Home / General / Did climate change cause the Great Colorado Flood of 2013?

Did climate change cause the Great Colorado Flood of 2013?


I don’t know anything about climate science, but the rain we got last week in Boulder was truly freakish — instead of a short intense thunderstorm (the usual mode of rainfall in these parts) we had many hours of non-stop deluges, of a sort I’ve only seen in the tropics before.

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  • Overbuilding on the flood plains certainly didn’t help.

    • Denverite

      I’m not sure this is right. Or at least it’s incomplete. Denver is as overbuilt as any part of the Front Range, and it escaped fairly unscathed — and this despite the fact that the South Platte and Cherry Creek run through the middle of the city, which itself is pretty much a bowl (the suburbs to the south, east and west are all about 200 feet higher than Denver). The reason (well, other than we got a bit less rain than Boulder) is that those waterways are constructed to withstand a lot of flooding. Boulder Creek isn’t.

      • It is not the whole story but it is a good bit of it. Also, according to a friend who is an expert on water and flood control projects in Colorado, Denver learned from its long history of floods and taken methods to alleviate them, whereas Boulder has not. Or not extensively enough anyway.

        • Denverite

          The last bit is certainly true. For example, below about 5350 feet or so, Cherry Creek has essentially been dug out about 20 feet below street level, and where it gets really potentially dangerous at the confluence with the South Platte, the floodwalls are set back an additional several yards. (Last week the water topped the bike path running alongside it by a couple of feet, but didn’t come close to breaching the floodwalls.)

          Boulder Creek, on the other hand, has none of that. Hell, we were hiking there a few weeks ago and marveled at the houses with backyards pretty much on the creek bank. They’re probably gone now.

          • DrDick

            In addition to increasing people’s exposure to damage by building in the flood plains, it also impacts on runoff patterns in ways that can increase flooding. Replacing porous soils (which act as a kind of sponge to collect and slow runoff) with concrete and asphalts means more of the water is accumulating and flowing into streams.

          • BoCo

            Boulder Creek was not the main cause of the flooding in Boulder.

            • DocAmazing

              Water was, or so I am told.

  • mattH

    In Utah we usually get monsoonal moisture starting in late July through August and into September. This year it was nonexistent until late August, with fewer storms that tended to be stronger. One of the suggested effects of climate change is changes in weather patterns.

    • DrDick

      Most of the models for the impacts of climate change on weather patterns in the northern Rockies indicates a shift from peak precipitation in winter as snow to a May-June peak as rain, owing to shifts in the flow of the jet stream. There are some pretty obvious, and deleterious, impacts of that on agriculture in the region.

  • Denverite

    This article would be a lot better if it actually explained the mechanism by which the storms may be linked to global warming. Like this:


    (Long story short: The unseasonably warm weather in the American Southwest — it was in the 90s as late as two weeks ago in Denver — caused an area of low pressure a lot farther north than usual, and that basically sucked tropical Pacific moisture up into Colorado. It pinwheeled counterclockwise into the Rockies and stalled, then cooled, then dropped all of the moisture.)

    • Anonymous

      As the article stresses, we can only say that global warming made such an event more likely, not that it is the “cause” as cause is typically understood.

      Whether global warming made this type of flood in Colorado more likely will require some further work, but right now it seems plausible. If this pans out, expect more of the same in the coming decades.

      In general no single extreme weather event can be directly linked to global warming, but the trend of record breaking and increased frequency severe weather events has a lot of evidence and the case is getting stronger all the time.

      It’s annoying to phrase it this carefully perhaps, but it does avoid one denialist nitpick.

      • Jordan

        “As the article stresses, we can only say that global warming made such an event more likely, not that it is the “cause” as cause is typically understood.”

        That is a bad understanding of causation.

        • Anonymous

          No it isn’t. You can say that smoking causes lung cancer.

          You can’t say that it caused a specific person’s lung cancer, even if they are a smoker.

          The situation is exactly the same.

        • Anonymous

          Just in case we’re talking past each other, here’s one I am saying, as expressed from the link you provided:

          “probability assignments should represent some objective feature of the world. There are a number of attempts to interpret probabilities objectively, the most prominent being frequency interpretations and propensity interpretations. Most proponents of probabilistic theories of causation have understood probabilities in one of these two ways. ”

          Global warming makes severe weather more frequent. Severe weather was not unknown before global warming. It will just occur more often. The causes of any specific weather event are too complex to attribute to specific causes (“Butterfly effect”) but we can speak about the frequency or propensity of severe weather increasing as a result of global warming. This is the type of causal terminology climate scientists must use.

    • GoDeep

      An informative link, Denverite, thanks.

      I don’t know that trying to immediately link every bad weather event to global warming is either good science or good politics. From what I can tell the writers tend to get out ahead of the scientists on these things & that doesn’t seem the wisest place to be to me…but fear often drives polls.

      One thing I’d like to see better explained is the statistical connection b/tn a 15yr flat lining in global warming and an increase in extreme weather. In the precipitation map shown in the link, for instance, it seems to me that rather than (potentially) cherry pick 1958 & 2011 for comparison purposes, they’d be on stronger ground comparing, say, the 15yrs b/tn 1943-1958 to the 15yrs b/tn 1997-2012. Their write up would then be more statistically valid.

