‘Threat Multiplier’. Several regions in the world already face a perfect storm of poor crop yields; water and food scarcity; young, underemployed, and growing populations; and weak governance. The UK’s ‘4 Degrees’ map uses the best available science to suggest how, later this century on a business-as-usual trajectory, these challenges would be seriously exacerbated and multiplied by the changing climate. Nor is it just a hypothetical debate about the future. The UN tells us that millions are already being affected – now – whether it be accelerated Himalayan glacial melt, increased storm intensity, or climate change-exacerbated drought.