Published in CEOs for Cities, on 7th September 2010.

Civilisation is the thin film of order that human beings with ingenuity and imagination have constructed around the chaos of events. In a rapidly changing climate this is at its most brittle in our cities.

More than half the world’s population now live in cities and in some countries it is over 75%. This proportion will grow as the century advances. Throughout human history the development of cities has marked the advance of civilisation. This advance is now at risk and with it the future of cities.

Cities are the centres of art, learning and culture. They are sources of immense creativity and innovation. They power economies, drive knowledge and skills ever upwards. They provide access to jobs and services of extraordinary value and diversity. For centuries they have delivered a higher quality of life to more people than is ever possible in rural areas.

It is not surprising that they have consistently been a magnet for migration both between and within nations. As a result they have grown larger ever more rapidly. In 1900, the London in which I live was the largest city in the world. Its population was six and a half million. Today it is about to drop out of the top twenty. Nine cities now have populations of more than ten million people and 650 over 1 million. In 1900 all of the top ten cities were in industrialised nations. Now only two are.

But size has been bought at a price. Once upon a time cities directly controlled most of the hinterland on which they depended for food, energy, resources and markets for their manufactures. The city states of Italy or the myriad principalities of Germany were the result. In the market near where I live there is still a board from the 19th Century detailing the tolls for driving the live sheep and cattle over London Bridge to feed the city’s inhabitants.

Now cities no longer have any direct control over the far flung logistical networks on which they depend for food, energy, raw materials and water. Rather they rely on being able to generate sufficient revenues to buy them on global markets and ship them from every corner of the world. These logistical systems themselves rely on huge, expensive and vulnerable reticulated networks of roads, power, pipe and rail lines, fibre optic cables and the rest of the complex infrastructure that underpins a modern city.

Cities are also the dominant centres of governance and political power. They are, in effect, the key nodes in the operating system that makes all the astounding possibilities of 21st Century life – the applications if you like – work. Dysfunctional cities mean dysfunctional government and the chaos that accompanies it.

We have seen what happens when that operating system collapses. Five years on, and with all the capabilities and resources of the United States to hand, New Orleans is a long way from having fully recovered from hurricane Katrina. You cannot claim that Katrina was caused by climate change, but you cannot doubt the graphic insight it gave into what climate change might mean.

Except that it will not only be happening in one city. The floods in Pakistan illustrate what happens when extreme weather events go to scale. More than a tenth of the country’s population has been affected, several cities inundated, millions of homes destroyed, businesses disrupted, infrastructure destroyed. Again, this may not be a consequence of climate change, but it is an example of what life might be like in a world 4°C hotter than today.

We are moving from an age of abundance to one of scarcity. Food, water and energy supplies are all under increasing stress. Demand for food is projected to double by the middle of the century. Almost half the world’s population will be experiencing severe water stress within twenty years. Global primary energy demand will increase by a third in the same period and with it carbon emissions will increase by forty percent.

Climate change is a stress multiplier making it more difficult to tackle these crucial resource issues. Energy security, food security, water security and climate security are the interconnected substrates of the economy. They are the pillars of prosperity. As the stability of those pillars degrades so too do the prospects for the economy.

As these resource pillars become more insecure so the stress on the logistical systems and infrastructure that makes life in cities not only tolerable, but possible at all, grows. And with it, the cost of keeping them viable. Eventually these burdens will become unbearable and life in cities will go from being desirable to being intolerable.

These stresses on the pillars of prosperity are not unmanageable. We already possess the essential knowledge, technologies and skills to do so effectively. It is also clear that there are no fundamental economic barriers to doing so. However, there will be fundamental changes in the current pattern of economic winners and losers. Some industries, the oil industry for example, will disappear. Others will grow dramatically. This makes the politics very difficult.

The world is currently on course for a 4°C temperature rise, possibly by as soon as 2060. The climate change we are now experiencing is the result of a rise of about 1°C. We have no idea of whether civilisation can cope with a change as rapid and dramatic as that which will occur with in the lifetime of anyone under forty if we do not urgently deal with climate change.

But we do know, from the windows on the future provided by New Orleans and Pakistan, just how difficult it will be for cities to cope. A 4°C hotter world will turn most of the advantages of city life into disadvantages. As stresses over food, water and energy mount, order and security will decline. The logistic ligatures that now tie cities to their extended hinterland will become overburdened and will progressively fail.