This paper explores evidence relevant to the hypothesis that human-generated climate change (global warming) is already, and will increasingly, add to the existing burden of disadvantage experienced by populations in low-income countries, the ‘Global South'. Well recognised health manifestations of global warming include from heatwaves and other extreme weather events, changes to infectious disease patterns, and undernutrition, arising from higher food prices, reduced food availability and reduced nutrient concentrations of many foods. These effects have been called ‘primary' and ‘secondary'. Although these manifestations will have effects globally, their biggest impact on health is and will be upon poor and vulnerable populations in low-income settings. Also well recognised, manual labourers are increasingly vulnerable from excessive heat and humidity. There is less recognition that climate change interacts with social and political determinants of health, contributing to ‘tertiary' health consequences including conflict, forced migration and famine. In turn, these effects may deepen poverty traps in the Global South. Human-generated climate change is principally caused by the policies and lifestyles of populations in high-income countries (the Global North). The recent recognition by the British government that climate change is an emergency is encouraging, and may help motivate the widespread global behavioural changes that are needed to reduce the many risks from global warming, including to the people of the South.