Late March of this year, the Intergovernmental Panel on Climate Change (IPCC) released the second part of its Fifth Assessment Report, AR5 Working Group II (WGII). The Global Climate and Health Alliance (GCHA) has recently released its briefing, outlining the implications of the IPCC report for public health and health professionals.

This briefing provides recommendations for national health systems, research and public health policy, and highlights the need for health professionals to advocate for solutions to protect human health against the risks of climate change.

Both the IPCC report and the briefing consider the direct and indirect impacts of climate change on health. Examples of direct impacts include excess mortality during heatwaves, or deaths and injuries caused by floods, storms or bushfires. Climate change also interacts with ecological and social systems to result in indirect effects. Ecologically-mediated impacts are those influenced strongly by ecosystems and include, for example, the spread of infectious diseases such as those caused by vector-, food- and water-borne pathogens, in a warmer climate. Socially-mediated impacts include, for example, the projections of markedly increased food insecurity leading to under-nutrition, mental stress resulting from climate-related extreme weather and economic losses, and downstream effects of climate change on social stability, conflict and migration.

The emphasis placed on indirect health impacts, and particularly on projections of food price rises and food insecurity, has noticeably shifted since the IPCC’s Fourth Assessment Report, and was highlighted in the Alliance’s briefing. One key element of the report is that it identifies limits to adaptation: threshold points beyond which given systems – whether human physiology, social systems or ecosystems – simply cannot cope, or can only adjust more slowly than the rate of external change. Two examples of limits discussed in the health chapter are those of thermal limits and food production.

Citing evidence that core body temperatures reach lethal levels under sustained periods of ‘wet-bulb globe temperatures’ above ~35°C, and that lower temperatures than this can harm health, the report’s authors highlight the very real problems we face in terms of reduced capacity for work, as well as the risks to health and survival. Interestingly, key stages in the production of many staple crops also have maximum thresholds of approximately 35°C.

Such thresholds are highly concerning with regards to their potential impacts on human health. The IPCC report states, “The existence of critical climatic thresholds and evidence of non-linear responses of staple crop yields to temperature and rainfall thus suggest that there may be a threshold of global warming beyond which current agricultural practices can no longer support large human civilizations, and the impacts on malnourishment and undernutrition described in Section 11.6.1 will become much more severe.” While acknowledging that current models are inadequate in their ability to forecast such non-linear effects, the authors estimate that the risk to global food security “becomes very severe under an increase of 4-6°C or higher in global mean temperature.”

Without urgent action to curb emissions, we are well on track to warming of this magnitude. Should the RCP8.5 scenario become reality, we will see an average rise in global mean temperatures of 3.4°C by 2100 and 6.2°C by 2200, relative to the period from 1861 to 1960.

At the same time, tackling climate change could be very good for health. Though the WGII report focuses primarily on impacts, vulnerability and adaptation to climate change, health “co-benefits” – activities that both improve health and help to mitigate climate change – are a key part of the narrative around climate change and heath. They include, for example, investment in cleaner energy and active travel infrastructure, which reduces air pollution-related illness and mortality while increasing physical activity in the case of walking or cycling. Other examples include home insulation, which prevents cold deaths and wasted energy, and the replacement of inefficient, polluting cookstoves with cleaner alternatives.

These impacts, risks and opportunities are the reasons why health professionals from countless countries around the world, and their representative bodies, believe they have a duty to speak out about the risks that inaction on climate change poses to health, and the health co-benefits of mitigation. Several public declarations [1],[2] by the GCHA and its many member organizations have highlighted the magnitude of the risks, their inequitable distribution, and the major health improvements that climate change action could bring about.

The Global Climate and Health Alliance was formed in Durban in 2011, following the inaugural Climate and Health summit, which took place during the 17th session of the Conference of the Parties (COP 17) to the UNFCCC. The Alliance consists of health organizations from around the world and aims to tackle climate change and to protect and promote public health.
[1] http://www.climateandhealthalliance.org/news/durban-declaration-on-climate-and-health
[2] http://climateandhealthalliance.org/doha-declaration