Global Change - Physical Evidence For Global Change

Physical Evidence For Global Change

Humans have always altered their environment. The advent of agriculture around 10000 years ago led to a radical change in land use that still continues. But, the relatively small human population had little impact on a global scale until the start of the industrial revolution in 1750. This event, followed by the invention of the Haber-Bosch process in 1909, which allowed large-scale manufacture of fertilizers, led directly to rapid changes to many of the planet’s most important physical, chemical and biological processes.

The 1950s marked a shift in gear: global change began accelerating. Between 1950 and 2010, the population more than doubled. In that time, rapid expansion of international trade coupled with upsurges in capital flows and new technologies, particularly information and communication technologies, led to national economies becoming more fully integrated. There was a tenfold increase in economic activity and the world’s human population became more tightly connected than ever before. The period saw sixfold increases in water use and river damming. About 70 percent of the world’s freshwater resource is now used for agriculture. This rises to 90 percent in India and China. Half of the Earth’s land surface had now been domesticated. By 2010, urban population, for the first time, exceeded rural population. And there has been a fivefold increase in fertilzser use. Indeed, manufactured reactive nitrogen from fertilizer production and industry now exceeds global terrestrial production of reactive nitrogen. Without artificial fertilizers there would not be enough food to sustain a population of seven billion people.

These changes to the human sub-system have a direct influence on all components of the Earth system. The chemical composition of the atmosphere has changed significantly. Concentrations of important greenhouse gases, carbon dioxide, methane and nitrous oxide are rising fast. Over Antarctica a large hole in the ozone layer appeared. Fisheries collapsed: most of the world’s fisheries are now fully or over-exploited. Thirty percent of tropical rainforests disappeared.

In 2000, Nobel prize-winning scientist Paul Crutzen announced the scale of change is so great that in just 250 years, human society has pushed the planet into a new geological era: the Anthropocene. This name has stuck and there are calls for the Anthropocene to be adopted officially. If it is, it may be the shortest of all geological eras. Evidence suggests that if human activities continue to change components of the Earth system, which are all interlinked, this could heave the Earth system out of a one state and into a new state.