'm starting a campaign to stop the earth's rotation. Who's with me?

Water [Re:Deforrestation of the Amazon]

[Geoffrey.landis]

Massive deforestation is not being considered? Seriously.

indeed. A fascinating image of carbon dioxide concentration in the atmosphere here: https://www.nasa.gov/feature/g...

The thing to look at is not merely the carbon dioxide being emitted from the northern hemisphere-- it's fascinating to look at the plume of carbon-dioxide depleted air wafting off of the rain forests of south America.

One unit of burnt coal or gas produces 1 unit of CO2 and one of H2O! Yes, water is a greenhouse gas.

Indeed, water is a greenhouse gas. But.

But water precipitates out of the atmosphere very very fast, so the water actually emitted by humans doesn't really contribute for very long. The carbon dioxide, on the other hand, sticks around for an estimated lifetime of about a hundred years. More to the point, the hundred and fifty million square miles of ocean surface evaporates so much water into the atmosphere that the amount emitted by humans really is, in this case, trivial-- the equilibrium water content of the atmosphere is driven by evaporation, not by direct emission.

For the most part, the humidity in the atmosphere is driven by the temperature, not vice versa.

Re:One active season and now everything is differe

[Geoffrey.landis]

You obviously don't know how science works. Here you go:

1) When you have unusually hot or volatile weather, that's evidence of man-made climate change.

No. One hot summer (in one place) or one warm winter (in one place) is not due to climate change. Say this over and over, this is important. Climate change is real, but it is global and it is long term.

No single event, no single warm summer, is evidence of climate change (nor is a single cool summer evidence against it.)

A continuous series of record breaking temperature, on the other hand, might be something to point at. But, again, even there, look for global temperatures-- regional temperatures (even regional temperature records) are just weather.

Re:One active season and now everything is differe

[sfcat]

And those trying to tie hurricanes in with climate change invariably focus on the North Atlantic because that's the storm basin whose recent history fits their desired narrative. Meanwhile, storm frequency in the East Pacific is flat. The West Pacific is mostly flat with a recent slight downward trend. The South Pacific is down, as is the North Indian Ocean.

It should be noted that most climate change models currently don't predict a significant increase in the number of hurricanes in a season. This was not true in the past but we get better with modeling over time so its not surprising. Most do however predict that the storms will be larger on average. That part seems to be holding worldwide.