Global warming and malaria, another myth debunked

Among the many scary scenarios attributed to a warming world is the claim that malaria will spread.  But new research, reported in Nature says: “that warmer temperatures seem to slow transmission of malaria-causing parasites, by reducing their infectiousness.”  The researchers say “that there are several possible explanations for why parasite survival falls as temperature increases: the parasite may not be able to cope with the higher temperatures, or mosquito immune systems may work better at warmer temperatures.”  This seems to support an earlier paper in Nature that found, “widespread claims that rising mean temperatures have already led to increases in worldwide malaria morbidity and mortality are largely at odds with observed decreasing global trends in both its endemicity and geographic extent.”

Although malaria is often thought of as a tropical disease, it was actually much more widespread.

In Canada:

“It was an important cause of illness and death in the past century in Upper and Lower Canada and out into the Prairies.”  -MacLean and Ward,  Journal of the Canadian Medical Association, Jan. 26, 1999.

In England:

“Present global temperatures are in a warming phase that began 200 to 300 years ago. Some climate models suggest that human activities may have exacerbated this phase by raising the atmospheric concentration of carbon dioxide and other greenhouse gases. Discussions of the potential effects of the weather include predictions that malaria will emerge from the tropics and become established in Europe and North America. The complex ecology and transmission dynamics of the disease, as well as accounts of its early history, refute such predictions. Until the second half of the 20th century, malaria was endemic and widespread in many temperate regions, with major epidemics as far north as the Arctic Circle. From 1564 to the 1730s—the coldest period of the Little Ice Age—malaria was an important cause of illness and death in several parts of England. Transmission began to decline only in the 19th century, when the present warming trend was well under way. The history of the disease in England underscores the role of factors other than temperature in malaria transmission.”  – Paul Reiter, Emerging Infectious Diseases, Vol. 6, No. 1, January–February 2000.

In the United States:

“Historically, malaria was a significant cause of morbidity and mortality throughout the western United States” as well as in the Mississippi, Ohio, and Missouri river valleys and along the Atlantic coast.  -Hayden et al. Journal of Medical Entomology, vol. 38, no. 2, pp. 341-343, 2001.

Malaria has largely disappeared from temperate climes through economic development and disease control.  Recent warming seems to have had no effect.  However, malaria remains a scourge in many undeveloped areas, a scourge made worse by another environmental policy: the banning of DDT, but that’s another story.


  1. Thank you, Jonathan, for a voice of reason, in a sea of fear….and ignorance.
    But keep praying…I pray the government, my soul to keep….it sure walks and talks like a religion.

    1. Roger, did you come to the conclusion that there is a “sea of ignorance” after you read the IPCC report? Maybe you could pass on some of your wisdom about climatology to those ignorant scientists who have spent lifetimes investigating earth’s climate. Then maybe you could move on to the ignorant geneticists, ignorant neuroscientists, ignorant oncologists and ignorant astronomers. Or is it just the climatologists that are ignorant? JP

  2. Although Jon deserves some props for sourcing from a reputable journal, as usual the subject is far more complex than his headline would have you believe.  

    Many of you may have asked the question: “If the optimum temperature for malaria carrying Mosquitos is 25-27 degrees C, won’t warming just change the distribution pattern?” The short answer is yes. The longer (and far more interesting) answer can be found by looking into a few other articles, also mentioned in the journal, Nature. Start here:
    and if you’re the curious type like me, follow the attribution trail for a much more interesting story.  From reading Jon’s article one might forget that other effects of AGW (precipitation changes among others)  might be as important, or more, than temperature for the development and transmission of malaria. And if you’d like to see what the IPCC actually said about malarial mosquitos and AGW see this:
    Or better still, read the IPCC synthesis report.

    Some of you may have also considered it odd that Jon would be concerned in any way with how mosquitos are affected by “Global Warming”. Isn’t Global Warming a myth? JP

    1. Global warming isn’t a myth and you know I haven’t said it is. What I do say is a myth is AGW as a major cause. John, I’m still waiting to see some physical evidence that human carbon dioxide emissions are the major cause of recent warming.

