Hurricane Irene is part of a worsening trend. Weather disasters have grown more frequent and more costly over the past 30 years in the U.S., according to data that was released today by the National Oceanic and Atmospheric Administration (NOAA).

On Thursday afternoon, NOAA posted a map of the 99 weather disasters that caused at least $1 billion in damages in the United States between 1980 and 2010.

Given that Hurricane Irene is the 10th billion-dollar weather disaster in the U.S. so far this year—breaking a record set in 2008—I wondered what sort of trend might show up over those three decades. By doing simple linear regression on the underlying data, I saw pretty clearly that we can expect to see a lot more frequent and a lot more costly billion-dollar weather events in the coming years.

In the following chart, based on the NOAA data, I focused just on the number of billion-dollar weather events:

And in the chart below, I focused on the total annual costs from these extreme weather events. Notice the spike in 2005, due in large part to Hurricane Katrina. The total damage estimate from Hurricane Irene has not yet been determined. But so far this year, the US has already experienced $35 billion in damage from billion-dollar weather events.

Oddly enough, the NOAA map does not make the trend data clear. Fortunately, it was easy enough to do on my own, using basic Excel and Acrobat tools.

I first learned about the NOAA map on Thursday afternoon when Justin Kenney of NOAA tweeted its existence. I followed the link and saw that all the information was in the form of .pdfs—not terribly useful for analyzing the data on your own. So I pinged Justin to find out how to get the underlying data and, as he suggested, contacted the National Climatic Data Center in Asheville, N.C.

They took my request and while I waited for them to get back to me, I manually entered the information from a NOAA table in pdf form into Excel to create a simple spreadsheet that totaled number of events and costs. Then I used Excel's chart wizard to generate a simple linear regression line on both the number of events and costs and used Acrobat to add source information.