Series of potent hurricanes stokes scientific debate

The devastation caused by Hurricane Irma on the Dutch Caribbean island of St Maarten
The devastation caused by Hurricane Irma on the Dutch Caribbean island of St Maarten

The rapid-fire formation of four unusually potent Atlantic hurricanes, including Harvey and Irma, has stoked scientific debate over what role global warming is playing in this phenomenon.

First came Harvey, which unleashed massive floods in Texas, then three devastating hurricanes roared across the Atlantic simultaneously—Irma, Katia and Jose.

"Currently we have three Atlantic hurricanes with 90-plus mile per hour winds—only the fourth time on record in Atlantic this has occurred," Philip Klotzbach, a research scientist at Colorado State University, said on Twitter.

The last time three hurricanes were active at once was 2010, when hurricanes Igor, Julia and Karl were classified as hurricanes, according to the National Oceanic and Atmospheric Administration (NOAA).

Katia weakend to a tropical depression on Saturday.

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."

Active cycle since 1995

For Gabriel Vecchi, professor of geosciences at Princeton University's Environmental Institute, the surge in cyclones is evidence of an "active era" for storms in the Atlantic since the mid 1990s, even if not every year saw strong storms.

A period of relative calm for hurricanes, stretching from 2013 to 2016, can be explained by the presence of the equatorial Pacific warming trend, El Nino, which produces wind shear that tends to discourage the formation of hurricanes.

Scientist are debating the role of climate change in the formation of four unusually potent Atlantic storms
Scientist are debating the role of climate change in the formation of four unusually potent Atlantic storms

There was also little hurricane activity in the 1960s, '70s and '80s.

"There is still a lot of debate in the scientific community," over what causes this shift between calm and tumultuous times for storms, Vecchi said.

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 activity," he told AFP.

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.

"We don't know how long the cycle may last," Vecchi said.

"We have a lack of historical perspective."

Warming's role

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 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 are no longer subtle. We're seeing them play out in real time, and the past two weeks have been a sadly vivid example."

Explore further

Why Irma is so strong and other questions about hurricanes

© 2017 AFP

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Sep 09, 2017
For the inevitable wave of denialist posts, I have to ask, where does thermodynamics break down?

Human activity produces CO2 faster than it can be absorbed. Atmospheric CO2 traps solar energy. Increased energy can be measured in increased average temperature. Increased temperature signifies increased evaporation and ocean energy. Both of those lead to increased storms.

I've yet to see an argument against global warming that addresses the very clear chain of reason.

While we're at it, can denialists explain why the primary support for denialism comes from CO2-emitting businesses and the political parties that support them, while the science behind global warming comes from, you know, climate scientists?

Sep 09, 2017
The cause of the warming is the question at hand, not if increased energy in the atmosphere leads to increasing storm frequency and intensity. No one is arguing against thermodynamics or the fact that CO2 traps outgoing terrestrial IR radiation.
It's quite clear that humans have a significant impact on the climate and environment but to what extent are humans impacting the natural environment? It's impossible to quantify and attribute humans to greater than 50% of the warming or to a single chaotic event. And then pigeon hole CO2 as the primary cause.
Models are imperfect and cannot apply significant sources of environmental variation. These "best fit" models are simplistic and lack the resolution for even modest analysis
How much does changing the landscape and land use impact flooding and inundation? What can the geologic and ice core record tell us about interglacial periods? 10.1038/nature11789
How much of an impact do fine particulates have on storm intensity?

Sep 09, 2017
Nevermind the Sun, couldn't have any effect....

Sep 09, 2017
How much wiggle room do you see in the system of temperature increase, human-created CO2? What possible explanation do you have for the rest of the temperature change? If there is no gap, what is the substance of the omnipresent denialist bleating?

Since the consensus is so strong, how does the entire climatographic community orchestrate the conspiracy so effectively? Why do otherwise skilled scientists put the method aside when there is so much to gain for breaking the supposed masquerade?

More specifically to your response, of course we can't say a particular storm was caused by CO2, any more than we can say, of a man who dove into the Chernobyl reactor, which of his many tumors were caused by the radiation. We can still say with confidence that he will have more tumors than a man not exposed to the risk factor.

Additionally, you'll find plenty of people in this very community who will happily argue against thermodynamics. And for EU.

Sep 09, 2017
I've already tried to point out that chemtrails have caused the number of tornadoes to skyrocket. Before 1950, they were an almost constant 180 per year. After 1950, when chemtrailing began but the trails were invisible, they began rising swiftly to seven or eight times that number now.
Shills insist, for example, that the population has grown so more people are seeing tornadoes. But the populations only grew about 250 percent since 1950, but the number of tornadoes grew 600 percent. Also, tornadoes almost all occur in {Tornado Alley", which was always one of the most heavily populated areas of the country. Also, tornado records even of small states show a precipitous rise in numbers. There's no way such huge numbers of tornadoes hid in small states.

Sep 09, 2017
I've already tried to point out that chemtrails have caused the number of tornadoes to skyrocket.

For the final time, it's the unicorns. The unicorns are behind everything. Why won't people listen to me?!?

Sep 11, 2017
Scientists can debate all day long but until they have evidence to support their theories they remain theories. The National Oceanographic and Atmospheric Administration (NOAA) knows a thing or two about hurricanes, meteorology and climate. The National Hurricane Center is a division of NOAA. On their Geophysical Fluid Dynamics Laboratory website they explore the issue of global warming and hurricanes. Of course they parrot the party line about hurricanes increasing in power sometime in the future but they also candidly admit that measurements of all past hurricanes through 2017 show essentially no trend.

statistical tests reveal that this trend is so small, relative to the variability in the series, that it is not significantly distinguishable from zero

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