Climate change is but one component of a set of wide-ranging human impacts on the environment, which also include urbanization, land use change and loss of biodiversity, deforestation, resource extraction on land and in the oceans, the growth of agribusiness, and conflict. It must therefore be borne in mind that climate change is part of a complex system of environmental disturbance and perturbation. The introductory quote by Merrill Singer makes it quite clear how embedded is the deeper structure of this complex system. The present chapter seeks to show how the climate crisis is also a health crisis.

There is abundant evidence of long-term climate change. For example, the United Kingdom's Meteorological Office reported in May 2022 that climate change has increased by 100-fold the chances of record-breaking heatwaves in northwest India and Pakistan; a heatwave (of more than 50°C) is projected to occur every three years (Met Office 2022). There was a fivefold increase in exposure to extreme heat events between 1980 and 2017 for the world's most populated cities, and current exposure to heatwave events is almost 15 billion person-days per year, with the greatest cumulative exposures occurring in southern Asia (7.19 billion), sub-Saharan Africa, and north Africa and the Middle East (Met Office 2022).

Any discussion of the impact of climate change on human health must begin with the monumental report from Working Group 2 of the Intergovernmental Panel on Climate Change (IPCC), which was delivered in February 2022 (IPCC 2022). At 3,675 pages this report is truly encyclopaedic, but the “Summary for policymakers” is an excellent starting point. My own focus is initially on impacts on vector-borne infectious disease (malaria and dengue), waterborne disease, nutritional deficiencies and food security. I then consider impacts on Indigenous groups before looking at the consequences for population displacement and migration. The latter, as with so much else on climate change, makes highly visible the “geographical connections” in this book title.