Sunday, November 1, 2015

Climate change and heath: primary, secondary and tertiary effects

This is a preview of part of chapter 31 ("Climate Change and Global Health 2014-2015: Many Concerns, Some Hope) the additional chapter I am now writing for the forthcoming softcover issue of my edited book, Climate Change and Global Health, (CABI, 2016).

"The health chapter of the recent IPCC report concluded with a three tier classification of the possible health effects (see box). Though no source is quoted it may have been influenced by the “primary, secondary and tertiary” structure used in my edited book, Climate Change and Global Health, which in turn is derived from two earlier papers (Butler, Corval├ín et al. 2005, Butler and Harley 2010) (see box).

Soon before the release of this book, I attended a meeting on climate change and health run by the World Health Organization. At it, I learned that the IPCC health chapter (to which I was a minor contributor) had concluded with a three tier classification of the likely health effects of climate change (see box 31.1). It was encouraging to see that my fellow IPCC authors appreciated the existence of a third broad category, which is the framework of this book, based on ideas and papers I have promoted for two decades (Butler and Harley, 2010, Butler et al., 2005, Butler, 2014). But I was also disconcerted. Contrary to the IPCC principle which recommends its material to be based on existing literature, the framework was unattributed. The IPCC conceptualisation placed mental “illness” in the third category, rather than seeing mental health as a crosscutting issue (see Figures 26.1 and 26.2). Frustratingly, this framework made no clear statement that the third (tertiary) category is likely to have a much higher burden of disease (BOD) than the others (see Figure 26.2). If enough people of influence, especially in the media and government can see the risk of the third category then we might collectively act to reduce and to defer it. For this to occur, the enormous BOD risk of tertiary effects needs to be explained and stressed.

[1] When the publisher of this book approached me I agreed to edit on condition that it followed a three tiered classification, of which the third (tertiary) category is by the most important, following ideas I first started to consider over 25 years ago, as discussed in Butler and Woodward, 2015).
BOX 31.1

“Climate change affects health in three ways; 1) Directly, such as the mortality and morbidity (including “heat exhaustion”) due to extreme heat events, floods, and other extreme weather events in which climate change may play a role; 2) Indirect impacts from environmental and ecosystem changes, such as shifts in patterns of disease carrying mosquitoes and ticks, or increases in waterborne diseases due to warmer conditions and increased precipitation and runoff; and 3) indirect impacts mediated through societal systems, such as undernutrition and mental illness from altered agricultural production and food insecurity, stress and undernutrition and violent conflict caused by population displacement, economic losses due to widespread “heat exhaustion” impacts on the workforce, or other environmental stressors, and damage to health care systems by extreme weather events”
(Smith, Woodward et al. 2014).

Both figures are from  Chapter 26 ( Butler C.D, Bowles D.C., McIver L., Page L. (2014) Mental health, cognition and the challenge of climate change. In: Butler C.D., editor. Climate Change and Global Health. CABI, Wallingford, UK: CABI; pp 251-258.)


No classification is perfect, none should be considered inviolable .. but the main idea of the third category is to try to convey that climate change related health risks are lot more significant (and terrifying) than (say) heatstress or a heightened chance of malaria.

To me, most conceptualisations are a bit like impressionist paintings. The other element involved with tertiary is causal distance .. there are still a lot of people denying climate change can influence conflict or migration, for example. (Which leads into the x access label in Fig 26.2) ..

Oreskes and Conway (2013), writing from the future, reflect on the collapse of civilisation, reflect on the bias most scientists have towards "type II" errors (ie waiting too long to make a conclusion). If, by say 2150 Miami etc has disappeared and WWIII has passed then we might agree
climate change contributed to the devastation that had transpired .. by which time it’s too late. 

The late Tony McMichael has called the tendency to not think hard enough about cause as "epidemiologising", or looking under the lamp post, because that's where the light is, even if the keys aren't likely to be.

When I give lectures on this (eg see slides given to the ANU medical students last month), I spend a lot of time on Fig 26.2. I tell people it’s the most important slide in the whole lecture, the whole book.. (No one so far has either challenged or explicitly agreed with me on that, so I’m not sure if people understand..)


Butler, C. D., C. F. Corval├ín and H. S. Koren (2005). "Human health, well-being and global ecological scenarios." Ecosystems 8(2): 153-162. 

Butler, C. D. and D. Harley (2010). "Primary, secondary and tertiary effects of the eco-climate crisis: the medical response." Postgraduate Medical Journal 86: 230-234. 

Butler, C. D. and A. Woodward (2015). From Silent Spring to the threat of a four degree world. The context of Tony McMichael’s career. Health of People, Places and Planet: Reflections Based on Tony McMichael’s Four Decades of Contribution to Epidemiological Understanding. C. D. Butler, Dixon, J., Capon A.G. Canberra ACT Australia, ANU Press: 11-30.

Oreskes, N. and E. M. Conway (2013). "The collapse of Western civilization: a view from the future." Daedalus 142(1): 40-58.  

Smith, K., A. Woodward, D. Campbell-Lendrum, D. Chadee, Y. Honda, Q. Liu, J. Olwoch, B. Revich, R. Sauerborn, C. Aranda, H. Berry, C. Butler, Z. Chafe, L. Cushing, K. Ebi, T. Kjellstrom, S. Kovats, G. Lindsay, E. Lipp, T. McMichael, V. Murray, O. Sankoh, M. O’Neill, S. B. Shonkoff, J. Sutherland, S. Yamamoto, U. Confalonieri, A. Haines and J. Rocklov (2014). Human health: impacts, adaptation, and co-benefits. Climate Change 2014: Impacts, Adaptation and Vulnerability, Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. C. B. Field, V. Barros and D. J. Dokken. Cambridge and New York Cambridge University Press.