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How Climate Change Contributed to Ellicott City’s Back-to-Back Historic Flood Events

Back when climates were more stable during the 20th Century, we would have expected Ellicott City to see the type of severe rainfall that occurred during 2016 to happen once every thousand years or so. But with the present global climate amped up by human forced warming, just two years elapsed before another such ‘1 in 1,000’ year event hammered the region yet again.

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(Climate change related factors that contributed to the second 1 in 1,000 year flood event to strike Ellicott City within two years.)

Back in 2016, a massive thunderstorm complex dumped 6 inches of rain over the Ellicott City region within just two hours. The storm crippled the downtown of this historic city, severely damaging more than 25 buildings, resulting in the loss of two lives, and spurring calls for a moratorium on development in such low-lying areas. This was the heaviest rainfall ever to hit Ellicott City on record. And though the city had experienced floods before, it had never seen so much heavy, short-duration, local precipitation.

Typically, Maryland does not see such severe rainfall amounts. In a normal climate, Ellicott City would expect to see such high rainfall totals once every 1,000 years. However, the climate is no longer normal. Atmospheric greenhouse gasses are now at higher levels than at any time in at least 15 million years. The Earth is warming up. Atmospheric moisture levels are rising. Severe rainfall events are proliferating across the world. And off the U.S. east coast, the Gulf Stream is slowing down as Greenland disgorges more of its ice.

(The second recent Ellicott City Flood dumped an amazing 9.6 inches of rain within just three hours. Climate change increases the ability of the strongest storms to generate more intense downpours by loading up the atmosphere with moisture and by increasing instability in certain regions. The Eastern U.S. is particularly prone to increasing rainfall intensity due to a warming Gulf of Mexico, a warming North Atlantic off the U.S. East Coast and due to an instability-generating cool pool off Greenland fed by glacial melt water. Image source: Radar Scope and The Washington Post.)

The Eastern U.S., in particular, is seeing increased potentials for heavy precipitation as a climate change related cool pool off Greenland is causing polar air masses to come into conflict with rising heat and increasing levels of atmospheric moisture streaming up from both the Gulf of Mexico and the middle Latitudes of the North Atlantic.

As a result, the chances that Ellicott City would see another historic severe storm of this kind were greatly increased. So much so that the region was hit again on May 27 of 2018. This time by a storm that was more severe than the one that occurred during July 30 of 2016.

 

(Due to human-forced climate change, the intensity of rainfall events, particularly in the strongest storms, is increasing across the U.S. with the greatest increase over the eastern half of the country. This record of increasingly severe rainstorms due to human-forced climate change isn’t just limited to the U.S. It is a global phenomenon. Image source: The National Climate Assessment and Katherine Hayhoe.)

This larger flood dumped 9.6 inches of rain just east of Ellicott City within only three hours. Hourly rainfall amounts during this event likely exceeded 4 inches at the storm’s peak intensity. And a new wave of massive flooding ripped through the historic district — re-damaging buildings that were on the verge of recovering and again resulting in loss of life.

Unfortunately, the climate dice are now loaded for more such ‘1 in 1,000 year events.’ So what happened in Ellicott City this weekend should not be attributed to some ‘fluke local weather event.’ Climate change increases the potential for these kinds of storms. So we’ll see more and worse such instances as we keep warming up our atmosphere, heating the oceans, and melting glaciers.

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38 Comments

  1. Erik Frederiksen

     /  May 29, 2018

    Another problem with these enhanced rainfall events has to do with the fact that coastal cities drainage systems are already filling up with rising seawater so there’s less place for the water from these rain bombs to drain off.

    Liked by 2 people

    Reply
    • rhymeswithgoalie

       /  May 30, 2018

      Aye, the drainage canals in South Florida, which had always relied on gravity to guide water to the sea, now encounters higher tides and therefore expensive pumps.

      Liked by 1 person

      Reply
  2. Shawn Redmond

     /  May 29, 2018

    Ha Robert of course you were away camping for the Ellicott event. If you’re in need of rain just plan an outdoor family gathering several weeks down the road and you’re all but guaranteed rain. I found this little math equation interesting a while back. The whole piece is kinda interesting for reasons beyond our stormy present. I’m never sure if the image will post or not so the second link is to the post proper. Its the math that was a bit of an eye opener as opposed to the article.

