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Tuesday, May 4, 2010

AP: Calling deadly Tennessee superstorm an “unprecedented rain event” did “not capture the magnitude” plus Dr. Jeff Masters on the link to warming (and USGS myopia)

AP: Calling deadly Tennessee superstorm an “unprecedented rain event” did “not capture the magnitude”

Plus Dr. Jeff Masters on the link to warming (and USGS myopia)

by Joseph Romm, Climate Progress, May 3, 2010

Tennessee Gov. Phil Bredesen called it an “unprecedented rain event,” but that statement did not capture the magnitude. More than 13 inches of rain fell in Nashville over two days, nearly doubling the previous record of 6.68 inches that fell after Hurricane Frederic in 1979.
“That is an astonishing amount of rain in a 24- or 36-hour period,” Bredesen said Sunday.
Don’t worry, anti-science disinformers who try to shout down any talk of a link between climate change and extreme weather, the AP/WashPost story never mentions global warming.  Indeed, I couldn’t a single story on the superstorm that did.

Not that there were that many stories on the deluge at all given (1) the other mega-stories of the weekend and (2) the fact this didn’t occur on one of the coasts where Big Media lives.

But the fact that this superstorm blew away rainfall records set from the remnants of a hurricane three decades ago bring to mind Weather Channel expert Stu Ostro’s discussion of Georgia’s record-smashing global-warming-type deluge.  Of course, Ostro pointed out there was no way to know if global warming had “caused” the record floods, but

Nevertheless, there’s a straightforward connection in the way the changing climate “set the table” for what happened this September in Atlanta and elsewhere. It behooves us to understand not only theoretical expected increases in heavy precipitation (via relatively slow/linear changes in temperatures, evaporation, and atmospheric moisture) but also how changing circulation patterns are already squeezing out that moisture in extreme doses and affecting weather in other ways.
Meteorologist Dr. Jeff Masters discusses the superstorm on his must-read WunderBlog:
Nashville, Tennessee, remains virtually paralyzed this morning thanks to that city’s heaviest recorded 1-day and 2-day rainfall in its history. A remarkable 7.25″ of rain fell on the city Sunday, breaking the record for most rain in a single day (previously 6.60″, set September 13, 1979). Nashville’s third greatest day of rainfall on record occurred Saturday, when 6.32″ fell. Nashville also eclipsed its greatest 6-hour and 12-hour rainfall events on record, with 5.57″ and 7.20″, respectively, falling on Sunday. And, remarkably, only 2 days into the month, May 2010 is already the wettest May on record for Nashville.
Rainfall records were smashed all across Tennessee and Kentucky, with amounts as high as 17.73″ recorded at Camden, TN, and 17.02″ at Brownsville, TN….   Tennessee had its rainiest day in its 63-year weather history on Sunday, 7.93″. Bowling Green, Kentucky had its heaviest 2-day precipitation event on record, 9.67″. Records in Bowling Green go back to 1870….
The record rains were accompanied by a surge of very warm air that set record high temperature marks at 21 major airports across the Eastern U.S. on Saturday; 19 more records were set on Sunday. This is not surprising, since more moisture can evaporate into warmer air, making record-setting rainfall events more likely when record high temperatures are present.
Masters discusses the link to global warming and the tragic shortsightedness of government officials:
According to the USGS web site, seventeen Tennessee streamflow gages with records going back up to 85 years will stop collecting data on July 1 because of budget cuts. With up to thirteen people in Tennessee dying from flooding this weekend, now hardly seems to be the time to be skimping on monitoring river flow levels by taking 17 of Tennessee’s 94 streamflow gages out of service. These gages are critical for proper issuance of flood warnings to people in harm’s way.
Furthermore, Tennessee and most of the northern 2/3 of the U.S. can expect a much higher incidence of record flooding in coming decades. This will be driven by two factors: increased urban development causing faster run-off, and an increase in very heavy precipitation events due to global warming. Both factors have already contributed to significant increases in flooding events in recent decades over much of the U.S. According the landmark 2009 U.S. Climate Impact Report from the U.S. Global Change Research Program, “the amount of rain falling in the heaviest downpours has increased approximately 20 percent on average in the past century, and this trend is very likely to continue, with the largest increases in the wettest places.”
… Tennessee is not the only state with streamgages at risk of closing down; fully 276 gages in 37 states have been shut down or will be shut down later this year [see Figure below -- more details at USGS.]

