Tuesday, April 25, 2017

Health and climate change: an appeal for a clearer effect classification

This letter (submitted March 20, 2017) was rejected by the Lancet on April 25, 2017, with no review and no explanation.  This version is different to that submitted in that it includes three figures. I have revised this and submitted it to the BMJ, as an 800 word opinion piece, with two figures from my edited book.


Since 2009 The Lancet has published three long articles on the health effects of climate change. These have involved 124 authors and 108 pages. (1-3) The first article described the potential health effects of climate change as “immense”, posing “potentially the biggest global health threat of the 21st century”. The second article endorsed this conclusion, adding that “temperature rises in the next 85 years may be incompatible with an organised global community”.(2)

The third, recent paper (3) focusses on tracking progress on health and climate change. While avoiding the term “catastrophic” it also argues that the health and social consequences of climate change are far-reaching, “ranging from reduced labour productivity and heat-related deaths, through to direct injury .. infectious diseases, and mental health effects.” It further states that climate change effects will be “heterogeneously mediated across different environmental and social systems, resulting in .. potential effects on food and water shortages, population displacement, and conflict.”(3) It reprints a figure from the second paper, showing six health endpoints, some of which are mediated by up to five social factors (see figure 1). 

Figure 1. Source: references 2 and 3

The earliest paper judged the “indirect” effects on “water, food security, and extreme climatic events” as likely to be the greatest.(1) The second paper identified four direct and four indirect physical effects, such as “heatwaves” (direct) and “water quality” (indirect). It also listed eight health impacts, all arising via direct and indirect effects, each modified by up to six kinds of “social dynamic”. These effects ranged from mental illness to poisoning. Again, there is no sense of hierarchy.

However, the literature contains a simpler, hierarchical classification of the health effects of climate change, not cited in any of these three articles (see figures 2,3).(4, 5) In this alternative framework, “primary” effects are the simplest, such as heat stress and injuries from a climate change fuelled superstorm. “Secondary” effects are less direct; including conditions such as allergies or malaria. “Tertiary” effects are potentially catastrophic, and with by far the largest burden of disease: large scale famine, conflict, migration, and social collapse. Mental health is cross cutting; post-traumatic stress can follow a cyclone or a war. Finally, as with the three Lancet papers, climate change is never conceptualised as acting alone, but instead via complex “eco-social” pathways.


Figure 2 (source ref 4, chapter 26)

Figure 3: This compares the likely burden of disease from the primary, secondary and tertiary effects of climate change with the time at which the effects are likely to be widely accepted as causally related by the general and even the scientific community. To date, my prediction this could take as long as 2050 appears on track! (source: ref 4, chapter 26).


1.             Costello A, Abbas M, Allen A, et al. Managing the health effects of climate change. The Lancet 2009; 373: 1693–733.
2.             Watts N, Adger WN, Agnolucci P, et al. Health and climate change: policy responses to protect public health. The Lancet 2015; 386: 1861–914.
3.             Watts N, Adger WN, Ayeb-Karlsson S, et al. The Lancet Countdown: tracking progress on health and climate change. The Lancet 2017; 389: 1151–64.
4.             Butler CD, editor. Climate Change and Global Health. Wallingford UK, Boston, US: CABI; 2014.
5.             Butler CD, Corvalan CF, Koren HS. Human health, well-being and global ecological scenarios. Ecosystems 2005; 8(2): 153-62.