    View story at Medium.com

    Liked by 1 person

    Reply
    • Shawn Redmond

       /  May 29, 2018

      Figures the one I thought might not work did and not the other. About par I’d say.

      View story at Medium.com

      Like

      Reply
    • Jim

       /  May 30, 2018

      Hi Shawn,

      I think I kind of follow your math – but didn’t RS reference a 1/1000 year event rather than a 1/100 year event? Assuming the math and assumptions are correct doesn’t this take the probability of another 1000 year flood within the 30-year window you’re looking at from 26% to 2.9% (.999^30), rather than 26% (.99^30)?

      Not trying to criticize, just trying to understand…

      ~ Jim

      Liked by 1 person

      Reply
      • Shawn Redmond

         /  May 30, 2018

        Jim that’s correct. The math above is at the edge of my skill. It has been 40 years since I’ve used such math. I copied the problem as I found it so as to avoid re-teaching myself the process. The symbols used to represent the equations now are different from my school days, owed I assume to the key board as opposed to the pencil, so it takes me a bit just to check if its close. I was only pointing out that be it 1 in 100 or 1 in 1000 it is only a long bet if you’re picking a specific date. These odds will be revised, lower I’m sure, by the financial community in the future. However by then we will be beyond that again. Their sensitivity seems somewhere around that of the ECS.(earth climate sensitivity)

        Liked by 1 person

        Reply
    • So the raw equation indicates a 1 in 500,000 chance of having two 1,000 year floods in the same place within two years. The probability equation is probably a bit more complex. But the chance of this happening in a normal world is vanishingly small. The factor that has changed is the climate.

      Liked by 1 person

      Reply
  3. It amazes me that the uphill developments were approved with the knowledge of this particular region’s vulnerability to floods. I don’t know the particulars but I’m willing to bet whoever signed off was warned about impermeable surfaces but had their palms too greasy to heed them.

    Liked by 1 person

    Reply
    • So there was a lot of talk about a moratorium on development. However, the talk faded as people tended to disbelieve the likelihood of another 1 in 1000 year rainfall event for this region occurring so soon. Again, the factor that changed was climate. If we didn’t get the 1 in 1000 year flood, development wouldn’t have been a problem.

      Liked by 1 person

      Reply
  4. wharf rat

     /  May 29, 2018

    MSP Temps Reach 100, Only 2nd Recorded Time In May – CBS Minnesota

    1 day ago – This is the earliest we’ve seen a 100-degree day in the Twin Cities in recorded history. Previously, the record was May 31
    http://minnesota.cbslocal.com/2018/05/28/100-degree-memorial-day-record/

    Liked by 1 person

    Reply
  5. Abel Adamski

     /  May 30, 2018

    I seem to have lost access to the reply function

    Like

    Reply
  6. Em Butrus Butrus Galli

     /  May 30, 2018

    There are probably people that own businesses that got flooded in 2017 and 2018 that are still in denial about GW even though they now face huge losses on top of loans taken out from 2017’s storms. It’s astounding how many people are still not getting it, as evidenced from posts on other websites. And it’s not a small percentage of Americans either. It’s most of the people that watch Fox News, Republicans, card carrying NRA members and the like. That’s about 34% of the country and nothing but nothing shakes their opinion that GW is a hoax. It’s as if their position is locked, like rebar in concrete, in granite, sealed in tungsten steel, wrapped in depleted uranium and dropped into the Marianna Trench, then covered in thousands of feet of sediment.

    Liked by 2 people

    Reply
  7. Andy_in_SD

     /  May 30, 2018

    Meanwhile on the other side of the Atlantic….

    Flash-flooding brings parts of London and Kent to standstill
    Thunderstorms and flash-flooding have brought parts of south-east England to a standstill as the region received a month’s worth of rain in a few hours.

    http://www.bbc.com/news/uk-england-44293941

    Liked by 1 person

    Reply
  8. B'more Hon

     /  May 30, 2018

    Old Ellicott City is the canary in the coal mine. This is our future.