      1. Jon, Thanks for clarifying your position. Here’s a brief description of how we know that the warming we see in our climate is due to human emissions of CO2 from the burning of fossil fuels. Confirmation that rising carbon dioxide levels are due to human activity comes from analysing the types of carbon found in the air. The carbon atom has several different isotopes (ie. different number of neutrons). Carbon 12 has 6 neutrons, carbon 13 has 7 neutrons. Plants have a lower C13/C12 ratio than in the atmosphere. If rising atmospheric CO2 comes from fossil fuels, the C13/C12 should be falling. Indeed this is what is occurring and the trend correlates with the trend in global emissions. 
        Further confirmation comes by measuring oxygen levels in the atmosphere. When fossil fuels are burned, the carbon in the fossil fuels are joined to oxygen, creating carbon dioxide. As CO2 increases in the atmosphere, oxygen decreases. Observations show oxygen levels are falling at a rate consistent with the burning of fossil fuels.

        Another line of empirical evidence can be found by looking at temperature trends in the different layers of the atmosphere. More atmospheric carbon dioxide should cause warming in the troposphere but cooling in the stratosphere. This is because the increased “blanketing” effect in the troposphere holds in more heat, allowing less to reach the stratosphere. This is in contrast to the expected effect if global warming was caused by the sun which would cause warming both in the troposphere and stratosphere. What we observe from both satellites and weather balloons is a cooling stratosphere and warming troposphere, consistent with carbon dioxide warming.
        If  human CO2 emissions were causing warming, we would expect nights to warm faster than days. This is because the greenhouse effect operates day and night. Conversely, if global warming was caused by the sun, we would expect the warming trend to be greatest in daytime temperatures. What we observe is a decrease in cold nights greater than the decrease in cold days, and an increase in warm nights greater than the increase in warm days. This is consistent with greenhouse warming caused by human emissions and definitively not the sun, as you have suggested. If I’m wrong about that, it would be helpful if you identified what you believe the mechanism of the present warming is.  

        You were gracious enough to invite a world class climatologist to comment here recently. Dr. Jerry Dicksen.  I would remind you of this quote from him right here on your site: “That humans…are causing a rapid rise in CO2 is really indisputable. The arguments and past evidence for a coupling between CO2 and Earth’s surface are not debated by anyone who understands the science.” And this, “… what happens when we superimpose carbon emissions of 8 Gt/yr (circa 2011 and growing) to a carbon cycle that had near steady state inputs (and outputs) of ~0.4 Gt/yr.” Now we know. JP

      2. No one is contesting that humans are putting more CO2 in the atmosphere, so that part of your answer is irrelevant. Both satellite and radiosonde measurements show that the troposphere is not warming as the models predict and you claim.

        I will have to get back to you on the day-night temperature data if true. Off hand, I can think of several alternative things that would cause such as the urban heat island effect, differences in cloud cover and variation in wind.

      3. Jon, How you can say that humans putting 8+ GigaTons of CO2 into our atmosphere each year is “irrelevant” is almost beyond comprehension. That aside, you are correct that tropospheric temperatures as measured by the modeling of microwave emissions of Oxygen in the atmosphere is only about 70% as high as coupled GCM’s predict. This subject has been extensively analyzed including by a panel that included John Christy, one of the true skeptics of the effects of AGW. In fact, the conclusion of the U.S. Climate Change Science Program (CCSP) document in 2006, on which John Christy himself was a lead author stated this:
        “These results could arise either because “real world” amplification effects on short and long time scales are controlled by different physical mechanisms, and models fail to capture such behavior; or because non-climatic influences remaining in some or all of the observed tropospheric data sets lead to biased long-term trends; or a combination of these factors.
        The new evidence in this Report favors the second explanation.” 

        I know you are skeptical about modeling Jon, so you should be made aware that the MSU (microwave sounding units) that satellites use to extrapolate tropospheric temperatures are entirely model based. These satellites do not carry thermometers. They blast microwaves off tropospheric oxygen molecules and the resultant emissions are subjected to models that infer temperature values at different atmospheric pressures. Roy Spencer, another well known skeptic is working on the sixth version of the UAH model to better capture the modeled temperature. It should be noted that the results of the previous model revisions has been to increase, with every significant revision, the inferred temperature. The radiosonde data, where balloons do actually carry thermometers (accurate to 0.001 degree C) does show temperatures very close to those predicted by the GCM’s. The discontinuity comes primarily from one modeled dataset (UAH) and even that relatively small variance is found solely in the mid-troposphere. The MSU datasets are largely in agreement for other parts of the troposphere. So if you are to be consistent about your skepticism of modeling, you would accept the radiosonde data. That data conforms to the GCM’s.

