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Climate Change Consequences - Often Unexpected

Posted on 16 May 2012 by dana1981

An increasingly common fallback position once climate change "skeptics" accept that the planet is warming and humans are the dominant cause is the myth that climate change won't be bad.  In fact, this particular myth comes in at #3 on our list of most used climate myths.  It's an ideal fallback position because it allows those who reject the body of scientific evidence to believe that if they are wrong on the science, it's okay, because the consequences won't be dire anyway.

One of my colleagues, Molly Henderson recently completed a Masters Degree program class on scientific research which focused on climate change, which she aced (way to go, Molly!).  For her final research paper, she examined the consequences of climate change on the prevalence of water-borne diseases in the US Great Lakes region.

This is obviously a very focused topic on a specific region and predicted consequence of climate change, but I think it also provides a perfect example as to why this notion that the effects of climate change will somehow be benign or good is fundamentally flawed.  As a general rule, climate change is not a good thing, because all species are adapted to the current climate in the region in which they reside.  There is a certain amount of climate change to which species can adapt and survive, but adaptation can be a difficult and ugly process.

As Molly's paper makes clear, while humans are a very adaptable species, at the same time we've built a lot of infrastructure whose specifications are based on the current climate.  We have large agricultural farms which depend on a relatively constant climate in order to successfully grow crops, for example.  As Molly's paper shows, there are some other climate change consequences on our infrastructure which we might not even normally think about.

The Problem

Molly states the problem as follows.

"Many cities that surround the Great Lakes are equipped with sewer systems that capture and combine sanitary sewage and stormwater as they are conveyed to wastewater treatment plants (McLellan et al., 2007).  The EPA estimates that 150 communities within the Great Lakes drainage basin are serviced by combined sewer systems (CSS) (U.S. EPA, 2012).   Extreme precipitation events can overcome the conveyance capacity of CSS and cause overflows, known as combined sewer overflows (CSO).  These overflow events result in untreated sanitary sewage and stormwater discharges into receiving waters (i.e, rivers, streams, lakes, etc.).  

Urban stormwater and sewage overflow water contains human pathogens including viruses, protozoans, and pathogenic bacteria that can cause adverse health effects if ingested.   The Great Lakes provide drinking water for an estimated 40 million people and there are more than 500 recreational beaches along lake shores (Great Lakes Legislative Caucus, 2012).  Waterborne disease outbreaks result when water supplies are contaminated with pathogens that infect humans.

It is well known that extreme precipitation events that cause CSO in the Great Lakes Region can lead to waterborne disease outbreaks, as seen in the 1993 outbreak of intestinal illness in Milwaukee, Wisconsin which affected an estimated 403,000 people (Curriero et al., 2001).   Observed and projected climate changes due to global warming infer that more frequent extreme precipitation events are on the horizon for this region, thus potentially leading to a higher incidence of waterborne disease outbreaks if mitigation measures are not taken to improve existing CSS infrastructure and reduce greenhouse gas emissions."

Personally when I think about the consequences of climate change, the possibility that increased heavy precipitation events could cause combined sewer systems to overflow, thus introducing pathogens into drinking water sources has never previously crossed my mind. 

Climate Literature Investigating this Problem

In retrospect this is a perfectly logical climate change consequence in regions which will receive increased precipitation, and indeed Molly shows that a great deal of research has been done on this specific concern in the specific region of the Great Lakes.  Sousounis & Grover (2002) used the  the Canadian Coupled Climate Model and the Hadley Coupled Climate Model to show that an increase in heavy precipitation events is among the expected climatic changes in the Great Lakes region.  A paper led by Katharine Hayhoe (who we've previously seen here and here responding to the wave of hate directed her way when she was asked to write a climate chapter for a Newt Gingrich book) also examined some of the expected climatic changes in the Great Lakes region, as described by Molly:

"Some positive impacts such as a decrease in energy use in the winter and risk of cold-related illnesses may result; however, a higher demand for energy in the summer and higher rates of heat-related mortality is likely to offset this positive impact.  This study also highlights the economic impacts on the Great Lakes due to projected lake level reductions and the article places emphasis on reducing greenhouse gas emissions."