    Like

    Reply
  9. Syd Bridges

     /  May 30, 2018

    I had seen a quick headline about flooding in Maryland, but until I read this post I did not imagine it could be Endicott City again. Where are places with the infrastructure to cope with this sort of rainfall? But this is nothing compared with what we will see in a decade or two.

    Liked by 2 people

    Reply
    • Jim

       /  May 30, 2018

      Syd,

      I was also surprised it was the same city that had cars float away, but I guess it kind of makes sense that certain cities, due to their geographies and terrain will be more susceptible to these kinds of events. Most of the [limited] climate MSM reporting has focused on coastal cities, but I suspect that a lot of inland communities are at significant risk. Too bad. Most people don’t recognize what is happening to them.

      Liked by 2 people

      Reply
      • Geography also appears to lend a tendency for storm prevalence over certain regions. But climate change tends to amp it all up. With that said, we are all more vulnerable. Particularly here in the Eastern U.S.

        Like

        Reply
  10. kassy

     /  May 30, 2018

    Good long piece about orchard farming in the Guardian

    Are avocados toast? California farmers bet on what we’ll be eating in 2050

    For farmers planting crops they hope will bear fruit in 25 years – including avocado trees – climate change must be reckoned with now

    https://www.theguardian.com/environment/2018/may/30/avocado-california-climate-change-affecting-crops-2050

    Liked by 1 person

    Reply
  11. wharf rat

     /  May 30, 2018

    Does global warming make tropical cyclones stronger?
    By Stefan Rahmstorf, Kerry Emanuel, Mike Mann and Jim Kossin

    What do the data show?

    Nevertheless, observational data support the expectation from models that the strongest storms are getting stronger. We focus here on the period from 1979, because this is the period covered by geostationary satellite data (thus no cyclones went unobserved) and also the period over which three quarters of global warming has occurred. These data show an increase in the strongest tropical storms in most ocean basins (Kossin et al. 2013). However, these data are not homogeneous but are estimated from a variety of satellite, and air- and ground-based instruments whose capabilities have improved over time. The homogenization of these data by Kossin et al. (2013), which is generally recognized as very careful, reduces the trends, but does not eliminate them. The strongest increase can be found in the North Atlantic (which is more than 99% significant) where the trend has likely been boosted by the decrease in sulfate aerosols over this period.

    One consequence of this increase is that in most major tropical cyclone regions, the storms with the highest wind speeds on record have been observed in recent years (see Fig. 1 based on reanalysis by Velden et al. 2017). The strongest globally was Patricia (2015), which topped the previous record holder Haiyan (2013).

    http://www.realclimate.org/index.php/archives/2018/05/does-global-warming-make-tropical-cyclones-stronger/

    Liked by 1 person

    Reply
  12. Syd Bridges

     /  May 30, 2018

    And this morning I go to the weather channel to check our weather at Red Feather Lakes, Colorado, and the headline I see is of a dam in danger in North Carolina after a torrential downpour.

    https://weather.com/news/news/2018-05-30-lake-tahoma-dam-north-carolina-evacuations

    Liked by 1 person

    Reply
  13. Tom Jerome

     /  May 30, 2018

    Off topic – but hopeful
    Off shore wind energy is finally happening for the NE United States.

    https://www.vox.com/energy-and-environment/2018/5/25/17393156/offshore-wind-us-massachusetts-rhode-island-zinke

    Liked by 1 person

    Reply
  14. socalledbob

     /  May 30, 2018

    New project will make MidAmerican Energy 100 percent renewable
    MidAmerican Energy Company announced Wednesday that it will be the first investor-owned electric utility in the country to generate renewable energy equal to 100 percent of its customers’ usage on an annual basis.
    MidAmerican Energy proposed an additional investment of $922 million with the announcement of its Wind XII project that will be formally filed with the Iowa Utilities Board later today. The project, if approved, is expected to be completed in late 2020.

    Like

    Reply
  15. I load pages and read them offline, and I am soooo sorry that this has happened – again.

    Like

    Reply

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