A look at two new studies and how the media has misled both the public and the sloppy authors of the Nature study
There are many reasons why the public doesn’t understand how dire the climate situation is. We have a well-funded disinformation campaign, generally poor messaging by scientists, and many progressives and environmentalists who have been persuaded to downplay talk of global warming risks.
And we have dreadful coverage by the status quo media. The media fails in countless ways, but one of its most insidious failings is to play up the occasional study that seems to suggest the threat of human caused global warming has been overblown.
Much as the media has been providing a false balance in its choice of experts to quote, creating the misimpression that there is a much greater debate among climate scientists on key issues than there really is, the media has been providing a false balance in its choice of articles to write about — and then, typically, utterly misframing the results. Such is the case with the big malaria study in Nature.
In a AAAS presentation this year, William R. Freudenburg of UC Santa Barbara discussed his research on “the Asymmetry of Scientific Challenge“:
New scientific findings are found to be more than twenty times as likely to indicate that global climate disruption is “worse than previously expected,” rather than “not as bad as previously expected.”
But you’d never know that from the coverage by the status quo media.
That’s because most of the media have been suckered by the antiscience crowd (and lame messaging by scientists and others) into believing that the threat of global warming has been oversold when, in fact, the reverse is true. So they will jump at any chance to push the “contrarian” message that some new scientific study confirms what they believe — even if they have to twist that scientific study and the scientific literature completely backwards to make their case (see, for instance, “Scientists withdraw low-ball estimate of sea level rise “” media are confused and anti-science crowd pounces“).
So it is with two new studies on the malaria/climate link — I say ‘two’ because the media has completely ignored one that doesn’t fit into their thesis, and they have spun up the second to make a case that doesn’t exist.
THE NON-HYPE ABOUT CLIMATE AND MALARIA
The overwhelming majority of those who report on the threat of human-caused global warming spend very little of their time on malaria. For instance, the word never appears in my entire book Hell and High Water and it appears exactly once in Straight Up as an aside (in a satirical essay). I’ve published more than 2 million words and nearly 5000 posts on Climate Progress and you can search “malaria” and find very little on it. [The disinformers have scrounged this blog and found about 3 instances where I reprint sentences by written by other people that bother them, which again, proves my point.]
Why? Many obvious reasons — it’s a second order effect from global warming, and we’ve long had intense global effort to fight the disease.
UPDATE: Revkin now writes:
The climate blogger Joe Romm and I agree (breaking news): Scientific research and assessments examining the link between human-driven climate change and malaria exposure have, for the most part, accurately gauged and conveyed the nature of the risk that warming could swell the ranks of people afflicted with this awful mosquito-borne disease.
How about the much-maligned IPCC report, Climate Change 2007: Working Group II: Impacts, Adaption and Vulnerability? Let’s start with, “126.96.36.199 Malaria, dengue and other infectious diseases,” a section with caveats that would make Judith Curry proud:
Studies published since the TAR support previous projections that climate change could alter the incidence and geographical range of malaria. The magnitude of the projected effect may be smaller than that reported in the TAR, partly because of advances in categorising risk. There is greater confidence in projected changes in the geographical range of vectors than in changes in disease incidence because of uncertainties about trends in factors other than climate that influence human cases and deaths, including the status of the public-health infrastructure.
Table 8.2 summarises studies that project the impact of climate change on the incidence and geographical range of malaria, dengue fever and other infectious diseases. Models with incomplete parameterisation of biological relationships between temperature, vector and parasite often over-emphasise relative changes in risk, even when the absolute risk is small. Several modelling studies used the SRES climate scenarios, a few applied population scenarios, and none incorporated economic scenarios. Few studies incorporate adequate assumptions about adaptive capacity. The main approaches used are inclusion of current ‘control capacity’ in the observed climate-health function (Rogers and Randolph, 2000; Hales et al., 2002) and categorisation of the model output by adaptive capacity, thereby separating the effects of climate change from the effects of improvements in public health (van Lieshout et al., 2004).
Malaria is a complex disease to model and all published models have limited parameterisation of some of the key factors that influence the geographical range and intensity of malaria transmission. Given this limitation, models project that, particularly in Africa, climate change will be associated with geographical expansions of the areas suitable for stable Plasmodium falciparum malaria in some regions and with contractions in other regions (Tanser et al., 2003; Thomas et al., 2004; van Lieshout et al., 2004; Ebi et al., 2005). Projections also suggest that some regions will experience a longer season of transmission. This may be as important as geographical expansion for the attributable disease burden. Although an increase in months per year of transmission does not directly translate into an increase in malaria burden (Reiter et al., 2004), it would have important implications for vector control.
