U.S. Just Experienced its Wettest 12 Month Period on Record

According to reports from NOAA, the U.S. just saw its wettest 12 month period since record keeping began 124 years ago. The fact that this stretch of extremely wet weather was preceded by a time of extraordinary drought during the 2010s is also notable. Because it is exactly this kind of swing from one extreme to the next that you would expect in a world being forced to warm by fossil fuel burning.

US Precipitation History

(Annual precipitation has increased by about 7 percent across the contiguous U.S. during the past Century. This jibes with our understanding of atmospheric physics in which the rate of evaporation and precipitation increase as the amount of atmospheric moisture climbs by 6-8 percent for each 1 degree C of global warming. It’s worth noting that though precipitation is increasing, it doesn’t mean that soils, in general, hold more moisture. This is due to the fact that rising temperatures also increase the rates at which soils dry. And because precipitation and drying are not spread evenly, you tend to get regions and times of preference for more intense storms or more intense drought. Image source: NOAA. Hat tip to Weather Underground.)

In this part 2 of our hydrology and climate change discussion, I’ll take a look at some of the drivers for the extreme swing from U.S. drought to deluge. The first being that overall global surface warming in the range of 1.1 C is having the effect of amping up global evaporation and precipitation rates by 6-8 percent. In the U.S. this larger climate change influence helped to spur the multi-year droughts across the U.S. west as well as severe drought years for the Central and Eastern U.S.

On the flip side of the hydrological spectrum, warmer land surfaces and oceans have helped to fuel storms through increased evaporation of water moisture — pumping more water vapor into storms and enabling convection. For the past 12 months this has manifest in the form of the powerful and moisture-rich Hurricane Florence. It has also generally loaded the dice for powerful storms and flooding rains as a persistent trough swung over the Central and Eastern U.S. during spring of 2019.

(Examining climate change’s influence on the wettest 12 months in the last 124 years.)

The recent 12 month record wet period thus fits into a regime of extremes. What these larger trends mean is that in the future the U.S. is likely to continue to experience bipolar precipitation patterns — with hard swings between deeper dry and more intense wet periods coming to dominate as the Earth heats up.

The primary mitigation for this continuing trend is tamping down human based carbon emissions. And a clean energy transition away from fossil fuel burning is central to that more optimistic prospect.

(Want to help fight climate change by switching to a clean energy vehicle? Get 1,000 to 5,000 free supercharger miles through this link.)


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  1. rhymeswithgoalie

     /  May 14, 2019

    What these larger trends mean is that in the future the U.S. is likely to continue to experience bipolar precipitation patterns — with hard swings between deeper dry and more intense wet periods coming to dominate as the Earth heats up.

    The water reservoirs have to be remanaged to handle a more “bursty” precipitation supply. One problem is loss from evaporation (e.g., several feet over a hot Texas summer). I used to advocated something like giant “lily pads” to cover parts of reservoirs, which could reduce evaporation, provide shade for some fish species, and attract bird species.

    This sort of wildlife-friendly approach doesn’t work for partially-treated reservoirs; covering those with plastic “shade balls” seems to work great.

    Liked by 2 people

  2. redskylite

     /  May 14, 2019

    From Jeff Masters, Weather Underground .

    Part 1 : America’s Achilles’ Heel: the Mississippi River’s Old River Control Structure

    . . .. An extended closure of the Lower Mississippi to shipping might cost tens of billions. Since barges on the Mississippi carry 60% of U.S. grain to market, a long closure of the river to barge traffic could cause a significant spike in global food prices, potentially resulting in political upheaval like the “Arab Spring” unrest in 2011, and the specter of famine in vulnerable food-insecure nations of the Third World.

    We now have a much safer situation than in 1973—but as we will see in Part II, ever-higher flood crests are threatening to put an end to this reprieve.


    Liked by 2 people

  3. redskylite

     /  May 14, 2019

    From Jeff Masters, Weather Underground .

    Part2 : Escalating Floods Putting Mississippi River’s Old River Control Structure at Risk

    Since 1988, flood heights have increased by 7’ for the same rate of flow.


    Liked by 2 people

  4. redskylite

     /  May 14, 2019

    Interesting piece from undark.org on methane’

    “My personal feeling is that the evidence is strongly pointing to a natural biogenic source behind the increase,” says Bruhwiler. “And if this is true, that’s important, because it may be an indication that there is a climate feedback going on between the natural terrestrial biosphere and warming.”



  5. Vic

     /  May 14, 2019

    There’s a federal election happening in Australia this weekend. The good news is Labor will probably win. The bad news is, that if they do win they’ll be building a $1.5b pipeline to the huge Beetaloo gasfields in the Northern Territory, releasing an estimated 4 – 7 times the greenhouse gas emissions of Adani’s proposed Carmichael carbon bomb.

    Some good detail here of the dark forces at play down under…

    And all the while the insidious, pervasive stench of Murdoch hangs heavy in the air…

    Economists, journalists and an ex-prime minister critical of News Corp coverage of Labor’s climate change policy. #MediaWatchhttps://t.co/JK8hngoaoT pic.twitter.com/fVEf1TqxML— Media Watch (@ABCmediawatch) May 7, 2019


    Liked by 2 people

  6. Online from the Equator only a few hours each week, I am delighted to see these new updates. If no one else appreciates the time it takes, one lone gringita certainly does. I won’t have to be cyber surfing for news about what’s happening this week. Thanks!

    Liked by 4 people

  1. April Showers Make New Record | Climate Denial Crock of the Week

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