Hurricane study takeaways

Existing data is inconsistent so far to analyze hurricane trends. The National Climatic Data Center study seeks to make it more consistent.

Researchers, though, do see trends of increasing storm intensity. So far, the statistical significance of the research is 90 percent confidence, which is considered marginal.

But the findings are what would be expected with climate warming.

Jim Kossin, National Climatic Data Center.

Not only have Atlantic hurricane winds gotten 27 mph stronger overall in the past 30 years, but they will keep getting stronger, and more quickly than in other regions.

That's not a model prediction that few people will have the patience to hear, after a quiet tropical cyclone season where "busy year" model predictions went bust. But the past season is a prime example why this model study might just be right.

The National Climatic Data Center study is the first analysis that sorts through as much as possible the "noise" of year-to-year variations in order to more accurately read trends.

The analysis found that hurricane winds across the globe have increased 2 mph each 10 years since 1982.

But in the North Atlantic, the winds increased 9 mph over the same period. The reasons include more rapidly warming water and high atmosphere temperatures, as well as weaker shear winds, said Jim Kossin, center atmospheric scientist.

There's also a lot of evidence that thicker particulate pollution from more densely populated coasts in the region is playing a role in those conditions, Kossin said.

He cautioned that so far the conclusions have only a 90 percent confidence level, which is considered marginal.

But "the kind of thing we're observing is about what we'd expect to" with climate warming, he said. If greenhouse gases continue to warm the atmosphere, "we should expect a slow and steady increase in how strong these storms get."

So far, the database has factored in differences such as improvements in satellite technology. The problem is dealing with widely swinging natural climate phenomena such as El Nino warming in the Pacific and the Bermuda High positioning in the Atlantic that affect the region's climate year to year.

"There's a sense of randomness to a lot of this," Kossin said, that can't be factored out of the analysis. But "every year we're getting a little closer" to high confidence as more data comes in with those annual variations, he said.

Patience with computer-model predictions has run short for many after a year in which no major hurricanes formed in the Atlantic Basin and only eight storms formed overall.

In the spring, federal meteorologists, academic researchers and private companies each called for a busy year. All the soothsaying signs were in place - warm seas, weak shear winds and so on.

Even as the season stayed relatively calm through August, they called for a late surge. Didn't happen.

One of those natural climate variations - intense Saharan dust storms blowing into the path of hurricane formation - was a chief cause.

"A combination of conditions acted to offset several climate patterns that historically have produced active hurricane seasons," said Gerry Bell, National Oceanic and Atmospheric Administration lead seasonal hurricane forecaster in the season wrap-up.

Meanwhile, Super Typhoon Haiyan roared into a monster in November with gusts of more than 200 mph - the strongest storm ever recorded in the Pacific. Sandy in 2012 became the largest hurricane ever recorded in the Atlantic, with gale-force winds pounding almost 500 miles away from its eye.

Three of the most intense Atlantic hurricanes on record have risen in the past 10 years - Wilma, Rita and Katrina in 2005 and Dean in 2007.

"Climate variability plays a large role in what happens year to year. This year is a great example of how it confounds models," Kossin said "You could take the short-term view and say we don't have to worry, or you could take the long-term view. Over time, these large events are going to become more probable."

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