      • guthrie

        Weell, firstly it isn’t a 15 year flat lining. If anything, its a slowing of the warming over the last decade. The 15 year thing comes form in innumerate science haters who pick 1998 as the starting point.
        Oddly enough when you remove the effects of el nino and volcano’s and suchlike from the temperature record, you get something that is still climbing:

        You’re definitely corect though that writers get ahead of the scientists, who usually have to sit and wait for a few years, gathering data.

        • guthrie

          oops, forgot to close tages, the link is under the text about writers.

          • GoDeep

            Thanks for the link, Guthrie. I’ve read 4 different scientific explanations for the ‘flat lining’, ranging from the oceans are now absorbing excess heat to the El Nino explanation you mention, to one today that asserts a plausible mathematical explanation. It, of course, could even be a combination of answers.

            The question for me is that even if there are sensible reasons why *temperature* (if not *global warming*) has plateaued, trying to link extreme events to stable surface temps is a statistically fraught exercise. The x-axis would be flat while the y-axis–measuring extreme events–would be increasing, no? How then could you draw good empirical conclusions?

            • Sockie the Sock Puppet

              Here’s a helpful hint: When someone talks about “global warming stopping/flatlining/reversing” and they use 1998 as the beginning point of this trend, they are intentionally misleading you. Period.

              Any argument that that falls apart when you take out one data point is bullshit. Take whatever chart these guys might show you, remove 1998, and look at them again. For that matter, take any temperature chart from any source and remove any single year you want — if the chart no longer shows the trend it was purported to show, then the guy with the chart is bullshitting you.

              Climate change denialists have been producing charts that showed temperature “reversals” or “flatlining” for a decade or more, pretty much since 1998, which was a world historical freaky, way above the trend year temperaturewise. Mostly they do this by starting with 1998 and showing only the data afterward, which reverted to the trend and continued slowly upward. Start with any other year, and there is no ambiguity about what’s going on. Or use rolling five-year averages or any other measure.

              Climate change has not disappeared.

              • GoDeep

                I’m not interested in the climate change deniers, Sockie, I’m talking abt what climate change believing scientists say… Those scientists don’t say that its cherry picking, they say El Nino is masking it, or that the oceans are masking it, or that underlying mathematics is masking it (warming increases logarithmically, CO2 increases exponentially)…

                Really nice analogy down below by the way…

                • guthrie

                  Well, on that point, there aren’t any climate change studying (note, not believing, unless belief also covers the sun rising in the East in the morning) who think there’s been a 15 year pause in warming.

                  You are correct about statistically fraught activities; however the fun thing is that actual physical reality can be and is being studied to explain things. Statistics is a useful tool but not of primary importance here.
                  And yes, the slowing of warming is probably down to a number of factors, such as the lower solar output co-insicindg with a lot of soot from China and India and weird ENSO behaviour. There’s a number of papers out about it in the last couple of years, it’ll take a couple more to tie it all together so they can give a definitive answer with numbers apportioned appropriately.

      • Meister Brau

        Here is a very nice visualization of temperature extremes in 10-year running averages:


        A longer writeup of it is here:


        The fundamental problem with analyzing the frequency of extreme events is that they are, by definition, outliers, and so their distribution can be quibbled with ad nauseum. But it’s tough to argue that the dice aren’t becoming more and more loaded.

    • DrDick

      There is a lot of information readily available on how global warming impacts on weather patterns. Firstly, warming means more energy in the climate system, which produces more extreme weather events (more and stronger hurricanes and tornadoes, for instance) and greater variability in weather patterns. Warming also changes the patterns of the jet streams which push weather systems across the US.

  • Elk

    I have seen late August/early September rain here before. Not on that scale, or even close, more like a baby version if last week’s storm, and definitely not the July/August afternoon monsoonal thunderstorm activity. Labor Day weekend 2003 comes to mind. Just last September we had rains on and off for about 10 days. I work outdoors, in the mountains, on the rivers, and pay pretty close attention to the weather.

  • guthrie

    Here’s some info:

    A quote which it in turn took from elsewhere:
    Here’s how it happened: A blocking pattern has set up over the western United States, drawing a conveyor belt of tropical moisture north from coastal Mexico. Blocking patterns form when the jet stream slows to a crawl, and weather patterns get stuck in place. When all that warm, wet air hit the Rocky Mountains, it had nowhere to go but up, pushed further skyward by the mountains themselves. By some measurements, the atmosphere at the time of the heaviest rains was the among most soaked it has ever been in Colorado.
    Gauge measurements show floodwaters in Colorado have now exceeded the legendary Big Thompson Canyon Flood of 1976, the flood of record for the region. In downtown Boulder, a meandering creek expanded 40-fold in just a few hours. More rain is on the way this weekend.
    Earlier this summer, similarly devastating floods have hit Las Vegas, Nevada, and Calgary, Canada, and the basic cause has been the same: tropical moisture making its way to places it shouldn’t be, in amounts rarely seen before. This is not a fluke event, nor something that’s going to go away.
    Why it will keep happening: Blocking patterns are fertile ground for extreme weather. A blocking pattern near Greenland was also to blame for steering Superstorm Sandy toward the east coast of the United States last fall. Persistent high pressure this year in the western United States has led to what is (so far) California’s driest year on record. That, in turn, fueled last month’s massive Rim Fire in Yosemite National Park, which grew to a size larger than New York City.

