(and it’s not very pretty)
By Sarah “Steve” Mosko
By mid-twentieth century, humans had altered the Earth to such an extent as to mark the start of a new geologic epoch named the Anthropocene, concluded an international consortium of researchers in a January issue of the preeminent journal Science.
Scientists divide Earth’s 4.5 billion year history into so-called epochs or time units based on major shifts in the composition and state of the planet as recorded in distinct stratifications in rocks, sediments and glacier ice. Previous transitions from one geologic epoch to the next were triggered by either cyclical drivers of climate change, like variations in the Earth’s orbit or solar radiation, or irregular events like volcanic eruptions. The most recent epoch for example, the Holocene, spanned ~12,000 years and was ushered in by a period of interglacial global warming.
Transition to the Anthropocene, in contrast, is driven by an unprecedented rate of change to the global environment caused by a convergence of three human factors: rapid rises in population growth, technological development and resources consumption, starting about 1950. So although Homo sapiens first emerged as a species about 200,000 years ago, it wasn’t until last century that their numbers and impact were sufficient to drive the permanent changes we now see to the Earth’s system.