        Jon, you stated: “Off hand, I can think of several alternative things that would cause such [sic] as the urban heat island effect, differences in cloud cover and variation in wind.” Think that through for just a moment Jon. Those mechanisms you mentioned, other than cloud cover, can only move heat from one place to another within the atmosphere. They cannot add heat from outside the atmosphere or as Jerry Dicksen taught us, they cannot change the energy budget of the planet. Differences in cloud cover could be a negative feedback mechanism, but it brings up the question: “Where has this negative feedback been for the last thirty years?” 
        There has to be a mechanism,  a forcing and/or a feedback that alters the energy budget and causes the warming we see. Human CO2 emissions are such a mechanism. A very well understood mechanism that is completely consistent with the empirical evidence.

        Jon, there becomes a point where you invoke Occam’s Razor. Or you present a viable alternative hypothesis.

         If you hear the clippity-clop of hoofbeats outside your window, don’t assume it’s a zebra. JP

      4. UPDATE:

        I’ve done some research on the apparent convergence of daytime vs nighttime temperatures. First, the phenomenon is not global, it is regional. Therefore carbon dioxide can’t be the cause. The studies I’ve seen show the that phenomenon occurs only in relatively developed areas and is attributed to the Urban heat island effect and other land use changes. Looks like Occam’s Razor cuts both ways.

      5. Jon, The phenomenon I referred to is not a localized one, but rather was determined by measurements throughout the globe. Two studies that make this phenomenon clear are [Alexander 2006] and [Fan 2010]. Could you please cite the studies you mention. Possibly we are not discussing the same topic, as I didn’t suggest that daytime and nighttime temperatures were “converging”. I’m not sure I understand what you mean by “… the apparent convergence of daytime vs nighttime temperatures.” The sources of your research will help to clarify that.

        Jon, My suggestion that we look to Occam’s Razor was in reference to your recognition of the factual basis for the warming we see in our climate. The vast majority of climate scientists have subscribed to the hypothesis that the mechanism for this warming is anthropogenic. Occam’s Razor doesn’t “cut both ways”, it favors parsimony. Neither I, nor your readers, can judge whether or not yours is a more parsimonious hypothesis if you don’t let us know what it is.

        You’ve asked me to present the evidence for the AGW hypothesis. I’ve done that. I now ask you for the hypothesis you believe explains the climate warming we see.

        Thanks for following up with me, as you said you would. I appreciate that. I will certainly take the time to seriously review the sources you provide. Thanks, again Jon. JP

      6. John, I will try to clarify:

        In contrast to your characterization of atmospheric layers, the IPCC said that the rate of warming should increase by 200-300% with altitude in the tropics, peaking at around 10 kilometers – a characteristic “fingerprint” for greenhouse warming. However, measurements by weather balloons and satellites show the opposite result: no increasing temperature trend with altitude.

        You wrote: “What we observe is a decrease in cold nights greater than the decrease in cold days, and an increase in warm nights greater than the increase in warm days.” This is an artifact of the urban heat island effect and station siting. What you wrote is true for urban stations but not for rural stations.

        Finally, there is a lack of correlation between rise of CO2 and temperature. Two cooling periods, 1940–1975 and 1998–2009, occurred while CO2 was rising. That means that CO2 is only a minor factor in temperature and hence climate control.

        The real drivers of climate are the Sun’s insolation (light and heat), its magnetic flux, and the relative position and orientation of the Earth to the Sun.
        There are three main positional variations of the Earth and Sun, called Milankovitch cycles: Orbital Eccentricity, Axial Obliquity (tilt), and Precession of the Equinoxes. These cycles affect the amount and location of sunlight impinging on the earth.

        The variations in the Sun’s magnetic flux controls the amount of cosmic rays impinging on the atmosphere. Cosmic rays produce ionizations and the ions form nuclei for cloud formation. Cloud cover has a great effect on global temperature, but this area is still poorly understood and not addressed in climate models.

        These variations produce the circulation patterns such as ENSO and PDO which drive climate. I have covered many of these cycles in my posts.
        In my opinion your proffered evidence fails to be convincing.

  3. Jon, You stated that “…measurements by weather balloons and satellites show the opposite result: no increasing temperature trend with altitude.”. But Foster and Rahmhoff [2011] thoroughly reviewed all the datasets and found: ” analysis reveals that the underlying human-caused global warming trend in the lower troposphere of between 0.141 and 0.157°C per decade in the two main satellite lower troposphere temperature data sets.” These figures are lower than the radiosonde results. Dr. Roy Spencer, a noted skeptic and leader of the UAH MSU team finds lower troposphere trends calculated from satellite data by UAH are +0.140 °C/d. Jon, please tell me where you find zero or negative TLT values. The troposphere is warming Jon, and no earth scientist that I can find says otherwise. Please point to where you find information to the contrary.