Patz et al. (2008) hypothesized that extreme precipitation events may overwhelm the common combined sewer systems in the Great Lakes region, causing potentially dangerous overflows into sources of drinking water and recreational waterways, and recommended upgrading sewage/stormwater infrastructure and greater protection of watersheds.

A National Resource Defense Council (NRDC) fact sheet highlights the fact that that more than half of the waterborne disease outbreaks in the United States over the past 50 years are linked to heavy rain events, lending additional credibility to this potential problem.  Curriero et al. (2001) examined the association between extreme rainfall and waterborne disease outbreaks in the United States between 1948 and 1994, and their conclusions were consistent with the NRDC fact sheet, finding that 51% of outbreaks in their study sample were preceded within a 2-month lag by an extreme level of precipitation.

Adaptation Has a Cost

The good news is that while most of us probably haven't considered this particular climate change consequence, obviously a number of scientists have investigated it.   While it may seem on the surface like a relatively minor regional concern, Molly notes that 40 million people rely on the Great Lakes Region as a water supply, and the recreational beaches along the shores of the Great Lakes are an important economic contributor to the region. Additionally, combined sewer systems serve roughly 772 communities containing about 40 million people in the USA.  It's also a larger region - over 30 million people live within the Great Lakes basin area; that's 10% of the US population plus 25% of Canada's. 

However, since we are aware of the problem, the Great Lakes region can adapt to it.  The bad news is of course that upgrading sewage and stormwater infrastructure is not a cheap undertaking.  As another example we recently discussed, adjusting to a rising frequency of heat waves resulting from continued climate change will be another costly adaptation, as will shifting the geography of our agricultural production.

There are alternatives to facing these types of climate change costs.  We can try to prevent the problems from occurring by addressing the source (greenhouse gas emissions), which is likely the cheapest option, or we can simply allow them to happen and face the consequences.  As renowned paleoclimatologist Lonnie Thompson put it:

"Three options remain for dealing with the crisis: mitigate, adapt, and suffer...Sooner or later, we will all deal with global warming. The only question is how much we will mitigate, adapt, and suffer."

Molly's research provides one specific example of this choice.  If we fail to mitigate these types of consequences, we will either have to pay the cost to adapt to them, or suffer the consequences of failing to act.  The good news is that we are aware of the problem both on a global and local scale.  Now we just have to decide how we want to address it.


McLellan, Sandra L., Hollis, Erica J., Depas, Morgan M., VanDyke, Meredith, Harris, Josh, and Scopel, Caitlin O. (2007).  Distribution and Fate of Escherichia coli in Lake Michegan Following Contamination with Urban Stormwater and Combined Sewer Overflows.  Journal of Great Lakes Research, (33), 566-580.

U.S. Environmental Protection Agency (2012).  National Pollutant Discharge Elimination System (NPDES).  Retrieved April 27, 2012 from

Great Lakes Legislative Caucus (2012).  Great Lakes Facts and Figures.  Retrieved on April 27, 2012 from

Curriero, Frank C., Patz, Jonathan A., Rose, Joan B., Lele, Subhash (2001).  The Association Between Extreme Precipitation and Waterborne Disease Outbreaks in the United States, 1948-1994.  American Journal of Public Health, 91(8), 1194-1199.

Sousounis, Peter J. and Grover, Emily K. (2002).  Potential Future Weather Patters over the Great Lakes Region.  Journal of Great Lakes Research. 28(4), 496-520.

Hayhoe, Katharine, VanDorn, Jeff, Croley, Thomas II, Schlegal, Nicole, and Wuebbles, Donald (2010).  Regional Climate Change Projections for Chicago and the U.S. Great Lakes.  Journal of Great Lakes Research, 36, 7-21.

