The Hard Questions of Climate Change


Pictured: Two vectors at work. Suwon City Mosquito Monument, Suwon South Korea. Image courtesy Flickr user wmjas via creative commons.

A wise person once said, "It's hard to make predictions, especially about the future."* When you start talking about the future of complex systems, it only gets more difficult. Case in point: The effects of climate change on vector-borne diseases.

Climate change: More pestilence-carrying pests in more places. At least, that's the fear. In 2008 alone, there were some 4000-odd peer-reviewed papers published on the topic, according to the journal Ecology. That should give you an idea of how twitchy this possibility makes actual scientists. Top it off with a glass full of TV news Kool-aid, and you've got yourself a regular panic. But there's currently a scientific debate raging over what, exactly, this means for people. Some researchers are now saying that the issue is more complicated than it appears on the surface. We can't simply assume that rising temperatures automatically equal higher rates of human disease, they say. At least, not all the time.

Why such a twisty answer? Because predicting the spread of disease involves more than just sticking out a thermometer. You have to account for a lot of other things, including where and how people live, the other ways they're changing the environment and how heat affects the disease, itself.

Case in point: Lyme disease. Rates in North America have skyrocketed since the 1970s, and the habitat of the Lyme-carrying deer tick has spread to cover large swaths of the U.S. At the same time, those same regions have also been getting warmer...yada, yada, yada, we're all gonna die.

Not necessarily. Deer Ticks and Lyme disease are moving North, says Durland Fish, professor of epidemiology at the Yale School of Public Health. But they're also moving East and South. In fact, he says, what looks like a climate-triggered expansion actually has more to do with reforestation, re-population of wild deer herds and suburban lifestyles that put more people in contact with both. So, then, hooray! Climate change isn't a problem and the hippies can suck it.

Well, again, not necessarily. By 2080, the global mean temperature is expected to increase by more than 5.4° F. Based on this, Fish and his colleagues mapped deer ticks' future habitat and found it'll likely grow by more than 20% in the U.S.--mostly in areas of Kentucky, Missouri, Kansas and Nebraska that aren't particularly Lyme-ridden today. Thankfully, those regions aren't terribly popular with humans, either, but Fish also says trends toward earlier Springs and warmer, longer-lasting Falls seem to favor a type of bacteria that causes more severe cases of Lyme. The result could be a future where Lyme doesn't infect significantly more Americans, but causes worse illness when it does.

The story for other vector-borne illnesses is equally complicated. For instance, the mosquitoes that spread malaria do favor tropical temperatures. So you'd think climate change would put more people at risk as regions bordering the tropics heat up. But Kevin Lafferty, a research ecologist with the U.S. Geological Survey, pointed out in the April issue of Ecology that rising temperatures also mean some currently malaria-prone areas will become too hot for mosquitoes. Equally important, according to Lafferty, is the fact that many of those border regions are far wealthier than current malaria hotbeds, so it's really unlikely malaria will make a comeback in places like the United States. Sure, the South is getting warmer, but Americans still live air-conditioned, indoor lifestyles, and still have relatively high levels of access to mosquito repellants and malaria treatments. In his Ecology paper, Lafferty reported data from computer models suggesting that, while the worst strain of malaria could expand beyond its current habitat to gain 23 million new human hosts by 2050, it's also going to lose access to some 25 million people.

*Also tough: Attributing pithy quotes. According to the Internets, this saying comes from Yogi Berra, Mark Twain, Woody Allen, Groucho Marx, Confucius, Will Rogers, and Niels Bohr. Presumably first uttered during a great conversation aboard the TARDIS.


  1. “Pull out! Pull out! You’ve hit an artery!” You gotta love a sculpture based on a Far Side cartoon. Too bad somebody’s stollen three out of four wings.

  2. I think the one given w/ climate change is increased variability.

    I wonder if we’re going to make it to 5.4F. The relatively minor slump we’re in cut containership emissions; what happens when – to take a for instance – failed monsoons destabilize south Asia and there’s an IndoPak nuclear exchange (dust, etc. – mini nuke winter + global economic effect – oil @ ßxxx per bbl (the ß is my invented notation for the ‘basket’ currency – Hi David Ricardo – that’s getting talked about)). Tough to be optimistic looking forward given where we are and how we got here.