So much for the notion that we are going to prepare or adapt for climate change.  Heck, we’re not even gonna pay to completely monitor the change.

For the sake of completeness, for those who haven’t read my recent posts on this subject — such as “Northeast hit by record global-warming-type deluge” and “Global warming means local (super) storming” — here’s some more background on the link between global warming and extreme precipitation.  Regular readers can skip the rest of this post.  You can find more here and there’s some terrific technical meteorological analysis here.

In 2004, the Journal of Hydrometeorology published an analysis by NOAA’s National Climatic Data Center that found “Over the contiguous United States, precipitation, temperature, streamflow, and heavy and very heavy precipitation have increased during the twentieth century.”

They found (here) that over the course of the 20th century, the “Cold season (October through April),” saw a 16% increase in “heavy” precipitation events (roughly greater than 2 inches [when it comes as rain] in one day), and a 25% increase in “very heavy” precipitation events (roughly greater than 4 inches in one day)– and a 36% rise in “extreme” precipitation events (those in the 99.9% percentile — 1 in 1000 events). This rise in extreme precipitation is precisely what is predicted by global warming models in the scientific literature.
In fact, the last few decades have seen rising extreme precipitation over the United States in the historical record, according to NCDC’s Climate Extremes Index (CEI):
An increasing trend in the area experiencing much above-normal proportion of heavy daily precipitation is observed from about 1950 to the present.
Here is a plot of the percentage of this country (times two) with much greater than normal proportion of precipitation derived from extreme 1-day precipitation events (where extreme equals the highest tenth percentile of deluges, from NOAA):
CEI-4 2009

It is the compounding of “typical” extreme weather events on top of human-caused climate change that creates the devastating, record-smashing “global-warming-type” events.  To re-excerpt the Must re-read statement from UK’s Royal Society and Met Office on the connection between global warming and extreme weather:
We expect some of the most significant impacts of climate change to occur when natural variability is exacerbated by long-term global warming, so that even small changes in global temperatures can produce damaging local and regional effects. Year on year the evidence is growing that damaging climate and weather events — potentially intensified by global warming — are already happening and beginning to affect society and ecosystems. This includes:
* In the UK, heavier daily rainfall leading to local flooding such as in the summer of 2007;
* Increased risk of summer heat waves such as the summers of 2003 across the UK and Europe;
* Around the world, increasing incidence of extreme weather events with unprecedented levels of damage to society and infrastructure. This year’s unusually destructive typhoon season in South East Asia, while not easy to attribute directly to climate change, illustrates the vulnerabilities to such events;
* Sea level rises leading to dangerous exposure of populations in, for example, Bangladesh, the Maldives and other island states;
* Persistent droughts, leading to pressures on water and food resources, and the increasing incidence of forest fires in regions where future projections indicate long term reductions in rainfall, such as South West Australia and the Mediterranean.
These emerging signals are consistent with what we expect from our projections, giving us confidence in the science and models that underpin them. In the absence of action to mitigate climate change, we can expect much larger changes in the coming decades than have been seen so far.
In short, get used to it.

And remember, this is all from about a 1°F warming in the last few decades.  We are on track to see nearly 10 times that over much of the United States on our current emissions path (see “Our hellish future: Definitive NOAA-led report on U.S. climate impacts warns of scorching 9-11 °F warming over most of inland U.S. by 2090 with Kansas above 90 °F some 120 days a year — and that isn’t the worst case, it’s business as usual!”)

In short, we ain’t seen nothing yet.

As always, the events I focus on here in this context are the record-smashing ones, the super-duper storms:
Global warming means local super-storming.


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