Patz, Jonathan A., Vavrus, Stephen J., Uejio, Christopher K., McLellan, Sandra L. (2008). Climate Change and Waterborne Disease Risk in the Great Lakes Region of the U.S. American Journal of Preventative Medicine, 35(5), 451-458. doi:10.1016/j.amepre.2008.08.026.

National Resources Defense Council (2010).  Rising Tide of Illness:  How Global Warming Could Increase the Threat of Waterborne Diseases.  Retrieved March 12, 2012 from

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Comments 1 to 19:

  1. I am quite convinced the "negative feedback" that the skeptics keep searching for will be a reduction in human population, most likely from a disease that finds it niche in a warmer, wetter world. The other choice, to voluntarily reduce emissions and maintain the world we have now, is deemed "to risky". This makes me sad.
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  2. Molly's observations are quite astute and accurate but fail to grasp the "real" problem with water. Imagine, if you will, 2 consecutive winters (N.Hemi.) in which western US states see less than 1/2 their "normal" precipitation. (Greater than 80% probability w/in the next decade.) Water levels in Lakes Mead & Powell (just 2 out of many) no longer have enough water to drive the turbines in the base of their respective dams. The power goes out, "permanently" (recall that most Americans have the attention-span of a gnat), for roughly 20+ million people from L.A., San Diego, Phoenix, Las Vegas, etc. That means NO water coming from anyone's tap, no pumps to fuel vehicles, no refrigeration... you get the picture, sorta'. The "thing" is, when the bottled-water runs out (off store shelves) there will not be a single "safe" drop of water to drink for anyone within 100 miles or more of those sprawling eyesores. At least 1/2 of those people will be dead within a couple of weeks. Sure, some may be able to haul out buckets from "found-water" and rub 2 sticks together to make a fire to boil the water. However, that will not eliminate all pathogens and does absolutely nothing to remove VOCs. Moreover, that is the situation for the inhabitants of every major metropolis on the face of the planet. If you live in a city, when (not if) the power goes out in "your area," the odds of your survival are not good and diminish exponentially (or at least geometrically) with each passing day. Note, there are a plethora of reasons for power-outages in every region, CME's, "terrorist" attack or another "economic" shock as bad or worse than the one we find ourselves in still. There are more than a few financial bloggers who perceive the latter as a high-probability event within the next decade.
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    Moderator Response: [DB] Please refrain from using all-caps (now converted to lower case).
  3. Pardon me, what do you (the "moderator") mean by "all-caps (now converted)"? I did not, and "your" [Preview]-button confirmed, that no more than a half-dozen words were "all-caps."
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    Moderator Response: [Sph] The rule is not "too much all-caps." It is no all caps. If you follow the link to the Comments Policy you will find instructions for how to use bold and italics for emphasis.
  4. colinc... On SkS it's preferred if you bold or italicize your emphasis rather than using all caps. If you're not familiar with the techniques for doing this you can click on the "Click for tips on posting..." and it will show you the HTML tags.
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  5. the 1993 Cryptosporidium outbreak in Milwaukee wasn't "Global; Warming" I drove by the Howard avenue purification plant every day on my way to work. And at that time there was a great deal of construction going on at the plant. I have no idea what it was, but the fact that there was never seemed to make it into the Milwaukee Journal. We talked about that fact at work. I live on the north side of Milwaukee and I wasn't affected. I don't recall that anyone at work was either. The reason for the overflow into Lake Michigan is that cities like Milwaukee have a combined sanitary storm sewer system and when it rains, shit flows into lake Michigan. It's been that way for years. We have the "Deep Tunnel" which is supposed to store water when there's a rain storm, but everyone knew that it really wouldn’t work for "cloud Bursts" which do occur "Global Warming" or not. I remember flying back to Milwaukee in 2008 the airline flew over the Milwaukee harbor on the approach, you could clearly see the sewage line spreading out into the lake. Local State and Federal government didn't want to spend the money to separate the storm and sanitary sewers and we got sold a bill of goods with the Deep Tunnel project which cost billions and really doesn't work. We all knew from the start that a few thirty foot diameter tunnels weren’t going to hold all the water from a big storm