  3. Can I point out that malaria is NOT a tropical disease. See for example, this “Memorandum” by Professor Paul Reiter – professor of medical entomology at Institut Pasteur in Paris – presented to the UK House of Lords:

    To quote: “Despite this remarkably cold period [the Little Ice Age in 15th to 18th Centuries], perhaps the coldest since the last major Ice Age, malaria was what we would today call a “serious public health problem” in many parts of the British Isles, and was endemic, sometimes common throughout Europe as far north as the Baltic and northern Russia. It began to disappear from many regions of Europe, Canada and the United States as a result of multiple changes in agriculture and lifestyle that affected the breeding of the mosquito and its contact with people” and

    “Transmission was high in many parts of Siberia, and there were 30,000 cases and 10,000 deaths due to falciparum infection (the most deadly malaria parasite) in Archangel, close to the Arctic circle.”

    And to confirm you point on the complex inter-relations of factors making it hard to point to a simple cause and effect between temperature rise and increased , I’ll quote again:

    “although temperature is a factor in its transmission (the parasite cannot develop in the mosquito unless temperatures are above about 15ºC), there are many other factors—most of them not associated with weather or climate—that have a much more significant role. The interaction of these factors is complex, and defies simple analysis. As one prominent malariologist put it: “Everything about malaria is so moulded and altered by local conditions that it becomes a thousand different diseases and epidemiological puzzles.””

    A very interesting memorandum, and well worth the read (not least for a discussion of how and why the IPCC reports make a much simpler warmer=more malaria claim). You may also be interested in reading “Global warming and malaria: a call for accuracy” in The Lancet Infections Diseases, Vol 4, June 2004 by the author of the above memorandum and 8 similarly qualified authors.

  4. i’m so glad the first post was about the gary larson cartoon. that was the first thing that came to my mind, and at first i thought, “oh, they put up a statue in honor of him, how cool!” — and then i realized it had nothing to do with him at all. whaaaa?

  5. I love how the mosquito monument has a bowl for stagnant water. Great place for mosquito larvae to grow!

  6. f crs, s c s t th sm lvls s 30 yrs g, tmprtrs hv bn fllng snc 1980, nd w hv th scnd yr f rcrd cld n th nrthrn hmsphr. Bt th fth n clmt chng rmns rslt.

    1. I’d also like to see these. Because I’ve seen quite a bit of data and graphs that say exactly the opposite.

      1. That’s some pretty perfunctory trolling.

        Not when you consider that this troll is the fifth sock puppet of a single homunculus.

        1. Homunculi have sock puppets? cool. I didn’t even know they made socks for them.

          It never ceases to amaze me that people can deny the obvious even when buried (or drowning) in it.

          There are so many frighteningly good reasons to believe we will have troubles unlike any experienced since humans started keeping records if we don’t act soon to radically reduce the burning of petrochemicals, it boggles the mind.

          It is not hard to imagine a world in which climate change has made almost all of the traditional lifeways obsolete because of radical alterations of local weather, coupled with a post-petroleum world in which no viable large scale energy alternatives were developed because of foolish, irrational optimism that things are not as they appear.

          The worst possibilities may not happen, but it seems foolish not to seek to avoid them, especially when the consequences of being wrong are so overwhelmingly bad.

  7. There’s a detailed report commissioned by the Lancet, which studied the effect of climate change on public health, and concluded that while the threat of more vector-borne diseases (i.e. mosquitos and stuff) was significant, the bigger threats come from water and food insecurity and extreme climactic events:
    or see this short summary:

    In other words, stop worrying about mosquitos, and start worrying about where your drinking water will come from once we’ve melted all the mountain glaciers that feed most of the world’s fresh water supply. And what you’re going to eat. And how you’re going to survive the heatwaves.

  8. YES! Glad the first post says this is a Far Side Cartoon. Thieves. I don’t even care what this post is about.

    It this a take on the biblical story of squeezing blood from a rock? hehehehe

  9. Sea ice area may possibly be similar to older levels but it’s worth remembering that the amount of ice is the integral of area and depth, plus minor corrections for density.

    If you melt a load of thick ice and then a cold spell creates a large area of thin ice you haven’t actually got back to the original situation. Ask an ice-skater sometime about the importance of ice thickness.

