Scientists in Australia and Sweden have developed the first mathematical formula to measure the impact of human activity on the earth.  They found that humans are causing the climate to change 170 times faster than natural forces.

The study from Australian National University's Professor Will Steffen and his team appears in the journal The Anthropocene Review.  The authors say that for the past 4.5 billion years, astronomical and geophysical factors have been the dominating influences on the Earth system - meaning the biosphere, the atmosphere, hydrosphere, cryosphere and upper lithosphere.  Or as Owen Gaffney from the Stockholm Resilience Center puts it, "The atmosphere, oceans, forests and wetlands, waterways and ice sheets and fabulous diversity of life."

But for the past six decades, human forces "have driven exceptionally rapid rates of change in the Earth system".  That has ushered in a new epoch scientists call the Anthropocene.  For all of human history prior to this new epoch, we lived within the forces of nature - until the most recent few decades, when nature has reacted to what we've thrown at it.  "Human activities now rival the great forces of nature in driving changes to the Earth system," the paper said.

"Over the last century or so, we can see that the impact of humans - through fossil fuels, through forest clearing, through all sorts of changes to the biosphere - have become more important than these other forces," said Professor Steffen.  But over five decades, greenhouse gas emissions from human activity "have increased the rate of temperature rise to 1.7 degrees Celsius per century, dwarfing the natural background rate," the professor added.

Gaffney and Steffen conclude their research with the stern warning that climate change could "trigger societal collapse", because human societies aren't as resilient as earth systems in adapting to rapid change.