Climate change will have broad impacts on human society. Changes projected to occur in the coming century or two will not have the apocalyptic, civilization-destroying character of, say, an all-out nuclear war or a direct hit from a large asteroid.

But climate change will be disruptive in many ways to a civilization whose planetary home is already under stress from the demands of billions of human beings. The physical impacts of climate change will not be evenly distributed around the globe. Low-lying coastal regions, for example, will suffer more from sea-level rise; continental interiors will see more drought; and high latitudes will warm disproportionately.

For that reason alone, impacts will vary from country to country. But social, political and economic considerations also alter the impact of a changing climate, because wealthier countries are better able to adapt to and counter deleterious effects. Wealthy countries can build protective seawalls to ward off the rising oceans; they can engineer massive water projects to ensure continuing supplies of freshwater; they can outbid poorer countries if declines in domestic agriculture require increased food imports; their advanced health-care systems can better cope with spreading tropical diseases; and their robust economies can speed recovery from extreme weather events.

We are forced to the unfortunate conclusion that climate change will exacerbate the gap between rich and poor nations, as those with the fewest resources will be the most vulnerable. This conclusion should be especially troubling because anthropogenic climate change is almost entirely the result of fossil-fuel consumption, deforestation and other activities carried out by or for the benefit of the developed world.