Sleep and warm nights don’t go together for me, and a string of them last week found me pondering, as you do, the state of the climate. Bear in mind that the most telling sign of greenhouse warming isn’t the midday maximum but the night-time minimum.
Inevitably the late great atmospheric scientist Will Steffen came to mind. Recognised globally for his work at the leading edge of Earth systems science from the 1980s, Steffen, who died last year, was also a formidable climate warrior in offices, law courts, boardrooms and town halls around the country – including here in Tasmania.
In July this year the Australian National University celebrated his illustrious career with the inaugural Will Steffen Lecture, delivered from Germany’s University of Potsdam by his long-standing friend and collaborator, the Swedish scholar Johan Rockstrom, whose video image was joined live on the stage in Canberra by Australian colleagues of Steffen.
There was distinguished ecologist Lesley Hughes, Steffen’s long-time colleague on the Climate Commission and its crowd-funded successor, the Climate Council. For a time she chaired Tasmania’s climate advisory council, until that body was rudely terminated in 2014 by Will Hodgman’s incoming government on the basis that it wasn’t worth the money.
Another ecologist, the ANU’s Brian Walker, recalled Steffen’s rare ability to draw together diverse talents in the manner of an orchestra conductor. And Penny Sackett, astronomer and Australia’s chief scientist under Kevin Rudd, spoke movingly of how her fellow US expatriate Will Steffen had become like a brother to her, the one she had yearned for as an only child.
The big-picture thinking of Steffen and Rockstrom was behind the 15-year-old concept of planetary boundaries, central to understanding what is at stake as we plough through the 21st century. Man-made climate change is one of nine planetary processes that Rockstrom, Steffen and others identified as critical determinants of our Earth system’s stability, resilience and life support – most of them now well outside their safe limit.
In Seattle at the height of this year’s fiery West Coast summer, Rockstrom told a TED audience that science had for many years underestimated climate risks. Current change is well outside what used to be considered realistic expectations. Earth’s surface was now the warmest it had been for 100,000 years, and in this “Great Acceleration”, the Earth system’s stability is being undermined by mass extinction of species and increasing stress on freshwater systems.
“After the enormous privilege of a planet at 14C for 10,000 years, ever since the last Ice Age,” our present pathway sees us warming by 2.7C in only 70 years, said Rockstrom. “Is it surprising that we scientists are getting really, really nervous?”
Two overarching risks to the Earth system are increasing, said Rockstrom. Earth’s buffering capacity – its ability to dampen shocks and stress – is being damaged, and the risk of the planet being pushed out of its exceptionally stable state since the last Ice Age, passing critical tipping points, is rising. Stressed plants and warming oceans losing their ability to take up and store excessive greenhouse gases are “sounding the alarm.”
Loss of buffering capacity, said Rockstrom, is increasing chances that tipping points will be crossed, pushing the planet out of its stable state and starting an unstoppable drift towards a hothouse Earth, where warming is self-amplified warming and life support is lost. If we ignore key indicators – the big ice sheets, the Atlantic overturning circulation, coral reef systems, the Amazon rainforest – “they will flip over from a desired state that helps us to a state that [takes us] in the wrong direction.”
As we have learned more about the Earth system, said Rockstrom, the danger threshold has come closer. Thirty years ago the UN’s Intergovernmental Panel on Climate Change determined that 5C of warming was needed to cause irreversible climate change. Now that mark is between 1.5C and 2C – perilously close to where we are now.
In other words, we have to attend to our planet’s natural systems or we are lost. It’s a bleak prospect, but it’s also a challenge. Rockstrom ended his Seattle TED talk with the usual gee-up for the audience: “Solving the planetary crisis is not only necessary, it is possible, and we all win if we succeed.”
Key to this message is not the words themselves but the humanity behind them. That was Will Steffen’s message to those whose lives he touched, including mine: big-picture science is important, but vastly more so is how we respond – a theme that will recur with rising urgency as this critical decade grinds on.