    You said that: “What you wrote is true for urban stations but not for rural stations.” Perhaps you didn’t have an opportunity to review the compilation of data from the Alexander paper that has measurements from over 70% of the earth’s land surface. This data was controlled for UHI as are all such datasets. The phenomenon of UHI is well understood and easily corrected for statistically. Even with a complete exclusion of urban and suburban measuring stations we see the same trend. This alone shows scientists that variations in insolation cannot possibly be the cause of the trends we see. And certainly not by UHI. But even if we didn’t have this information, NASA’s Earth Observatory has measured the energy the earth receives from the Sun in literally dozens of ways. All show only a very small change in Earth’s energy budget from variations in insolation. Please see empirical evidence at NASA’s website. You can see for your self that Total Solar Irradiance has dropped in the last thirty years from 1366.5 W/m^2 to 1365.5 W/m^2, while at the same time the temperature has increased more than .5 degrees C. See, Poanli, NASA, GISS and PMOD.

    Jon, for you, a geologist, to say that, “Finally, there is a lack of correlation between rise of CO2 and temperature.”, is breathtaking. I contacted Dr. Berner in regards to the graph you use in your tutorial to purportedly show this “lack of correlation. I’ll let you know more about his personal communication to me at a later date ( along with others). But for now, here is the last sentence he wrote as a separate paragraph for emphasis, “Paleo-climate and CO2 correlate.” Dec. 12, 2011. Here is what Dr. Dicksen said to you directly,. “The arguments and past evidence for a coupling between CO2 and Earth’s surface are not debated by anyone who understands the science.” Dec. 6, 2011. The fact that you can find periods of time when well known phenomenon such as ENSO can cause short term variations is only going to fool those who have little understanding of the difference between climate and weather.

    The one thing you said that I can agree with is that our knowledge of how clouds will act in a warming world needs to be better understood. What we do know: during the last thirty years of warming, clouds have not stopped the temperature from rising.

    Jon, I know myself, and I sure many others, would be grateful if you would give us citations or other attributions to some of these statements you make. JP

      1. Jon, There are eight citations and two attributions in my last comment alone. Yours: zero. jP

      2. Attribution such as ” Foster and Rahmhoff [2011]” is not helpful. We need the complete citation to find the paper.

  4. Jon, You can find the paper here: Environmental Research Letters Volume 6 Number 4
    Grant Foster and Stefan Rahmstorf 2011 Environ. Res. Lett. 6 044022 doi:10.1088/1748-9326/6/4/044022
    If you ever have problems with my citations, just let me know and I’d be happy to assist.

  5. Jon, For reader’s who might have to pay to read the paper, here is a synopsis: “The researchers, statisticians, and climate experts came from Tempo Analytics and the Potsdam Institute for Climate Impact Research. Their study was published Tuesday in the journal Environmental Research Letters.
    They combined and analysed the five leading global temperature datasets covering a period from 1979 to 2010. They then factored out the three major short-term temperature fluctuations – El Niño, volcanic eruptions and variations in the Sun’s brightness – allowing them to show that the global temperature increased by 0.5°C in the past 30 years.

    In addition, according to all five of datasets, 2009 and 2010 were the two hottest years, and in average over all five datasets, 2010 is the hottest year on record.
    “Our approach shows that the idea that the global warming trend has slowed or even paused over the last decade or so is a groundless misconception. It shows that differences between the five datasets reside, to a large extent, in their short-term variability and not in the climatic trend. After the variability is removed, all five datasets are very similar,” said study co-author Stefan Rahmstorf.
    The five separate datasets, when combined, allow researchers to see through the individual complications and uncertainties that a single dataset may have. Of the five datasets, three were surface records collected by NASA, the National Oceanic and Atmospheric Administration (NOAA), and the Hadley Centre/Climate Research Unit in the UK, while the remaining two datasets were gathered by satellite microwave sensors in the lower troposphere.
    “The unabated warming is powerful evidence that we can expect further temperature increase in the next few decades, emphasizing the urgency of confronting the human influence on the climate,” says Grant Foster, lead author of the study. JP

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