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  6. colinc @ 2, the irony is that your scenario also plays for Peak Oil: when energy gets too expensive for the average family to use, the outcome is the same as if that energy was not available at all. Perhaps PO, which is likely to be a creeping crisis rather than a crunch, will give us the incentive to progressively wean ourselves off the fossils and onto renewables, in a time and manner that gives us a better chance of survival. Having said that, your scenario of drought-induced blackouts is apocalyptic, but not unreasonable. This is just another negative impact that the nay sayers are happily blind to. The OP should be a wake-up call to the fact that AGW is likely to have profound and unpleasant effects that, at the very least, balance any possible benefits.
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  7. To me, I find mitigation worthwhile if just to prevent large portions of the Great Plains of my home country (USA) from turning into a desert climate. Though, I guess the regional research indicates we may be too late to prevent that, since the region is marginal prairie. Sad, but the farmers and ranchers will have to make due or quit, reducing America's proud farming heritage in the region (and food production). Aside from my sentimental value attached to that, I do not get the ridiculous risk management practices that some contrarians follow. We have a very manageable, human-controlled risk to the economy on one hand, maybe even a benefit to the economy according to some analyses. On the other hand we have a quite likely uncontrollable and irreversible risk to livelihood, ecosystem services, and economies. Sounds like a no-brainer unless you believe in a conspiracy theory that the whole climate change risk portion was made up (a position even my father took for a short while).
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  8. Here something that may be unexpected... but certainly is shocking.... when we close the border what happens to the animals....? "While the fences around Israel are necessary, according to Soffer, so too are corridors to allow the free passage of animals. Such passages could be monitored by soldiers for days at a time to allow the animals, such as snakes, to cross both ways." Defending Israel’s borders from ‘climate refugees'
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  9. Steve Case @5 - the point is that due to the increased frequency of heavy precipitation events in the Great Lakes region as a consequence of global warming, the sorts of sewage problems you describe will happen more frequently. Nobody is claiming that the problem wouldn't exist in the absence of global warming.
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  10. colinc, whatever other reasons there may be, the use of all-caps is also an accessibility issue.
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  11. Pertinent to the points raised by Steve Case & dana1981, Skeptical Science has one or more posts discussing the ecological impacts of global warming in which a graphic is shown with relative current and projected future weight of global warming and other concurrent impacts. All of these impacts, of course, are in action at the same time, meaning that each is a 'force multiplier' of the others. The impression I get from such articles, which is an impression that crosses into the impact of global warming on weather and economic affairs, is that much of the damage from global warming is not really a result of its direct effects, but rather from its action as a force multiplier of other, concurrent events. The Moscow heat wave in particular springs to mind as an example.
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  12. I seem to remember the same issues in Pittsburgh, PA, in the 1980's-1990's - older sewage systems that shared overflow with storm drains, resulting in river pollution when overstressed. Just a fact of life for older drain systems - but unfortunately affected by changes in precipitation. Change always affects more than you expect, plus and minus - because nobody has a good grasp on all the side effects.
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  13. Good point raised in this article. Thanks dana and Molly. I think more alike points will be raised in future. I begin to realise that our adaptivity to changing climate as the society is far smaller than our adaptivity as individuals. Deniers don't understand that: they will keep saying "1 or 2 degrees, no big deal, I can deal with that...". However, a society is as fragile as the echosystem within which it lives... I am waiting for more evidence of that type of vulnerability, which would eventually convince the contrarians that climate change is real and will affectr them, just like smokers are convinced that lung cancer is real and affects them (as the overal group, even though some narcistic individuals think they can escape it).