  10. This reflects what I’ve believed for years, and whenever a politician or pundit comes up with some simple answer to a complex problem I say “Oh, really?” Whether it’s conservative loudmouths blaming all our problems on illegal immigrants, or shifty politicians claiming “X” will solve all our budget woes, I disbelieve it until I see it– complex systems can’t be predicted with anything close to 100% accuracy.

    I have no doubt climate change will cause problems, mainly because we are used to the world being a certain way, and when it shifts suddenly we have new issues to deal with– like all the plants in our gardens suddenly being in a climate zone they can’t withstand, or increased rains bringing on mudslides, are those things worth the bonus of a milder winter? Plus something as monumental as Earth’s weather has never been something humans could ever control (any more than we could stop a volcano from erupting), so if we inadvertently change it we better get used to it remaining that way for a long time.

  11. Well, there are problematic sides to the global warming debate. One of them is the universally negative assessment made by scientists, who ought really, to know better.

    Rising sea levels are indeed bad for humans who live near the beach, the conception seems to be that everything is going to get worse. That’s simply not true. Changes in rainfall patterns for example, will cause disruption, but chaos and change are as positive as they are negative.

    Would I give up the San Jaoquin Valley for the ability grow more food in Saharan Africa? Sure ~ What if they start getting a bit more water in Australia? Or the American Southwest? Or Northern Mexico? What if things get better for a lot of people who don’t have it so good now?

    And by the way, it’s still gonna snow. Most water does NOT come from glacier run-off ~ that’s just silly. If it did, we wouldn’t have glaciers. What scientists measure when they’re worried about water is snowpack. And I’m afraid to say it, but 5 degrees isn’t going to destroy the snowpack on an annual basis.

    Year to year, for example the snow pack can vary widely, and wildly. About 10 years ago or a bit more, there was vast concern in Oregon about the drought, etc., “how are we going to survive?!” As it turns out, nature isn’t required to observe the niceties of our theories, and threw Oregon a storm that gave a snowpack that was +200% of the annual snowpack, BY DECEMBER. Upshot? All the resevoirs were full in the spring, and Oregonians were happily back to wasting water, waterskiing, fishing, drinking water, water water water ~ it was everywhere, and full to the brim.

    Some of you are about to start yelling, “Hey! One year doesn’t change anything!” … you’re right ~ averages are averages, but humans don’t have to waste water ~ we can control, reduce, reuse. And what a gift if the rain patterns shifted enough that rain started falling where it hasn’t, and slowed down a bit where it has…


    1. @Lanval
      There is quite a bit technically wrong with what you put forward in your comment, but I’ll pick one. Rainfall and temperatures aren’t the only factors needed for good agriculture. You need viable land. Humans currently use most of the best, most fertile land for agriculture already.

      A desert is not suitable for long term agriculture because of the low soil quality. Same with tropical rain forest, as the plant life there pulls almost all the nutrients from the soil as it is, leaving behind poor soil. More rain on a sandbox does not a farm make.

      Warming would displace millions (if not billions) and disrupt agriculture in our most vital areas. Not good…

    2. Well, there are problematic sides to the global warming debate. One of them is the universally negative assessment made by scientists….

      (Near) universal agreement about the negative impact of global warming by scientists is problematic for the debate about global warming? Seriously?

      I guess it depends which side of the debate you are on.

  12. In other words, stop worrying about mosquitoes, and start worrying about where your drinking water will come from once we’ve melted all the mountain glaciers that feed most of the world’s fresh water supply. And what you’re going to eat. And how you’re going to survive the heatwaves.

    I will never stop worrying about mosquitoes and I have always worried about where our drinking water will come from. Too many people…well that could be a statement in itself…are self centered and only concerned with their own wants and desires without looking at the “big picture”. Most of my life I’ve heard about over-population yet the only country that has done anything about it has been vilified for it. But out west polygamous families are producing 30+ children. Two television shows center around over sized families. The overcrowding is already having results were water is concerned with Georgia, Alabama, and Florida battling over a rivers flow and out west they be fighting over water for over a century. One source of water that hasn’t been explored, that’s mainly due to cost and other efficiencies, is extracting it from the air. With a several billion of these extractors going the Deep South possible could become a comfortable place to live!

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