Current models of Earth's climate capture physical and biophysical processes. But the planet has entered a new state: humans are adapting to, as well as causing, environmental changes. This major feedback must be modelled. Projections of the future climate based on simple economic narratives1— from cuts in greenhouse-gas emissions to unmitigated growth — are unrealistic.
Faced with droughts and rising sea levels, people alter their behaviour. Even if global climate policy is effective, and nations deliver on ambitious green-energy-production and sustainability targets, societies will be different in a warmer world. People will move to places that are richer in resources, or stay where they are and be pushed further into poverty. Population growth, urbanization, migration2 and conflict3 will compound reactions to global temperature rises.
To understand the underlying patterns, we need to collect behavioural statistics on grand scales. How do people of different backgrounds respond to extreme weather, for example? Under severe drought, do people in sub-Saharan Africa behave differently from those in southern Australia? How do the decisions made by lower- and middle-income families differ?
Ultimately, we must establish an international data-collection effort involving the public, private and voluntary sectors. Much as we take global stock of forests or biodiversity, we should regularly assess how people are being changed by the climate that they are changing.This is a call to action, not a definitive road map, but it's a start. I'm chairing a session on the "Spatial Demography of Population and Envirnment" at the Population Association of America meetings that will be held here in San Diego next Spring. The deadline for submission is 1 October and here's the link if you want to submit a paper. Let's get to work.