Few models project the impact of climate change on malaria outside Africa.
I know, the alarmism is unbearable.
Seriously, not only have they reduced the magnitude of the projected effect from the Third Assessment, but then there is Table 8.2 itself, the “main results” for “Malaria, global and regional”:
Estimates of the additional population at risk for >1 month transmission range from >220 million (A1FI) to >400 million (A2) when climate and population growth are included. The global estimates are severely reduced if transmission risk for more than 3 consecutive months per year is considered, with a net reduction in the global population at risk under the A2 and B1 scenarios.
The decrease comes about because of increased drought. On page 400, in the section on “188.8.131.52 Drought and infectious disease,” the IPCC finds:
In the long term, the incidence of mosquito-borne diseases such as malaria decreases because the mosquito vector lacks the necessary humidity and water for breeding….
Malaria has decreased in association with long-term decreases in annual rainfall in Senegal and Niger (Mouchet et al., 1996; Julvez et al., 1997).
What about the impact to date of climate change on malaria? Section 184.108.40.206 on Malaria says:
The effects of observed climate change on the geographical distribution of malaria and its transmission intensity in highland regions remains controversial. Analyses of time-series data in some sites in East Africa indicate that malaria incidence has increased in the apparent absence of climate trends….
In southern Africa, long-term trends for malaria were not significantly associated with climate….
There is no clear evidence that malaria has been affected by climate change in South America (Benitez et al., 2004) (see Chapter 1) or in continental regions of the Russian Federation (Semenov et al., 2002). The attribution of changes in human diseases to climate change must first take into account the considerable changes in reporting, surveillance, disease control measures, population changes, and other factors such as landuse change (Kovats et al., 2001; Rogers and Randolph, 2006).
And so on and on and on.
And there’s even more important non-alarmism. After all, policymakers don’t actually read all this stuff, they read the Summary for Policymakers, which gets signed off on word for word by every member government. Surely the government hype-meisters have oversold the story. In the 16-page summary for WGII, here is everything they say on malaria under the Health Section:
Climate change is expected to have some mixed effects, such as a decrease or increase in the range and transmission potential of malaria in Africa. ** D [8.4]
If you aren’t pissed off at this kind of typically extreme alarmism from the IPCC, well, then you just don’t spend enough time reading either the mainstream media or the anti-science crowd.
Before getting to the incredibly lame media coverage, let’s look at the study that got all the attention, “Climate change and the global malaria recession,” in Nature (subs. req’d). It concludes:
First, 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. Second, the proposed future effects of rising temperatures on endemicity are at least one order of magnitude smaller than changes observed since about 1900 and up to two orders of magnitude smaller than those that can be achieved by the effective scale-up of key control measures. Predictions of an intensification of malaria in a warmer world, based on extrapolated empirical relationships or biological mechanisms, must be set against a context of a century of warming that has seen marked global declines in the disease and a substantial weakening of the global correlation between malaria endemicity and climate….
The quantification of a global recession in the range and intensity of malaria over the twentieth century has allowed us to review the rationale underpinning high-profile predictions of a current and future worsening of the disease in a warming climate. It suggests that the success or failure of our efforts against the parasite in the coming century are likely to be determined by factors other than climate change.
Hmm, you may be wondering what those “widespread claims” and “high-profile predictions” are, since they clearly are not from the most high-profile source, the IPCC. Well, the only reference to this in the body of study says:
A resurgence in funding for malaria control10, the existing efficacy of affordable interventions, and a growing body of nationally or sub-nationally reported declines in endemicity or clinical burden11 have engendered renewed optimism among the international malaria research and control community. In marked contrast, however, are model predictions, reported widely in global climate policy debates3, 6, 7, that climate change is adding to the present-day burden of malaria and will increase both the future range and intensity of the disease. In policy arenas, such predictions can support scenario analysis or serve as a call to action, but the modelling approaches used and the accuracy of their predictions have not always been challenged.
And what is foonote 6? It is IPCC’s Working Group II report!!
