“Prediction is very difficult - especially about the future”
So Niels Bohr, Nobel Laureate in Physics, is supposed to have said about the difficulties of divining that which is to come. The world is a complex place, and determining the state of the world in coming decades might seem like a fool’s errand. Few anticipated transforming events like the recent global economic crisis, the terrorist atrocity of 9/11, or the collapse of the Soviet Union. However, while such social, political and economic upheavals are near impossible to foresee, certain fundamental trends in the physical state of the planet are clear and directional, and do provide firmer foundations for what coming decades might hold. Scientists have dubbed a new geological era, the Anthropocene, to describe the period of accelerating change that followed the advent of the industrial revolution at the end of the 18th century. It is this suite of changes, rather than the transient perturbations in economies and political systems, that will ultimately decide our fate.
What trends define the Anthropocene? The clearest signal of all is the rapid change in the composition of the Earth’s atmosphere, which now holds more carbon dioxide, methane, and nitrous oxide than it has for millions of years. Other gases that have never been seen before are present in strong enough concentrations to alter fundamental atmospheric processes, such as the formation of stratospheric ozone. In response to these changes, global surface temperatures have risen by an average of 0.7°C. The oceans have become more acidic as they absorb some of the additional carbon dioxide, glaciers and ice-sheets are melting ever-more rapidly, sea levels are rising, and weather is becoming more extreme in many parts of the world. Also, tropical forests continue to be cleared, fresh water and fertiliser use are accelerating, fisheries are collapsing, agricultural soils are eroding away. Material consumption is accelerating: there are more cars, more fast food restaurants, more international flights, more disposable goods. There are whispers that the era of easily available oil and natural gas is coming to an end. And behind all this, the growing human population, estimated to reach more than 8 billion by 2020, more of whom are living in growing cities. These trends show clear trajectories. We could be forgiven for simply extrapolating to a world devoid of tropical forests and coral reefs, with no viable fisheries, no fresh water or freely-flowing rivers, poor agricultural soils,