When presenting the UWA Joseph Gentilli Memorial Lecture two years ago, Pitman admitted that researchers face some "truly scary" challenges.
What are the problems ahead?(37.20min.) Cimate science has three problems. The first problem is everything we do is extraordinarily computationally expensive. Not as expensive as the astronomers. We are not as bad as the astronomers yet, but we are working really hard [to get there] (laughter).
Just as a guide, if you divide the globe into one degree-by- one degree cells – about 65,000 cells – and you run it out for 100 years, it means 40,000,000,000,000,000 calculations. If I want to do probability density functions, I have to do this simulation a thousand times and you can do the math.
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But what happens if there is a glitch, or if a few of the 65,000 cells have dodgy data or dummy variables.
Practitioners of the black art of climate simulation prefer to keep their views about such matters to themselves, especially after Climategate (here and here).
Exhibit A: A UNSW Newsroom media release of 15 October 2015 on a recent study - 'The multi-millennial Antarctic commitment to future sea-level rise' - warned that "2 degree Celsius warming locks in sea level rise for thousands of years."
It also stated that the study: "predicts how the Antarctic ice-sheet will respond to future atmospheric warming."
But do the ice sheet/shelf computer model simulations used in the above study have predictive power? Can their outcomes be described as genuine predictions?
On the NZ TV Newsworthy program of 15 October, "Professor Tim Naish talks Antarctic Ice Melt", Professor Naish said that:
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If global warming is more than 2C, then our study shows that the Antarctic ice sheet will result in a significant amount of sea-level rise (4.27min). Those ice shelves we talked about? It just so happens that 2C is their stability threshold. If we warm the planet to more than 2C then we commit ourselves to many metres of sea-level rise –up to ten metres – if we continue on the business-as-usual scenario.
How did Professor Naish and his team deduce that 2C is the 'stability threshold' of the Antarctic ice shelves? What empirical scientific evidence do they have to support their analogy that ice shelves act like the 'cork-in-the-bottle preventing the Antarctic ice sheet from sliding into the ocean and melting'? How would this analogy work in nature, given that ice sheets and valley glaciers flow by plastic creep – not 'sliding' – and apparently some of the Antarctic ice sheet occupies basins that are below sea level?
Alarmism is easy. Discussing goat-entrails (aka assumptions) in public clearly less so.
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