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  14. Doug H @ 6 From what I can see we are already at Peak Oil, or rather the plateau at the top before the decline. The important point is that supply is only just keeping up with demand while the developing economies are building and buying more and more cars and other products which use oil, which can only exacerbate the situation. (China now buys more cars each year than America does.) An IMF research team is now warning of $220 oil per barrel by 2020, so I guess we will soon find out what happens when people cannot afford the stuff. As for unintended consequences, catastrophic collapse of food production might be another. It is obvious that growing regions will move polewards or upwards as the climate warms, indeed it is already happening. We can analyse the matter scientifically. If we plot food production on the ‘y’ axis of a graph, and put time on the ‘x’ axis, we can put rate of change on the ‘z’ axis. If this graph follows Catastrophe Theory, then we can expect a sudden and dramatic collapse in food supply to occur as part of the process. Perhaps not all crops, and not those that do collapse all at the same time, but catastrophic nonetheless. We might adapt to a gentle change, but hardly the almost complete loss of a staple food. Perhaps this has already been studied and all is well. But if it hasn’t, one wonders if those that are so opposed to taking action to combat Climate Change realise the magnitude of the risk they want us to take.
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  15. I think the value of this post is in pointing out the unexpected, undramatic impacts of warming the Earth, which will end up being costly to solve. I don't believe predictions that half the population of Los Angeles is going to die from lack of water within the space of two weeks in the next few decades - that is really alarmist and I don't think it helps the task of convincing people that climate change is a serious issue. As for peak oil, it may well have already happened, and we'll only know for certain once it's behind us. The fact that oil producers haven't been able to increase their production in response to dramatic price increases, even in a world economic crisis which one expects to dampen demand, points to an inability to pump more oil. I've read several conflicting studies on the issue. Some suggest that the increasing cost of fossil fuels will prompt a switch to renewable and low-carbon energy sources whatever our climate policy. Others have a gloomy scenario in which we switch to non-conventional oil sources such as the Athabasca tar sands in Canada, Venezuela's Orinoco Belt tar sands, coal-to-liquids technology as used by SASOL in South Africa to produce synthetic diesel etc, which would combine catastrophic warming with economic depression brought on by trying to continue an economic model based on cheap oil in an era of expensive synthetic oil.
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  16. It is much simpler for bureaucrats to design a giant expensive system and not coincidentally the Cloaca Maxima was built by the last King of Rome and most projects like the State Tunnel Project in RI are mostly federally funded. They are not cost effective. The RI project contains 1.5 inches of storm water at a cost of $359 million. If the same amount of water were impounded in 1/100 of the land area it would be 150 inches deep. But in reality the depth and surface area would be much less with straightforward and practical measures described here'A_RelazioniGenerali/F-Relazione_Mem_Marsalek.pdf In a suburb, every impervious area should have an associated holding area with 1.5 inch capacity without runoff. That's obviously more difficult in the city, but hardly stretches the imagination in Providence which has more than enough elevation to build runoff channels for excess storm water. These solutions are an example of the failure of centralized authority (EPA mandates) and local government run amok.
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  17. Here's a well written brochure with some cost data on page 16: Deep tunnel cost is $2.42 per gallon. Green roofs are double that cost but have other benefits. Rain gardens cost more too, but with benefits. However lots of other solutions are much cheaper.
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  18. Lonnie Thompson link is broken. Please note that it leads to a PDF. Thanks...
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  19. The sewers went in long before the sewage treatment plants - i guess basilget et al welcomed the odd storm surge to give the system a really good flush now and then - they were designed to take it hence the upside down egg shape. So we have a 70s work around bolted onto a victorian 'just move it away a bit' system, just as we do with flue gas abatement. We use a resource, drinking water, to move another rescource, humanure, then add another resource, rainwater, and let it spill out into our rivers where it is least wanted. London mixed sewage overflow events now happen dozens of times a year instead of a couple; partly because of higher water use, partly more high rainfall events but also stupid things like front gardens being paved over with impermeable hard surfaces. I swam in raw sewage as a child i thought those days were over sigh.
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