By the way, WGII also states, “Health services provide a buffer against the hazards of climate variability and change. For instance, access to cheap, effective anti-malarials, insecticide-treated bed nets and indoor spray programmes will be important for future trends in malaria.” So one hardly accuse the IPCC of using malaria as a “call to action” to reduce greenhouse gas emissions as opposed to a call to action to do the kinds of non-climate things the Nature article suggests matter more.
I doubt that the authors of the Nature article even bothered to go back to read the IPCC report they cited or spend a few minutes searching it for the word “malaria,”since that would have made clear it is inappropriate to cite it as they did. I suspect the authors just swallowed the media/disinformer myth that the IPCC has overhyped the malaria-climate link and threat. The same goes for the reviewers, who should have pointed out that this footnote was inappropriate here.
And what is footnote 7? It is “US Environmental Protection Agency, Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act (Technical Support Document) (US Environmental Protection Agency, 2010).”
They mean 2009, not 2010, I think. The original April 9, 2009 document is here. The final December 7, 2009 document is here. Their discussions of malaria are identical and reprinted below in their entirety:
Although large portions of the U.S. may be at potential risk for diseases such as malaria based on the distribution of competent disease vectors, locally acquired cases have been virtually eliminated, in part due to effective public health interventions, including vector and disease control activities. (Ebi et al., 2008; Confalonieri et al, 2007).
The IPCC concludes that human health risks from climate change will be strongly modulated by changes in health care, infrastructure, technology, and accessibility to health care (Field et al., 2007)….
And from the EPA’s section on “Overview of International Impacts”:
Mosquito-borne diseases which are sensitive to climate change, such as dengue and malaria are of great importance globally. Studies cited in Confalonieri et al. (2007) have reported associations between spatial, temporal, or spatiotemporal patterns dengue and climate, although these are not entirely consistent. Similarly, the spatial distribution, intensity of transmission, and seasonality of malaria is observed to be influenced by climate in sub-Saharan Africa (Confalonieri et al., 2007). In other world regions (e.g., South America, continental regions of the Russian Federation) there is no clear evidence that malaria has been affected by climate change (Confalonieri et al., 2007). Changes in reporting, surveillance, disease control measures, population changes and other factors such as land use change must to be taken into account when attempting to attribute changes in human diseases to climate change (Confalonieri et al., 2007)….
I assert that it is also absurd for the authors to cite this EPA document in this sentence: “In marked contrast, however, are model predictions, reported widely in global climate policy debates3, 6, 7, that climate change is adding to the present-day burden of malaria and will increase both the future range and intensity of the disease.”
How the heck does the EPA — or IPCC — get lumped in with references that are “widely reported in global climate policy debates” that find “model predictions” conclude “climate change is adding to the present-day burden of malaria”? Same for the assertion that they report model predictions that “climate change will increase both the future range and intensity of the disease.”
This kind of sloppy citation does not inspire confidence.
UPDATE: My critiques of these two inappropriate citations have not been challenged by the authors (see “My critique of malaria paper, media coverage holds up“), though at least one disinformer has tried to pretend the authors used a different citation.
Now it is true that their third reference — Chapter 20 in a 2004 WHO report — did find climate change was adding to the present day burden of malaria. But that doesn’t mean their third reference was wrong, even if this sloppy Nature article questions that conclusion.
After all, a new and very thorough literature review of 70 studies on the subject supports that overall conclusion. The article is “Climate Change and Highland Malaria: Fresh Air for a Hot Debate” (subs. req’d) published in The Quarterly Review of Biology in March. That journal isn’t as sexy and high profile as Nature, but one must pay attention to a comprehensive literature review like this.
The lead author, Luis Fernando Chaves is from Emory University and their release on the subject says:
Climate change is one reason that malaria is on the rise in some parts of the world, according to new research by Emory environmental studies’ Luis Chaves, but other factors such as migration and land-use changes are likely also at play…. Their review of 70 studies aimed to sort out contradictions that have emerged as scientists try to understand why malaria has been spreading into highland areas of East Africa, Indonesia, Afghanistan and elsewhere in recent decades….
After careful examination of the statistical models of previous studies, the researchers concluded that climate change is indeed likely playing a role in highland malaria. “Even if trends in temperature are very small, organisms can amplify such small changes and that could cause an increase in parasite transmission,” Chaves said.