    The hypothesis at the moment is that more such blocking events will occur as the climate tries to equilibrate. Maybe in 20 or 30 years they’ll decrease in frequency, or maybe get worse…

  • BigHank53

    I was looking at the damage to Rt. 34 (west of Loveland) and found that flooding in 1976 blew out a lot of Rt. 34 then, too.

    • Denverite

      The drive on 34 from Estes Park to Loveland is one of my favorite in the state (well, the Front Range, at least). It’s mile after mile through this narrow canyon right next to a pretty raging river. Though you definitely can see how the Big Thompson Flood was so devastating — there’s just nowhere to go for a lot of the canyon.

  • Sockie the Sock Puppet

    Did climate change cause the Great Colorado Flood of 2013?

    Does living in a crime-prone neighborhood “cause” your apartment to get broken into? Not exactly, but more apartments get broken into in crime-prone neighborhoods and as the neighborhood goes downhill, the more likely it is that your apartment will get broken into.

    The relationship between climate and weather is analogous. As the global climate goes downhill, there are going to be more instances where the weather comes in and does serious property damage (and, obviously, worse). That doesn’t mean that any given weather event was caused by climate change — there have been fires, floods, and F5s for time immemorial. But the best way to cut the odds of another bout of weather violence is by cleaning up the climate.

  • Trollhattan

    I doubt this is relevant to the Intermountain West and summer monsoon season, but for the left coast, an increasing understanding of “atmospheric rivers” is likewise enhancing our understanding of our vulnerability to massive rainfall events in relatively small geographical regions. It is suspected that climate change increases the frequency and intensity of the phenomenon.

    One outcome we’re pretty confident of is the shift from snowfall to rainfall as warming progresses. The western water storage and delivery system simply doesn’t work under that model–a future worth pondering


  • Edmund

    As usual, Salon is long on agenda and short (real short, like nada) on evidence.

    • Philip

      That is what the massive scientific consensus is for. Well, it has two purposes. The other is generating pancakes.

      • guthrie

        Ahh, but what is the science behind good pancakes and syrup?

    • DrDick

      For all values of “short on evidence”=in keeping with the consensus among atmospheric and climate scientists. You do really astound with the depth and breadth of your ignorance. Is there actually anything you do know?

      • NonyNony

        He knows he’s going to fail Mrs. Krebapple’s keyboarding class if he doesn’t get off the internet and back to his typing exercises!

        Keep at it Edmund – you’ll pass the 8th grade one of these days!

  • Anonymous Troll

    The “floods” are a hoax. Those pictures are all ‘shopped. You can tell by the pixels.

    It’s a conspiracy by “experts” to get Washington to send them your money, the money they take from you as “taxes”. That’s why Obama signed the “emergency” declaration last Friday. It was payoff to his supporters.

    Haven’t you seen those hacked emails that talk about “fixing” the data to hide the dryness?

    C’mon, sheeple, wise up. Colorado was actually a lot wetter before the Laramide Orogeny. It’s getting dryer. You can look it up, if you can get them to release the data.

    Also, their measurements are all taken from guaging stations near rivers. Of course there’s water in the rivers. Of course measurements taken in water will show wetness.

    Besides, it’s God’s plan. Why do you think Boulder got hit, but not Colorado Springs?

  • God

    Chust you vait, Cholly.

  • David

    I thought it was because God was angry that Colorado voted against gun control and was surprised to see this theory not get wider play.

    • Jordan

      Actually, didn’t (some) Colorado types just vote AGAINST those gun control types in recall elections?

      That is clearly the source of God’s wrath.

  • Halloween Jack

    Another great reason to forget that Salon even exists:

    What has changed in 11 months? For one thing Obama is again just President Obama rather than Candidate Obama. He’s no longer trying to convince leftists of his bona fides. Nor is he trying to show, for the benefit of swing voters, that climate-devastation deniers and their standard bearer Mitt Romney are ludicrously out of touch with reality. His attitude toward Boulder epitomizes his reversion to do-nothingism. During the 2012 campaign, when Obama needed the electoral votes of swing-state Colorado, he visited Boulder three times — three times, to a city of 100,000! He came because he knew we would give good crowd, and we did. (Well, my friends did. I’ve long thought the man a con.) But we haven’t heard from him since. We’re just his good-time girl of the past, forgotten in his respectable present. Compare, for example, the number of words he has given to the limited tragedy of the Naval Yard shooting versus the vaster calamity in Colorado, let alone the calamity’s probable cause. And why would he do otherwise? To talk too much of the consequences of climate devastation would open himself to the suggestion that he has been one of its primary handmaids.


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