GFDL study: Fewer, but stronger, hurricanes as world warms

[Chacor]

'Fewer hurricanes' as world warms

Hurricanes and tropical storms will become less frequent by the end of the century as a result of climate change, US researchers have suggested.

But the scientists added their data also showed that there would be a "modest increase" in the intensity of these extreme weather events.

The findings are at odds with some other studies, which forecast a greater number of hurricanes in a warmer world.

The researchers' results appear in the journal Nature Geoscience.

The team from the National Oceanic and Atmospheric Administration's (Noaa) Geophysical Fluid Dynamics Laboratory (GFDL) said its findings did not support the notion that human-induced climate change was causing an increase in the number of hurricanes and tropical storms.

"There have been some studies published that have suggested that this is the case, but this modelling study does not support that idea," observed lead author Tom Knutson.

"Rather, we actually simulate a reduction in hurricane frequency in the Atlantic."

[Ed Mahmoud]

If climate change is real.


While many scientists agree its is real, I'd suggest checking your favorite internet search engine for "Oregon Institute of Science and Medicine’s Petition Project of 2001".

Also, see http://petitionproject.org/gwdatabase/GWPP/Home_Page.html

[HurricaneJoe22]

Study says global warming not worsening hurricanes
By SETH BORENSTEIN
AP Science Writer

WASHINGTON — Global warming isn't to blame for the recent jump in hurricanes in the Atlantic, concludes a study by a prominent federal scientist whose position has shifted on the subject.

Not only that, warmer temperatures will actually reduce the number of hurricanes in the Atlantic and those making landfall, research meteorologist Tom Knutson reported in a study released Sunday.

In the past, Knutson has raised concerns about the effects of climate change on storms. His new paper has the potential to heat up a simmering debate among meteorologists about current and future effects of global warming in the Atlantic.

Ever since Hurricane Katrina in 2005, hurricanes have often been seen as a symbol of global warming's wrath. Many climate change experts have tied the rise of hurricanes in recent years to global warming and hotter waters that fuel them.

Another group of experts, those who study hurricanes and who are more often skeptical about global warming, say there is no link. They attribute the recent increase to a natural multi-decade cycle.

What makes this study different is Knutson, a meteorologist with the National Oceanic and Atmospheric Administration's fluid dynamics lab in Princeton, N.J.

He has warned about the harmful effects of climate change and has even complained in the past about being censored by the Bush administration on past studies on the dangers of global warming.

He said his new study, based on a computer model, argues "against the notion that we've already seen a really dramatic increase in Atlantic hurricane activity resulting from greenhouse warming."

The study, published online Sunday in the journal Nature Geoscience, predicts that by the end of the century the number of hurricanes in the Atlantic will fall by 18 percent.

The number of hurricanes making landfall in the United States and its neighbors — anywhere west of Puerto Rico — will drop by 30 percent because of wind factors.

The biggest storms — those with winds of more than 110 mph — would only decrease in frequency by 8 percent. Tropical storms, those with winds between 39 and 73 mph, would decrease by 27 percent.

It's not all good news from Knutson's study, however. His computer model also forecasts that hurricanes and tropical storms will be wetter and fiercer. Rainfall within 30 miles of a hurricane should jump by 37 percent and wind strength should increase by about 2 percent, Knutson's study says.

And Knutson said this study significantly underestimates the increase in wind strength. Some other scientists criticized his computer model.

MIT hurricane meteorologist Kerry Emanuel, while praising Knutson as a scientist, called his conclusion "demonstrably wrong" based on a computer model that doesn't look properly at storms.

Kevin Trenberth, a climate scientist, said Knutson's computer model is poor at assessing tropical weather and "fail to replicate storms with any kind of fidelity."

Trenberth, climate analysis chief at the National Center for Atmospheric Research in Boulder, Colo., said it is not just the number of hurricanes "that matter, it is also the intensity, duration and size, and this study falls short on these issues."

Knutson acknowledges weaknesses in his computer model and said it primarily gives a coarse overview, not an accurate picture on individual storms and storm strength. He said the latest model doesn't produce storms surpassing 112 mph.

But NOAA hurricane meteorologist Chris Landsea, who wasn't part of this study, praised Knutson's work as "very consistent with what's being said all along."

"I think global warming is a big concern, but when it comes to hurricanes the evidence for changes is pretty darn tiny," Landsea said.

Hurricane season starts June 1 in the Atlantic and a Colorado State University forecast predicts about a 50 percent more active than normal storm season this year. NOAA puts out its own seasonal forecast on May 22.

In a normal year about 10 named storms form. Six become hurricanes and two become major hurricanes. On average, about five hurricanes hit the United States every three years.

[x-y-no]

It seems to me this disparity in results is due to lack of resolution in the models being used.

The full climate models (GCMs) don't resolve mesoscale weather, so what these various attempts do is run a nested model within the boundary conditions supplied by the GCM. But even there Knutson's nested model is on a 20km grid - too big to resolve the inner core of intense hurricanes.

It's a mistake to get too excited about this research - we really don't have the information to make a good prediction about the effect of AGW on tropical systems.

I have to agree with Chris Landsea when he says:

"I think global warming is a big concern, but when it comes to hurricanes the evidence for changes is pretty darn tiny," Landsea said.

That may change in years to come, but for now that's the state of our knowledge.

[Ed Mahmoud]

This image is from link above. No mention of increase in major's making landfall, but I do recall Florida had a bad stretch in the mid-late 1920s, Texas had majors in 1900 and 1915, New England had big storms in 1938 and 1944.

[StormspinnerD2]

It's not the number of hurricanes that make landfall - it's the number of hurricanes period that's being looked at. There may not necessarily be fewer landfalls if there are fewer hurricanes in each season.

[KWT]

Yeah I'm not sure there would be any link to GW and increasing landfalls simply because the steering effects are always going to be random. I suppose in theory the higher number of storms the greater chances of a landfall but its rarely correlates all that well...for example the 1985 had lots of US landfalls but weren't that active really overall.