European countries are buffeted by two global forces: One is climate change. The other is

demography. Both prevalent pressures silently transform. societies and the assumptions of public policy.

The two have a lot in common. Both are easily recognized but less easily understood. Both are products of complex forces and unobtrusive influences. Both create huge effects from minuscule changes. A rise in global temperature by one degree or a fall in fertility by one point may sound trivial but, over 100 years, will make the earth unbearably hot, or reshape the size and composition of societies.

Yet though every rich country has a climate-change policy, few have a population one (there are historical reasons for that). And just as everyone whinges about the weather, but does nothing about it, so everyone in Europe complains, but does nothing, about population.

Received opinion holds that "demography is destiny" and that Europe is doomed by its death-spiral population numbers. American observers argue that Europe is fast becoming a barren, ageing, enfeebled place. Vast numbers of old people, they reckon, will be looked after, or neglected, by too few economically active adults, supplemented by restless crowds of migrants. The combination of low fertility, longer life and mass immigration will put intolerable pressure on public health, pensions and social services, probably leading to upheaval.