05 September 2023

Betting against worst-case climate scenarios is risky business

Illustration by Erik English

As the world is hit my mind-boggling, even-more-extreme climate events, records are busted and some events are way beyond scientific expectations, it’s time to ask the question: "Are the worst-case scenarios coming true too often, and what does that for the way we approach climate risks in policy making?"

And this is relevant to the way the Australian government constructs its emission-reduction targets, based on some very risky analysis.

The IPCC and the climate-economy models it uses to produce carbon budgets and emission scenarios focus on the probabilities, not the possibilities. Is this a fatal mistake? 

 These issues are explored in a new article in the “The Bulletin” (US):

Betting against worst-case climate scenarios is risky business

"Would you live in a building, cross a bridge, or trust a dam wall if there were a 10 percent chance of it collapsing? Or five percent? Or one percent? Of course not! In civil engineering, acceptable probabilities of failure generally range from one-in-10,000 to one-in-10-million.

"So why, when it comes to climate action, are policies like carbon budgets accepted when they have success rates of just 50 to 66 percent? That’s hardly better than a coin toss.

"Policy-relevant scientific publications, such as those produced by the Intergovernmental Panel on Climate Change, focus on the probabilities—the most likely outcomes. But, according to atmospheric physicist and climatologist Hans Joachim Schellnhuber, “calculating probabilities makes little sense in the most critical instances” because “when the issue is the survival of civilization is at stake, conventional means of analysis may become useless.”

"Have scientists and policy makers given too much weight to middle-of-the-road probabilities, instead of plausible-worst possibilities? If so, it’s an appalling gamble with risk. Humanity could end up the loser."
Read the full article