The Science Daily story adds:
“We assessed “¦ conclusions from both sides and found that evidence for a role of climate in the dynamics is robust,” write study authors Luis Fernando Chaves from Emory University and Constantianus Koenraadt of Wageningen University in the Netherlands. “However, we also argue that over-emphasizing a role for climate is misleading for setting a research agenda, even one which attempts to understand climate change impacts on emerging malaria patterns.”
Malaria, a parasitic disease spread to humans by mosquitoes, is common in warm climates of Africa, South America and South Asia. The development and survival, both of the mosquito and the malaria parasite are highly sensitive to daily and seasonal temperature patterns and the disease has traditionally been rare in the cooler highland areas. Over the last 40 years, however, the disease has been spreading to the highlands, and many studies link the spread to global warming. But that conclusion is far from unanimous. Other studies have found no evidence of warming in highland regions, thus ruling out climate change as a driver for highland malaria.
Chaves and Koenraadt re-examined more than 70 of these studies. They found that the studies ruling out a role for climate change in highland malaria often use inappropriate statistical tools, casting doubt on their conclusions.
For example, an oft-cited 2002 study of the Kericho highlands of western Kenya found no warming trend in the area. But when Chaves and Koenraadt ran the same temperature data from that study through three additional statistical tests, each test indicated a significant warming trend. Similar statistical errors plague other comparable studies, the researchers say.
In contrast, most studies concluding that climate change is indeed playing a role in highland malaria tend to be statistically strong, Chaves and Koenraadt found. But just because climate is one factor influencing malaria’s spread does not mean it is the only one. What is needed, the researchers say, is a research approach that combines climate with other possible factors.
So on the one hand we have a sloppy Nature article that seems to have read media accounts of their references more than they actually read their references. And on the other we have a thorough literature review.
But most of the media doesn’t seem to bother reading actual scientific studies any more. And so we get nonsense like this from Clive Crook of the Atlantic Monthly and Financial Times last week:
The idea that malaria and climate change are strongly connected still has wide currency among casual environmentalists, even though those who know what they are talking about have been quietly retreating from this position for some time.
And this nonsense from the Economist, which asserts the Nature study is “an attempt to re-examine, and perhaps close down, long-running debates about malaria and climate change.” I know, it kills you, doesn’t it? The status quo media keeps telling us that the science isn’t settled, yet now it asserts that one sloppy article can override dozens of others.
But the Economist has a phony storyline it wants to sell: “If one is going to be optimistic about the future of malaria, one might also, with caution, be optimistic about the future of assessments of climate change.” Ironically, it’s now pretty clear the 2007 IPCC report didn’t go as far as an accurate review of the scientific literature would allow.
Normally I wouldn’t have spent so much time blogging on a study on climate and malaria. But I didn’t see much choice after people sent me this DotEarth “opinion” piece by Revkin, “Cooling Fear of a Malaria Surge from Warming,” which spins an alternative universe storyline that would make the writers of the TV show Lost proud:
As various arguments for action on global warming have failed to blunt growth in emissions in recent years, environmental groups and international agencies have sometimes tried to turn the focus to diseases that could pose a growing threat in a warming world “” with malaria being a frequent talking point.
Yes, doctors and scientists and others spun up the malaria concern not because of what the scientific literature said but because other messaging stuff wasn’t working. Seriously, this is X-Files and Fringe type stuff. The fact is a comprehensive review of the scientific literature makes clear that it is quite legitimate to raise concerns that human-caused could put more people at risk of malaria than would be at risk absent the warming. You can go to Revkin’s links and see for yourself that again and again the statements are well caveated and fully consistent with the literature.
I would note that, for instance, Revkin’s language for his first link somehow suggests that “researchers at Harvard Medical School” = “environmental groups.” Here’s what the piece he links to says:
Kidney stones, malaria, Lyme disease, depression and respiratory illness all may increase with global warming, researchers at Harvard Medical School said….
The Harvard center also found climate change will increase deaths from heat waves, raise the incidence of waterborne diseases and spread afflictions such as Lyme disease and malaria.
Revkin says such assertions “shouldn’t be.”
I would also note for the umpteenth time that even the business as usual case for global warming has a high risk of radically changing the Earth’s climate (see “M.I.T. doubles its 2095 warming projection to 10°F “” with 866 ppm and Arctic warming of 20°F“). And The Lancet‘s landmark Health Commission found last year: “Climate change is the biggest global health threat of the 21st century.”
