Humans are driving the warming of the Earth 170 times faster than natural forces, according to a new mathematical formula.
Scientists in Australia and Sweden have developed the equation, which assesses the impact of human activity on the climate and compares it to events such as volcanic eruptions and changes to the planet’s orbit.
Professor Will Steffen, a climate scientist from the Australian National University (ANU), said no natural events came close to the impact humans have made.
“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,” he said.
Professor Steffen’s formula, created with scientists from Sweden’s Stockholm Resilience Centre, uses a variety of measurements of the natural world.
“This uses things like changes in solar intensity, changes in the Earth’s orbit around the sun, massive volcanic eruptions, perhaps a meteorite strike like the one that knocked out the dinosaurs,” he said.
“These sorts of things are traditionally the forces that change the state of the entire Earth over long periods of time.”
‘The Anthropocene Equation’
Professor Steffen, who is also on the Climate Council, and his fellow researchers have labelled the formula the Anthropocene Equation.
Officially, the Earth is in the Holocene period, but scientists such as Professor Steffen are pushing for the modern era to be reclassified to reflect the massive impact humans have had.
“We have estimates of how temperature has shifted through the Holocene – the last about 12,000 years of relatively stable climate,” he said.
“We go back 7000 years in that and look at from 7000 years to the present, where we have pretty good estimates.
“And climate was shifting very, very slightly to a cooler state at about one hundredth of a degree per century, and that’s a very, very slow rate.“
Biggest change to climate in five decades
The scientists behind the formula found the biggest change in the climate has come since 1970.
“Since 1970, temperature has been rising at a rate of about 1.7 degrees per century,” Professor Steffen said.
“When you compare those two, since the 1970s, the climate has been changing at a rate 170 times faster than that long-term background rate.”
Climate change scientists say the effects of those changes are already wreaking havoc across the globe.
“When you compare what’s happening now to the way the climate was 50 years or so ago, yes, it’s become hotter.”
Professor Will Steffen
He said the change in climate would also have other effects on the weather.
“Certainly there’s evidence that the massive rainfall and flooding that Queensland saw in 2011 to 2012, that was exacerbated by record high sea-surface temperatures just north of Queensland,” he said.
“These sort of observational records show quite clearly that extreme weather events are becoming more extreme and it’s due to the burning of fossil fuels and the increase in greenhouse gases in the atmosphere.”