What seems to be the case if one reads the literature is that climate change may well have played a role in some malaria today and it threatens to put more people at risk in the near- and medium-term (compared to the non-warming case), but that public health measures have a larger impact, and, finally, in the long term, warming may actually reduce the total area at risk but only by creating widespread conditions of severe drought that would have dire consequences for those living in the vicinity (see NOAA stunner: Climate change “largely irreversible for 1000 years,” with permanent Dust Bowls in Southwest and around the globe).
I’m not the only one who thinks the Nature piece by itself has flaws. Scidev.net reports:
Matthew Thomas, researcher at Pennsylvania State University, United States, said that the study “plays down the potential importance of climate [change]“.
“It is very easy to come up with a superficial model,” he said, adding that this controversial area requires better science and more investigation of basic biology before reaching any firm conclusions about climate effects on malaria.
He pointed out that the Nature study predicts a background expansion and intensification of malaria, which needs to be taken into account when designing approaches to the disease.
“Drug and insecticide resistance could make future interventions less effective,” he added, and so even small effects of climate have to be seen in that context.
He said that the malaria map published in Nature shows that in some areas malaria has in fact increased with global warming, in spite of overall decline over the last century. The map shows such areas in Latin America, South and South-East Asia, and Sub-Saharan Africa.
“If I was in a village where malaria went up, it would matter to me and I would want to know why it happened.
Climate Wire (subs. req’d) reports:
“This is an attempt to counter something that isn’t being said,” said Paul Epstein, associate director of the Center for Health and the Global Environment at Harvard Medical School. “You can’t prove disease incidence.”
It is a subtle point, but the incidence of a disease refers to its actual occurrence within a population. Climate models such as the one by the Intergovernmental Panel on Climate Change predict that with rising temperatures, the conditions that favor insect vectors such as the mosquito will allow disease transmission to become more prevalent.
Whether they will actually lead to a greater incidence of the disease will be complicated by factors including control measures, the availability of drugs, and even other indirect effects of climate change, such as population changes, migration and urbanization.
Critics say the conclusions are overstated
… “During a century in which global temperature increases have been unequivocal, we have documented a marked, global decrease in the range and intensity of malaria transmission,” states the paper.
Though the results sound intuitive, the correlation between climate change and the disease is simplistic, according to Kevin Lafferty, research ecologist at the U.S. Geological Survey.
“They have done a less convincing job matching malaria decline with climate change, besides noting that temperatures have increased over the past century,” wrote Lafferty in an e-mail.
The researchers need to make more sophisticated connections between climate, malaria and the economics and control measures that will mitigate the disease, to get a full understanding of the issue, according to Lafferty.
“This is certainly difficult to do,” he wrote. “It is useful that the authors repeat the point that projection of a global increase in malaria transmission have been overstated by some. But they overstate the overstatement.”
Recent studies have suggested that climate change will cause shifts in the regions where malaria will be best transmitted, said Lafferty.
But Revkin has his storyline and he’s sticking to it:
This paper is sure to please longtime critics of climate overstatement “” reinforcing the reality that efforts to get attention that go beyond the science are bound to kick back.
It will please them only to the extent that they either don’t understand — or choose to misrepresent — what the recent scientific literature actually says.
Again, the IPCC seems to have understated what the literature says, and you’d be hard pressed to find a major report that isn’t adequately caveated and consistent with the full scientific literature as reviewed in the March Quarterly Review of Biology piece. And if you are the kind of person who is pleased by a possible long-term decline in the area at risk to malaria because of severe drought over much of the currently habited planet, well, you probably don’t read this blog.
Revkin issues this challenge at the end of his piece — which his amen chorus assert was aimed at me:
Well, I’m covering it. But the issue isn’t who is covering it, the issue is who is covering it accurately and who is covering what the scientific literature actually says on this subject and on the full array of climate impacts we face if we stay anywhere near our current path of unrestricted greenhouse gas emissions.
Remember, “New scientific findings are found to be more than twenty times as likely to indicate that global climate disruption is ‘worse than previously expected,’ rather than ‘not as bad as previously expected’.” Who isn’t covering that?
This post has been updated.
- An illustrated guide to the latest climate science
- Boykoff on “Exaggerating Denialism: Media Representations of Outlier Views on Climate Change”: Freudenburg: “Reporters need to learn that, if they wish to discuss ‘both sides’ of the climate issue, the scientifically legitimate “other side” is that, if anything, global climate disruption is likely to be significantly worse than has been suggested in scientific consensus estimates to date.”